Vancouver, Washington – March 30, 2026. US Digital announced today expanded resolution options for the L2 Low-Profile Motor Encoder, now offering up to 5000 CPR (20,000 PPR with quadrature).  

 

The L2 motor encoder maintains its compact 0.398 in. profile and simple, direct-to-shaft mounting, making it well suited for space-constrained applications. It supports 12 shaft sizes ranging from 2 mm to 8 mm and 1/8 in. to 5/16 in. and is compatible with NEMA 17 through NEMA 34 and larger motors.

Now the L2 supports the following resolutions: 2000, 2048, 2500, 4000, 4096, and 5000 CPR. These additions extend the encoder’s capability for applications requiring higher positional resolution and finer motion control, while maintaining the same compact form factor and straightforward installation.

 

L2 Features
• Low profile — only 0.398 in. tall
• Resolutions now available up to 5000 CPR (20,000 PPR with quadrature)
• Uses field-proven EM1 and EM2 optical encoder modules
• Simple, quick installation

Lower resolutions continue to use US Digital’s EM1 optical encoder module, while higher resolutions are enabled by the EM2 module, providing expanded performance options across a wider range of applications.

The L2 provides two-channel quadrature TTL square wave output with an optional index channel. A high-retention connector and cable system is available and sold separately.

Like all US Digital products, the L2 is designed and manufactured in Vancouver, Washington, USA. It is backed by prompt access to our technical and customer service teams. The L2 is immediately available for shipping worldwide. Learn more at usdigital.com.

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Our encoders have not been tested in a radioactive environment. We believe the encoders will perform just fine in this environment. Regardless you will need to test them to determine if they will work in your application or not.

Encoder resolution identifies the smallest measurement that can be made. Encoder accuracy is the term used to compare the target position with the actual position. Encoder precision refers to the repeatability—comparing the change in successive measurements.

Some of the electronic components of encoders are susceptible to ESD which is why we recommend wearing a grounding strap when handling encoders and encoder components.

Single-ended is the most frequently used encoder output where commonly the output alternates between 0 and 5VDC. For an encoder with a differential output, for each channel that alternates between 0 and 5VDC, there is a complementary channel that at the same time, alternates between 0 and -5VDC. A differential signal allows for longer cable runs and can be used in electrically noisy environments.

This chart shows the tolerances for both bore size on encoder kits and shaft diameter on shafted encoders.

As a general rule of thumb, our single-ended output encoders work for cables up to 10 feet in length assuming they are not in an electrically noisy environment. For applications longer than 10 feet, a differential output encoder and shielded cable is recommended. If you have questions about a specific application, please reach out to Technical Support.

For encoders using 1" diameter disks, CPR values range from 32 to 5000. Those are the resolutions available on the following encoders: E2, E5, S1, S5, H1, H5, HB5M)

For encoders using 2" diameter disks, CPR values go from 64 to 10000. Those resolutions are available on these encoders: E3, E6, S2, S6, H3, H6, HB6M, HD25 For linear strips LPI values range from 120 to 500 using the EM1 module and 1000 to 2000 using the EM2 encoder module.

E4T & S4T CPR values range from 100 to 1,000.

E8T CPR values go from 180 to 720

EC35 CPR values range from 500 to 60,000

E16 CPR values range from 250 to 4,096

M3K CPR ranges from 1 to 8,192 for Incremental and 12-bit PWM for Absolute

Using an encoder with a differential output and using a shielded cable will often mitigate signal distortion caused by an electrically noisy environment. Other steps that can be taken include ensuring proper grounding and using a Faraday shield.

We provide a vibration and shock rating for each encoder. The encoders have been tested to that standard. Any vibration or shock exceeding those standards can negatively affect the output of the encoder.

Incremental encoders provide an output as to the movement of a shaft but upon power up, shaft angle position is unknown. But if the encoder has an index, position can be determined by performing a homing cycle. Absolute encoders report exact angle position upon power up with no movement required.

The robust design of our encoders provides for consistent functioning even when a disk has small imperfections, scratches and specks on it. “Cleaning” a disk can cause more problems than it might fix. US Digital has a post and video addressing this topic in more detail.

An index is a unique mark at one or more points on a disk or linear strip. The index enables an exact angle position to be known when the encoder detects that mark.

For the available bore sizes, review the datasheet for the encoder you select. Use this comparison chart to see the bore size range for all our encoder kits.

The right encoder depends on many factors. We’ve created a white paper that will help you through the process. Things you will need to consider are:

Are you measuring rotary or linear motion?

Will the encoder mount onto an existing shaft or do you need an encoder that has a shaft built into it.

Do you need an encoder that can always report the exact position when powered up or do you only need it to report how much it is moving and the direction it is moving.

If you are choosing an incremental encoder, do you need an index? 

Which resolution do you need? If choosing an incremental encoder, do you need a differential output?

Which encoder output is compatible with your data acquisition system?

What voltage encoder would work best for your system?

Is the encoder rated to be able to function properly at the maximum speed you anticipate using?

Is an IP rating required?

Encoders use a medium with a consistent pattern which passes by a sensor, producing an output that can be used by a control device to determine speed, acceleration, and/or position of some part of a mechanical system. Some technologies often used are optical, magnetic, and capacitive.

An encoder is an electro-mechanical device that translates physical motion into an electrical signal. That data can be used by a control system to determine speed, acceleration, direction, and/or position.

Symmetry is the relationship of the on time to the off time (x,y) for any encoder channel. This specification is shown on the datasheet in electrical degrees for the EM1 and the EM2 encoder modules.

Stiction is a combination of the words stick and friction. Stiction exists when the static (starting) friction exceeds the dynamic (moving) friction. An example of stiction would be a shaft sticking when small changes are attempted, requiring a larger input force to initiate movement. The result is that the force required to start the shaft moving is more than what is needed to go to the desired shaft position, causing the movement to be jerky.

Single-Ended Output is the most basic kind of output on an encoder. Each channel only has one wire which provides a train of pulses alternating between 0 to 5 volts in relationship to ground. While it is the most common, it is inherently susceptible to electrical noise and the length of the cable is quite limited. Using a differential output will resolve both of those issues.

Shaft Runout is the deviation of a shaft from true circular rotation. This can be caused by a bent shaft or a loose bearing. US Digital’s datasheets for encoder kits have a rating of TIR—Total Indicated Runout and is specified in thousandths of an inch. If an encoder is installed onto a shaft exceeding those specifications, the output of the encoder can be unreliable.

Shaft Loading is the specification used on shafted encoders and refers to the force applied perpendicular to the shaft. An increase in the amount of force on a shaft will decrease the bearing life. Use the formula provided on the datasheet for shafted encoders.

Shaft Axial Play is the movement of the shaft in the axial direction. US Digital states the maximum shaft axial play in thousandths of an inch.

Revolution is one complete rotation of the encoder shaft, 360 mechanical degrees.

Resolution relates to the quantity of increments an encoder has in one rotation (for a rotary encoder). An encoder disk has a specified number of lines on it providing for a native resolution equal to the number of line/window pairs on the disk. Resolution can be increased via interpolation, multiplying the native resolution by any number of times. This output, either native or interpolated is the encoder resolution which US Digital refers to as the CPR—cycles per revolution. Using two channels (A & B) of a quadrature encoder enables the output of the encoder to be decoded up to four times the native or interpolated encoder output. US Digital refers to that special decoding as PPR standing for Pulses Per Revolution.

Quadrature is the most common digital incremental encoder output. It uses two channels (typically referred to as channels A and B) which are offset from each other by 90 electrical degrees. This output enables one to determine the direction of movement (by viewing which channel is leading the other) and allows for resolution multiplication—providing up to four times the CPR resolution.

A Pseudo-Absolute Encoder is an incremental encoder used as an absolute encoder on single turn applications which use a homing cycle. This requires that the media (disk or linear strip) include an index. On power-up, the system performs a homing cycle, moving until the index is detected. At that point the exact position is determined. To reduce the amount of movement required to find the index, the media can use more than one index with a unique number of line/window pairs between the indices. During the homing cycle, as soon as the second index is located, the exact position is determined.

PPR is the term US Digital uses to refer to the number of pulses after 4x quadrature multiplication. US Digital uses CPR to identify the before quadrature resolution of an encoder. (Note: Some vendors of encoders use the same acronyms of CPR and PPR with differing definitions.)

Phase jitter is the variation between the rising edges of channel A and channel B from one cycle to another.

See Cycle Error

Phase Relationship identifies which channel (A or B) leads (goes high first) the other channel based on the rotation of the shaft. The perspective from which the relationship is viewed is also included in this specification.

A Phased Array is a pattern of photodiodes used on US Digital encoders to detect several lines and windows simultaneously. The array averages these pairs to provide an output that is more consistent than those using fewer sensors. In US Digital’s design, there are also two photodiodes for every line and window. The phased array allows for a wider gap tolerance and excellent tolerance to some disk contamination.

A Phase the delay in time or degrees between the rising edge of channel A and the rising edge of channel B. Also defined as the delay between the center of the high state on channel A to the center of the high state on channel B.

Output Waveforms are the relationship of the output signals to each other, normally shown in a diagram as below. This shows the sequence of all output signals including channels A, B, and I as well as their inverse signals for differential output encoders.

An Optical Encoder is an encoder using a light source, detector and interrupting medium to provide an output based on the speed and direction of the lines on that medium. Optical encoders can be transmissive—often with the light on one side of the medium and the detector on the other side or they can be reflective—the detector seeing the light reflected off of the patterned disk.

The interrupting medium is a disk for rotary encoders and a linear strip for linear encoders. The output is dependent on the quality of the pattern on the disk or strip. US Digital makes the code wheels for all of our encoders. The code wheel patterns are created using precision digital plotters and cut using a precision laser cutter. US Digital uses a highly collimated solid-state light source. Most of US Digital’s optical encoders are transmissive. The collimated light rays pass through the disk (or strip) pattern. The image of the pattern is detected using a phased array monolithic sensor and is converted to TTL digital quadrature outputs. Reflective type encoders (E4T / S4T) bounce the collimated light off a patterned reflective code wheel. This means all of the electronics are one side of the code wheel making for a more compact design. See Magnetic Encoder

Open Collector Output is an output that allows the user to set the voltage level of the output signal by installing a pull-up resistor between the output channel and a power supply of the desired voltage.

Noise is any unwanted electrical signal that can potentially interfere with a desired signal. The potential sources for electrical noise are numerous. Electrical noise can be mitigated by using a differential output or by shielding the desired signal.

A Magnetic Encoder is an encoder that uses a magnetic code wheel to provide an output based on the speed and direction of the shaft. A magnetic sensor in the encoder detects the changes in the magnetic fields as the wheel rotates and can produce an incremental or absolute encoder output. US Digital’s magnetic encoders include the models MAE4, MA4, and M3K. Also see Optical Encoders

The Moment of Inertia is the point at which the rotational force being applied to a shaft equals the resistance to change in angular velocity.

A Linear Strip is the mylar material used by US Digital on which is placed an evenly spaced pattern of windows and lines. When that pattern passes between an LED and detector the encoder provides a corresponding output. The number of line/window pairs provide the native resolution.

A Line Driver is a circuit designed to increase the maximum recommended cable length for an encoder, and/or to add immunity from electrical noise or interference on the signal lines. US Digital has a differential output option available on some of its encoders.

Line Count is the number of equally spaced lines on a linear strip or disk. The space between each line is referred to as a window. Each line/window pair is the basis for creating each electrical cycle as the disk turns. The line count for a rotary disk is stated in CPR (cycles per revolution) while it is stated in LPI (lines per inch) on a linear strip.

IP Ratings identify the ability of an enclosure to resist intrusion. Common examples are IP64 and IP69. The first digit indicates the protection against the ingress of solids (eg. dust) and the second digit indicates the protection against the intrusion of liquids (eg. Water). The higher the number, the better the protection.

An Inclinometer is a device that reports the angle of an object with respect to gravity. Also known as a "tilt sensor."

A HubDisk assembly consisting of an aluminum hub and an optical encoder disk.

A Homing Cycle is the movement of an incremental encoder to find its index. This is helpful upon power-up as without an index and homing cycle, the location within the encoder’s rotation cannot be determined. A homing cycle on a rotary encoder is completed by rotating the shaft until the index is detected. An encoder using this process is sometimes referred to as a Pseudo-Absolute Encoder.

Frequency is the number of cycles per second which can be read by an encoder. Each encoder is rated at specific frequencies based on how fast the encoder can read the information on a disk. Higher resolutions may reduce the read rate which limits the speed (RPM) at which the encoder is effective.

An Encoder Module is an electronic component made by US Digital which incorporates an LED and detector through which a medium with evenly spaced lines and windows passes to provide an output which can be used by a control device to determine speed, acceleration, direction, and position. US Digital’s encoder modules are used in many of its encoders.

Interpolation is the internal multiplication of a signal in an encoder providing a higher resolution than the native disk resolution. This is executed via the internal circuitry in an encoder or encoder module. The stated CPR of the encoder includes any interpolated multiplication.

The Index is a unique location on an encoder disk or linear strip used as a reference point. The index output is provided via a third channel on quadrature encoders and is often referred to as the “I” channel (index) or the “Z” channel (zero position). The index enables position to be determined after a homing cycle. US Digital index outputs are internally gated to coincide with the low states of channels A and B. This provides a precise index position that is ¼ of one quadrature cycle wide. The use of a single index is most common, but some applications use multiple indices with distinctive spacing requiring less movement to determine the exact position. US Digital specializes in creating custom disks to match applications.

An Incremental Encoder is an encoder that provides information via a waveform output as to the movement of a shaft. It does not provide positional information but that can be calculated after performing a homing cycle if the encoder includes an index. Incremental encoders can use optical, magnetic, capacitive or other technologies. Quadrature output is most common and can be used to determine the shaft’s speed, acceleration, direction, and position. The resolution of an incremental rotary encoder is stated in cycles per revolution (CPR). An incremental encoder can also be used as a human interface device with a knob to adjust some parameter such as temperature, volume, or speed.

An Encoder is an electro-mechanical device that translates physical motion into an electrical signal. That data can be used by a control device to determine speed, acceleration, direction, and position. Encoders can use optical, magnetic, capacitive, or other technologies to detect motion. Encoders can be used for rotary or linear motion and can provide incremental or absolute outputs. 

An Electrical Degree (°e) is 1/360 of an electrical cycle. Electrical degrees are used in encoder specifications to indicate the width of a pulse, the Rise and Fall times of a signal, to compare the on and off times for symmetry, and the phase lag time between quadrature channels.

Eccentricity Error is the measurement in the error of a rotary encoder caused by an eccentricity in the mounting of the encoder disk.

Duty Jitter is a variation from pulse width to adjacent pulse width.

A disk is the round mylar material used by US Digital on which is placed an evenly spaced pattern of windows and lines. When that pattern passes between an LED and detector the encoder provides a corresponding output. The number of line/window pairs provide the native resolution. The disk is also available mounted on an aluminum hub and is called a HubDisk.

Differential Output is an output employing a complementary channel for the standard encoder output channels. Each complementary channel provides -5VDC simultaneously as the original channel provides +5VDC. These complementary outputs can be transmitted over much longer distances while maintaining the signal integrity. Differential outputs also help to reduce the effects of electrical noisy environments. Using a differential output does require a differential input or differential receiver to which the other end of the cable is connected. US Digital has several encoders which have a differential line driver option.

Cycle Error is the difference between the target (theoretical) position of the shaft and the actual position indicated by the encoder cycle count.

A Cycle refers to one complete four-state quadrature cycle. One quadrature cycle is generated by one line and one window called a line pair on the encoder disk.

Each cycle is divided into 360 electrical degrees (°e) and can be decoded into 1, 2, or 4 counts, referred to as x1, x2, or x4 resolution multiplication.

CPR is the number of full quadrature cycles per full shaft revolution (360 mechanical degrees). A 200 CPR encoder can provide 200, 400, or 800 positions per revolution depending on whether x1, x2, or x4 quadrature decoding is done. See Resolution.

Vancouver, WA – US Digital in May celebrated its 40th anniversary as a U.S. Manufacturer of optical encoders and other motion control components.

“Looking back on these 40 years, I couldn’t dream of anything that would be more of a blessing than this experience,” US Digital Founder and CEO David Madore said. “Not only for me, but for our team – many of them have been here for decades as well.”

US Digital began in 1980 when David, who was working as a design engineer at a medical imaging company, couldn’t find an affordable, reliable optical encoder to use for a control knob on a product design. He thought he could make something better and set off to do so. He and his wife Donna started US Digital in their family garage in Southern California.

Not only did David want to design encoders and other products that met the needs of engineers like himself, he also wanted his business be focused on building meaningful relationships with its customers, employees and business partners, rather than being focused on the bottom line.

US Digital Chief Operating Officer Neal Donowitz says that foundation is core to the company’s success over the past 40 years.

“Our customers don’t value us just because we make encoders,” Neal said. “They value us because of how we treat and value them as a customer.”

Operations Manager Mike Pomerinke joined the company in 1995 in an entry level assembly position. He says those values are just as much alive today as they were when he first walked in the door.

“Sure we’re in business to make money – absolutely – but valuing people in that way is a very important thing here,” he said. “From when I started, that’s what it’s always been about – making sure we provide that top level customer service and value our relationships.”

Since Mike first joined US Digital, the company has moved twice to make more space for additional personnel and equipment as the company began to vertically integrate key manufacturing processes. He is now one of more than 120 employees who work at US Digital’s facility in Vancouver, Washington where the company makes optical encoders, magnetic encoders, inclinometers and various other motion control components and tools. Products are shipped globally and are used in multiple industries including additive manufacturing, robotics, textiles, solar energy and motor manufacturing.

In 2009, US Digital donated an unused 17,000-square-foot section of its building and administrative and IT services to dozens of local non-profit organizations and ministries to use as office space. The US Digital Outreach Center is now more than 10 years old and US Digital is looking to expand the space to further invest in the local community. After the next buildout, US Digital will be providing around 30,000 square feet of space for non-profits.

As for US Digital, the future looks a lot like the past. Technology, products and processes will change – but the customer focus cannot, founder David Madore said.

“We will always continue to invest in the future,” he said. “Our foresight comes from listening to requests and questions from our customers and potential customers. We don’t dread problems. Solving them is how you advance.”

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Our most popular motor encoders offer motor design engineers precise position measurement with reliability in the parts-per-million range.

• All encoder models offer multiple mounting options.
• US Digital offers multiple adapters to convert single-ended encoder signals to differential.
• Push-on hubs provide fast assembly and symmetrical weight distribution for high RPM applications.
• These encoder models are part of our standard inventory and are available for same-day shipping*.

*Orders placed before 11:00 AM (PST) ship the same day.

The best tool for testing an encoder and being able to see the signal output is an oscilloscope. US Digital does have a QSB which when connected to a computer does have the ability to provide some information like encoder CPR, count, position and current speed.

Most of our encoders require 5VDC power. However, some of our encoders operate on 12VDC power, and several of our encoders can operate on voltages from 7.5 to 30VDC.

The most common source of erratic signals from an encoder is misalignment. We provide alignment and spacer tools with our encoder kits to ensure consistent signal output. Electrical interference can also cause erratic signals.

Once you configure an encoder on our website, you can find compatible products, cables and connectors listed near the bottom of the product page.

Our encoders have been tested and verified to work in non-condensing humidity environments but are not designed to be used in a condensing humidity environment.

Our encoders use an LED with a phased array detector. This essentially means that the sensor is not just focused on only one point of the disk but is looking simultaneously at multiple line and window pairs. That way, a flaw at one spot on the disk is easily averaged out. This robust design allows for a consistent signal output even when dust or other imperfections exist, such as those you would expect from everyday use and the handling of encoders. Furthermore, our LEDs operate in the infrared spectrum, which means they're less susceptible to physical obstructions than visible light.

Our encoders have not been tested in a vacuum. We believe our encoders should work fine in a low vacuum environment, but you will need to test them to determine if they will work in your application or not.

The assembly instructions for each encoder are located near the top on each encoder kit product page on the website, but they, along with accompanying videos, can be found on the Encoder Assembly Instructions Page.

Each encoder has specifications on its datasheet giving the alignment tolerances. Not staying within those tolerances may cause anything from no output to an inconsistent one. We provide assembly tools with each encoder kit to ensure proper alignment.

As each application is unique, we are unable to give definitive instructions on how to mount the linear strip. A common method we have seen is clamping the back portion of the linear strip between two solid surfaces, with just the required quadrature track exposed.

It is technically possible to change the resolution of our kit encoders, however, doing so requires swapping out core components for new ones that support the desired resolution. Changing the disk alone will not change the resolution. For encoders that use our EM1 and EM2 modules, you’d need to buy a new HubDisk and module. For miniature encoders, you’d need to buy a new HubDisk and board. You may find it simpler and less expensive to buy a new encoder.

This is a calculation you need to perform based on the smallest increment you need to monitor for the application. For example, if your application is measured in degrees as on a rotary encoder, you will divide 360 degrees by the number or fractions of a degree you have determined you need to be able to measure (360/X). The result will be your minimum resolution. Having determined that, you will choose a resolution equal to or greater than that number. Keep in mind that depending on the capability of your data acquisition system, it may be able to take the CPR and measure up to four times that amount (PPR).

Just like the different divisions a measuring tape (inches, ½ inch, ¼ inch etc.), the resolution on an encoder defines how coarse or fine of a measurement can be determined. The higher the resolution, typically called out in CPR, the more unique positions can be resolved in the rotation of an encoder.

The surge in popularity of drones in recent years has been remarkable. Although sometimes we hear about them when they cause trouble—like flying too close to commercial aircraft—more frequently we hear about drones because of the interesting new ways they're being put to use.

Drones are used in agriculture, to monitor crop growth and field conditions. Home inspectors for insurance companies use drones to check on the condition of a roof—without having to risk injury by climbing ladders. Workers on oil pipelines have used drones to improve pipeline inspection.

And of course, many companies are developing autonomous drones that will deliver packages—or pizza—directly to a customer's doorstep. The company Flirtey, for example, has made successful pizza delivery demonstration flights; their next step is to develop a service to deliver automated external defibrillators (AEDs) to 911 callers, via autonomous drones.

No matter what type of drone or how it's put to use, there are often many moving parts. Drone developers who need to sense the position, angle or speed of mechanisms in motion find that encoders are ideal for the task.

Typical applications for encoders used on drones include the following:

• Control Surfaces : flaps, ailerons, vertical elevators, speed brakes
• Airflow Indicators : angle of attack (A0A); angle of sideslip (AOS)
• Landing Gear : to verify extension or retraction
• Payload : gimbals for video cameras and optical devices; packages

Let's look at a few examples of how people who develop drones use encoders in their research.

The Angle of Attack (AOA) probe is a sensor that measures the angle between an aircraft control surface and the oncoming airflow. The video shows a probe moving up and down in the wind. Notes below the video reveal that the sensor that converts probe motion to an electrical signal is an absolute magnetic encoder.

Groups of drones can be flown in coordinated formations, sometimes known as "swarms". This is useful if you need to monitor a large area, or measure many points at once. In our next example, researchers are developing sensors to measure angle of attack (AOA), and angle of sideslip (AOS). The information is shared between drones to coordinate their flight formation. 

The AOA and AOS sensors each use a magnetic absolute encoder, as the authors mention in their research paper (in the paper, see the paragraphs immediately above and below the photo).

The payload for a drone is often a video camera, used to transmit images from the air to the ground. The camera can be mounted in a gimbal, which allows the camera to move in the roll, tilt and pan directions. You can see a gimbal mounted below the nose of Georgia Tech's research helicopter, the GTMax, in the article below.

 GTMax article

Here's a close-up of the gimbal. In their research paper, the authors explain that the gimbal uses three incremental encoders, each with an Index. The quadrature output from the encoders transmits information about the roll angle, the tilt angle, and rotation about the pan axis, as well as direction of motion.

The Index channel transmits one pulse per encoder revolution; the system uses that pulse to enable positioning at power-up.

The requirements for a sensor used on a drone can be demanding, but with light weight and low power consumption, the right encoder can meet the test.

Sources:

• Test flight video: youtube.com/EnacUAVLab
• https://newatlas.com/uav-learns-to-think-for-itself-now-technology-will-transition-to-military/3745/

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Many manufacturers are structured to run a low mix of product variations. That model supports high-volume efficiencies, but it also makes it difficult to introduce anything outside the standard configuration—especially lower-volume or custom builds. Customization can disrupt production flow, require separate documentation and validation, demand additional capital equipment, and consume valuable engineering and machining resources.

US Digital is structured differently. From the beginning, we have built our manufacturing model to efficiently support both high-volume production and custom projects—many of which are lower volume. Customization is not an exception to our system; it is an intentional capability aligned with our vertically integrated philosophy.

 

 

Our culture has always been open to custom requests because it aligns directly with our values. We have a relentless drive to solve customer problems and to make it easy for people to do business with us.

As a vertically integrated manufacturer, US Digital has invested many millions of dollars in advanced production infrastructure to support rapid customization across our line of encoders and accessories. Because we control critical processes in-house, we reduce reliance on outside vendors and overseas supply chains—allowing us to respond quickly, protect quality, and maintain consistency from prototype through production.

Our manufacturing capabilities include:

• Precision waterjet cutting system
• Wire EDM and sinker EDM machines
• Multiple 3-axis CNC machining centers
• Conversational and traditional mills
• Conventional and CNC lathes
• NC and CNC grinders
• Several laser cutters
• A bank of 5 and 6-axis CNC screw machines

 

 

This combination of advanced machining technologies allows us to modify housings, shafts, mounting configurations, and other mechanical features efficiently—without outsourcing critical processes.

Examples of customizations we have delivered in response to customer requirements include:
• Gear-driven encoders
• Single encoder disks up to 24 inches in diameter
• Segmented encoder disks over 36 inches in diameter
• Custom size, shape, and spacing of holes on disks
• Multiple indices
• Custom index alignment

 

 

Depending on the scope and complexity, some custom projects have been completed within weeks, while others require longer development cycles. What remains consistent is our commitment to delivering solutions efficiently from concept to production.

Your application should not be limited to stock items. If it matters to your design, it matters to us. We look forward to hearing from you.

This is the fourth post in a series demonstrating that “making it easier” at US Digital is not just a slogan; it is who we are.

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A Channel is an electrical output signal from an incremental encoder. Channels are designated A and B for the two quadrature outputs and I or Z for the index output.

Encoder Accuracy is the difference between the target position and the actual position. It is typically specified in degrees, arcminutes or arcseconds. US Digital has a white paper and blog with video discussing this topic..

An Absolute Encoder is an encoder that provides a unique output for each resolvable position even after a power cycle. Unlike incremental encoders which provide an output designated in cycles per revolution (CPR), absolute encoders are called out in bits. For example, a 12-bit (2¹²) rotary encoder has 4096 resolvable positions in 360 degrees of rotation. US Digital employs both optical and magnetic technologies in their absolute encoders. US Digital’s optical absolute encoders are field programmable from 2 to 4096 codes per revolution. Absolute encoders can be single turn or multi-turn—keeping track not only the position of the shaft but also the number of rotations of the shaft.

Encoders are critical elements in a motion system because they provide position and/or velocity feedback to the motion controller, enabling the controller to close the positional control loop. The number of applications which require encoders is extensive and the types and sizes of encoders that serve these applications are just as numerous.

Encoders may be categorized in various ways but in this post, we're going to look the difference between linear and rotary encoders.

What is a linear encoder?

As the name suggests, a linear encoder measures the position or velocity of an object moving in a straight line.

Typical linear applications are the control of linear motors or X-Y tables such as those found on 3D and inkjet printers as well as laser etching and engraving machines. Linear encoders are also commonly found in devices such as metrology instruments including digital calipers.

What is a rotary encoder?

A rotary encoder, on the other hand, is used to measure the angle or velocity of rotation of an object. Some typical uses include motor speed control, or the angular control of a movable PV array for solar tracking, or controlling the angular position of a robot arm.

Rotary encoders are available with different physical specifications to serve different working environments. For example, those used in harsh industrial applications must be designed to withstand rugged and extreme working conditions. Extreme temperatures, vibration, dirt and debris are some of the challenges that these encoders have to survive on a daily basis. As a result, industrial encoders tend to be big and solidly built to withstand the tough environment, and typically include some form of IP rating. For less harsh environments, such as those in electronics manufacturing, the emphasis may be on smaller size, lower cost or the ability to take advantage of more configuration options, while not compromising on longevity or high quality.

Bonus: What is an Inclinometer?

Inclinometers, also known as tilt sensors, provide feedback so that the angle of tilt of an object can be calculated with respect to gravity. Typical usages of inclinometers are for concentrated solar power (CSP), industrial equipment, aerial work platforms and dredges.

Linear encoder drawing source - https://www.epiloglaser.com/laser-machines/legend-laser/legend-linear-encoders.htm

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A Motor Encoder is a rotary encoder designed for installation onto a motor shaft, typically a motor tail shaft. They can be installed on other shafts in a mechanical system.

What do Motor Encoders do?

Motor encoders translate the motor shaft movement into an electrical signal. This output can be used to determine shaft angle, shaft speed, and shaft direction.

Why are Motor Encoders used?

Encoders act like a GPS for your motor. Depending on the encoder used, you can know the angle of the motor shaft, the speeds at which it rotates, and the direction it is rotating.
Having this information can allow a control system to send a command to the motor or other device to make sure it does what you need in your application—like keeping a flow rate of liquids in a pump constant, moving a robotic arm to the proper angle, or cutting a cable at the proper length.

How do Motor Encoders work?

They consist primarily of a disk and a sensor, though depending on the design they may also include an emitter like an LED. As the disk rotates, the sensor provides an output proportional to the movement of the shaft. 

Optical Motor Encoder

These encoders have a specially patterned disk rotating between an LED and a detector sensor—reporting is based on when the LED light is seen by the sensor and when it is not for transmissive encoders. For reflective encoders, the light beam bounces off the reflective disk to the photodetector, producing the same results.

 

Magnetic Motor Encoder

This encoder type has a magnet on a shaft whose movement is monitored by a magnetic sensor—reporting is based on the change in the magnetic field as the magnet rotates.

 

Capacitive Motor Encoder

These encoders have a specially patterned rotor which is monitored by a stationary capacitive plate commonly called a stator—reporting is based on the capacitance change between the rotor and the stationary plate as the rotor rotates.

 

What is the difference between an Incremental Motor Encoder and an Absolute Motor Encoder?

Rotary incremental encoders

These encoders provide an output indicating the changes in the shaft movement. In other words, if all you need to do is monitor the speed of the shaft, or the direction the shaft is turning, or the relative distance turned, an incremental encoder is a great choice. If the encoder has an index, it can also provide information as to the number of turns the encoder has rotated or provide a fixed starting position for distance measurements. Without an index, incremental encoders lose position data after a power cycle, until the encoder (with an index) performs a homing cycle. However, a power cycle would also cause the encoder to lose any information about the number of turns the encoder has rotated.

Absolute rotary encoders

This type of encoder can do everything an incremental encoder can do, plus, as each resolvable position provides a unique output, even after a power cycle, the output of the encoder provides the information as to the angle of the shaft. Multi-turn encoders add one more piece of information, keeping track of the number of turns the encoder has rotated. even after a power cycle.

What kind of output do Motor Encoders produce?

Quadrature

The most common encoder output is referred to as quadrature output. The term quadrature is used because the signals of the two main channels are offset by 90º or ¼ of a complete cycle. Below are several interface types using quadrature.

 

Incremental Output Interface Types

Single-Ended

The quadrature output is a square wave signal produced on two channels typically referred to as Channels A & B. As stated above, these channels are offset by 90º electrical degrees which allows for direction detection also.
These encoders can also have an Index channel, often referred to as channel I or Z, which provides an output just one time in the rotation of the disk.

 

Open Collector (NPN)

 A drawing of the signal for this output would look identical to the one above. The difference is that an open collector output doesn’t send out its own voltage but instead relies on the connected device or system to complete the signal. An example of this type of output is when a 5VDC encoder provides an output of 24VDC.

Differential Output

A differential encoder output provides a quadrature signal and a complementary signal, which is the inverse of the main signal. This larger signal differential makes it an excellent choice for long cable runs and for installations in an electrically noisy environment. It does require a differential receiver.

 

Absolute Output

An absolute output can be an analog voltage or pulse width modulation (PWM) where the output varies in relation to the 360º rotation of the encoder/shaft—lowest before 1º and highest after 359º.
Absolute encoders also often use serial interfaces which include such protocols as SEI, SSI, BiSS-C, Profibus, etc.

Drawing of an Analog Absolute Encoder Output	Drawing of PWM Absolute Motor Encoder

 

Commutation Output

Encoders with a commutation output provide UVW signals allowing the control system to determine the rotor’s position and properly sequence current delivery to the motor windings. BLDC motors need commutation output to operate at the proper speeds.

Which Kinds of Motors Use Encoders?

Note – Servo motors are typically BLDC motors with some brush style motors being used as well. A stepper motor is a specialized version of a BLDC motor and some applications use stepper motors as servo motors in simple low cost servo systems.

Servo Motors

It is estimated that over half of all motor encoders are used on Servo Motors. They demand high-resolution feedback from encoders to hit exact positions. Application examples include CNC machines, robots and surgical devices.

AC Motors

AC Induction Motors are the second most common motor on which encoders are used. Because of the environment in which these motors are often installed—Motor Encoders used in these applications may be required to tolerate more vibration and shock. Application examples include industrial pumps, power conveyers, and maybe even the high-powered blender in your kitchen.

DC Brushed Motors 

Often due to their low cost and simple design, DC Brushed Motors are used with encoders in simple automation, electric scooters, and other smaller electric vehicles.

Stepper Motors

Hybrid Stepper Motors probably comprise another 20% of motor encoder applications. Encoders can be used to monitor the movement—make sure it moved the correct distance, or it can be used to report that information to a controller to close the loop and modify the position. Application examples are labeling machines, automated arms, textile machines, and semiconductor equipment.

Brushless DC Motors (BLDC)

BLDC motors provide good efficiency, longevity, and high performance. Adding an encoder can provide position control, speed regulation, and error detection. Some encoders used with BLDC motors can also provide a commutation output which monitors rotor position used to determine which coils to energize. Application examples include drones, gate operators, medical devices, and HVAC.

Linear Motors

Linear Motors can use several of the above motor technologies, but they would require a linear encoder—which is not traditionally thought of as a “Motor Encoder” as motor encoders are typically, rotary encoders.

How do Motor Encoders Mount to a Motor?

While a shafted encoder can be mounted to a motor via a coupler, besides being less expensive, it is simpler and will typically last longer if an encoder is connected directly to a motor shaft.

Encoder Kits

Motor encoders, which are sometimes referred to as kit encoders, encoder kits, or modular encoders, are designed for easy installation to a motor with standard bolt hole patterns. Many motor manufacturers provide motors with motor encoders already installed on them—some refer to those as encoder motor sets.

 

Hollow bore

Also known as hollow shaft encoders, they mount directly to motors, but as they have their own bearing, a flexible coupler is required to tether the encoder base to the motor or other mounting surface. This encoder type is often used in an environment where it might be subjected to some abuse. Typical applications include use in manufacturing environments, dynamometers, and printing presses.

 

 

Conclusion

This is a high-level overview of motor encoders for a more detailed look, check out our white papers like this one, our corporate video, our educational videos, our Glossary, or our FAQ's. But, more importantly, if you need assistance choosing an encoder for your next project, we have a great team ready to assist you in any way you like.

Technical Support 360.397.9999 support@usdigital.com

Sales Support 360.260.2468  sales@usdigital.com

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TIR is a measurement of shaft runout—deviation of a shaft from true circular rotation.

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If a picture is worth a thousand words, what is the value of a video? If you, like many engineers and technicians, are a visual learner, it is hard to put a price on that value. That is why US Digital invests heavily in video resources to make working with our products easier, faster, and more engaging.

Our team enjoys working directly with you to solve problems and support your success. But because we are only available during business hours, our video library plays an important role. These resources are available 24 hours a day, 365 days a year, giving you access to answers whenever you need them.

Over the years, we’ve built a growing library of videos designed to support you at every stage of your projects. These include educational videos that explain encoder fundamentals, assembly videos that walk through installation step by step, and product comparison videos that clarify differences between similar models. Instead of guessing which encoder is right or which mounting options are available, you can see the details clearly before making a decision.

We also produce practical how-to and troubleshooting videos that address common questions and real-world challenges. Whether it’s aligning an encoder, confirming resolution, or diagnosing a signal issue, these videos help reduce downtime and get your systems back up and running quickly. Our FAQ videos answer recurring questions in an engaging format, but your phone calls and emails are always welcome. Who knows, maybe your question will be the target of our next video.

Beyond technical support, our video library also includes “about us” content, which shows how we are really “about you”—customer-focused. Those videos introduce the people, processes, and values behind US Digital. We want you to know not just what we make, but our commitment to your success. And yes—one of our videos even went viral, reaching more than 75 million views, demonstrating that clear, engaging technical content can resonate far beyond our traditional audience.

By creating dozens of targeted, easy-to-follow videos, US Digital provides our customers with a wealth of information available with just a click. It’s one more way we focus on making things easier—before, during, and after the sale.

This is the third of several posts that demonstrate "making it easier" at US Digital is not just a slogan; it is who we are.

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What type of applications call for an absolute encoder vs incremental? Let’s get into it.

Incremental encoders report relative movement. If that encoder has an Index, it can report shaft position in relation to the Index once the Index is found. Absolute encoders can report exact shaft position whenever they are powered. (If you’re looking for more information on the difference between absolute encoders and incremental ones, we wrote an entire blog post on the subject.)

If your application requires that you know the actual orientation of the shaft following any power cycle before movement is made, you’re going to need an absolute encoder. Why would that be? In some cases, even the slightest movement to find an Index could be harmful to the process being performed, the product being handled or possibly hazardous to the automated equipment. In other cases, your system doesn’t have the ability to find a home position.

Example use case: Using an absolute encoder to determine reel tension

One of our engineers used our MAE3 absolute encoder to trigger a drive motor that unwinds a reel of stamped lead frames into an injection molding machine in our plant. How does it work?

A pivoting arm rests on the bare lead frame entering the molding machine (see photo above). The absolute encoder is attached to the axis of that pivot arm. When the arm hangs down vertically there is no tension and the absolute angle is set to zero.

Approximately every 30 seconds overmolded parts exit the mold as the next section of bare lead frame enters. The molding machine pulls in more of the bare lead frame causing tension to the incoming reel and the pivot arm to rise. The encoder is used by the system to quantify the absolute angular position with respect to the set zero position.

Whenever the pivot arm is raised to a predetermined angle range indicating tension, the system unspools more of the bare lead frame. If the arm is outside of the tension angular range, feeding stops.

Maintaining a proper feed rate is necessary to make sure that the lead frame is not being stretched or bent before being overmolded thus preventing damage to the equipment.

In this case our engineer used an absolute encoder because the arm itself isn’t motor driven and angles detected are with reference to a fixed zero angle. The absolute encoder mitigates the need to zero or return to a home position if there was a loss of power.

If your application is susceptible to the issues above, you’re going to want an absolute encoder. If not, you could use an incremental encoder with Index. In that case, when the encoder loses power, you’d just need the system to perform a home cycle to find Index again and then it could report its position in relationship to that Index.

Side note: You may even consider an incremental encoder with multiple Indices, which could limit the amount of turning the shaft would need to do to reach a known Index position. To learn more, be sure to reach out to us and ask about our custom solutions.

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Vancouver, WA, October 31, 2013 - US Digital, U.S. manufacturer of motion control products, announced they have achieved the ISO 9001:2008 certification based on standards established by the international organization. US Digital received the certification from PRI Registrar, which involved a rigorous audit of business processes, manufacturing processes and products. Scope of Registration includes design, manufacturing, assembly and distribution of motion control products and accessories.

As part of the ISO certification process, US Digital implemented an ISO compliant Quality Management System to ensure commitment to customer satisfaction and strengthen performance through improving and streamlining processes.

"US Digital's commitment to the ISO 9001:2008 framework demonstrates quality is our priority, from products and processes to customer support and delivery. Our customers can be confident that we will work to exceed their quality expectations and continue to analyze and improve our processes," said Bob Willoughby, President of US Digital.

ISO 9001:2008 Certificate

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What is the best way to clean rotary encoder disks or linear encoder strips of small dust and particles? When it comes to our optical and transmissive encoders, the best option is probably to actually just leave things alone. Why is that? Our encoder modules use an LED and phased array instead of a single photo detector. That means that small imperfections — the kinds that you would expect to see from everyday use and handling of encoders — typically just get averaged out by the array. Furthermore, our LEDs operate in the infrared spectrum, which means they're less susceptible to physical obstructions than visible light.

If you're dead set on trying to remove dust or particles, we have a few suggestions on how to do it correctly:

Don't use water or any type of liquid.

Most of our optical encoders are transmissive and the disks/linear strips are on a mylar material that is developed much like photography. Water and cleaners can actually damage the printing on the disk and create more problems than the dust, specks and minor scratches.

If you're going to use air, make sure it isn't compressed.

Compressed air, whether that be hooked up to an air compressor or the kind that comes in a can could potentially dislodge the encoder disk from its hub, and the resulting misalignment will create far more of an issue than you would have had with the specks.

The best way to take care of disks and strips is through prevention.

We always recommend that people wear gloves or finger cots during assembly to further protect the disks and strips. This is one of the best ways to prevent fingerprints and exposure to dust and other particulates.

All this being said, if you see dust, dirt, fingerprints or minor imperfections on your encoder disk and are concerned that there may be an issue with performance, you have two options:

First, you can test your encoder much like we did in the video above and make sure your waveforms are acceptable.

Second, you are always more than welcome to send us a photo of your encoder disk.

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	1 in. Disk		2 in. Disk
CPR	No Index	Index	No Index	Index
32	EM1-1-32-N	--	--	--
50	EM1-1-50-N	EM1-1-50-I	--	--
64	--	--	EM1-1-32-N (1)	--
96	EM1-1-100-N	EM1-1-100-I	--	--
100	EM1-1-100-N	EM1-1-100-I	EM1-1-50-N (2)	EM1-1-50-I (2)
120	EM1-1-100-N	--	--	--
192	EM1-1-200-N	EM1-1-200-I	--	--
200	EM1-1-200-N	EM1-1-200-I	EM1-1-100-N (3)	EM1-1-100-I (3)
250	EM1-1-250-N	EM1-1-250-I	--	--
256	EM1-1-250-N	EM1-1-250-I	--	--
360	EM1-1-360-N	EM1-1-360-I	--	--
400	EM1-1-400-N	EM1-1-400-I	EM1-1-200-N (4)	EM1-1-200-I (4)
500	EM1-1-500-N	EM1-1-500-I	EM1-2-500-N	EM1-2-500-I
512	EM1-1-512-N	EM1-1-512-I	EM1-2-500-N	EM1-2-500-I
720	EM1-1-720-N	EM1-1-720-I	--	--
800	EM1-1-800-N	EM1-1-800-I	--	--
900	EM1-1-900-N	EM1-1-900-I	--	--
1,000	EM1-1-1000-N	EM1-1-1000-I	EM1-2-1000-N	EM1-2-1000-I
1,024	EM1-1-1024-N	EM1-1-1024-I	EM1-2-1024-N	EM1-2-1024-I
1,250	EM1-1-1250-N	EM1-1-1250-I	--	--
1,800	--	--	EM1-2-1800-N	EM1-2-1800-I
2,000	--	EM2-1-2000-I	EM1-2-2000-N	EM1-2-2000-I
2,048	--	EM2-1-2048-I	EM1-2-2048-N	EM1-2-2048-I
2,500	--	EM2-1-2500-I	EM1-2-2500-N	EM1-2-2500-I
3,600	--	--	--	EM2-2-3600-I
4,000	--	EM2-1-4000-I	--	EM2-2-4000-I
4,096	--	EM2-1-4096-I	--	EM2-2-4096-I
5,000	--	EM2-1-5000-I	--	EM2-2-5000-I
7,200	--	--	--	EM2-2-7200-I
8,000	--	--	--	EM2-2-8000-I
8,192	--	--	--	EM2-2-8192-I
10,000	--	--	--	EM2-2-10000-I
Please note the following... (1) US Digital's two-inch disk with 64 CPR uses the same EM1 module as the one-inch disk with 32 CPR. (2) US Digital's two-inch disk with 100 CPR uses the same EM1 module as the one-inch disk with 50 CPR. (3) US Digital's two-inch disk with 200 CPR uses the same EM1 module as the one-inch disk with 100 CPR. (4) US Digital's two-inch disk with 400 CPR uses the same EM1 module as the one-inch disk with 200 CPR.

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Robots, rocket ships and deep space sound may sound like parts of a work of Science Fiction, but for FIRST Robotics Team #2471 Team Mean Machine it’s just another year competing in one of the world’s largest robotics competitions.

In late December members of the team, which represents a handful of students from high schools in Clark County, Wa., visited US Digital to show off their 2019 robot and thank the company for its continued support.

The demonstration gave US Digital employees an opportunity to see first-hand how company products are used. (Be sure to check out the video at the top of this post to see the robot in action.) It’s also a great way for US Digital to support the innovators of tomorrow.

“Supporting FIRST is an investment in the people and businesses of the future,” US Digital COO Neal Donowitz said.“ Programs like this give students an opportunity to challenge themselves and build confidence while learning something new. That’s something they don’t get at home surfing the internet, watching TV or playing video games.”

The team’s robot, named Epsilon, was designed to attach hatch panels (large disks) to the outside of rockets (large wood columns) and then load cargo (large rubber balls) inside the rockets. The robot needed to be able to be controlled remotely or work autonomously for portions of the competition.

It might seem like a game, but it’s the kind of thing many of them will see in future careers at companies like US Digital.

“We don’t use people like robots, we give people robots to use,” US Digital Founder and CEO David Madore told the team. “The skills that you’re learning, they have real world applications in companies like this.”

After the demonstration, Madore gave students a tour of the production facility and talked about how STEM and problem solving skills they were learning through FIRST, would be of use in their future careers.

During the tour the team learned about injection molding, 3D printing and how US Digital uses automation to enhance its manufacturing processes. All of those are things the team has been learning about in the FIRST program.

“It’s super cool to see that applied in the real world and how we might use it,” Team Mean Machine Treasurer Jacob said after the tour.

US Digital is a proud supporter of FRC #2471, as well as several other teams around the United States and the FIRST Robotics Program.

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So far in this blog we've written about encoders that are moved by something else. They're attached to a motor shaft, or a linear actuator, or conveyor belt. Their job is to report their position as they're moved by an external force; other than that, they're just along for the ride.

Well, sometimes - the encoder is the ride! Sometimes the encoder moves first, and everything else reacts to what the encoder does. In this blog post, we'll be writing about those times. We'll discuss some existing applications, and consider possibilities for new applications.

Human Machine Interface (HMI)

When do encoders take control? Here's a prime situation: a system needs input about what it should do. That input often comes from a human. At the Human Machine Interface (HMI), there are many ways for the input to be entered: computer keyboard, touch screen… but for certain things, nothing beats a control knob. And attached to that knob, the part that rotates when you turn the knob? An encoder.

Two quick examples. You're driving in your car, and want to turn up the music. What's the best way? Type in a command on a keyboard? Search for a 'button' on a touch screen? Of course not! It's much better to reach over, grab the volume knob and twist it till cars near you start to vibrate. You can probably even do that without taking your eyes off the road.

Another example: consider an ultrasound technician in a hospital, conducting an exam. One rubber-gloved hand presses a probe against the patient, the other gloved hand reaches to adjust a setting on the machine. Again, keyboard or touch screen wouldn't work. It's a knob the technician needs, and if the machine is well designed, that's what will be there.

What about Potentiometers?

You might be saying, "Wait, those control knobs you're talking about, aren't they just potentiometers?" In the past, you'd be right; and many devices still use 'pots', but encoders have made potentiometers obsolete in many areas. Pots have problems: they're electrically noisy, they have parts that corrode and wear out, they're analog, and in most cases they're limited to one turn. Encoders don't have any of those limitations, plus they can do things potentiometers never dreamed of.

Broad Range of Applications

Here's a quick survey of places where you might find an encoder driving a system. Let's start with this fellow.

If this old salt were to helm a ship in modern times, he could be turning an encoder to steer the ship instead of a rusty old wheel; and he'd probably be doing it from a comfortable, enclosed command bridge, too, with lots of other encoders on the control panel.

More applications where the encoder moves first, and the system follows:

• Power plant control rooms and large, complex machines
• Medical devices: imaging equipment, patient monitors, ventilators
• Test and measuring equipment that requires high precision

• Stage lighting controls, sound equipment and recording studio consoles
• Avionics systems, navigation devices, and radio communication systems
• Antenna aiming systems, satellite dish alignment controls

Although they may not realize it, many people have firsthand experience using encoders every day–when they're driving their cars. Thanks to encoders, we've gone from this:

To this:

Automotive entertainment systems and climate controls are particularly well suited for using encoders as input devices. Almost every auto manufacturer has replaced their potentiometers and mechanical sliders with encoders.

If Fingers Turn the Encoder

Question: Is it always better to have the least possible amount of friction (or drag) in an encoder shaft?

Answer: No! Not if you're going to turn the encoder with your fingers.

When you use an encoder as an input device, the way that shaft rotation feels to your fingers is very important. The control knob should provide a comfortable feeling of touch, and if there's zero drag–as would be the case with a ball bearing encoder, for example–then the control just won't feel right.

Manufacturers intentionally design tactile feedback into their products. Using detents–that clicking feeling as the knob turns–is one familiar method. An even simpler method is to use the right type of lubrication.

Here's US Digital’s miniature magnetic absolute encoder. It's a very popular model for panel mount, human interface applications.

In the specifications for this encoder, the manufacturer explains, "Three shaft torque versions are available: high torque; low torque; and ball bearing." (By torque, they mean the amount of drag present.) The high and low torque versions have a stainless steel shaft and lubricated brass bushing. The ball bearing version has a brass shaft and precision ball bearings.

The lubrication matters.

When you order this encoder, the manufacturer can vary the lubrication, based on how you intend to turn the encoder:

Turn Encoder by:	Specify this Option:	Lubrication:	"Feel"
Fingers at low RPM	"High Torque" Version (D)	Viscous gel	Most Drag
Motor at low RPM	"Low Torque" Version (N)	Grease	Lighter Drag
Motor at high RPM	"Ball Bearing" Version(B)	None needed	Least Drag

This is an important point: Usually we try to eliminate friction and drag. But if you plan to turn an encoder with your fingers, make sure you order the encoder version that has more drag built into it. You probably do not want a ball bearing encoder. (Unless you're making a spinner knob.)

As an added benefit, the increased drag will help prevent unintentional adjustment. (Just in case you, like us, are sometimes careless with elbows and knees. Ouch!)

Possibilities

Once you decide to use an encoder as an input device, a world of new applications opens up. You can do things with an encoder that you just can't do with a potentiometer.

Fast and Far - your data acquisition system can log not only position data from the encoder, but also rate information. If a user turns the encoder knob rapidly, the controller can deduce, "They must want to go far; let's speed everything up," and get the user to the destination faster. Then when the user slows down: "Ah ha! We're close to the end. Let's reduce speed, for fine positioning."

Scale it Down - suppose you want to design a machine for micro-surgery, a device that could "sew stitches on the skin of a grape." If you use encoders as inputs from your surgeon's fingers, your motion controller can scale down the surgeon's full-size hand motions, and appropriately control tiny micro-instruments.

Scale it Up - at the other extreme of size, encoders could send an operator's arm and hand motions to a controller, which could then scale up the information and control a large robotic arm to stack crushed cars in a junkyard, or unload containers from a ship. Science fiction? Perhaps; but who knows for how long?

Teachability - ordinarily when a device like a robotic arm is operating, motors move the arm, while encoders report the arm's positions. But how does a robot learn where to move in the first place? You can reverse the process, and use the encoders as teaching inputs. Shut off power to the arm's motors to reduce torque, and then have a human operator move the arm from one desired position to the next. Data log the positions and paths, and use that information to teach the robot its moves.

We hope this post has given you some ideas about how and where to use encoders.

Sources:

• Ancient mariner; ship command bridge; sound amplifier: pixabay.com
• Antique car radio: Photo by Daniel von Appen on Unsplash
• Modern car radio: Photo by Mpho Mojapelo on Unsplash
• Magnetic encoder: US Digital Miniature Absolute Magnetic Shaft Encoder Model MA3

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In this world three things are certain: death, taxes and electrical noise -- to paraphrase Benjamin Franklin.

Electrical noise can wreak havoc by injecting false signals onto encoder lines, or by overwhelming real signals entirely. It’s often intermittent, which can make diagnosing and fixing it a nightmare. But if you use a few simple techniques you can drastically reduce electrical noise so that it doesn’t cause problems for the transmission of the signals from your encoder.

Avoid EMI by using twisted pair cables instead of straight wires

If you use long, straight wires for your encoder signal lines, the wires can act as antennas and receive unwanted electromagnetic interference from longer wavelengths—the ones which cause the most trouble. If you shorten the ‘antennas’ less interfering energy is received.

Fortunately, there’s an easy way to ‘shorten the antenna length’ of signal-carrying wires: you can twist them together. Each section between locations where the wires cross becomes a very short antenna, tuned for short wavelengths where much less energy is available.

Twisted pair wiring will pick up much less noise than straight wires of the same length. Inductive coupling, a form of EMI that relies on loops to transmit noise from one wire to another, is also lessened because the loop area only extends between the sites where the wires cross.

Here are some tips for using twisted pair cables with encoders:

• Keep paired encoder outputs, e.g. A/A-, in the same cable pair. This minimizes crosstalk between adjacent signal lines: A/A- won’t show up on the B/B- signal lines, for example.
• Keep loops tight against each other, to minimize loop area where inductive and magnetic coupling could occur.
• You don’t have to do the twisting yourself! Buy premade twisted pair cables, which are available with color-coded pairs already twisted together, and with various quantities of pairs per cable.

Use differential output in noisy environments or for long cable runs

Incremental encoders are often available with two types of outputs:

• Single-ended outputs use one wire for each output—this is the most common output type
• Differential outputs convert each output into two complementary signals, carried on a pair of wires

Of the two, differential outputs offer much better noise immunity.

With differential outputs, a differential line driver on each encoder output channel converts the output to two complementary signals, mirror images of each other. At the controller end, a differential line receiver compares the voltage difference between the two signals. Any noise injected onto the two wires—EMI transmitted by an arc welder, for example—will move the voltage on both of them in the same direction. This is known as common mode noise, and can be canceled out by the differential line receiver.

Here are some tips for using an encoder with differential outputs:

• Use twisted pair cables for your differential outputs
• Make sure paired encoder outputs are on the same twisted cable pair
• Keep twisted pair loops tight against each other, to minimize loop area for inductive coupling

Use shielding to protect your encoder signal from EMI

If sensitive equipment is placed inside a Faraday shield, the enclosure will keep that equipment from being bombarded by EMI. It also works in the other direction: if noisy equipment is placed inside a Faraday shield (think equipment cabinet), the EMI from the noisy equipment can’t escape to cause trouble for sensitive devices.

You can use cables and equipment that act like Faraday shields to help control EMI and electrical noise.

Shielded cables are available with shields made from metal foil, braided conductors, or a combination of both. Use shielded cables to keep EMI away from your sensitive encoder signal lines. You can also use shielded cables for your noisy equipment wiring—the shielding can keep EMI contained within the cable so it doesn’t cause problems elsewhere in the system.

Metal conduit can be a very effective shield. EMI from electrically noisy equipment can be contained when wiring is run inside conduit. If sensitive signal lines are placed inside their own conduit, the conduit can block EMI from interfering with the signal lines.

Metal equipment enclosures can provide a shield to keep EMI inside, so that it doesn’t interfere with external devices; or to keep EMI out, when sensitive equipment is located inside the shielded equipment cabinet.

Here are some tips for using shielding:

• Use shielded cables for sensitive signal lines, and for noisy equipment as well
• Use conduit when possible, especially for noisy power lines
• Use equipment cabinets made from conductive materials

In all of these cases, the shielding will work best if it is properly grounded.

Grounding can help mitigate impacts of EMI

Proper grounding can provide a low resistance path to ground, which leads EMI and electrical noise away from your equipment and dissipates it in the grounding system.

You can direct the path of unwanted noise and show it where to go by using good grounding techniques. One of the most important things to do is to connect the shield of the encoder cable to a single ground point.

If you have multiple grounds in your system, theoretically they should all be at the same voltage. But in real systems, they may differ; if so, current can flow from one point to another—sometimes through your equipment, which can cause electrical noise and problems.

Here is a tip for grounding the shield of an encoder cable: Connect the encoder cable shield to ground at one end only, typically at the controller end.

Grounding is a complex topic, and affects everything from the power grid down to the smallest components in a microprocessor. If you spend some time to get it right for your system, good grounding will help diminish electrical noise problems.

Electrical noise happens but with these tips, you'll be ready

Electrical noise happens. It’s often impossible to eliminate it entirely, but it can be reduced. The techniques we’ve presented are a first line of defense; they can help lower noise to a level where it doesn’t cause problems for the signals from your encoder.

For serious electrical noise situations, there’s more that can be done, such as the use of filters, ferrite absorbers, conductive sprays, P-clips, capacitors, MOVs, surge suppressors, special grounding techniques and a host of other methods. Should those refinements be necessary in your system, we hope that as you investigate them, this post gives you an understanding of why they might work.

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Anaheim, California - February 8, 2017 - US Digital, a US manufacturer of quality motion control since 1980, today announced the introduction of the E8T miniature optical encoder. Combining small form factor and resolutions up to 720 CPR, the E8T is ideally suited for medical and other space sensitive applications that require reliable position and velocity feedback. The E8T's small package footprint fits motors as small as National Electrical Manufacturers Association (NEMA) size 11 with more than 40% reduction in package height compared to other commercially available solutions.

Utilizing US Digital's proprietary OPTO-ASIC technology, the newly announced E8T supports up to 2,880 pulses per revolution with excellent repeatability. The E8T is available in over 3,240 different configurations and features either single-ended or differential signal outputs. Moreover, the E8T features a simple and secure, push-on hub disk design and a high-retention connector for quick, easy and reliable installation that keeps assembly cost and complexity to a minimum.

Product Features

• 9 resolutions up to 720 CPR
• 3,240 configurations available, including single and differential output
• Compact, low profile form factor
• 1.120 inch (in) / 28.45 millimeter (mm) package outside diameter
• 0.460 in / 11.68 mm package height
• Fits NEMA 11, 14 and 17 motors
• Simple and efficient assembly process
• Four-piece construction
• Push-on hub disk design, patent pending
• High retention connector
• 100 kilohertz frequency response
• Functional replacement for US Digital's E7P and E8P

"Whether its portable technology or diagnostic equipment destined for the laboratory floor, today's medical applications face increasing pressure to become smaller and lighter without compromising functionality," said Donna Peterson, Vice President of Marketing and Sales at US Digital. "The E8T's small, low profile package and available resolutions make it uniquely positioned to help address these requirements while delivering excellent value and reliability relative to alternative motion control solutions."

Availability

Sample and production quantities of E8T are now available. To learn more about the E8T product line, or for complete technical specifications, including mechanical drawings, visit usdigital.com/E8T.

About

With over a million off-the-shelf configurations, plus any number of custom product offerings, US Digital has delivered quality in motion since 1980. Located in Vancouver, Washington, the vertically integrated facility and the stellar service team provide customers with lead times significantly shorter than the competition, offering same-day fulfillment on most orders. Please contact US Digital for more information at 1.800.736.0194 or sales@usdigital.com.

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How do you attach an encoder to a liquid? Encoders usually attach to a part of the system that moves—and in a pump, the part that moves is a liquid! How do you attach an encoder to that?

In actual practice, you don't. Every pump has a mechanism that moves a fluid. You attach the encoder to that mechanism. If a motor drives the mechanism, for example, you can mount the encoder to the motor shaft—and information reported by the encoder can be used to control fluid moved by the pump. You can improve pump performance when an encoder is part of the system.

WHAT CAN ENCODERS MEASURE ON PUMPS?

In any pump with an encoder, there is usually a relationship between the mechanical system's basic motion (revolution, stroke etc.) and the amount of fluid that is pumped with each motion. The pump's job is to perform the motion; the encoder's job is to report the motion, so that the pump's controller can calculate quantities like volume or speed.

Volume Metering - Sometimes the important quantity is the total volume moved, and speed of delivery is less important. When you pump gasoline at a gas station, it might take 3 minutes to fill up the tank, or it might take 5 minutes. The time isn't critical; you're not paying by the minute, you're paying by the gallon or liter. The key measurement you're interested in will be the volume—the pump has to get that right, and an encoder on the pump can help ensure accurate volume metering.

Speed Metering - Sometimes a pump's job is to keep a liquid moving at an optimum speed, and the precise volume might not be important. In a water treatment plant, for example, pumps move fluid slurries long distances. Irregularities in the speed of flow can cause unwanted vibrations and even dangerous pressure buildup in the pipe. When a pump is commanded by a controller to accelerate or decelerate to maintain a constant flow, an encoder can report the change and help verify desired speed.

Speed/Volume Combinations - Sometimes a pump has to deliver an exact volume at a specific speed. This is common in the healthcare setting, where encoders are used on pumps that administer medicines at a precisely controlled flow rate.

In the sections below, we'll look at three examples from the life sciences and medical industries, where encoders are used on pumps in hospitals, clinics, research laboratories and by individuals at home.

AUTOMATED PIPETTORS

The IVEK Corporation makes automated pipettors and displacement pumps for original equipment manufacturers (OEMs). Their AutoPipettor is a good place to start for understanding encoders on pumps. What's an AutoPipettor? It's similar to an eyedropper—but it's automated.

Scaled up versions of eyedroppers are used in laboratories, pharmacies and drug manufacturing facilities. The tube is called a pipette; various sizes are used, ranging in length from an inch to more than a foot. The part that creates pressure to move liquid in or out of the pipette—the equivalent of the eyedropper's bulb—is called the pipettor.

Because the process of pipetting might be performed thousands of times each day in busy labs and manufacturing facilities, OEMs have developed automated machinery for the task. Automated pipettors can draw fluid into pipettes at the touch of a button or computer command.

In her right hand, the technician in the photograph below holds an automated pipettor which is attached to a pipette.

Pipettors equipped with encoders can move the required amount of fluid automatically, without the need for a technician to visually check the levels. This means they can be used in automated production lines, either individually or ganged together into multiple units.

IVEK's AutoPipettor uses a close-fitting ceramic piston and cylinder set. When the piston is drawn into the cylinder, suction is created which moves fluid into a pipette. When the piston moves in the other direction, the pressure created dispenses the liquid. A linear actuator driven by a stepper motor is the mechanism that moves the piston.

You can see an encoder mounted to the stepper motor if you click on the AutoPipettor link.

AUTO-INJECTORS

An auto-injector delivers a measured dose of a drug. Many are spring-loaded syringes intended to be self-administered for quick, one-time use, such as the EpiPen® Epinephrine Auto-Injector.

For long term drug therapy patients, a more sophisticated auto-injector is required. Large-volume injections require long delivery times; high viscosity drugs require extra force to deliver the drug; insulin might require differing flow rates, based on blood sugar levels. Motorized auto-injectors can meet these requirements, while being portable and discreet for patients who use them in public.

To administer drugs, auto-injectors can use a combination of electric motors, gearboxes, and linear motion assemblies. When the mechanism is equipped with an encoder, the auto-injector can precisely deliver medicine at an accurately controlled rate of flow.

INFUSION PUMPS

In a hospital setting, many different medications and fluids may be given to a patient. Some can be given within a few seconds: a nurse can inject the contents of a syringe under the skin, or through an IV (Intravenous Tube). However, some medications take hours to administer. To free up nursing staff so they can attend to other duties, a pump with an encoder may be used—particularly when a large volume of medicine or a slow injection speed is involved.

Infusion pumps accomplish the task of delivering medications automatically. Of the many types available, peristaltic pumps are often selected. Inside these pumps, one or more rollers mounted on a rotor push against flexible tubing. Fluid is delivered into one end of the flexible tube, typically by gravity feed. With each pass of a roller, a set amount of fluid is pushed down the tube and through the IV.

Instead of rollers, a linear peristaltic pump uses a series of mechanical fingers driven by a camshaft; the fingers sequentially press against the tubing to pump liquid through the tube. Both types of pumps—rotary and linear—are used for infusion.

When the motor that drives the rotor or camshaft is equipped with an encoder, the pump's internal control system can receive position reports from the encoder. Since a known amount of fluid is delivered with each pass of a roller, speed of flow can be verified from the encoder reports.

With the precise control an encoder provides, medical staff can program the pump to deliver fluids at a constant rate or a variable rate; large volumes quickly, or small volumes over many hours; and many other flow rate choices.

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If you need an encoder that can measure very small distances, which of the following is most important to you: high accuracy, high precision or high resolution?

If you said "high resolution," nice work. You got the answer right. If you didn't, don't worry you aren't alone.

In this post, we're going to discuss the actual meaning of resolution, accuracy and precision when it comes to encoders to clear up any confusion and help you select the best encoder for your application.

Josh from our tech support team says that most of the time when people call asking for a "high accuracy" or "high precision" encoder, they are actually looking for an encoder that can measure small distances. In other words, they’re looking for a high resolution encoder.

Why the misunderstanding? Accuracy and precision are often used informally in the everyday world, as if they mean the same thing. Someone might say that measuring to the nearest sixteenth of an inch is more accurate (or precise) than measuring to a quarter of an inch, for example.

In the world of encoders, however, accuracy and precision have nothing to do with how small or fine the level of detail measured. That, instead, is a function of resolution.

Let's get into the details.

What is encoder resolution?

Resolution is the number of counts per 360 degrees of rotation for a rotary encoder or per inch for linear encoders. For an optical encoder this can be either lines that are physically printed on the disk or strip or interpolated resolution.

An optical encoder, for example, has lines and windows printed on the disk or strip. As the number of line and window pairs increase, they become smaller and closer together, and smaller distances can be measured. This results in higher resolution.

We list resolution in Cycles Per Revolution (CPR) for rotary encoders, or in Lines Per Inch (LPI) or Cycles Per Inch (CPI) for linear encoders. These terms are used for all encoder types—optical, magnetic and capacitive.

You can use higher resolution to measure very small distances, but more resolution isn’t always better.

Josh from tech support says often times people he speaks with by default just go for the highest resolution available with whatever encoder they are interested in buying. That’s not something that he always recommends.

"You want to make sure you pick the right tool for the job," he said.

Imagine going on a road trip and trying to calculate how far you traveled in inches (or centimeters for our metric friends) rather than in miles (or kilometers). Sure you can convert the smaller unit of measurement into the larger one, but you would be dealing with more information than you actually need and would be spending unnecessary brain power to do the calculations.

It's similar with encoders.

In general, higher resolution encoders are useful in applications where precise positioning is critical, when motion occurs at extremely slow speeds or when very small distances need to be measured.

Lower resolutions are typically better where approximate positioning is acceptable or in high-speed applications where bandwidth limits could be an issue.

To determine the resolution you need, first calculate the smallest increment you must measure. That will determine your minimum resolution. You can increase your resolution from there to a number that might work better for your data acquisition system, or maybe to a stock resolution. Just keep in mind the advice in the previous paragraphs—make sure the resolution will work in your application. For more details, see our white paper on resolution, accuracy and precision of encoders.

How is encoder accuracy defined?

Accuracy is a term used to describe the difference between target position and actual position. Encoder accuracy is specified in degrees, arcminutes or arcseconds.

Within the encoder itself, accuracy can be affected by several variables.

• Imaging: location of the lines on the disk must be exact, or accuracy will suffer
• Installation: mounting an encoder hubdisk off center on the shaft can decrease accuracy
• Size: an encoder with a larger disk will be more accurate than one with a smaller disk

External to the encoder, other mechanical parts of the application affect system accuracy. Gear backlash, leadscrews, shaft and bearing play can add up and have much more of an effect than the encoder's accuracy contribution.

What is encoder precision?

Precision is a term that describes repeatability. It's the amount that successive measurements at the same location differ from each other.

If an encoder is off by 2 degrees at a particular position, but it is always off by the same 2 degrees at that location, then the encoder has good precision.

Most encoders are reasonably accurate and precise. Of the three terms we've discussed, people are usually most concerned with resolution, then accuracy, and finally precision.

Encoders provide the resolution, with the number of lines on their optical components (disk and sensor); accuracy is related to alignments in the mechanical system that affect the encoder; and precision can be a product of either—or probably both. Josh from tech support says that issues about precision rarely come up when people call.

Putting it all together

In daily life, normal people use resolution, accuracy and precision differently than we do in the encoder world. We hope the descriptions above and the summary below will prove helpful in your understanding of encoders.

• Resolution - The smallest distance that can be measured
• Accuracy - The difference between target position and actual position
• Precision - The difference between repeated measurements at the same location
• How they are related? They are NOT related!

If you haven't already, check out our video on the difference between resolution, accuracy and precision at the top of the page to go a little more in depth and to see all of this illustrated through archery.

Want even more? Please see our White Paper: Resolution, Accuracy and Precision of Encoders.

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US Digital Earns Microsoft Dynamics® Dynamic Business: Small and Medium Business Award

Vancouver, Washington, USA, February 12, 2014 - US Digital Corporation was recognized by Microsoft® with the 2014 Dynamic Business: Small and Medium Business Award as part of the Microsoft Dynamics Customer Excellence Awards program. They will be honored by Microsoft executives at an awards luncheon on Wednesday, March 5, at Convergence 2014 Atlanta, the premier Microsoft Dynamics user conference.

The 2014 Customer Excellence Awards, which are presented in 17 categories, recognize and celebrate Microsoft Dynamics customers that have achieved notable accomplishments using their Microsoft Dynamics solutions.

Established in 1997, the Customer Excellence Awards are awarded each year at the Convergence user conference in the United States. Microsoft Dynamics is a line of financial, customer relationship and supply chain management solutions that help businesses work more effectively.

Learn more about US Digital's award-winning implementation of Microsoft® Dynamics here.

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Products mentioned in this release are registered trademarks or trademarks of their respective holders.

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NASA doesn't just make spaceships!

Who Made the First Optical Encoder?

We have been researching the answer to that question for some time and although we have been able to gather some great information both from encoder manufacturers and my own research, at this point we do not have a definitive answer.

When we initially tried searching for an answer, someone had answered the question online stating that the first optical encoder was made by David Cronin in 1964 - based on the date of his patent application (seen above).

First Encoder Used in Space

According to chapter 14 on encoders in Space Vehicle Mechanisms: Elements of Successful Design (A textbook that has been used by NASA), Tim Malcolm states that optical encoders were developed about 1951 to address a need for higher resolutions than what was available with other kinds of sensors. In 1958 Baldwin Electronics (now BEI Precision Systems and Space Company, Inc.) provided 18-bit optical encoders which were used in the Atlas missile guidance system. Those encoders were still functioning 36 years later when that article was written.

Back at the beginning, the life of the light source limited the encoder life. Many illumination sources were used based on the technology available at the time. Some light sources used include xenon flash tubes, incandescent lamps, and neon lamps. The first encoder used in space incorporated a redundant gas-filled incandescent light source but it only had a life requirement of 12,000 hours.

First LED Optical Encoder Used in Space

LED's were a big step forward by providing extended lifetimes with very little degradation. You may have heard a statement that optical encoders have reduced life due to dimming or burning out of the LED. Statements to that effect are contradicted by the chief scientist at BEI. In this same chapter, Tim Malcolm states as of the writing of the chapter (1996), "the concerns with the quality and life of these devices (LED's) which were common years ago have largely disappeared." He also noted that some encoder manufacturers had more than 10 years of continuous use with no encoder failures. Based on those statements, it would be safe to conclude that if your encoder supplier is using high-quality LED's, this should not be an issue.

We were fortunate enough to be able to get in touch with Timothy Malcolm and found out that the first optical encoders were actually made near the end of WWII. Although war is very costly, it has always been a great driver for the the development of new technologies. We will plan to share more about that in our post on May 28th.

Heidenhain's Digital Optical Measuring Instrument

In a future post, we will provide information on how several of the oldest encoder companies came into being. The above photograph shows an optical counter made by Heidenhain, in the early 1960's, for accurate, reliable and easy positioning of slides and carriages on machine tools, gauges, and other instruments. It could actually measure measurements as small as 0.0001" - which is remarkable for that time period.

Encoders have been a key ingredient to space exploration in general from its inception. This is definitely true for NASA. We recommend checking out NASA’s website and articles like this one which mentions how they are used on the International Space Station on cameras to view earth. Here is also a video which gives some background on Valkyrie, the humanoid robot at the top of this post.

Heidenhaim DOM Source - Heidenhain.de
Early space encoder pictures were provided by Timothy Malcolm.

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• All models have a "push-on" hub with a spring-loaded collet design.
• All models use a single +5V supply.
• The E16, E4T, and E8T are part of our standard inventory and are available for same-day shipping*.

*Orders placed before 11:00 AM (PST) ship the same day.

	E16	E4T	E8T
Outside diameter	16mm	22mm	25.61mm
Bolt circle	10mm	.586 in. (14.88mm)	0.75 in. (19.05mm), 1.28 in. (32.51 mm)
Compatible shaft sizes, metric (mm)	1.5, 2	2, 2.3, 2.5, 3, 4, 5, 6	3, 4, 5, 6, 7, 8
Compatible shaft sizes, standard (inches)	N/A	1/8, 5/32, 3/16, 1/4	1/8, 5/32, 1/4, 3/8
Index	✔	--	--
Native resolutions (before quadrature)	250, 256, 500, 512, 1000, 1024, 2000, 2048, 4000, 4096	100, 108, 120, 125, 128, 144, 200, 248, 250, 256, 296, 300, 360, 400, 500, 512, 720, 800, 1000	180, 200, 250, 256, 360, 400, 500, 512, 720
Output options	Single-ended	Single-ended, Differential	Single-ended, Differential
Hub style	Push-on	Push-on	Push-on
Cover options	Default	Default, Through-Hole	Default, Through-Hole

Related Content

• E16 Micro Optical Kit Encoder
• E4T Miniature Optical Kit Encoder
• E8T Miniature Optical Kit Encoder

 

Introducing PayLink from Nodus Technologies, Inc.. PayLink is a fast, secure, and convenient way for US Digital customers to make credit card payments 24 hours a day, seven days a week from anywhere!

With a one-click link to review invoice details and make payments, the PayLink process is fast and easy. There's no need to log into a website, a payment portal, or retype financial information with every online payment. You can store these details for future use within a private and secure environment.

Please note: With this new service - as of May 21, 2018 - US Digital will be transitioning away from accepting fax order forms. Questions? Please feel free to contact the customer support team at sales@usdigital.com or call (360) 260-2468.

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Here at US Digital, we’re always looking for ways to improve our existing processes and how we can use automation to enhance what our people can do. Sometimes a challenge with one particular product can lead to a solution that benefits our entire product line.

After releasing our E4T and E8T miniature optical encoders, we decided to take a look at improving efficiency in our surface mount technology (SMT) line. Up to that point, our SMT technicians had been loading PCBs for all our products manually. A new board needed to be fed into the system every few minutes. Between loadings, our technicians would do other tasks in the area including visual inspections and loading components.

The PCBs for the E4T and E8T went through the SMT line in about 20 seconds, which meant that manual loading wasn’t practical anymore. If technicians were manually loading PCBs, they weren’t able to get to other tasks without stopping the line temporarily.

“It’s not a problem if a board take 5 or 10 minutes (to go through the line),” said Peter Semenov, US Digital Soldering Technician. “But when it takes 20 seconds, that’s a different story.”

To solve the problem, we challenged our in-house engineering talent to find a way to automate the process and free up technicians time.

“Rather than have our people help machines, we find ways to have machines help our people,” said Neal Donowitz, Chief Operating Officer at US Digital. Donowitz asked Richard Somerville, one of our mechanical engineers, to partner with Semenov to develop an automated machine to feed the SMT line.

It was important that the new machine would work with Semenov’s workflow, instead of dictating it. That meant that the machine needed to have the ability to do a few different things.

1. It needed to be able to quickly change between different board sizes.
2. In addition to being able to work fully automated, Peter needed the ability to stop the machine and manually send boards through with the push of a button if he needed to fix something or keep an eye on part of the process.

Off the shelf loading solutions didn’t quite meet all those requirements, so Somerville started working on a custom solution using a few off the shelf components, including linear actuators with our E6 Optical Encoders preinstalled and our MD3 Microstepping Motor Driver.

“Most commercial off-the-shelf feeder systems are designed for loading/unloading from a fixed magazine,” Somerville said. “With the high mix and low volume of PCB sizes and shapes we use, a fixed magazine system wouldn’t be as flexible as we need.”

Somerville developed a magazine that could expand and contract to fit different size PCBs. Two of the motors raise and lower the magazine to feed individual PCBs, with a third motor used to push individual PCBs onto the conveyor system on the SMT line.

To control the motion of the three motors, Somerville connected the motors and encoders to MD3 drivers and those drivers to a PLC. The drives count the quadrature output from each encoder and store the count locally in internal memory.

The E6 incremental optical encoders worked well in this application because Somerville didn’t need to track absolute position. Because high resolution wasn’t critical in the application, he chose a 200 CPR model.

Sommerville designed a frame to support the board stack assembly and conveyor, and chose an equipment cabinet to house the MD3 drives, the PLC, and power supplies. For operator controls, he consulted Semenov again.

“He was particularly interested in laying out the user interface, and setting up the controls and workflow of operating the machine,” Somerville said.

Once the design was complete and the board feeder was working as expected, Somerville released it to production. Semenov is pleased with the results. He can now load a stack of boards and start the machine. While it is busy doing its work, he is free to do his work.

Developing the automated loading method not only allowed our technicians to continue doing other tasks in their area while making E4T and E8T PCBs, but it also increased the SMT line’s efficiency across our entire product line.

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When it comes to encoder size, there are a few things to keep in mind: the overall dimensions of the encoder housing, the bolt circle and shaft/bore size.

In this post, we’ll go over each item in detail to help you make the right decision.

How do you find an encoder’s overall dimensions?

Perhaps the most obvious thing to look at when it comes to picking an encoder, are the overall dimensions of the encoder itself. The image above shows the relative size of our most popular small rotary encoder kits. You can also find the dimensions of our encoders by clicking on the “Mechanical Drawings” tab beneath the product photos.

 

If you look at our E5 Mechanical Drawing (also posted above), you can see multiple dimensions called out both of the top-down and profile view of the encoder. The first numbers listed are Imperial (inches) and the numbers in brackets are Metric (mm).

These dimensions are fixed for each encoder and don’t really change, however there are different encoder size variables that do.

Different bolt circle options for different mounting configurations

An encoder’s bolt circle is also important when considering the right encoder for your next project. To clarify, an encoder’s bolt circle is the space between the center of the two holes where the mounting screws will be installed.

Unlike the overall dimensions of the encoder which don’t really change, many encoders have different bolt circle options to suit a variety mounting configurations. These are available by selecting a different base option when ordering.

For instance, our M3K Miniature Magnetic Encoder is available with a bolt circle of 0.586 in. or 0.750 in. (The two different base sizes can be seen in the image above.)

By the way, we have the ability to quickly turn around custom configurations for our encoders. If you’re looking for a bolt circle option that isn’t available now, that doesn’t necessarily mean we can’t make one for you. Be sure to contact out technical support team to learn more.

What shaft/bore size do you need for your encoder?

So far, we have covered physical dimensions that relate to the mounting of the encoder to your motor or system. The final topic we need to discuss when it comes to size, is making sure that your encoder is compatible with the shaft that it is being connected to. That’s where shaft/bore size comes in.

Just as it sounds, bore size of an encoder dictates what size shafts will work with the encoder. (In the case of a shaft encoder, shaft size is the size of the shaft.) Our encoders come with a variety of bore size options ranging from 1.5mm to 1 in., depending on the encoder.

While finding the right dimensions, bolt circle and bore size are the main considerations of finding the right size encoder, it’s only the beginning of the encoder selection process. Next, you’ll have to narrow down other key electrical specifications including resolution, whether you need an Index or not and what kind of output you need, among other things.

If you’re looking for more information on how to specificy an encoder for a project, be sure to check out our “Encoder Basics for Motion Control Engineers” white paper.

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In our latest “Fascinating Tales of Imagination & Ingenuity in Automation” video, you’ll see what happens when our core principles of insourcing processes and continuous improvement collide.

We recently installed a new injection molding machine to add redundancy to the manufacturing of lenses we use in our EM1 and EM2 optical encoder modules. Instead of duplicating our existing automation, Mechanical Engineer Camilla Garcia was tasked with improving upon our initial design and solving some of the production team’s pain points with how it works.

Watch the video to see the final result.

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The US Digital ED4 is a color display with touchscreen that is easily configured to show the readings from a pair of incremental, analog or PWM encoders. The ED4 is configured over USB with a Graphical User Interface (GUI) PC Application

ED4 Quick Start Guide

This PCN is a formal notification that US Digital is discontinuing the following product:
ED3 Digital Encoder Display

The new ED4 Digital Encoder Display is our next generation of the ED3. Please consult the ED4 datasheet for full details.

Last Order Acceptance Date: Orders will be accepted until current inventory is depleted. Stock is limited. 
Last Shipment Date: Shipments will continue until existing inventory is fully depleted. 
Note: All purchase orders are non-cancelable and non-returnable

Download PCN 7516

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New Miniature Encoder Disks Caused Production Difficulties for Operators

When US Digital introduced the E4T, a new, miniaturized optical encoder, the people who processed components during production—the system operators—faced difficulties. Previous methods that worked perfectly for larger encoders were too cumbersome to use with the new, smaller encoder disks.

To improve the operators' working conditions and free up their time for higher-level tasks, the company decided to automate a process that had always been done by hand. Because US Digital is a vertically integrated company with extensive engineering expertise and resources, it began working to solve the problem internally.

Developing a new automation system is never easy. There were occasional roadblocks along the way, but with perseverance US Digital designed an entirely new system, based on a delta robot, and achieved a successful outcome.

The Previous Method - Before Miniaturization

At the heart of a US Digital optical encoder is a transparent Mylar disk with a pattern of black lines on it. Operators produce the disks in US Digital's photo darkroom using high-precision photo plotters at resolutions up to 50,000 dpi. The Mylar film is developed in the darkroom, and then transferred via a conveyor system to the laser cutting room next door.

At the laser cutting table, the operators place the film on a backing sheet of paper. They set up the laser cutter to run, start the automated process, and then are free to do other tasks while the laser cuts out individual disks from the Mylar sheet.

The automated laser begins by using its vision system to locate fiducial marks, which are small crosshairs or unique marks printed on the film and used for alignment. Once it knows where the disks are located, the laser cuts a circle around each disk's outer diameter, and a smaller circle around an inner diameter, as well as specific features needed for the unique disk design. The heat of the laser slightly melts the edges of the disks, and they adhere to the backing sheet of paper underneath.

Operators return and move the sheet of disks to a worktable. In a manual process called 'disk picking', they pick the adhered disks from the sheet and stack them on a rod for storage in inventory.

A New Method - After Miniaturization

For years, disk picking had been an occasional minor task for the operators. It was something they could easily fit in during their busy workday and it didn't take much time—until a new product disrupted the status quo.

US Digital's E4T optical encoder was designed to satisfy the demand for miniaturized motion control products, used where space is limited. The Mylar disk for the E4T is only half an inch in diameter, roughly the size of a shirt button, though much thinner at seven thousandths of an inch.

E4T disks are produced in quantities of more than a thousand disks per sheet.

Their tiny size and large quantities made the new disks more difficult for the operators to pick, but there was an additional problem. On each disk, two tabs protrude into the space of the inner circle; these tabs align with grooves in the hub to which the disk mounts later in the assembly process.

The operators had to precisely align the tabs on the new, smaller disks with grooves cut into the stacking rod—something that they never had to do with other encoder disks. The grooves helped prevent damage to the tabs while they were stored in inventory—but aligning the tabs with the grooves made it much harder for the operators to stack the disks.

"The E4T was really a problem, as far as picking them off and stacking them. It was a painful process," said Neal Donowitz, Chief Operating Officer at US Digital.

After the E4T was introduced to the market it became very popular. Sales grew rapidly, and the operators found that they were spending more and more time at the intensely laborious job of disk picking. They had less time for their other tasks in the darkroom and laser cutting room.

"We look for ways that machines can help our people, rather than having our people help machines," said Donowitz.

He thought the disk picking procedure could be updated and performed by an automated robotic machine. But rather than send the job out to be done by contractors, he followed the US Digital core value of vertical integration, and chose to do the development in-house. The robot would be a purchased part, but Donowitz knew that US Digital engineers, machinists and operators had the advanced skills to build everything else needed for the job.

Kyle Viestenz, a mechanical engineer at US Digital, was tasked with heading the automation project. Viestenz saw that there was another benefit of using a robot for disk picking.

"We wouldn't be handling the disks as much," he said. "The operators use gloves, and they're really nimble and quick, but a half-inch outer diameter, seven thousandths of an inch thin—these are tiny little things that are easy to drop or bend. Building a machine would help take care of these types of issues."

But first, he had to find the best type of robot for the job.

Choosing a Robot

When Viestenz began considering options for a robot that could perform the disk picking job, he heard about delta robots from company founder and CEO David Madore.

"Delta robots are great, because all the heavy parts, like the motors, don't have to move through space," Madore said. "They're rigidly mounted to the top of a frame, and only the lightweight arms hang down."

Their other advantage, according to Madore? Unlike traditional assembly robots, which have to be beefed up to move the massive arms, motors and grippers, Delta robot arms have very little moving mass.

"They can accelerate quickly and move at high speeds. They're ideal for transferring lightweight loads very quickly," he said.

Viestenz decided on a delta robot.

"Its speed was the key," he said. "It was also within the accuracy we needed, and it had the workspace we wanted. A delta robot seemed like a good fit for this project."

Building a System around the Robot

Selecting and purchasing a robot was only the beginning. The robot came as a unit, but it required a system to be built around it. Viestenz needed a frame to support the robot, a table to support the disks as the robot worked on them, tools to handle the disks, vacuum and forced air systems, a vision system and many other items. Everything in the next picture—except the robot—had to be designed and built.

It turned out Viestenz would need to solve many problems as he built a machine around the robot.

The Frame

Surrounding the entire system is an outer frame, 4.5 by 4.5 feet and 7 feet tall. The main frame members are made from 3-inch by 3-inch by 1/4-inch wall steel square tube, and the brackets are made from 1-inch thick steel plate.

The robot mounts inside the top of the frame, and a work surface is mounted halfway down, under the robot's arms. Viestenz tailored the design of his frame to accommodate the required workspace for disk picking.

The frame had to be very rigid. "You can really lose positioning accuracy if there's movement of the frame during robot motions," Viestenz said. "That's why the frame is so massive; it weighs just over 800 pounds—just the frame, without anything else."

The frame also had to fit into the room where it would be used. Viestenz designed it with 1/4 inch of clearance between the top of the frame and the doorway to the room.

At one point Viestenz considered having the frame built by outside suppliers, but ran into several problems with that approach. Vendor lead times were considerable. And the frame had to be square to a tight tolerance; otherwise, the robot would lose accuracy. When Jeff Conner, one of US Digital's skilled machinists with excellent welding skills looked at the plans, he said, "I can build that." He got the opportunity, and the frame he made turned out to be sturdy, rigid, square and delivered on time.

Eliminating Vibration

When Viestenz was developing the machine in US Digital's engineering test area, the frame stood on a concrete floor. He said that even with that massive frame, "When I put the machine together and ran it, it shook quite a lot; you could feel it vibrating." He knew he'd have to find a way to damp the vibrations. Whenever the machine made a fast move and then stopped, its final position needed to be accurate; any lingering vibrations could cause errors.

Viestenz found a simple solution. Rather than bolting the frame to the concrete floor, as is commonly done, he used vibration-isolating rubber padding under each foot. The padding did a good job of damping the structural vibrations of the frame. As an added benefit, Viestenz found that the padding compressed a bit under the weight of the frame, which helped smooth out unevenness in the floor.

The Work Table

A work table is mounted inside the frame, 38 inches above the floor, where the sheet of paper with disks is placed.

Viestenz designed the table with adjusting bolts on its four corners. He can move each corner up and down as needed, to adjust height, pitch and roll independently of the frame. "I can effectively make the table parallel to the robot's horizontal plane of travel," Viestenz noted.

Vacuum Channel and 'Picture Frame' Hold-Down System

One of the challenges Viestenz faced was how to hold down the large sheet of backing paper while the robot picked disks from it. He first tried placing a vacuum channel in the work surface, under the perimeter of the paper; it's a machined groove with holes in it which are connected to a vacuum source. He found, however, "The paper is porous. When we tried to pull a vacuum on the paper, it wouldn't do anything—air would go right through the paper."

He came up with an ingenious solution. He made a 'picture frame' out of Mylar that fit around the edges of the paper, and rested above the vacuum holes in the channel. The Mylar created a seal around the vacuum channel, which successfully held the paper down.

The Vision System

At the start of each run, a camera mounted at the end of the robot's arm takes an image of the fiducial (location crosshair) at each corner of the sheet. "Originally I had the camera mounted high up on the frame. The camera was going to look down at a small portion of the sheet, to get the sheet oriented within the robot's coordinate system," Viestenz said. But he found that looking at only a small area and extrapolating positions for the rest of the sheet wasn't good enough. He had to know the skew of the sheet exactly. "I found I had to move the camera down to the end of the arm of the robot, and get a lot closer to the sheet. Then I could actually move around, grab locations of the fiducials anywhere on the sheet."

Once the camera takes images of the four corners at startup, the system computes the skew of the sheet, and orientation within the robot's coordinate system is complete.

The Tool

The robot does not use fingers or grippers to pick up disks. Instead, Viestenz designed a tool that attaches to the end of the robot's arm and uses a combination of vacuum channels and spring-loaded hold-down pins to pick up the disks; it uses compressed air to help release the disks.

The tool is shaped like an elongated cube. O-rings are embedded in its bottom surface, with adjacent tiny vacuum channels. As the tool comes down, the O-rings create a good seal on the disk, and the vacuum channels deliver suction. Spring-loaded pins around the periphery of the tool push against the paper to hold it down as the tool presses against the disk, picks it up and begins to move away. The pins release from the paper after the tool has moved a fraction of an inch from the sheet.

"There's a spring-loaded pin in the middle, too," said Viestenz, "which helps us hold down the ID crosshair." It's helpful to leave the fiducial in place; that way, if the operators do part of a sheet and then stop, they can still locate the fiducial and re-orient the machine at a later time.

During development, Viestenz discovered that he had to account for small variations in flatness of the table, to get good alignment between the tool and the table for optimum suction. When the robot lowers the tool, it can only move up and down, and in the X-Y direction. Viestenz designed a spring-loaded plate to address this issue; the plate adjusts in the pitch and roll directions, via the springs. The tool previously mentioned is mounted to this spring-loaded plate.

Viestenz designed not just one, but a series of tools to accommodate the various disk sizes that US Digital makes. The tools were precisely machined in-house by US Digital machinists. Viestenz also designed a rack to hold the tools when they are not in use; it fits conveniently between the frame and work table.

"The system is flexible enough for new tools to be made and new programs to be written which can accommodate future products," Viestenz noted.

Stacking Rods

After picking up a disk, the robot moves at full speed to the edge of the table, where it stops and hovers above a vertical stacking rod.

The vacuum turns off, and to help the disk on its way, a jet of compressed air blasts the disk off the tool and down the rod.

Viestenz designed a series of stacking rods for the various sizes of disk that are processed on the machine. For the rods used with E4T disks—the ones with the two tabs protruding into their internal diameter—he created matching grooves in the rods to accept the tabs. The robot precisely aligns the disk above the rod, so that the tabs line up perfectly with the grooves when the disk is discharged from the tool.

To allow for tolerances while discharging the disks, Viestenz designed a removable, tapered tip to fit on the end of the rod. This creates relief to account for position errors of up to 20 thousandths of an inch as the robot moves into position.

To keep the rods at a reasonable length, Viestenz created two stations—two rods stand side by side. When the robot processes E4T disks, it stacks 600 disks on one rod, and 600 on the other rod.

Transfer Station

Once a rod is full, the disks are transferred to another rod for transport and storage in the inventory area. Viestenz designed a transfer station where the operators can perform this delicate task. They remove the tapered end from the stacking rod, and insert it onto the end of the storage rod. It's then a simple task for the operator to slide the disks from one rod to the other.

Human Machine Interface (HMI)

Viestenz designed the HMI to be intuitive and reliable. The interface is a large, touch-sensitive flat panel display, mounted to the frame at a convenient height. Operators can control machine functions by selecting menus and touching buttons on the screen. Viestenz said, "We tried to keep it simple, and usable as well. It keeps track of elapsed time, and how many disks have stacked up. It makes a rough prediction of how much longer it's going to take, and how long it's taking for each disk."

During development, operators Igor Korotin and Paul Fedorenko contributed to the design of the HMI, and Viestenz included many of the special functions they knew would be needed. Because the robot arms, high above, are equipped with absolute encoders, position information is retained if the operators need to stop midway through processing a sheet of disks. When resuming, the operators can choose to start in a different location, identified by row and column. They can also choose how many disks they want to pick up. "Most of the time, you'll pick a whole sheet," Viestenz explained, "but Igor and Paul knew these other options would be nice to have. I put them into the interface, to give them the flexibility."

Light Curtain for Safety

When the robot operates in high power mode, it moves very quickly. For the safety of the operators, Viestenz installed a light curtain in front of the machine. Multiple infrared beams create an invisible barrier; if someone moves too close and interrupts any of the beams, an emergency stop is triggered and the robot halts immediately. When ready, the operator can restart the robot from where it left off. No homing move is necessary, thanks to the absolute encoders that report the robot's tool position.

Discoveries During Development

As the parts came together and the machine began to take shape, Viestenz could begin to operate it—slowly at first, with motion limited to short moves, and then eventually at full speed while picking disks from an entire sheet. Much of the development went as planned, but he had to solve many unexpected problems along the way.

Motion Programming

When he programmed the machine for motion, Viestenz had to adjust speeds and accelerations. It took time to get everything just right. As the tool began lifting the disk from the sheet, he experimented with the tool's speed, searching for the right amount of time to get a good vacuum seal and not leave the disk behind. At the other end of travel, when the tool discharged the disk onto the rod, he adjusted speeds there for precision. He also put the robot through high speed motion, searching for the fastest possible velocity once the disk was picked off the sheet. His goal was to reduce total cycle time.

Rotation about the Vertical Axis for Positioning

Delta robots move up and down in the Z direction, and maintain orientation of the tool in the X-Y plane—the tool usually does not rotate about the vertical axis. At the start of the project, Viestenz realized that these three axes of motion would not be enough.

For this system, the tool had to drop the disks onto the stacking rod with their tabs precisely aligned with the matching grooves in the rod. If the sheet of disks was perfectly aligned and square in relation to the table, things worked perfectly. But Viestenz needed a way to allow for some skew in the sheet.

To compensate for skew, he ordered an optional 4th axis when he purchased the robot. A splined rod can extend in and out, and rotate the flange to which the tool is attached. This extra rotation about the vertical axis solved potential alignment problems by allowing the skew angle to be incorporated into the robot's coordinate system. Each disk's tabs could now be positioned correctly above the grooves in the stacking rod.

Some Disks Wouldn't Release from the Backing Sheet

Occasionally a disk adhered so tightly to the backing sheet that the robot couldn't pick it up. Viestenz had to find a way to determine when this happened, and instruct the robot what to do in that event.

He installed a sensor and programmed it to check vacuum pressure after each disk was picked up. If the reading wasn't above a certain level, it indicated that the disk had been left behind. In that case, "It will try one more time," Viestenz said, "and if the second attempt fails, the robot moves on to the next disk." The stuck disk remains behind on the paper.

Aerodynamics and Disk Diameter

The most efficient way for disks to stack is for them to leave the tool face quickly, and rapidly shoot down to the bottom end of the stacking rod. If they were to float down slowly, there is a chance they could hang up on the rod before reaching bottom, and potentially cause a jam as more disks arrive. The machine is designed to run unattended, so jams and overflowing disks are unacceptable.

Viestenz used a quick burst of compressed air to push the disk from the tool and onto the stacking rod, in what is called a 'blow off' procedure. "I thought the smallest disks like the E4T were going to be the tougher ones," Viestenz recalled. "But for them, the blow off works really well—it just shoots it down to the bottom, you can't even see the disk, it moves so fast."

The larger 1-inch disks caused problems. They dropped more slowly, perhaps because their larger diameter caused increased air drag. When Viestenz tried increasing the air pressure to get the disk to move downward faster, he was surprised to find that the additional air caused the disks to stick to the face of the tool, and not release quickly enough. It seemed the fast-moving air and the larger disk diameter combined to create a slight vacuum suction between the disk and the tool. Getting it right turned out to be a delicate balancing act.

Success!

One by one, Viestenz solved each problem as it came up. Development is now done, integration of all the parts is complete, and the disk picking machine is working away in the production area. It's accomplishing all the goals that Viestenz and Donowitz outlined at the beginning of the project.

Donowitz concludes, "We use the robot to help people, and let the people go off and do the higher level work. They can do all kinds of other tasks, at the same time the machine is running. It's efficient in that way."

Instead of laboriously picking and stacking the disks themselves, the operators can now set up the machine, push a button, and let the robot perform the entire process.

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Our encoders are used in a variety of fields – everything from manufacturing automation, aerospace, textile manufacturing, solar power to exercise equipment. In this post we’re excited to put the spotlight on one of our customers who is revolutionizing the rowing machine.

The Hydrow® Live Outdoor Reality™ rower features a patented drag mechanism that is electromagnetic and computer-controlled that was designed to make the machine feel as close as possible to actually being on the water. Precise position feedback was an important part of the design.

“While the design team wanted to create a unique machine that was elegant and sophisticated for the home, it was just as important to engineer a machine that was unmatched in performance and built to last,” Hydrow said.

The innovation doesn’t stop with hardware. Hydrow also includes a built-in HD display that gives its users access to an extensive library of courses taught by professional trainers from locations around the world.

The concept clearly resonates with people. The rowing machine started as an Indiegogo project and was 100% funded within 4 minutes when it launched in late 2018. By the time the project closed, the rower had gained 1030 backers and raised more than $1M, far surpassing its initial goal of $100,000.

We’re thrilled to be a part of a product as innovative as Hydrow. To learn more about the rower, be sure to visit them at www.Hydrow.com.

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When our engineering team looked for opportunities to improve processes in our injecting molding department, they set their sights on creating a machine vision system to automate the manufacturing of a key component.

The machine, called LIAS or the Lead frame Inspection Automation System, visually inspects our EM1 and EM2 lead frames for manufacturing defects and packages them for transport to our clean room and the next step of the manufacturing process.

Previously, machine operators would do visual inspections and packaging by hand, which meant they would spend anywhere from 30 minutes to a few hours at the machine each day, depending on how many lead frame reels ran through the machine.

“No process starts fully automated,” US Digital Founder and CEO David Madore said. “In order to get there we start manually and find ways to improve over time.”

Building a custom machine vision system

David recently has been working with the engineering team to streamline processes in our injection molding area. He designed LIAS in SolidWorks and then worked with Software Engineer Steve Smith and Machinist Trevor Goforth to make his design a reality.

Steve and Trevor updated and improved features of the design as they went.

“When you design something custom like this, you’re not going to design everything perfectly in software,” David said. “As the machine comes together, we’re going to find opportunities to make it better as we go.”

When Steve and Trevor ran into issues with the machine, they developed solutions. In one case, the lead frames would travel too far in the testing station so they added a mechanical stop to briefly hold them in place before they continue in the process.

The build process took several months, but it was a fun learning experience, Trevor said.

“The back and forth between Steve and I was my favorite part of the build,” he said. “Taking our different skill sets and combining them helped make the project easier to accomplish and I learned a lot from him throughout the process.”

While Trevor didn’t feel any additional pressure working on a project designed by the owner of the company, he viewed it as an opportunity to make sure the machine was robust and as efficient as possible.

“I wanted to make sure we built something that David and, most importantly, the machine operators would be happy with.” Trevor said.

When the final result came online, David couldn’t help but laugh at seeing his design come to life.

“It’s these little unexpected surprises that give us joy,” he said of watching the machine running for the first time.

The Results

If you frequent our blog, you’ve probably heard that we use automation to create new opportunities, not to replace people. Our machine operators are still working in the plastics area, but are managing the process instead of doing it themselves.

The machine is now up and running and gives our plastics area employees a bit more freedom to manage multiple machines at once, instead of manually inspecting each lead frame as it comes off the punch press.

How does it work?

As lead frames come off the punch press, they are transported via a conveyor belt to LIAS. Along the way, a series of rollers flatten the lead frames which are then sent to the inspection station.

At the inspection station, a silhouetted image is created using a high-powered light below the lead frames and a camera above. The image is then analyzed by Steve’s custom software for manufacturing defects.

Good lead frames are put into containers that can then be taken to our clean room for the next part of the manufacturing process. If the system identifies a bad lead frame, it is put into a reject area. If there are multiple defects in a row, the machine stops and alerts the operator to come investigate.

To see the machine working and more detail on the process, be sure to check out our video below.

What is next for our machine vision system

While the team is proud of their accomplishment, there is still more work to be done.

“It’s 100 percent functioning, it’s 100 percent working,” David said. “Is there room for a little improvement? Yes, but it’s already doing its job.”

Our belief in continuous improvement, means that no process or procedure is ever really done. We’re always keeping our eyes open for ways to further improve our efficiency and automation. Some of those ideas to further improve LIAS will be incorporated into the design of a second version in the near future. The second machine will be used on an additional punch press we recently purchased that will increase our lead frame output capabilities and give us a backup option for redundancy.

US DIGITAL ENCODERS AND CONTROL DEVICES USED AS PART OF CUSTOM AUTOMATION SYSTEM

When we are designing our own in-house automation systems, we try to use as many of our products as practically possible. We used our own encoders and control devices when designing LIAS.

• We used our USB4 Encoder Data Acquisition Devices to connect encoder output signals to the PC at the core of LIAS.
• We used an E3 Optical Kit Encoder to track position of a stepper motor used on the pick and place machine. The encoder provided good accuracy, precise movement and an Index so the picker could return to a home position.
• We also used a MD3 Microstepping Motor Driver to control a stepper motor.

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You can save some cash on your encoder purchase if you order in bulk, but that might not be the best for option for you. In this blog post we’re going to do a deep dive on our packaging options to help you make an informed decision.

For packaging on most of our encoder kits, we have three options: bulk and two individual configurations. These different options look similar when you’re ordering four or less encoders but when you’re ordering in larger quantities, things can look quite a bit different. Part of that has to do with how things are packaged. Part of that has to do with how many tools you get with your order.

What is encoder bulk packaging?

If you select bulk packaging, denoted by a "B" at the end of your part number, our kit encoders ship with like components packaged together in individual bags or containers. Modules ship in plastic tubes, disks ship in clamshells, covers, bases and hardware ship in plastic bags. 

With bulk packaging, you receive one set of assembly tools per order and an additional set of tools for every hundred additional encoders.

In other words, if you order 100 encoders or less, you’ll get one set of assembly tools. If you order 101 encoders, you’ll get two sets. If you order 201, you get three, etc.

This is a great option for an assembly line where one person will be assembling all of the encoders.

What is individual packaging (option 1)?

If you select the first individual packaging option, "1", each encoder kit will be packed separately. In this case, all the components necessary to assemble one encoder, except for the tools, will be grouped together in one package, either an ESD tray or bag.

Just as with the bulk option, you will receive one set of assembly tools with each order and an additional set of tools for every additional hundred encoders you purchase.

This is a great option for a service person who doesn’t need multiple sets of tools but will only be installing one encoder at a time. 

What is individual packaging (option 2 or 3)?

If you select individual packaging option "2" or "3", each encoder kit is packaged separately, and you get one set of assembly tools with each encoder.

This is a great option for selling the complete kit with tools for individual sales to your customers or if you are a service person who may not always have encoder assembly tools.

Side note: Option 2 is available for encoders with push-on hubs. Option 3 is available for encoders that have HubDisks that are secured with set screws. Option 3 comes with a hex tool to secure the HubDisk. Option 2 does not include a hex tool because a set screw is not used for push-on hubs.

Wrapping it up

The different packaging options also come with different prices. Bulk is the cheapest, with individual option 1 and 2 being the middle option and option 3 being the most expensive.

We hope this helps clear up product packaging, but if you have any questions don’t hesitate to reach out to us.

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You may have seen reports from MIT researchers that say that – on average – each robot added to manufacturing replaced 3.3 workers nationally and lowered wages. There’s a lot more to the data than that, so be sure to check out more details on the study on the Robotics Business Review.

While we can’t speak for other industries or manufacturers, we can say that automation and robotics enhance the jobs of our employees and lead to more, sustainable jobs in the long run.

In fact that’s one of our core beliefs: We don’t treat people like robots, we give people robots to use.

“Anytime there’s a person sitting in a chair doing a repetitive operation, it’s violating that principle,” US Digital CEO and Founder David Madore said. “Tedious tasks are better performed by robots. We don’t always start that way but we end up that way as we progress.”

Over the years we’ve found putting more effort into improving internal systems, automation tools and employee training pays great dividends back on the investment, Madore said.

So how does it play out in real life? Let’s look at our cleanroom as an example.

In 2009 we had 4 specialists working in the clean room assembling encoder modules by hand.

At the end of the year, our employees were able to assemble about 40,000 modules. It was an impressive feat, but not something that was sustainable long-term, particularly if we were going to be using the modules in most of our products in the future.

“We asked ourselves if there was a better way to be doing this,” US Digital COO Neal Donowitz said. “The answer was, of course, yes.”

US Digital engineers designed automated machines that now handle encapsulation, wire and die bonding, inspection, marking and packaging of the modules. People are there to feed the machines, make sure they are performing as expected and do visual inspections that are better suited to the human eye.

Last year we produced more than 1,000,000 encoder modules using various automation systems. We now have seven full-time cleanroom technicians who visually inspect parts and help us solve problems and further streamline our processes.

“We often ask ourselves not only how we can work smarter, but we ask why we do things the way that we do,” Madore said. “That leads to new opportunities for improvement.”

In this case, automation allowed us to increase our manufacturing capability 25X, promote the four original employees and hire three additional ones, and all along keep our focus on providing our customers with high quality cost competitive solutions.

If we hadn’t used automation, we’d need to have something more like 100 employees to do the same job, not to mention the additional space required for that many people. That wouldn’t be feasible from a cost perspective and we would have either not grown the business or looked to outsource the manufacturing to somewhere with cheaper labor, like so many other manufacturers are doing these days. Now we’re set up for growth.

“American manufacturers will not successfully compete in the world market if human fingers are doing the assembly with mind numbing repetition,” Madore said. “But the cost for automation is the same worldwide and jobs are more satisfying when people get to work smarter. We continue to grow and provide more and better jobs by designing and equipping our team with fascinating automation machines to do the tedious work. It’s a lot more fun and satisfying.”

And that fun never ends. Our in house engineers are working on updated versions of some of the machines in our clean room that will further increase our efficiency and create more room for future growth.

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Most companies will tell you that they have a stellar customer service team, but we are confident we can actually back up that claim. That’s because one of our core beliefs is that we are here to help our customers succeed.

There’s a couple of ways we do that:

INFORMATION ABOUT ENCODERS IS JUST A CALL OR CLICK AWAY

Let’s say you’re designing a motion control system but it’s been a struggle to find detailed product specifications, pricing, and other info you need to make a decision. That’s why we make it easy to find that information easily on usdigital.com.

If you need additional help, our experienced customer service team can help you find the right product for your job. If you need help with installation or troubleshooting, our tech support team is here to help.

WE VERTICALLY INTEGRATE KEY MANUFACTURING PROCESSES

Did you know we design and manufacture our encoders in house? That means when you call us for help or to check on the status of an order, our customer service team can talk directly with the people responsible for making it. They don’t have to make long-distance calls or email people in a different part of the world to see what is going on with your order. And best of all, because we make our key components and products in-house, we can often ship orders within a few days of your purchase – in fact, if your order before 11 a.m. Pacific Time, chances are we can ship that order the same day.

OUR CUSTOMER SERVICE TEAM CAN GET CREATIVE

We think the best way to help our customers is to empower our customer service team to listen to their needs and act accordingly. They aren’t locked into scripted responses and predetermined outcomes, said US Digital COO Neal Donowitz.

“It’s not about just giving (our customers) information, but helping them,” Neal said. “They’re actually helping them find a solution.”

Whether that means we build a last-minute order so a customer doesn’t miss a deadline; we drop an order off at the FedEx or UPS store to get it shipped after our normal pickup time; or we schedule a Zoom call so a customer can work with a design engineer to troubleshoot an issue, our team has the flexibility to work with every department to make things happen for our customers.

“While we’re often the starting point for our customers, the overall US Digital structure and focus allows us to all work together to satisfy our customer needs,” Customer Service Supervisor Heidi Smith said.

It all goes back to our core principle: We make life easy for our customers.

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Do you have a question or need some help, don’t hesitate to contact us online via email at info@usdigital.com or by phone at 1–360–260–2468.

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Our MD3 stepper motor driver can drive size 14 to 42 stepper motors from full stepping up to 256 microsteps per step. In this blog post we’re going to walk you through how to set up the MD3 and configure it using a Windows PC.

If you prefer to learn with visuals, we also created a video that goes into the basics, which is available below:

Step 1: Connect your MD3 to a stepper motor, power and an encoder.

The J3 connector, which can be seen at the lower left of the MD3 (when looking at it from the top) is used to connect to a stepper motor.

The J2 connectors on the other side are used the connect to an encoder and power. You can use pins 6 and 1 of the J2 to provide isolated power if noise is an issue, or you can use jumper wires with a single power supply (see photo below.)

For further instructions on wiring, please refer to our MD3 user guide, which details what is connected to each pin.

Before we continue, a few words of warning: Do not connect or disconnect the motor leads when the MD3 is powered. Make sure that all connections are made and J3 is plugged in before applying the main power. Do not unplug J3 when the drive is powered. Failure to follow these instructions may damage the drive.

Once you have made your J2 and J3 connections, you can turn on the power supply.

Step 2: Connect the MD3 to a Windows computer

The P1 port on the top left of the MD3 is used to connect an RS485 adapter such as our CA-MD3. Connect the MD3 to your computer’s USB port.

Step 3: Install and run the software

The latest MD3 software can be found on our support tab. Download and install the software. Once installed, you’ll see there are two applications: MD3 Setup and MD3 Demo. The MD3 Setup application makes the MD3 function like our discontinued MD2S. We’re going to ignore that for now and look at the MD3 Demo software.

Software overview

Once in the MD3 Demo software, use the "COM Port" pulldown to choose the PC COM port the RS485 adapter is using and click on "Connect." The program will scan and connect to the MD3.

From here there are multiple tabs that give you control of the MD3 functions.

Motion Control: The motion control tab gives you control over speed, acceleration, steps to move, power settings and encoder configuration. There also are quick motion commands we programmed into the software. You can also configure how you want the J2 pins to work on the MD3.

Communication: The communication tab can be used to configure the baud rate and some other communication parameters. This is particularly useful if you’re using your own software or hooking the MD3 up to an existing system.

Registers: This tab is used to read or write directly to the MD3 registers.

Activity Log: This tab logs Modbus serial commands and replies exchanged between the MD3 and host PC. You can also monitor errors here if the “error log” box is checked.

Maintenance: The maintenance tab can be used to check for and install firmware updates for the MD3 or rest the device if you want to go back to the previous settings saved in EEPROM.

Please note, any changes you make in the software will modify the internal RAM registers of the MD3 and take effect immediately, but they will not be saved to non-volatile EEPROM on the MD3 until the "Save Configuration to EEPROM" button is pressed.

If the current configuration is not wanted, the unit can be power cycled to reload the previous settings from EEPROM or you can click the "reset device" button on the maintenance tab.

That should be enough to get you started with the MD3. If you want to go into greater detail, please refer to the user guide. If you have any questions, don’t hesitate to reach out to us. We’d love to help answer any questions we can.

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Small rotary encoders are a big thing these days.

As motors (and all electronics for that matter) continue to get smaller, we realize we need to shrink our own products to better support our customers needs.

Our E16, E4T and E8T optical encoders provide digital quadrature feedback for high volume, restricted space applications. The E16 Micro Optical Kit Encoder offers high resolution and Index. The E4T Miniature Optical Kit Encoder and E8T Miniature Optical Kit Encoder offer differential output and support a larger range of shaft sizes.

Learn more about our line of miniature encoders and download the specification sheets using the comparison chart below.

	E16	E4T	E8T
Diameter	16mm	19.51mm	25.61mm
Shaft size	1.5 & 2mm	2mm to 0.250 in.	3mm to 0.375 in.
Bolt circle	0.394 in. [10mm]	0.586 in. [14.88mm]	0.750 or 1.53 in. [19.05 or 32.51mm]
CPR	256–4096	100–1000	180–720
Index	Yes	No	No
Differential Output	No	Yes	Yes
Specifications	DOWNLOAD E16 DATASHEET	DOWNLOAD E4T DATASHEET	DOWNLOAD E8T DATASHEET

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In the motion control industry, accuracy is the difference between target position and actual position. For rotary encoders, we measure accuracy in degrees, arcminutes or arcseconds.

• 1 degree = 1/360th of a circle - used with low accuracy encoders
• arcminute = 1/60th of a degree - used with medium accuracy encoders
• arcsecond = 1/60th of an arcminute - used with high accuracy encoders

Degrees, arcminutes, arcseconds… smaller and smaller units of measurement. So small, they can be hard to visualize.

For this blog post, we thought it would be fun to blow things up! No, not like an explosion—more of an expansion. We'll start off small, then get really big, so we can see what an arcminute and arcsecond would look like in our world, rather than in the small scale of the microelectronics world.

It's All Relative

If someone asks, "How small is an arcsecond?" the answer is relative—it depends on how big the circle is, of which the arcsecond is a part.

For example, encoder disks come in several common sizes, including 1-inch and 2-inch disks. As the disks get smaller, the distance (arclength) spanned by each measurement—degree, arcminute, arcsecond—gets smaller, too. The table below shows arclength distance measured at the outer rim for two disks:

Measurement	2-inch Disk	1-inch Disk	50.8 mm Disk	25.4 mm Disk
1 degree	0.017 inches	0.009 inches	0.44 mm	0.22 mm
1 arcminute	0.000291 inches	0.000145 inches	0.0074 mm	0.0037 mm
1 arcsecond	0.000005 inches	0.000002 inches	0.00012 mm	0.000062 mm

Going in the opposite direction, larger disks have larger circumferences; when you divide them into degrees, arcminutes and arcseconds, those sectors are larger, too.

Let's Go Huge

Let's take a 180 CPR encoder disk, and blow it up—I mean, expand it—so that a single degree measures one foot, or 12 inches in arclength, along the outer rim.

The disk will now have a circumference of 360 feet—one foot for each degree. A 180 CPR disk has 180 lines and 180 windows, for a total of 360; at the rim, each line or window is 12 inches in width.

Which works out great for this blog post, because 360 feet—the circumference of the disk—also happens to be the length of an American football field, including the end zones.

Let's fly our giant encoder disk into a stadium, land it in the middle of the field and make some size comparisons.

In the drawing below, each foot of the 360-foot-long field matches one degree of the enlarged disk.

The short white lines on the field, called hash marks, occur every three feet—they match up with three segments on the disk: a line, a window and another line, for example.

Now let's take that center window—12 inches long—and divide it into 60 equal pieces.

Each one of these new mini-segments would be equal to one arcminute—0.2 inches or about 5mm—literally the size of a pencil eraser.

Divide that pencil eraser—or arcminute—into 60 parts, and you have an arcsecond.

In this case: 0.0033 inches. Just over 3 thousandths of an inch, or 0.083 mm. The thickness of a human hair. 

So if you're in the stands at a football game someday, and you happen to notice a pencil slip out from behind a coach's ear and fall onto the sidelines…

…see if you can spot the pencil eraser from where you're sitting.

In the huge stadium, that small eraser spans an arcminute. And if there happens to be a hair stuck to that eraser, well—it's the size of an arcsecond. Can you see it? Probably not without some very powerful binoculars; or maybe a telescope.

We hope this example gives you some idea of the relative scale of accuracy that encoders can achieve. A medium accuracy encoder might have accuracy in the range of a tenth of a degree, or 8 – 10 arcminutes—a few pencil erasers in a football stadium. And a high accuracy encoder might measure only a few arcseconds—a few hair-widths, in all of that space.

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An encoder is a sensor that translates physical motion into electrical data. That data can be used by a control device to determine speed, acceleration and position.

Encoders can track two different kinds of motion. Linear encoders track motion in a straight line. Rotary encoders track changes in shaft rotation and are often attached to motors.

Encoders can be found in all types of machinery in numerous industries, including solar, additive manufacturing (also known as 3D Printing), aerospace, robotics, medical, and textile manufacturing — to name a few. A lot of times, you’ll even find encoders built into motors you buy from electronics parts distributors and catalogs.

Looking for a few examples of how encoders can be used?

Encoders come in a variety of configurations, but they all translate physical motion into an electric signal that can be interpreted by a motion control system.

• A 3D printer may use multiple encoders to track the position of the print head. The information from the encoders can then be sent back to the motion control system so it can verify that the print head is in the correct position to print the desired object.

• A delta robot uses a series of motors to control the position of the arms. Some kind of encoder is most likely attached to each motor. The data from each encoder is used to understand the shaft rotation on each motor, which impacts the position of the end effector—the robot’s “hand.”

• An automated assembly line could use rotary encoders to track motion of a conveyor belt system. With an encoder attached to a motor that moves the belt, the shaft rotation and total revolutions could be used to extrapolate the distance an object on the conveyor traveled.

So, if you are looking to track speed, acceleration or position of any part of a mechanical system, an encoder might be just what you need.

We offer a wide variety of encoders on our website. If you have any questions, or need help finding the right one for your project, don’t hesitate to contact us. Our customer service and tech support teams are more than happy to help you find the right encoder for your application.

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An absolute encoder can tell you the exact position of the shaft in its rotation at any given time (and how many rotations have transpired on a multi-turn absolute encoder). An incremental encoder can only report a change in position.

It may not sound like a big difference, but it’s night and day if the system has a loss of power.

Once power is restored, an absolute encoder can report exact position without any movement. An incremental encoder will need to find an Index or home position before it can do so – and if it doesn’t have an index, it won’t be able to tell you it’s position at all.

Let’s get into why by talking about how both types of encoders work.

How incremental encoders work

Our incremental optical encoders, an LED, photo detector chip, and a patterned disk to report shaft position.

Our incremental encoders have an LED on one side of a transparent disk and a photo detector chip on the other. The disk has a series of lines and windows on it. The windows allow light to be transmitted from the LED to the chip. The lines do not. This alternating pattern of light is how the encoder reports position information back to the mechanical system.

Each set of lines and windows looks identical. Incremental encoders can determine relative shaft position based on the number of windows and lines that pass in front of the detector chip. If power is lost and then restored, that relative position is lost.

In some applications - for instance when using an encoder to determine speed, distance or direction of movement - this may be perfectly fine.

In other applications an exact position is needed.

The only way for an incremental encoder to report its exact position after it’s been power cycled is for the shaft to rotate until the encoder reaches Index (if it has one).

If you’re designing a system where it’s critical that you know the exact shaft position, including after power to the encoder has been cycled, you should consider an absolute encoder.

How absolute encoders work

Absolute optical encoders use an LED array, optical disk and photo sensors, like an incremental encoder but the disks patterns are slightly different.

Absolute optical encoders can use a series of lines and windows and multiple bands to create a binary pattern that gives a unique position.

Some designs use multiple bands to create a unique pattern at each point on the disk. For instance, using the photo above you can imagine that each position can either have a 1 or a 0, depending on whether the photo sensors detects light from the LEDs. The disks current position would be 1001, which does not occur anywhere else in the shaft rotation.

Other designs, like our current optical absolute encoders, use a unique pattern of line spacing and thickness in one band to create absolute position. The design is different but each position on the disk still has a unique pattern that doesn’t occur anywhere else in the rotation, eliminating the need to rotate to find an index position after a power cycle.

For many applications there is no advantage to using an absolute encoder over an incremental one. However, if you are working on a design where rotating to find a home position after a power cycle isn’t ideal or possible, an absolute encoder is the right tool for the job.

For instance, if you are building a robotic arm or other automation project where rotation to find an index could be dangerous to the equipment or people in its environment, choosing an absolute encoder would ensure that you know the exact position at all times.

Of course, there is much more to learn about absolute encoders than we can fit into one blog post. Lucky for you we have an expanded intro to our absolute encoders blog post.

And hey - if you are looking for an encoder and still have more questions, be sure to check out our latest white paper that helps you find the right encoder for your project. In it we go through resolution, type of motion, CPR vs. PPR and just about everything else you could imagine related to encoder selection.

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PCN 7115 - Hubdisk-2 Packaging

As part of our ongoing continuous improvement efforts, US Digital is implementing a change to the packaging of our 2 in. Hubdisk assemblies.

Download PCN 7115

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The MD3 User Guide describes the MD3 Microstepping Motor Driver in-depth and includes the setup and operation of the programs used with the MD3.

MD3 User Guide.pdf (Version 1.7, 1.06 Mb, 3/8/2023)

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As part of our ongoing continuous improvement efforts, US Digital is changing the case color and label type of the SEI-USB. This change does not affect form, fit or function.

If you have any questions or concerns about this PCN, please contact US Digital Customer Support at 1-800-736-0194 or email sales@usdigital.com.

Download PCN 5514

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Encoders can use a variety of technologies to turn physical motion into electrical data. In this post (and the above video) we look at how optical incremental encoders work.

Before we begin, we want to clarify that this is an oversimplified explanation of how our rotary incremental encoders work. If you want a more detailed explanation, check out our blog post on quadrature.

Our incremental encoder modules have an LED on one side and a photo sensor on the other. A HubDisk is attached to a shaft on a motor and aligned in such a way that its transparent disk passes between the LED and photo sensor in the module. A series of printed lines on the disk block light from the LED from reaching the sensor. The spaces between the lines do not.

The pattern of light and dark is how an encoder reports information back to the mechanical system. The encoder reports 0 volts DC when light is blocked and 5 volts DC when light reaches the sensor. By connecting an oscilloscope to an encoder, you would see a pattern similar to this:

Encoders have a defined number of lines on each disk — this determines the resolution. The distance between lines represents a percentage of the disk’s rotation, and can be used to calculate speed, acceleration, direction, and position.

Regardless of what industry (or application), encoders are a great way to provide feedback you need to monitor and control physical movement.

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HOW THE T7 NETWORKED ABSOLUTE INCLINOMETER DRIVES DOWN THE COST OF SOLAR ENERGY IN CONCENTRATED SOLAR POWER SYSTEMS

As with most systems, the accuracy is limited by the accuracy of the sensors used in that system. There are a number of different types of sensors that can be used in these systems. This paper discusses why an absolute inclinometer is the most effective sensor solution and why the US Digital T7 is superior to other inclinometers available today.

DOWNLOAD WHITEPAPER

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In an earlier post to this blog, we introduced Absolute Encoders. We illustrated the differences between absolute and incremental encoders, and showed that an absolute encoder can give a unique report for each different position on the encoder disk. But we didn't talk about what that report looks like.

Looking back to incremental encoders for a moment, each part of their output waveform looks like every other part. (Except for the Index signal—that's unique). From one cycle to the next, we expect a high and a low… and then what looks like the same high and low, repeating… and repeating. What matters is the increment—the change from this cycle, to the next cycle, and so on.

Absolute encoders have a different requirement. The output waveform must change constantly and consistently, never repeating a position report until a full rotation is completed. What's the solution to this requirement for unique reports? There's not just one solution—manufacturers have come up with many.

In this post, we'll discuss the most frequently used output types. We'll start with the simplest, the analog voltage output. Then we'll move on to PWM (Pulse Width Modulation) outputs, and finish with serial communication interfaces.

More Information Must Mean More Pins - Right?

The outputs have to connect somehow to a motion control system. If we compare connections for an incremental encoder with those for an absolute encoder, we start to see the range of possibilities. The next table shows pinouts for several encoder types.

Pin No.	Incremental - Single Ended	Incremental - Double Ended	Absolute - Analog Voltage	Absolute - PWM	Absolute - Bus Interface
1	Ground	Ground	Power	Power	Ground
2	Index	Ground	Analog Output	PWM Output	Busy +
3	Channel A	Index -	Ground	Ground	Busy -
4	Power	Index +			Power
5	Channel B	Channel A +			Data L
6		Channel A -			Data H
7		Power
8		Power
9		Channel B -
10		Channel B +

At the simplest, an Analog Voltage or PWM output can be transmitted on a single pin. Surprising, considering how much information can be conveyed over that one pin. Even the more complex bus-based communication interface requires only six pins for power supply, data, and transmission synchronization.

Analog Voltage Output

Let's start with a picture. Here's what a typical analog voltage output waveform looks like. The drawing is for a single-turn magnetic absolute encoder.

For this type of output, 0 volts is the starting position, and represents position 0 at 0°. As the encoder disk turns, the output voltage rises, with each voltage increment representing a new position. The voltage will reach the maximum at 359°. As the disk rotates past 359° and reaches the zero position again, the voltage drops to zero. The output is a scaled ratio of the power supply voltage, from 0 - 5 VDC in this case.

Why choose an encoder with an analog voltage output? It's very simple to use. Many PLCs and motion controllers can accept analog voltage signals as inputs, and making connections is easy. Basic point to point wiring is often all that is needed.

PWM Output (Pulse Width Modulation)

Here's another way for an absolute encoder to tell you where it is. The encoder transmits a "pulse" - the output goes high. The width of that high, or pulse, corresponds to the position the encoder is reporting.

A picture helps. The next drawing shows some PWM output pulses for different positions as an absolute encoder rotates.

For example, a 10-bit encoder has a resolution of 1,024 codes per revolution. These codes are typically numbered 0 - 1023, for a total of 1,024 positions.

For starting position 0, the shortest pulse width is transmitted—1 microsecond is typical. As the disk rotates, longer and longer pulse widths are transmitted. Half way around, near 180°, the pulse width would be 512 microseconds. The longest pulses are transmitted when the disk has almost completed a full revolution.

It's that simple: short pulses at the starting position, longer pulses as the disk rotates, and the longest just before the disk reaches the starting position again. Count the microseconds; they correspond to the reported position.

Another way some controllers use the same information is to measure both time_on and time_off (see the drawing above) and calculate the shaft angle from the duty cycle.

Communication Interfaces

An absolute encoder that is equipped with a serial communication interface can be networked on a bus. PLCs or other motion controllers can then send commands to the encoder. The encoder executes those commands by sending position information back to the PLC.

Here is a typical pinout for a 12-bit optical absolute encoder.

Pin	Description
1	Ground
2	Busy +
3	Busy -
4	Power
5	Data L
6	Data H

The Data lines are bidirectional, and carry commands from the host computer or controller, and responses from the encoder. The Busy lines are used to control the flow when multiple devices are networked together. When an encoder receives a command, it drives the Busy+ and Busy- lines to acknowledge the command. The lines stay asserted until the encoder completes the command. While the encoder drives the busy lines, all other devices on the bus ignore the data flow.

A typical application might work like this. An encoder continuously reads and stores positions in its internal data register. When the encoder receives a command to report position, it asserts the busy lines, and then transmits the latest stored position to the controller, in the bits and bytes of digital words. When the transmission is complete, the encoder releases the busy lines, and goes back to reading and storing positions—until the next command is received from the controller.

Absolute encoders deliver many benefits when they're equipped with communication interfaces. They can be joined to a network via existing cabling, and avoid the expense and complexity of point to point wiring systems. Many encoders and other devices can be connected to a network, which increases system functionality and allows them to be programmed in the field.

If an encoder is not field programmable, then all variables must be set by the manufacturer when the encoder is ordered. With programmability, though, those variables can be changed in the field. For example, a 12-bit absolute encoder might arrive with its resolution set to 4,096 codes per position. If you need the encoder's resolution to be 3,600 codes per position (one code per tenth of a degree), you can program that resolution.

In another example, you can program the present position to be the new zero position. This is handy during system setup; you don't need to find the zero position on the encoder, and then coordinate that with the machine's position. Instead, position the machine where it needs to be, and program that as the zero position.

Which Communication Interface is Best to Use?

That's a trick question. There are many types of communication interfaces, used in a huge range of applications. Fieldbus development began in the 1980s, and has spawned many variations, such as Profibus, CANopen, DeviceNet, Modbus and so on. EtherNet started in the relatively tame office environment, but "hardened" Industrial Ethernet versions for use in more grueling industrial settings have been developed, such as Ethernet/IP, EtherCAT, ProfiNET and others.

We recommend that you understand the requirements of your communication interface, and pick an encoder that can meet those requirements.

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As part of our ongoing continuous improvement efforts, US Digital is implementing a change to the packaging of our 1-inch Hubdisk assemblies.

We are replacing the current plastic tube packaging with a 25-count plastic tray. The tray is a two-piece design with snap-on lid and anti-static coated for ESD sensitive environments. This change is designed to enhance the ease of handling for our customers, easy removal of the individual hubdisk, and protection against potential damage due to long-term storage of hubdisk assemblies.

This change does not affect form, fit, or function of the final product.

Download PCN 6297

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Vancouver, Washington, USA, November 11, 2011 - US Digital introduces the EC35, a high performance 35mm commutation kit encoder ideal for BLDC motors. The EC35 is high resolution, has more accurate timing than Hall effect sensors, and provides simple assembly for OEM applications. The EC35 features include:

• A/B/Z Differential Outputs
• Frequency Response from DC to 1 MHz
• 500 - 10000 Cycles Per Revolution (CPR)
• 2000 - 40,000 quadrature states per revolution
• U/V/W commutation outputs (differential or open-collector)
• Fits shaft diameters from 0.197" (5mm) - 0.394" (10mm)

The EC35 is ideal for high volume, low cost, OEM motion control applications. "The EC35 encoder is being introduced into the BLDC motor motion control market to fill customer's needs for a cost competitive, simple to assemble, high performance commutation encoder that has the virtue of being manufactured in a vertically integrated, US encoder factory. This vertical integration enables the EC35 to be an extremely reliable product for supply chain management," states Jim Stevens, VP of Sales & Marketing.

Like US Digital's current encoder offerings, the EC35 will feature quick delivery, high reliability and competitive pricing. US Digital manufactures precision motion control products, including incremental and absolute encoders, inclinometers, interfaces, drives and more. For more information on the EC35, please visit www.usdigital.com/ec35.

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This document describes installing and using the T7 DLL on a PC running Windows using the RS232 port or the US Digital USB-232 USB interface.

T7 DLL User Guide.pdf (Version 2.1, 8/08/18, 652KB)

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1. Unplug any attached USB4 device.

2. From the Windows Start menu, run Add or remove programs and remove USB4 Device Software x.xx and USB4 Drivers X64 x.xx.

4. Once the software and drivers have been uninstalled, run the latest USB4Setup_x.xx.msi install program.

5. Plug in the USB cable to a USB4 device and ensure the power cord is also plugged in.

6. To confirm operation of the device, run the USB4_VBDemo program and ensure the Time Stamp field is updating.

To view the Cypress driver version used by the USB4 device, open the Device Manager and expand the Encoder Interface node and then double-click on the US Digital USB4 full functional node. Click on the Driver tab and view the Driver Version. The USB4 Drivers and Libraries READ MORE (Read me file) identifies the latest Cypress driver used. cyusb3.sys x.x.x.x  

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This document describes the host serial port communication protocol of the T7-1-232/T7-1-485.

T7 Communication User Guide.pdf (Version 1.7, 8/08/2018, 758 KB)

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The primary purpose for this change is to create a more durable and longer lasting solution compared to the previous stick on label solution. The E5 encoder covers will now have the US Digital logo, part number, lot code, and pin-outs laser marked onto the top surface.

Download PCN 1009

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Vancouver, WA - US Digital on Sept. 16, 2020 announced a new small encoder would make a big addition to its product offering.

The new E16 Micro Optical Kit Encoder has a 10mm bolt circle, fits 1.5mm (0.059″) and 2mm (0.079″) shafts and provides A, B and Index digital quadrature signals. It comes in a variety of resolutions ranging from 250/256 to 4,000/4,096 CPR.

It was designed to work in high volume, restricted space applications, particularly with small diameter stepper motors.

“We’re always listening to the needs of our customers for new product ideas and updates,” US Digital COO Neal Donowitz said. “A while ago one of our customers told us they were working on new, small diameter stepper motors and couldn’t find encoders that would work with them. We thought this was a great opportunity and started working on what would become the E16.”

After development, and internal testing US Digital sent beta units out to customers to be tested. The feedback was positive.

“The customers in our beta program were pleased with the encoders’ performance,” said US Digital Director of Customer Relations Steve Mathis. “One customer said they planned on using it for an upcoming project ‘very soon.’.”

The E16 encoder is connected using a 5-conductor, polarized, 0.8mm pitch connector. And is powered by a single +5V supply.

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As with all US Digital products, the E16 encoder is designed and manufactured in Vancouver, Washington USA and is backed with five-star customer service, same-day fulfillment and high reliability. It is now available for worldwide shipping starting today. Find more information at usdigital.com/E16.

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This notice is to inform our customers of a PCB design change that is being implemented for all of the E4T and S4T product lines. The new PCBs will improve overall product performance and enhance robustness of these product lines. The new PCBs can be identified by their blue color (instead of black) and have two mounting holes that mate with the base plate instead of one hole and one slot. This change has no impact on form, fit or function for either the E4T or S4T.

Download PCN 6466

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This PCN is a formal notification that US Digital is discontinuing the following bore sizes for the MAE3 product line:

• .079 (2mm)
• .091 (2.3mm)
• .098 (2.5mm)
• .156 (5/32")

If you have any questions or concerns about this PCN, please contact US Digital Customer Support at 1-800-736-0194 or email support@usdigital.com.

Download PCN 5549

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As part of our ongoing continuous improvement efforts, and in order to enhance both function and appearance, multiple improvements are being incorporated into a plastic component redesign.

The plastic base mounting holes and center hole counter-bore are increasing in size, and the four press-fit threaded inserts are being replaced with thread inserts that are over-molded into the base.

With exception of the features outlined below, the new parts are dimensionally equivalent and will fit within the same envelope of the previous parts.

Download PCN 6804

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The COMTool is an easy-to-use serial communication terminal program that transmits and receives bytes to practically any device connected to a PC's COM port. The COMTool User Guide describes how to install the software and provides instructions on using the available features.

COMTool User Guide.pdf (547 KB, 3/30/2023)

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