MA3 Miniature Absolute Magnetic Shaft Encoder

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Overview

  • Patent pending
  • Miniature size (0.48" diameter)
  • Non-contacting magnetic single chip sensing technology
  • -40C to 125C. operating temperature range
  • 10-bit Analog output - 2.6 kHz sampling rate
  • 10-bit PWM output - 1024 positions per revolution, 1 kHz
  • 12-bit PWM output - 4096 positions per revolution, 250 Hz

The MA3 is a miniature rotary absolute shaft encoder that reports the shaft position over 360° with no stops or gaps. The MA3 is available with an analog or a pulse width modulated (PWM) digital...

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Product Specifications

ParameterValue
Operating Temperature -40C to +125C
Storage Temperature -55C to +125C
Humidity, Non-condensing 5% to 85%
Vibration (5Hz to 2kHz) 20 G.
Electrostatic Discharge, Human Body Model ± 2 kV
SpecificationSleeve BushingBall Bearing
Moment of Inertia 4.1 x 10^-6 oz-in-s² 4.1 x 10^-6 oz-in-s²
Angular Accuracy @ 25C
  12-bit PWM
  10-bit PWM
  10-bit Analog

± 0.5 deg.
± 0.75 deg.
± 1.0 deg.

± 0.5 deg.
± 0.75 deg.
± 1.0 deg.
Max. Shaft Speed (1) 100 rpm 15000 rpm
Max. Acceleration 10000 rad/sec² 250000 rad/sec²
Max. Shaft Torque 0.5 ± 0.2 in-oz (D - torque option)
0.3 in-oz (N - torque option)
0.05 in-oz
Max. Shaft Loading 2 lb. dynamic
20 lb. static
1 lb.
Bearing Life (2) > 1,000,000 revolutions L10 = (18.3/Fr)³ †
Where L10 = bearing life in millions of revs, and
Fr = radial shaft loading in pounds
Weight 0.46 oz. 0.37 oz.
Max. Shaft Total Indicated Runout 0.0015 in. 0.0015 in.
Technical Bulletin TB1001 - Shaft and Bore Tolerances Download

(1) When a pulley, gear, or friction wheel drives the shaft, the Ball Bearing option is recommended instead of the Sleeve Bushing.  The chip that decodes position uses sampled data. There will be fewer readings per revolution as the speed increases.  The formula for number of readings per revolution is given by:

n = (60 / (rpm * 96 usec)) 

(2) only valid with negligible axial shaft loading

ParameterValue
Hole Diameter 0.375" +0.005 / -0.0
Panel Thickness 0.125" max.
Panel Nut Max. Torque 20 in.-lbs.
ParameterDimension
Shaft Stainless
Bushing Brass

The MA3 absolute encoder contains a small internal magnet, mounted on the end of the shaft that generates a weak magnetic field extending outside the housing of each encoder. If two MA3 units are to be installed closer than 1 inch apart (measured between the center of both shafts), a magnetic shield, such as a small steel plate should be installed in between to prevent one encoder from causing small changes in reported position through magnetic field cross-talk.

ParameterMin.Typ.Max.Units
Power Supply 4.5 5.0 5.5 Volts
Supply Current - 16 20 mA
Power-up Time - - 50 mS

10bit-analog.gifAnalog output is only available in 10-bit resolution. The analog output voltage is ratiometric to the power supply voltage and will typically swing within 15 millivolts of the power supply rails with no output load. This non-linearity near the rails increases with increasing output loads. For this reason, the output load impedance should be ≥ 4.7kΩ and less than 100pF. The graphs below show the typical output levels for various output loads when powered by a 5V supply.


ParameterMin.Typ.Max.Units
Position Sampling Rate 2.35 2.61 2.87 kHz
Propagation Delay - - 384 μS
Analog Output Voltage Maximum (1) - 4.987 - Volts
Analog Output Voltage Minimum (1) - 0.015 - Volts
Output Short Circuit Sink Current (2) - 32 50 mA
Output Short Circuit Source Current (2) - 36 66 mA
Output Noise (2) 160 220 490 µVrms
Output Transition Noise (3) - 0.03 - Deg. RMS

(1) With no output load. See graphs below.
(2) Continuous short to +5V or ground will not damage the MA3.
(3) Transition noise is the jitter in the transition between two adjacent position steps.


pullup.gif

pulldown.gif

The magnetic sensor chip in the MA3 has an on-chip RC oscillator which is factory trimmed to 5% accuracy at room temperature (10% over full temperature range). This tolerance influences the sampling rate and pulse period of the PWM output. If only the PWM pulse width ton and the nominal pulse period is used to measure the angle, the resulting value also has this timing tolerance. However, this tolerance can be cancelled by measuring both ton and toff and calculating the angle from the duty cycle.

ParameterMin.Typ.Max.Units
PWM Frequency (-40C to 125C)
  10-bit
  12-bit

0.877
220

0.975
244

1.072
268

kHz
Hz
Minimum Pulse Width
  10-bit
  12-bit

0.95
0.95

1.00
1.00

1.05
1.05

μS
μS
Maximum Pulse Width
  10-bit
  12-bit

974
3892

1025
4097

1076
4302

μS
μS
Internal Sampling Rate
  10-bit
  12-bit

9.38
2.35

10.42
2.61

11.46
2.87

kHz
kHz
Propagation
  10-bit
  12-bit

-
-

-
-

48
384

μS
μS
Output Transition Noise, 12-bit version (1)   0.03   Deg. RMS 
Output Transition Noise, 10-bit version (1)   0.12   Deg. RMS
Output High Voltage (V OH: @4mA Source) (2) Vcc -0.5 - - V
Output Low Voltage (V OL: @4mA Sink) (2) - - 0.4 V

(1) Transition noise is the jitter in the transition between two adjacent position steps.
(2) Continuous short to +5V or ground will not damage the MA3.


10-bit PWM:


x = ((t on * 1026) / (t on+ t off)) -1

If x <= 1022, then Position = x

If x = 1024, then Position = 1023

10bit-pwm-rev3.jpg

12-bit PWM:


x = ((t on * 4098) / (t on+ t off)) -1

If x <= 4094, then Position = x

If x = 4096, then Position = 4095

 12bit-pwm-rev3.jpg

Analog Output (MA3-A):

PinNameDescription
1 5 +5VDC power
2 A Analog output
3 G Ground

PWM Output (MA3-P10, MA3-P12):

PinNameDescription
1 5 +5VDC power
2 A PWM output
3 G Ground

3-pin Micro:

Part #Description
CON-MIC3 Connector
CA-MIC3-W3-NC Connector on one end with 3 wires
CA-MIC3-SH-NC Connector on one end with shielded cable
  • Connector built into encoder: Molex# 53398-0371.
  • Mating connector housing: Molex# 51021-0300.
  • Mating connector individual crimp-on pins: Molex# 50079-8100.
  • To install connector pins, a special crimp tool is needed: Molex# 50079.

Product Description

Restriction of Hazardous Substances

The MA3 is a miniature rotary absolute shaft encoder that reports the shaft position over 360° with no stops or gaps. The MA3 is available with an analog or a pulse width modulated (PWM) digital output.  

Analog output provides an analog voltage that is proportional to the absolute shaft position. Analog output is only available in 10-bit resolution.

PWM output provides a pulse width duty cycle that is proportional to the absolute shaft position. PWM output is available in 10-bit and 12-bit resolutions. While the accuracy is the same for both encoders, the 12-bit version provides higher resolution.

Three shaft torque versions are available. The standard torque version has a sleeve bushing lubricated with a viscous motion control gel to provide torque and feel that is ideal for front panel human interface applications.

The no torque added option has a sleeve bushing and a low viscosity lubricant (that does not intentionally add torque) for low RPM applications where a small amount of torque is acceptable.

The ball bearing version uses miniature precision ball bearings that are suitable for high speed and ultra low torque applications. The shaft diameter for ball bearing version option is 1/8" rather than 1/4".

Connecting to the MA3 is simple. The 3-pin high retention snap-in 1.25mm pitch polarized connector provides for +5V, output, and ground.

Product Notes
  • Cables and connectors are not included and must be ordered separately.
  • US Digital warrants its products against defects in materials and workmanship for two years. See complete warranty for details.

Cable/connector assembly not included and must be ordered separately.

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