MA3 Miniature Absolute Magnetic Shaft Encoder

(1) 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:

10-bit PWM:

n = 625200 / rpm

12-bit PWM / Analog:

n = 156600 / rpm 

(2) only valid with negligible axial shaft loading

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 the reported position through magnetic field cross-talk.

Analog 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.

(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.

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 t_on 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 t_on and t_off and calculating the angle from the duty cycle.

(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

12-bit PWM:

x = ((t _on * 4098) / (t _on+ t _off)) -1

If x <= 4094, then Position = x

If x = 4096, then Position = 4095

ANALOG OUTPUT (MA3-A):

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

3-PIN MICRO:

• 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.