MA3 Miniature Absolute Magnetic Shaft Encoder

Photos (4)
Mechanical Drawings (1)

MA3 Features

Miniature size (0.48 in. 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 - 1,024 positions per revolution, 1 kHz
12-bit PWM output - 4,096 positions per revolution, 250 Hz

See more info below

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MA3 Product Description

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 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 a higher resolution.

Three shaft torque options are available:

Default (-D): sleeve bushing with higher damping for human interface applications.
Ball bearing (-B): miniature precision ball bearings suitable for high-speed applications (1/8" diameter shaft only).
Light static drag (-N): sleeve bushing with lower damping for low-speed applications.

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 Specifications

ENVIRONMENTAL

PARAMETER	VALUE	UNITS
Operating Temperature	-40 to +125	C
Vibration (5Hz to 2kHz)	20	G
Electrostatic Discharge, Human Body Model MIL-STD-883E, Method 3015.7	± 2	kV

MECHANICAL

SPECIFICATION	SLEEVE BUSHING	BALL BEARING
Moment of Inertia	4.1 x 10^-6 oz-in-s²	4.1 x 10^-6 oz-in-s²
Max. Shaft Speed (1) (mechanical)	100 RPM	15000 RPM
Max. Acceleration	10000 rad/sec²	250000 rad/sec²
Max. Shaft Torque	0.5 in-oz (D-option) 0.3 in-oz (N-option)	0.05 in-oz (B-option)
Max. Shaft Loading	2 lb. dynamic 20 lb. static	1 lb.
Bearing Life (2)	> 1,000,000 revolutions	L₁₀ = (18.3/F_r)³ Where L₁₀ = bearing life in millions of revs, and F_r = radial shaft loading in pounds
Weight	0.46 oz.	0.37 oz.
Max. Shaft Runout	0.0015 in. T.I.R.	0.0015 in. T.I.R.
Technical Bulletin TB1001 - Shaft and Bore Tolerances		Download

(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

MOUNTING

PARAMETER	VALUE	UNITS
Hole Diameter	0.375 +0.005 / -0.0	in.
Panel Thickness	0.125 max.	in.
Panel Nut Max. Torque	20.0	in-lbs

MATERIALS

COMPONENT	MATERIAL	TORQUE OPTION(S)
Shaft	Stainless	Sleeve Bushing (-D and -N options)
Brass	Ball Bearing (-B option only)
Bushing	Brass	-

MAGNETIC FIELD CROSSTALK

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.

ELECTRICAL

PARAMETER	MIN.	TYP.	MAX.	UNITS
Power Supply	4.5	5.0	5.5	Volts
Supply Current		16	20	mA
Power-up Time			50	mS

ANALOG OUTPUT OPERATION

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.

PARAMETER	MIN.	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		0.046		Deg. RMS

(1) With no output load. See graphs below.
(2) Continuous short to +5V or ground will not damage the MA3.

PWM OUTPUT OPERATION

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_onand 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.

PARAMETER	MIN.	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

12-bit PWM:

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

If x <= 4094, then Position = x

If x = 4096, then Position = 4095

PIN-OUTS

ANALOG OUTPUT (MA3-A):

PIN	NAME	DESCRIPTION
1	5	+5VDC power
2	A	Analog output
3	G	Ground

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

PIN	NAME	DESCRIPTION
1	5	+5VDC power
2	P	PWM output
3	G	Ground

CABLES / CONNECTORS

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.

Additional Information

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.

Datasheets

MA3-Datasheet.pdf

Absolute Encoder Selector Guide

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