MA4 Miniature Absolute Encoder Product Description The MA4 is a magnetic absolute encoder that reports the shaft position over 360° with no stops or gaps. This shafted encoder is available with an analog or a pulse width modulated (PWM) digital output. This is the new generation of the US Digital MA3 absolute encoder, magnetic.
Analog output provides a DC voltage that is proportional to the absolute shaft position with 12-bit resolution.
PWM output provides a pulse duty cycle that is proportional to the absolute shaft position. PWM output has 12-bit resolution with 2 different output frequency options.
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.
The MA4 is connected using a 3-pin latching, 1.25mm pitch polarized connector.
*There are three torque options for the 1/8 in. shaft and two options for the 1/4 in. and 6 mm shaft sizes.
Product Specifications
ENVIRONMENTAL
PARAMETER
VALUE
UNITS
Operating Temperature
-40 to +125
C
Vibration (10Hz to 2kHz, sinusoidal)
20
G
Shock (6 milliseconds, half-sine)
75
G
Electrostatic Discharge, IEC 61000-4-2
± 4
kV
MECHANICAL
SPECIFICATION
SLEEVE BUSHING
BALL BEARING
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)
0.05 in-oz (B-option)
Max. Shaft Loading
2 lb. dynamic
1 lb.
Bearing Life (2)
> 1000000 revolutions
L10 = (28.3/Fr )³L10 = bearing life in millions of revs, and Fr = radial shaft loading in pounds
Weight
0.42 oz.
0.31 oz.
Max. Shaft Runout
0.0015 in. T.I.R.
0.0015 in. T.I.R.
(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:
n = 400000 / 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)
Bushing
Brass
-
MAGNETIC FIELD CROSSTALK
The MA4 absolute encoder contains a small internal magnet that generates a weak magnetic field extending outside the housing of each encoder. If two MA4 units are mounted closer than 1 inch apart (shaft center to center distance), install a magnetic shield such as a thin steel plate between the two encoders. This prevents magnetic field cross-talk from causing small changes in the reported positions.
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
The analog output has 12-bit resolution. The analog output voltage is ratiometric to the power supply voltage, which is typically 5.0V. To prevent excessive jitter of the output at the 0 to 360 deg. transition point, 10-LSB of hysteresis is applied to the angle position at this point.
PARAMETER
MIN.
TYP.
MAX.
UNITS
Position Sampling Rate
6.667
kHz
Propagation Delay
286
μS
Output Noise (1-σ)
0.043
Deg. RMS
Max Output Voltage
V
Min Output Voltage
V
Capacitive Load
1000
pF
PWM OUTPUT OPERATION
The PWM duty cycle has 12-bit resolution. To measure the angular position accurately, calculate the position from the duty cycle (ton / (ton + toff )) instead of just measuring ton . This will cancel out the effect of the PWM frequency tolerance. To prevent excessive jitter of the output at the 0 to 360 deg. transition point, 10-LSB of hysteresis is applied to the angle position at this point.
PARAMETER
MIN.
TYP.
MAX.
UNITS
PWM Frequency
Hz
PWM Duty Cycle
2.942
97.058
%
Position Sampling Rate
6.667
kHz
Propagation Delay
286
μS
Output Noise (1-σ)
0.043
Deg. RMS
Output High Voltage
V
Output Low Voltage
V
Capacitive Load
1000
pF
.(1) PWM cycle time is 4351 internal clock periods. There are 4096 possible values of the duty cycle with a minimum value of (128/4351) and a maximum of (4223/4351).
PIN-OUTS
ANALOG OUTPUT (MA4-A):
PIN
NAME
DESCRIPTION
1
5
+5VDC power
2
A
Analog output
3
G
Ground
PWM OUTPUT (MA4-H, MA4-L):
PIN
NAME
DESCRIPTION
1
5
+5VDC power
2
P
PWM output
3
G
Ground
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.
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