SPECIFICATIONS
Power: » +15 V dc, 150 mA from integrator
Temperature: » -20 to 55° C (-4 to 130° F)
Input: » bi-directional shaft rotation
» 0.3 to 75 rpm operating input
Output: » open collector sinking output, max. 25 mA at 5 V dc
» 2048 pulses / revolution
» 10 to 2,560 Hz operating output
Enclosure: » general purpose
» material : - standard : aluminum
- optional : 304 stainless steel
Cable: » Belden 8770, 3 wire shielded, 18 AWG or equivalent
» max run 305 m (1000 ft)
REFERENCE
Associated Milltronics integrator:
CompuScale III
BW100
BW500
GENERAL
The MD-2000A speed sensor is used to monitor the speed of a weighfeeder or low speed belt conveyor ( see
input specification ). The sensor, coupled to a pulley shaft, converts the rotation of its input shaft into an
encoded speed signal. The speed signal is transmitted to the integrating electronics for use in computing the
rate of material flow.
CIRCUIT OPERATION
The speed sensor is made up of a main shaft rotating in a bearing assembly fixed to the enclosure. The shaft
turns an encoder which produces two square wave quadrature (90° electrically out of phase) outputs which
are fed to the speed sensor board to determine direction of rotation as well as the speed of rotation.
Power is provided by the integrating device. The 15 V dc supply is regulated to 5 V dc for use by the encoder
circuit and output drive transistors of the speed sensor board.
As the shaft rotates, the two quadrature square waves from the 2048 pulse per revolution encoder are
converted into clockwise (CW) and counter clockwise (CCW) square wave output signals by the intermediate
counter logic. When the shaft rotates in the CW direction, the logic produces pulses at the CW output and the
CCW output is disabled. When the shaft rotates in the CCW direction, the logic produces pulses at the CCW
output and the CW output is disabled.
The logic diagrams detail the operation of the electronics for both clockwise and counter clockwise output
generation. The speed sensor is immune to external vibration that would cause the encoder to oscillate 1/8 of
a revolution or less.
PL-361 1
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