Interlock System PLC Analog Scales
for Telescope Drive Motor Voltage and Current
October 4, 2000
The Allen-Bradley Programmable Logic Controller (PLC) analog input modules are configured to read
VDC inputs in engineering units of 1 mV per count for the motor amplifier voltage and current read
The motor amplifiers are capable of producing +/-60 volts at +/-20 amps. To scale the amplifier outputs
to the PLC input module, the motor
amplifier internally reduces the signals sent to the PLC for voltage by a factor of 6 and current by a
factor of 2.
As an example:
if the motor voltage reading is 4500, the actual motor voltage is
4500/1000*6 = 27 volts.
if the motor current reading is 6000, the actual motor current is
6000/1000*2 = 12 amps.