Valve actuator stepping motor potentiometer circuit - has two additional wipers setting upper and lower limits of main tapping wiper

摘要

The servomotor for a valve actuator has a potentiometer circuit to provide a feedback signal from the first wiper (10a) with two additional wipers (10b, 10c) which are adjustable to give a predetermined voltage range to the potentiometer track. The two wipers (10b, 10c) are connected to the voltage supplies (12, 14). An operational amplifier for use as an impedance converter (16) is connected into the feedback signal line. As an alternative the two additional wipers are connected into a control circuit, the track ends being part of an amplifier feedback circuit and the positive inputs of the amplifiers being connected to a voltage divider chain between the supply rails (12, 14).