Network for determining potentiometer settings in situ - tests the potentiometer voltages and gives a digital display

摘要

The test network is for finding potentiometer settings in an operating circuit-typically a control circuit-without the need for switching off or conducting a detailed examination. Typically, the gain of a PID controller might be set by means of a potentiometer, and the setting of this may require to be examined without interfering with the control system operation. The circuit (3) for doing this tests the voltage across the potentiometer at a particular instant and by means of suitable storage and comparator circuitry finds the potentiometer setting which it then displays in digital form. It achieves this with two sample and hold circuits (11, 12) constructed of linear feedback amplifiers and sampling switches (18, 19). The output of one of these is fed via a further amplifier (10') to an analogue digital converter (13) to a digital display unit (14).