NULL BALANCE INDICATING AND CONTROL APPARATUS AND PHASE SENSITIVE PULSE RESPONSIVE CIRCUITS FOR USE THEREIN

In apparatus and circuits especially suitable in instrumentation for indication and control of nuclear power plant coolant systems, a bridge contains in a sensing arm a resistance thermometer or a differential transformer. The output of the bridge is supplied to a servo amplifier which feeds a servo motor which is operatively connected to a bridge arm to utilize an error signal to rebalance the bridge and reduce the error signal to zero, and at the same time supply an input to a counting or indicating device. Unique circuits provide control set points, isolation being provided between the indication and control functions. New and improved phase sensitive monostable multivibrator transistor circuits are employed.