This is a substitute for a battery. It is mains operation, and delivers a continuously variable current of 0 to 10 Amps. The current is controlled electronically. To start with null point determination, potentiometer should be in the minimum position. The current in the bridge is increased gradually. The magnitude of current supplied to the bridge depends upon the current capacity of the unknown resistance connected to the bridge. The current should be such that the test specimen does not get warmed up. just enough so as to give a sharp and fairly accurate null in the galvanometer. the output terminal of the D.C. source are connected to terminals marked “D.C. source “ on the bridge
