The Model 425A DC Microvolt-Ammeter is an extremely sensitive measuring device which measures voltages from 1 microvolt to 1 volt and currents from 1 picoampere to 3 milliamperes. An input resistance of 1 megohm on all voltage ranges minimizes errors due to circuit loading. The Model 425A can make measurements in circuits which are off ground potential, for the chassis and input circuit may be isolated from the cabinet. The Model 425A provides an output which will drive either potentiometer or galvanometer recorders. It will deliver up to 1milliampere at 1 volt .