A multiplied-deflection A-C potentiometer

The power required for the operation of an indicating instrument frequently makes its use prohibitive because of the disturbing effect it has on the circuit being measured. If the measurement is in a d-c circuit, the difficulty is overcome readily by using a d-c potentiometer. In a-c measurements, the indicating instruments have a much greater disturbing effect on the circuit, and the use of an a-c potentiometer is very desirable. Furthermore, a-c potentiometers are very useful for measuring power in circuits where the power is too small to be measured with a dynamometer wattmeter.