SOLUTION

A null method of measurement is a simple, accurate and widely used method that depends on an instrument reading being adjusted to read zero current only. The method assumes:

(i) If there is any deflection at all, then some current is flowing;

(ii) If there is no deflection, then no current flows (i.e. a null condition).

E.g of null detection method is DC potentiometer, Kelvin double bridge, AC potentiometer, Wheatstone bridge.