Example: An ohm meter has a meter movement along with a 100 µA full-scale deflection. An open circuit voltage at terminals ab is 24 V. An ohm meter is zeroed and then an unknown resistance Rx is measured, that generates quarter-scale deflection. Find Rx.
Solution:
First find Ro.
Ro = V/Im
= 24/1 x 10-6
Ro = 2.4 x 105? or 240K?
Then solve for Rx:
Rx = (1-D/D)Ro
=((1-1/4)/(1/4))(240)
=(3)(240)
Rx= 720 K?
Thus, quarter scale deflection of this ohm meter face would read 720 K.