Shunt Type Ohmmeter

Shunt Type Ohmmeter Points : Shunt Type Ohmmeter The circuit diagram of a shunt type ohmmeter is shown. In this instrument a battery is connected in series with a D, Arsonval galvanometer and an adjustable resistor R_se. The resistance under test is connected across the terminals A and B in parallel to the meter. In this circuit it is necessary to provide a on-off switch in order to keep battery from running down when the instrument is not in use. When terminals A and B are shorted i.e. when R_x = 0, the meter current is zero, and if R is removed i.e. when R_x, the pointer rises on the scale and can be adjusted to the full scale point by proper selection of the Resistance R_se So this ohmmeter, accordingly has zero mark at the left and mark at the right of the scale which is just opposite to the series type ohmmeter.

The distribution of scale marking is almost linear in the lower part and it becomes progressively more crowded as R increases.

Half full scale reading will be when

R_h = R_se R_m/ R_se + R_m

This type of ohmmeter is particularly suited for measurement of low values of resistances.