Question

What is the main disadvantage of a true r.m.s responding voltmeter?

(a) presence of transducer

(b) presence of thermocouple

(c) presence of transformer

(d) presence of oscillator

This question was addressed to me by my college director while I was bunking the class.

The above asked question is from True RMS Responding Voltmeter in chapter Electronic Instruments of Electrical Measurements

Answer 1

Right option is (b) presence of thermocouple

The explanation: Thermocouples have non-linear voltage and current characteristics. This is the major drawback of the true r.m.s responding voltmeter. This is overcome in some instruments by making use of an additional thermocouple in the same thermal environment.