Question

An average responding rectifier type electronic ac voltmeter has its scale calibrated in terms of the rms value of a sine wave. If a square wave voltage of peak amplitude of 100 V is measured using this voltmeter, what will be the reading indicated by the meter?
1. 111 V
2. 100 V
3. 90.09 V
4. 70.7 V

Answer 1

Correct Answer - Option 1 : 111 V

Concept:

When an average responding rectifier type electronic ac voltmeter has its scale calibrated in terms of the rms value of a sine wave, then reading indicated by the meter is given by

V_rms = 1.11 V_avg

Where, V_avg = Average value of given voltage

Calculation:

Given that,

Peak value of square wave voltage, V_m = 100 volt

We know that for square waveform

V_m = V_rms = V_avg

∴ Average value of square wave voltage, V_avg = 100 volts

∴ Reading indicated by the meter can be calculated as

V_rms = 1.11 × 100 = 111 Volts