Question

Can a multi-meter measure a sine wave? (give reasons for your answer)

Answer 1

Hello there,

First let us see what are different parameters of a Sine wave

1) Peak value

2) RMS value, Average value

3) Frequency, Time period

4) Phase angle

Now, a good true RMS Multimeter can show RMS value of the sine wave accurately within certain range of frequencies. Unlike traditional MI instruments, multimeters have in built circuits consisting of rectifiers, potential dividers, amplifiers, averaging circuits etc. The input sinusoidal signal first gets rectified and then the average value of this signal is calculated using averaging circuit. A conversion factor(1.11 for sine wave) is multiplied to this average value to get RMS value. This value is then displayed on the screen. The conversion factor is different for different wave forms.

If the input signal is not a true sinusoidal signal or if it has harmonics, then the RMS value shown by multimeter may be inaccurate because it is calibrated for perfect sinusoidal signals.

This is how generally multimeters work, but to get accurate measurement more complicated measurement methods are used in certain multimeters which are expensive.

To measure other parameters such as frequency, phase etc we need oscilloscope.

Hope this explanation helps you!

Thank you.