Question

The value indicated by electrical measuring instrument is (average value or rms value)

Answer 1

Answer:

rms value........... .....

Answer 2

Answer:

There are digital and analog meters.

For analog meters, RMS is often simulated by using some averaging and marking a meter face with the equivalent RMS value assuming that the input is a sinusoid. THis give inaccurate readings if the waveform is significantly not a sinusoid, like a square or triangle waveform. However, in meters used to measure AC Mains powered equipment the waveforms from power line driven sources will be sinusoidal.

It is also possible to make true RMS analog meters where the signal is processed through a RMS reading circuit and then displayed on a linear marked meter face.

For digital meters, you have the same thing, the reading is averaged and the units scaled to read the correct RMS for sinusoids. This works fine for powerline related circuits in which all waveforms come from the AC mains which are dependably sinusoids.

You can also have true RMS digital meters; in this case there are a couple of options - one the analog signal is run through an analog RMS converter and then measured by a A/D and displayed.

The other is a fast sampling A/D; a multiplicity of samples are taken within a cycle of AC, then the N samples are mathematically processed through the RMS algorithm (Square root of 1/N times the sum of the squares) and then displayed.