Measuring AC signal with a digital multimeter

[verpies]

If the meter's manual states "averaging" then it is not very likely that the marketing people would write that instead of boasting about the TrueRMS feature which requires an expensive multiplier such as the Gilbert cell.

[ayeaye]

I maybe figured out how it measures in the AC range. I think it has to be some simple algorithm, it doesn't do anything fancy. But it doesn't bother to measure values below zero, it only measures values above zero, assuming that values below zero are a mirror image, like in a perfect sine.

I also measured square waves with different duty cycles. In the DC range they were perfectly the average with the given duty cycle. But in the AC range it appeared to be the peak value, multiplied by how much the duty cycle was greater than 50%. That is, when it was 25%, the values were 0.5 times the peak value, and when it was 75%, it was 1.5 times peak value.

By that i guess what it does in the AC range is, it calculates the squares of the values above zero, multiplies each square by two, then adds them all and divides by the number of all measured values, then takes square root of it. By testing it with more complex signals, it could be found out whether this is indeed what it does. Who does it may post the results here.