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I would like to know what instruments or methods can be used to obtain true RMS readings from DC biased or unidirectional a pulsating current
Here are some examples.

Finding the true RMS current of a load driven from half or full wave rectified source with no smoothing capacitors. The voltage comes to zero every 1/120 second, but the current is unidirectional.

DC voltage with a significant amount of ripple, such as AC rectified with a full bridge, and smoothing capacitor sized to give a ripple of 30v p-p. With the meter in "AC true RMS mode" the AC coupling rejects the DC bias, but in DC mode, it wouldn't properly calculate the ripple component.

True RMS voltage of thyristor DC motor drive (such as elevator motors)

Any idea?

I would like to know what instruments or methods can be used to obtain true RMS readings from DC biased or unidirectional a pulsating current

Finding the true RMS current of a load driven from half or full wave rectified source with no smoothing capacitors. The voltage comes to zero every 1/120 second, but the current is unidirectional.

DC voltage with a significant amount of ripple, such as AC rectified with a full bridge, and smoothing capacitor sized to give a ripple of 30v p-p. With the meter in "AC true RMS mode" the AC coupling rejects the DC bias, but in DC mode, it wouldn't properly calculate the ripple component.

True RMS voltage of thyristor DC motor drive (such as elevator motors)

Any idea?