SHenion wrote:

RMS = Root Means Squared, an average power of an AC signal. Many meters measure peak voltage and display an approximate RMS value. Not accurate for distorted or non-sine AC signals.

RMS is the value displayed when you measure current (or voltage) with a regular panel meter.

Technically. RMS is the heating value of an AC waveform.

If you apply 10 volts RMS to a non-inductive load (a carbon resistor), its temperature will rise to exactly the same value as it would if you applied 10 volts DC.

The 232 (and 249) measure AC by rectifying it and filtering it, just as you would do in a power supply. The voltage across the filter capacitor is the peak voltage since there is essentially no load on that system.

The meter measures that peak voltage, then displays it on a meter scale that shows its equivalent RMS voltage. That is accurate for a true sinewave and for many other waveforms of similar shape.

This whole exercise came about when televisions became popular. The video signal in a TV set is a complex signal with a known peak-to-peak amplitude. Meters such as the 232 were designed to measure that waveform and display a meaningful value.

Note there are two pairs of scales with the black scales labeled

**DC-RMS** and the red scales labeled

**P-P**, the latter meaning Peak-to-Peak. At any point, the upper and lower voltages are equivalent.

- Leigh