Re: Heathkit V-7AUK ac readings
The V7AU uses an AC coupled peak to peak responding rectifier for its AC ranges, so for non sinusoidal signals (eg square waves) the p-p scales will be valid, and are the ones to use.
The RMS scales are, as Laurence points out, 2.8 times lower than the p-p scales and are equally valid where the signal being measured is a sine wave. Since the majority of the usage of this type of instrument will be with sine waves, Heathkit chose to make the RMS AC scales and range switch legends match the DC scales as the default scales and legends.
It’s sometimes useful to have a meter such as the V7AU with a p-p response available for measuring non-sinusoidal waveforms such as measuring p-p ripple on a DC supply rail, the amplitude of a square wave (with or without a DC offset), or tasks such as comparing the output of a solid state audio amplifier on music peaks to its supply voltage. For these tasks, an average responding meter such as an AVO would give misleading results.
Stuart
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