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Old 12th Jul 2018, 10:00 pm   #3
Radio Wrangler
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Default Re: VCM163 Calibration Question

The EA113 uses FET-input amplification and an input attenuator of very high resistance. It drives a diode rectifier and so responds to peak voltage, not RMS, but it is scaled to show what the RMS voltage would be on the assumption that the waveform is a sinusoid.

Without the careful language, it'll read RMS on sinewaves, and it'll be wrong on anything else.

With some of the waveforms floating around in valve testers (halfwave rectified and things like that) meter readings are very wrong, though the sinusoid applied to the grid for gm measurements ought to be sensible. Other voltages in the machine may have values where you do need the cited meter to get the same amount of wrongness

I checked my EA113 some time ago and found the accuracy excellent on DC and sines. On AC, it seemed OK up to 200kHz. Checked against the Datron calibrators in HP's standards lab. With 10mV FSD on its most sensitive range, it's a useful audio millivoltmeter, and the 10mV DC range is most unusual on an analogue meter.

David
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