Kevin,
I beg to differ with you. While the 20,000 ohms per volt meters were
great with vacuum tube circuits (except when attempting grid
measurements), they will cause significant loading of many solid state
circuits creating measurement errors.
A DMM or VTVM has an input impedance in the range of 10 to 11 megohms
and will not usually cause significant loading.
There were several good quality VOMs available in the 60s having a
20,000 ohm per volt specification. Simpson, Tripplett and Avometer are
among some of the names. Great VOMs, but their usefulness with solid
state circuits has diminished because of their relatively low impedance.
73,
Don W3FPR
KBG Luxford wrote:
I think the analog meter par excellence is the Avometer. Avo was a
British company that made avometers and tube testers. I think that
the company has been taken over by Megger. Anyway, the Avometer has a
sensitivity of 20,000 ohms per volt, a physically large scale with a
mirror backing to avoid parallax errors. Expensive new, but I got
mine from that watery place for about $100 plus the petrol for a 60
mile round trip to pick it up.
Incidentally, I would not be without my DMM and my AADE LC II meter
(for measuring capacitance and inductance.)
73
Kevin
VK3DAP / ZL2DAP
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