VOMs (WAS Re: SBC6120 (a build-it-yourself PDP-8 clone) grammer checked)

Scott Quinn compoobah at valleyimplants.com
Fri Jun 16 00:31:10 CDT 2006


> For many years I used an analogue VOM only. To be honest, it's rare that
>you need to make an accurate meashuremnt when repairing a classic
>computer (you want to know if the 5V line is pressent and correct, but if
>it's acutally 4.95V, things will still worl fine). Then I picked up a
>cheap Fluke 85. I use that almost exclusively now, but the analogue meter
>stays on my bench, it's better for osme things.

On this (semi) subject, I vividly remember for a while seeing a "solid state VTVM"
that had the extremely high input impedance of a VTVM/DMM + the good low-range
response with an analog output. Now, all I see are the "classic" passive VOMs.
What happened to the VTVMS? were they "not necessary"? I'd possibly be worried about
meter loading messing up some computer circuits with a passive VOM (10-20k vs 10M
meter resistance).

Scott






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