"NSM" wrote in message newsHY5e.17073$vt1.97@edtnps90...

"Do Little Jr" wrote in message
...
"Asimov" wrote in
message ...

[.... ]

Rare VTVM's used a 100 Meg ohm input but the standard was 10 Meg.

Sorry Asimov, I find that questionable at best.
For even in 1950 - 60' any 'industrial workhorse' like the tube-type
HP 410B used 100 Meg ohms input as a standard input
It was only when the DVM came on the scene that most inputs
appeared to drop to 10 Meg Ohms.

It was a rare VTVM example that wasn't 11 Meg, 1 Meg in the DC probe.

Just for fun I looked up that old HP 410B. I still have one unit here, for
nothing in the modern digital world can replace it with just 'one' unit!

The HP410B input as listed in the manual (complete with circuit diagram)
was 122 Meg Ohm. Now, lets compare that to today's DVM, first of all,
where are the circuit diagrams? (true, one cannot find custom IC's anyway,
so it immediately becomes junk)

As for RF measurement does the modern DVM with a max reading of
100 KHz or if lucky maybe 2 MHz, really qualify or compare to that
old tube-job (RMS 1 - 350 Volts) that was stable to 700 MHz and
even useful to 1000 MHz? DVM still have some catching up to do...