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Strange note in old DMM User Manual

I got an AEMC model 9100 at a swap meet. Google found nothing on it, but I called the AEMC number and they dug into the paper files and scanned a User Manual for me.

The instructions for DC voltage had the following: [quote] V DC When the power supply resistance level is high, it is necessary to adjust the reading according to the following formula: Actual voltage (in V) = display voltage (V) x (1 + power source resistance (ohms)) / 10 [\quote]

There must be a mistake: its input impedance is 10M, so the "power supply resistance" would have to be of that order to affect the reading, yes? They must mean a source resistance in M. And then greater than 10M.

Or am I just confused?

BTW - the meter is very nicely made. It's in their "Bouncer" line & the case is a thick rubbery plastic. Made to bounce? Age unknown, but PCB's are hand laid out & it uses a Maxim ICL7136 LCD driver that dates from 1996.

Reply to
Bob Engelhardt
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Many of the tube radios have resistors of 1 to 2 megohms in the circuit. That could throw off the measurements by a bit. It all depends on how accurate you need to be. Some of the older schematics had several voltages shown on them. It depends on if a 1000 ohn/volt or 20,000 ohm/volt or a VTVM which usually was 10 meg input impedance.

Reply to
Ralph Mowery

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