[ARC5] Meter Calibration and HV probe

[Kenneth G. Gordon]

On 3 Aug 2013 at 16:38, D C _Mac_ Macdonald wrote:

> Somewhere in the recesses of my memory I seem to remember that the 11
> Megohm rating of so many VTVMs "back in the day" consisted of 10 Meg
> in the instrument and another 1 Meg resistor in the probe!

You're absolutely correct, Mac. I have two Heathkit VTVMs here, which I use regularly, and 
both are set up the same way: 10 meg in the instrument and 1 meg in the probe.

Someone some time ago published on the web a modification to include the 1 meg inside the 
instrument instead of in the probe. However, that turned out to not be such a hot idea after 
all.

Also, I have two Heathkit HV probes here (up to 30 KV) and a Simpson version. I have used 
those with a couple of different versions of DMMs and the voltage readout was always very 
close to the readout when connected to a Simpson 260. In fact, it was close enough that I 
never bothered about "calibrating" it any closer. The difference between 10KV and 10.1 KV 
isn't enough to worry about at that level.

Ken W7EKB