[ARC5] Meter Calibration and HV probe

[brianclarke01 at optusnet.com.au]

The reason for the 1 M-Ohm in the probe was to give approximately the
same response to DC and AC - the 1.11 form factor of a sine wave comes
to mind. And the AC / DC switch was right on the probe to short out
the resistor.If you switched the resistor in and out, the difference
would be 10% not 1%, as hinted in your third paragraph.
73 de Brian, VK2GCE.

OnSat, 03 Aug 2013 21:58:03 -0000, Ken said:

 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

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