vtvm question??

[Gary L. Sanders]

The 1Meg resistor in the probe prevents dangerous high Voltage shorts if
the probe is carelessly disconnected while on a high Voltage. This
divider results in the meter having to be calibrated to compensate for
the .90909 loss. When a Hi Voltage probe is used, a 909Meg resistor is
used in the probe resulting in a 100:1 divider that is only off 1%. If
there is some leakage around the big resistor, such as sweat, oil, or
grime, then the accuracy is off in the right direction to get better.
--
Regards,
Gary L. Sanders, Staff Analog Eng., gsanders at csidaq.com
Celerity Systems, Inc. --- http://www.csidaq.com
Cupertino, CA USA (408) 873-1001 fx (408) 873-1397
Ultra Fast Acquisition & Data Generation Systems

Steve Lords wrote:

> greetings
>  does anybody know why heathkit on the
> im-13 vtvm put the extra 1 meg resistor in the
> probe and not in the unit,without the probe
> the vtvm is only 10 meg
>
> when reading articles about rf probes
> they mention the probe will work with
> 11 megohm vtvms however without the probe that
> comes with the im-13,the input is only 10 megohm
> which will affect the reading,
> maybe the 1 meg should be put into the rf probe
> when using the im-13...
> thanks
> steve
> wa7isl :)
>
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