vtvm question??

[Alan Dean Martin]

Additionally the 1 meg resistor helps isolate the effect of cable
capacitance from the circuit under test. This permits testing grid d.c.
voltages, for example, which might otherwise become erroneous reading if the
cable capacitance were connected without the 1 megohm isolation.

Alan Martin
Linear Technology Corporation

Gary L. Sanders wrote:

> 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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