Re: HV voltage divider

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Richard,
            I'd also like to add to the notes below that if you are 
using a very high value of resistance in a divider chain, expect less 
than accurate results if the frequency is much more than mains. In 
effect, you end up with a low pass filter due to stray capacitance 
and it doesn't take much capacitance to end up with a capacitive 
reactance significantly lower than the resistance in the circuit. A 
decent HV probe will have some equalizing capacitances across the 
resistors. Also, do not expect an accurate result if it is TC output 
voltage you are attempting to measure. Anything hooked to the top 
terminal and connected with wires back to a test instrument is going 
to have a significant impact on the readings. For the measurements to 
verify the tssp modelling, quite different techniques were used.

Regards,
Malcolm
 
 
On 1 Mar 2002, at 16:28, Tesla list wrote:

> Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<davep-at-quik-dot-com>
> 
> Tesla list wrote:
>  
> > Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <jimlux-at-earthlink-dot-net>
>  
> > Exactly how you'd do it....
> >Is the meter impedance really 10 Meg, or is it 11Meg?...
> 
> 	Concur.
> 	with one minor comment:
> 	Suggest checking the power rating of the high meg resistor.
> 	(yes.  The resistance is high, so the currents low, BUT THE
> 	Voltages high.  Also look at the sparkover possibilities
> 	'along' the multiplier R.  (One such probe i ahd worked the
> 	resistor in liquid freon...)  If the high r resistor fails,
> 	or sparks over, the voltmeter is toast....
> 
> > You can always calibrate it with a known source...
>  
> > Tesla list wrote:
> 
> > > Original poster: "Richard Williams by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <richardwwilliams-at-earthlink-dot-net>
> 
> > > I have a 990meg ohm resistor salvaged from a HV DC probe whose
> >>meter was shot.  Can I add a resistor in series, 10 meg ohm?, to
> >>ground to measure HV? Haven't tried it since I'm leary of inflicting
> >>damage to my digital meter since I've never done this before. Input
> >>impedence of the meter at the 700vac range is 10meg so would that
> >>"look" like a 5 meg resistor overall?
> 
> 	best
> 	dwp
> 
> 
> 
>