Original poster: Sparktron01@xxxxxxxxxxx
Steve, David
Error term on my OHVM oil immersed divider network with increasing voltage
followed a square law relationship. Absolute error terms (below 25kV
rms) was < 0.4%. At 50kV rms (70kV BIL pk), error term was ~
1.2%. Dielectric polarization of oil was my take on root cause of error
term, more plausible with error term square law relationship with applied
voltage observed...
Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA. USA
> Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx>
>
> David,
>
> I had a similar problem with a high voltage divider. Very mysterous. I
> finally decided the cause was corona that was ionizing the air around the
> string of resistors and in effect adding some parallel resistance, thus
> making the reading creep up. I put the string of resistors in some vinyl
> tubing and that cured the problem, at least for me. You could try taking
> the cover off your probe so that air circulates around the divider
> components and see if that reduces the problem. If so, then suspect some
> sort of ionization is happening. Perhaps your probe is supposed to be
> insulated with oil, and the oil is no longer there??
> --Steve
> ----- Original Message -----
> From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Monday, February 07, 2005 8:29 AM
> Subject: High Voltage Probe Instability
>
>
> > Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
> >
> > Hi all,
> >
> >
> > I have a question that I was hoping that some of you would have
> > some insight on. I have been trying to measure the output voltage
> > of my x-ray transformers with 1000:1 HV probe that I have. I mea-
> > sure the input voltage while carefully controlling it with a variac
> > and, at the same time, measure the output of one of the HV term-
> > inals to ground and thereby obtain a ratio for the output/input
> > voltage so I can have a pretty close approximaton of the output
> > of the transformer. Sounds simple enough but the problem that I
> > am having is that the high output voltage measured through the
> > HV probe keeps slowly but steadily climbing while the input re-
> > mains relatively constant. For instance, with an 80 volt input,
> > the HV output initially reads around 28,400 volts but after around
> > 10 minutes of constant measurement, the HV output has crept
> > up past 30,000 volts, at least according to my HV probe/DVM
> > combo. Of course, all measurements are taking with no load
> > on the transformer. Is my measurement equipment defective or
> > is this a normal phenomena? Should I wait for the output mea-
> > surement to reach as high as it will go and go with that as an
> > accurate measure or should I take the first initial measurement
> > as the true measure of the voltage? Could the resistor of the
> > 1000:1 probe be heating up and causing the instabiltiy of the
> > reading? Any comments are welcome.
> >
> > David Rieben
> >
> >
> >
> >
>
>