Re: High Voltage Probe Instability - Part II

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Sparktron01@xxxxxxxxxxx 

David

Another thought just dawned on me.  Copper has a +TCR of 0.3937% per deg C. 
Maybe wire heating as well adding to stacking error?

FWIW

Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA. USA


> 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
>
>