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High Voltage Test Equipment




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From:  Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent:  Thursday, March 05, 1998 11:57 PM
To:  Tesla List
Subject:  Re: High Voltage Test Equipment

Hi Jim,

> From:  Homer Lea [SMTP:HomerLea-at-aol-dot-com]
> Sent:  Thursday, March 05, 1998 2:05 AM
> To:  tesla-at-pupman-dot-com
> Subject:  Re: High Voltage Test Equipment
> 
> In a message dated 98-03-05 00:46:30 EST, you write:
> 
> > From:  terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
> >  Sent:  Wednesday, March 04, 1998 5:22 PM
> >  To:  Tesla List
> >  Subject:  Re: High Voltage Test Equipment
> >  
> >  Jim,
> >          Having just gone through the HV voltage divider design zoo with my
> >  equipment, I have one caution.  At 60Hz the long string of resistors will
> >  work fine.  However, if you wan't to measure voltage waveforms at say
> 200KHz
> >  the frequency response will be bad.  I am now persuing vacuum molded epoxy
> >  encapsulation to get small size, reasonable power dissipation, and high
> >  frequency response.  Your oil bath should do the same just a little more
> >  "fluid" :-)  Do try to make it very compact.
> >  
> >          Terry
> >  
>   Terry:
> I just sent off new specs:
> -------------
> post script: I ended up getting 400 15meg resistors. They are small (1/8)
> watt. My plan is to string them in series, put them in a Tygon tube and fill
> with oil. I will coil up the tube so it isn't 20 feet long. I assume the
> inductive reactance will be zilch compared to the 6 billion ohms of resistors
> The resistors will be in series with a  50 or 100 ua meter connected through a
> full wave rectifier bridge. Does anyone know how much voltage I can put across
> each resistor?? I am hoping for at least 500 v each and dreaming of 1000 v.
> ------------------
> A 20 foot tube it not small, even coiled up. Is that going to screw me up? My
> original thought was simply to measure the output voltage of coils rather than
> wave forms.
> jim heagy

I agree with Antonio. you will have to add compensation capacitors to 
a string like that because of shunt capacitances. I had to do exactly 
this in a much smaller HV probe.

Malcolm