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High Voltage Test Equipment
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From: terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
Sent: Thursday, March 05, 1998 11:21 PM
To: Tesla List
Subject: Re: High Voltage Test Equipment
Jim,
At 07:11 PM 3/5/98 -0600, you wrote:
>
>----------
>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
>
>
Hi Jim,
My latest voltage divider is 1 inch long! I thing you and I will
have the length extremes covered :-)) 1/8th watt surface mount resistors
are typically rated for 400V max. However, in oil, I would push that to
4KV! (I used to build the damn things).
You will have a little trouble getting the resistor string in the
tubing but I can help there. Using air (pressure or vacuum) blow (or suck)
a fuzzy string through the tubing. Once through, you can pull the resistors
into the tube using the string and some TLC.
I would use an op-amp circuit to amplify and rectify the signal from
the resistors. Common bridge rectifiers have voltage drops and minimum
currents that might mess with your system. I would suggest 1N34 diodes
(Radio Shack 276-1123) if you use a rectifier. They will give good
performance (I hope). If the resitors are thick film surface mount types I
would use them in a straight line. If not, talk to Jim Lux. He knows much
more than I about this.
I would not commit all the resistors to the first test. 6G ohms is
high for any voltage. Fewer resistors may work better. If you could
explain a little more about what you want to measure and how I could give
suggestions on this.
It will be very interesting to see what you come up with and how it
works. I have not heard of anyone actually trying this. Much will be learned.
Terry