[AMPS] High Volt Fluke type probes

[Ian White, G3SEK]

Rich Measures wrote:
>>I would like to build a high voltage probe for my multimeter, any
>>suggestions or construction tips would be appreciated, as i do not
>>want to pay a few hundred bucks just for one or two measurements.
>>
>I found a 400M ohm high voltage MOF resistor at a swap meet.  I mounted 
>it in a long plastic box.  I used banana jacks for the in and out 
>connections.  I connected a precision R and a 20 turn trimpot across the 
>output of the divider.  Feeding 1000V in, I adjusted the output for 
>1.000V, which calibrated the multiplier box for x1000 .  I can measure up 
>to 30kVDC accurately with my Fluke DMM. 

I did almost exacty the same as Rich, except for using a long string of
small oxide film resistors (20 x 1.5M, 500V rating). 

The resistors are mounted inside a plastic tube (ball-pen case) with a
test prod on the end, and the other end of the pen case is glued into a
small plastic box that contains the trimpot. Use a 1W MOF safety
resistor in parallel with the trimpot.

Finally, connect a long flying lead with an alligator clip to the bottom
end of the voltage divider, and a two-wire lead terminating in plugs for
your DMM. Calibrate for 1/1000 division as Rich described, at the
highest voltage that your DMM will safely measure without the probe.

Whichever way you build it, make sure that the high-voltage end of the
probe is a LONG way away from the place where you hold it in your hand!

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.demon.co.uk/g3sek

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