[sdiy] diy HV probe?

[Ken Stone]

I will admit I did make my own, and I did know what I was doing - however it
was used on only 3kV (deadly enough) and it was "hard wired" into the
circuit I was testing. 

If you need to ask how to make one, you really shouldn't be trying, because
even with a 100% correct answer on how to do it, you may take a short cut,
either accidently or deliberately, the result being fatal.

Ken

>I strongly recommend that hobbyists NOT diy their own high voltage probes. Yes 
>it can be done fairly easily, and would probably work just fine, but unless
you 
>really know what you are doing you are risking your safety and possibly your 
>life. There are many special considerations when working with high voltage
that 
>don't normally apply at lower voltages, and they will bite you when you least 
>expect it. I personally have many years of professional experience with high 
>voltage electronics, and I diy virtually everything I own, but yet I will not 
>make my own HV probe. There is no way that you will find me on the other
end of 
>some tape-coated straw full of resistors with 30KV on the other end!!!
>
>Of course maybe I'm just a little paranoid, but I'd sure hate to lose any 
>members of this list over a $60 tool. :-(((  Mr Hendry, what do you think?
>
>Take care,
>Doug
>______________________
>The Electronic Peasant
>
>www.electronicpeasant.com
>
>
>Quoting "R. D. Davis" <rdd at rddavis.org>:
>
>> Quothe Mark Romberg, from writings of Sun, Jun 27, 2004 at 02:44:50AM
>> -0500:
>> > i have an o-scope thats on the fritz, so i find myself in need of an HV 
>> > probe, as my multimeter can only handle 600V.  but, i dont want to 
>> > spend more than about $10 for something im only rarely going to use, 
>> > and the commercial HV probes seem to be far above that.  would it be 
>> > safe/possible to build an HV probe?
>> 
>> Yes... IIRC, hypothetically spealking, you'll need a plastic drinking
>> straw, heat shrink tubing, about ten 10M-ohm 1/2W resistors, soldered
>> closely together in series, and a roll of electical tape to wrap the
>> heat-shrink tubing covered straw with, multiple times.  As you've
>> probably guessed, the resistors go inside the straw.  For the sake of
>> thriftyness, perhaps it's possible to use a very short portion of a
>> resistor lead can be used as the probe tip.  I used heat-shrink tubing
>> around the resistors as well for added insulation... they just barely
>> fit in the straw that way.  There are a few examples of doing
>> something like this to be found on the WWW.  Do this at your own risk
>> and don't skimp on the layers of insulation... mistakes can zap you
>> into a permanent otherworldly existence!  This is not offered as
>> advice, but as a hypothetical example of measuring high voltage at a
>> low cost.  It's also possibly not a good idea to use it to measure the
>> output of the multiplier with, but rather the lower (3KV to 5KV or so)
>> outputs of the HV supply with before the multiplier; either way,
>> playing with high voltages can be dangerous.
>> 
>> All that having been said, you might be able to do with out building
>> that.  Are there any signs of HV being present, such as a staticky
>> sound when powering the 'scope on or off, or will a piece of paper
>> stick to the CRT surface?  What about the low voltage circuitry in the
>> power supply, such as the HV oscillator?  Any signs of life there?
>> 
>> Good luck!
>> 
>> -- 
>> Copyright (C) 2004 R.D. Davis The difference between humans & other animals:
>> an
>> All Rights Reserved            unnatural belief that we're above Nature &
>> her
>> www.rddavis.org 410-744-4900    other creatures, using dogma to justify
>> such
>> I support Addams Family values!  beliefs and to justify much human cruelty.
>> 
>
>
>
_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au or sasami at cgs.synth.net
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>