[sdiy] diy HV probe?

[The Peasant]

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
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>