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Re: high voltage probes
Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net>
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
Sent: Sunday, September 28, 2003 9:57 AM
Subject: Re: high voltage probes
> Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org>
> This sounds like a good idea. I do have a 50's vintage tube scope that I
> view as expendable. I realize that "ground" is not really at ground
> potential in a Marx. I suppose I could make two and connect them to A and
> B to make a poor-man's differential probe.... No, I do not have a UPS nor
> access to one that is viewed as expendable.
Anyone doing serious HV work might consider lashing together an inexpensive
floating AC supply for just this sort of thing. Go get a deepcycle battery
and one of those inexpensive 200-300W inverters. <$100 all told, and yes,
fairly non-optimized for a number of reasons, but cheaper than your basic
battery operated scope. Sears has a selection of batteries. I suppose one
could plug stuff into one of those transient suppressing plug strips
advertising $75,000 replacement guarantee, and work your way through their
mill when everything dies...
> Calibration is an issue, since I would rather like to figure out how a
> rectifier was overvolted when only 20kV should have been across it. We've
> also lost two capacitors to what looks like overvoltage despite never
> getting above about 65% of their voltage rating (22kV).
Calibration is fairly straightforward. All you need is a suitable source to
calibrate from. Most dividers are voltage independent.. that is, if you
build a 50:1 divider and calibrate it at 110V, it will work pretty much the
same at 11kV..
> Would a resistor divider with some 10Meg 1/4W resistors (I have plenty)
> work in place of the HV probe?
Sure... string them together appropriately... Watch the power dissipation,