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Re: Homemade Voltage Divider
Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
At 12:45 PM 1/27/2006, Tesla list wrote:
Original poster: "James Zimmerschied" <zimtesla@xxxxxxx>
I am pondering a way to reliably measure 10 KVDC
across the terminals of (2) 100 µFd energy dis-
charge caps Original poster: "David Rieben"
David
Richard Hull showed the use of a NST is reverse
to measure high voltages. This might be bulky but reliable.
Jim Zimmerschied
But for DC, you need some sort of resistive divider.
How accurate do you need to be? 1% is fairly easy to get with good design.
Do you care about transient response? If not,
Buy yourself a bunch of 1 -10 Meg 2 Watt
resistors and build a 1000:1 divider. Figure
500V per resistor to keep the dissipation to a
minimum, so you need, say, 30 resistors in
series. You want the dissipation low so that the
heating doesn't change the value. Say you're
using 1 Meg resistors, you'd have 30 in series,
for 30 Meg, and a 30 kohm resistor at the bottom,
across which you'd put your volt meter. In
practice, you'd use a 50 k ten turn pot, and adjust it to calibrate.
500V across 1 meg is 0.5 mA and will dissipate 0.25 W.
Even better would be to use 5.6 Meg or 10
Meg.. At 10 Meg, each resistor would only
dissipate 25 mW, and heating would be
negligible. The load resistor would be
150k-300k, so the several meg input impedance of
the typical meter wouldn't load it all that much,
but if you hooked a 1 Meg scope input across it, you would have a problem.