Re: high voltage measurement w/ divider

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <dhmccauley-at-spacecatlighting-dot-com>

HV dividers are much more than just resistors.  There is a large
compensation network of both capacitors and resistors in a good high voltage
divider.
I recently designed a 45kV high voltage divider (10000:1) and will post the
schematic tomorrow.  This should help you in any design you might have.

Dan




 > Hey all,
 >
 > I was wanting to build a voltage divider out of some spare 10
 > meg resistors that I had laying around to safely measure the
 > charge voltage of my 200 uFD, 10 kV energy discharge cap bank
 > for my can crusher/quarter shrinker assembly. I was wondering
 > if I could accurately measure the known fraction of the total
 > voltage by placing 10 of these resistors in series and measur-
 > ing 1/10 of the total voltage across just one of the resistors?
 > I know this principle works because of Ohm's law and all, but
 > what my real question is would the 100 megs be too much resis-
 > tance to get an accurate and reliable reading on my Sperry DVM?
 > I think most DVMs have at least 20 kOhms /volt deflection so
 > it seems that measuring up to 1000 volts (1/10 of the 10 kV)
 > should be ok since 20 megs (20 K X 1000 volts) is greater than
 > the 10 meg for each resistor. BTW, these are the Digikey 10 meg
 > resistors that many of you are using as bleeders for your MMCs.
 >
 > Also, I think these are 1/2 watt resistors and if my math is
 > right, they should be dissapating 1 watt when the caps are
 > charged to the full 10 kV (10*4 V/10*8 Ohms= 10*-4 amps or
 > 0.1 mA and therefore 10 kV X 0.1 mA = 1 watt. I think this
 > doubling of their wattage rating on such an intermittent ba-
 > sis should be ok?
 >
 > Thanks for any help,
 > David Rieben
 >
 >
 >
 >
 >