The part I struggle with is “make one” as T ohm meters are ridiculously sensitive to things like fingerprints, for example. I had a hard time just putting cables together that had the particular… I was going to say insulation, but it was more than that, basically everything is important and specific when you are dealing with T ohm meters. Setting aside the stupid tri-bnc connector on most of them.
How about just using a voltage divider with a standard electrometer? I’m sure you thought of that though. I like playing around with my Keithley 616 as you can show the kids how electrostatics work. Regards, Jerry > On Mar 22, 2018, at 6:00 PM, Bob Albert via volt-nuts <volt-nuts@febo.com> > wrote: > > What about an electrostatic voltmeter? Those have been around for decades > and draw zero static current. You didn't indicate how accurate your > measurement needs to be. I am trying to recall the maker of the unit, I think > ESI but not sure. > They were somewhat popular in the 1950s as I recall and there should be some > around, gathering dust and mold, in storage places. They were large, which > is a benefit because they had a long scale with good resolution. > Bob > On Thursday, March 22, 2018, 5:33:28 PM PDT, Dr. David Kirkby > <drkir...@kirkbymicrowave.co.uk> wrote: > > I want to measure a high voltage, but put minimal load on the circuit. > Looking at the Keithley electrometers, the input resistance is at least 200 > T ohms, but they tend to have a maximum of 200 V FSD. > > A 2000 V source, and a 200 T ohm resistor gives a current of 10 pA, which > itself is easy to measure. But one can't buy 200 T ohm resistors. I looked > at RS in the UK, and the highest value resistor I could find is 1 T ohm, > and they are £163 each (around $200). > > Maybe fabricating ones own resistor is possible, but I suspect there's a > better way. Keithely manage to keep a 200 T ohm resistance on the 200 mV > range, and there's no way that can be measured with an ammeter, which would > require an ammeter with a full scale deflection of 1 fA, which is much > smaller than the 2 pA FSD on its most sensitive range. > > Any thoughts? > > Dr David Kirkby Ph.D C.Eng MIET > Kirkby Microwave Ltd > Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD, > Essex, CM3 6DT, United Kingdom. > Registered in England and Wales as company number 08914892 > http://www.kirkbymicrowave.co.uk/ > Tel 01621-680100 / +44 1621-680100 > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
