[volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?

[kc9ieq]

I guess I don't see what the issue is.  No, impedance is not infinate when not nulled, but this is why V supply #2 Is adjustable by whatever convenient means.  Rough adjust, connect, adjust for null, measure.  Rinse and repeat.  If it were my project, I'd just run up an HV transformer on a variac, with a rectifier, cap, and probably some series R thrown at it to limit current through the meter.  Curious to know what the application is, if this will not work.  
Good luck with whatever solution you choose.  
Regards, Chris 


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-------- Original message --------From: "Dr. David Kirkby" <drkirkby at kirkbymicrowave.co.uk> Date: 3/22/18  8:58 PM  (GMT-06:00) To: kc9ieq <kc9ieq at yahoo.com>, Discussion of precise voltage measurement <volt-nuts at febo.com> Subject: Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms? 
On 23 March 2018 at 01:49, kc9ieq via volt-nuts <volt-nuts at febo.com> wrote:
How about using (or building) an additional 2kV power supply and a sensitive meter movement like a differential voltmeter, adjusting for/measuring the null?  Impedance at null will be theoretically infinate, current will be theoretically zero, and you can measure/monitor the voltage of your second supply directly with the probe/meter of your choice.  

Regards,Chris 

No, that will not work for me, as while the impedance at null is infinite, it is not when not nulled, and that will mess up the measurements. 

Absolute accuracy is not important. +/- 10% or even 20% would be okay. I want to measure a couple of voltages and compare them. As long as the meter reads the same with identical input voltages, that is fine. 

Dave