Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
Vibrating capacitor non contact field probe in feedback loop to create a voltage follower: https://www.monroe-electronics.com/ESD/pdf/244a_m.pdf Bruce > > On 23 March 2018 at 15:12 Neville Michiewrote: > > Improvise by holding a metal disk over an electronic balance and > measuring the force of attraction. > Calibrate it with a lower known voltage. > > cheers, > Neville Michie > > > > > > On 23 Mar 2018, at 12:58, Dr. David Kirkby > > wrote: > > > > On 23 March 2018 at 01:49, kc9ieq via volt-nuts > > 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 > > > > ___ > > 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.
Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
Improvise by holding a metal disk over an electronic balance and measuring the force of attraction. Calibrate it with a lower known voltage. cheers, Neville Michie > On 23 Mar 2018, at 12:58, Dr. David Kirkby> wrote: > > On 23 March 2018 at 01:49, kc9ieq via volt-nuts 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 > ___ > 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.
Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
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 Sent from my SMRTphone Original message From: "Dr. David Kirkby"Date: 3/22/18 8:58 PM (GMT-06:00) To: kc9ieq , Discussion of precise voltage measurement 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 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 ___ 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.
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-nutswrote: > 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 ___ 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.
Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
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 Sent from my SMRTphone Original message From: "Dr. David Kirkby"Date: 3/22/18 7:33 PM (GMT-06:00) To: Discussion of precise voltage measurement Subject: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms? 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.
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 01:07, Bob Albert via volt-nutswrote: > I found several electrostatic voltmeters on ebay. The brand I remember > is Sensitive Research. > Bob > So something like this? https://www.ebay.com/itm/Singer-ESD-7-Sensitive-Research-Electrostatic-Voltmeter-1500-Volt-Range/122976453378 1500 V would probably do. I must admit, I don't understand how these work. Do you need to have a power supply to balance the voltage? I can't see how taking almost no current can physically make a meter needle move, as that needs energy. I see some are contact, and some non-contact. It is 01:45 here, so I am just about to go asleep, but will read any replies later today. I would be interested in making a more modern version, but really don't know how. Dave ___ 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.
Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
How about using a high voltage probe that used to be commonly used to measure anode voltages of TV picture tubes. There were probes that had a KV meter built into the probe and there are ones that were used with VOM'S. Joe K3WRY In a message dated 3/22/2018 8:59:08 PM Eastern Standard Time, bruce.griffi...@xtra.co.nz writes: Electrostatic voltmeter? Either the classical version or the modern electronic variant perhaps? Bruce > > On 23 March 2018 at 13:33 "Dr. David Kirkby"> 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.
Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
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> 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 > 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.
Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
I found several electrostatic voltmeters on ebay. The brand I remember is Sensitive Research. Bob On Thursday, March 22, 2018, 6:00:39 PM PDT, Bob Albert via volt-nutswrote: 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 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.
Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
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 Kirkbywrote: 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.
Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
Electrostatic voltmeter? Either the classical version or the modern electronic variant perhaps? Bruce > > On 23 March 2018 at 13:33 "Dr. David Kirkby" >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] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
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.