If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Patrick wrote ...
hey Proud Mary... i got out my old 2 giga ohm, 1000:1 resistive voltage divider and connected it up too a 270vDC (+- 1.2 %)source then used a miliVolt meter to mearsure the low side but it wasnt stable it should have read 27mV but instead it would go down to 9mv and up to 41mv very slowly, no loose leads seemed to be the cause,i have no idea if its become and antenna or not? i need help. any ideas?
With only 135 nA bottlenecking through your 2G @ 270V, you'll get erratic performance alright, Paddy.
Firstly, the the input offset current of the DVM input device will become significant in the nA regime. Then the input of your meter should be considered as Rin parallelled by Cshunt, a combination which has a time constant, as Cshunt takes time to charge.
With only 135nA to be split between Rmeasure, Rin, the offset current and the charging of Cshunt, no wonder it takes time!
If you measure charging time t, then you'll be able to back calculate Cshunt, and see whether the answer looks plausible or not.
Leakage currents and input offset current will be signicant when contrasted with your miserable 135nA, and perhaps induced exogenous noise currents too, I would think, as you suggest, so you're most likely looking at a multifactorial error.
My advice: put an electrometer transconductance amplifier ahead of your DVM, but failing that, put some real voltage across it!
Added Much Later: Pity I didn't think of all this when designing my own voltage divider!
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
ok ill turn the dial up then, i forgot about burden current, and the input draw of the meter.
and ill be waiting to see your finished device, i would like to have another instrument and person to duplicate test result to see how predictable our stuff is, though the HV source would play a roll in this.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.