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 #58
Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317
Lately the DMM has been acting really odd giving messed up readings, so I thought replacing the battery was a good idea. Well when I opened it out half of a resistor :O. I guess last time I took it apart the resistor must have bent againt the case and cracked ( the resistors are standing up in the air on the board, not laying down) Well it looks to be a green black black yellow space green resistor. Which should be a 5M .5% tolerance resistor. Closest I can find is on mouser a 5M 1% tolerance for $1.50. Would that work or does anyone have some better ideas? Thanks, Mike
Edit: heres a 55cent one that might work What do you think? Mike
Ugh now i just noticed that place requires a 25 $ min order so no luck there :(
Registered Member #32
Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549
wrote ...
You could also use several resistors in series to get the value you want.
To give some detail to what I think EVR's saying, two %5 tolerance resistors in series should have better than 5% tolerance.
If you assume Gaussian distribution with the proper mean (which you can't really in practice), the tolerance is improved by a factor of 1.414 (root two). In general, using n resistors improves the tolerance by a factor of root n, if you have a normal distribution with the right mean.
A case where this might fail is if the production line had a whole batch with a 1kohm bias. Then the whole batch will be out, but still possibly within tolerance.
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
Resisters are often built out of two materials: one with a positive temperature coefficient, and the other with a negative temperature coefficient. When combined and laser corrected (always dead on at 20’C) they should in theory give almost consistent performance over varying conditions. Generally I never use anything above 1% for most equipment (unless things like NiChrome power resisters are needed etc.)
Sometimes on old equipment if the device is part of a divider bridge it may be critical that they are matched and aged the same. Personally I would try to replace it with the identical part as its instrumentation.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Well, actually what i meant about seriesing resistors, was you can get whatever value you need. Instead of a 0.1% 10k resistor, you might use a "measured" resistor of 9.99k and a "measured" resistor of 9.8 ohms to get a 0.1% 10k resistor.
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.
A slight problem with my new Digital Multimeter..
