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 #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I have a vintage 5v AC volt meter for a project. I am measuring the voltage drop across about a 300 ohm resistor. There is an AC and DC component on the resistor, but I am only interested in measuring the AC part. When I use a digital ohm meter with a high impedance I can measure 3 volts. When I connect the vintage meter I read only 2v. When I put the digital meter across simultaneously with the the vintage meter I can see that there voltage is actually under 1v. I guess this is due to the lower impedance of the vintage meter.
In the past I used a capacitor to pass the AC component, rectified the signal and used a vintage DC meter.
Is there anything I can due to fix this problem without using a high impedance meter so the AC meter correlates with the digital meter?
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Do you know anything more about the meter? There are several different types of AC meter available long ago.
The old meter is going to read RMS, but you could convert it to peak readings in a lot of different ways. 1. You could play with a rectifier circuit and see if the meter will respond to DC. This probably won't work very well, but its a lazy approach, and worth a shot because it only takes maybe 10 minutes to rig up. It would sacrifice your input impedance though. 2. An amplifier or buffer 3. A small transformer.
There's probably a few more ways to do it too. This is for only one frequency right? Because if its for a range of frequencies then that is another problem.
What I would point out though is that since your measured value has dropped using a very low impedance meter, the older one, the problem may not be your meter, it might be that your source is being loaded down too much by the meter.
What is the internal resistance of your meter?
3V across 300R, so that's 10mA RMS, 14mA p-p, and the reading with the old meter is ~1V, so its dropping 2V @10mA, I'm getting 202R as the parallel resistance, approximately.
I get about 618R for the meter resistance, which is pretty low compared to your 3M or 10M input impedance of the modern meter.
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.
Problem with Vintage AC meter
