How to measure resistors below 1R - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th June 2005, 10:48 AM   #1
diyAudio Member
 
Join Date: Jun 2004
Location: HKSAR
Default How to measure resistors below 1R

Hi

It might seem nuts. I never measure the resistors below 1R. It seems that the DVM or moving coil meter (that I had ) are unable to measure such. Do I need any special meter for this?
  Reply With Quote
Old 16th June 2005, 11:00 AM   #2
masfe is offline masfe  Spain
diyAudio Member
 
Join Date: Mar 2004
Location: Elorz
Look at this: http://www.comunidadelectronicos.com...os/med-res.htm

In spanish.

good bye

José Ramón
  Reply With Quote
Old 16th June 2005, 11:34 AM   #3
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
The best way to measure them is either to use a four-point system (where a known constant current is passed through the resistor, and the voltage drop is measured) or to put a bunch of them in a series string, run a voltage through the string, then measure the voltage drop across each resistor. The latter method is most suitable for matching, rather than getting an absolute value.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 16th June 2005, 12:06 PM   #4
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
you can also use a Wheatstone bridge which you'll find in most high school physics labs --

since EBay is now taken up more by dealers than garage sales it is getting trickier to score a bargain on an HP3468 or HP3478 -- but good 5.5 digit meters from Fluke, Racal Dana, Keithley still abound. RLC bridges tend to be "clunky" but can be very, very acurate and comparatively inexpensive.
  Reply With Quote
Old 16th June 2005, 12:34 PM   #5
diyAudio Member
 
cocolino's Avatar
 
Join Date: May 2002
Location: Bavaria (south of veal sausage equator)
Quote:
originally posted by SY
The best way to measure them is either to use a four-point system (where a known constant current is passed through the resistor, and the voltage drop is measured)...........
Commercial 4-point resistance measuring equipment can be quite expensive.
You can DIY such a thing relatively cheap.


The following photo is taken from my DIY constant-current 4-point measuring adapter. It is used together with a conventional DVM in the 200mV DC measuring range.

3 precision resistors (the 2 lengthy blue things and the smaller black one aside), 1 FET, 2 batteries, 1 switch, 1 OP-Amp and that is it almost.

It is made according (with modified PCB) an ELEKTOR puplication.
Works fine!
If You`re interested I can look up which ELEKTOR publication it was.
Attached Images
File Type: jpg mikroohm_01.jpg (74.6 KB, 365 views)
__________________
Christoph
STEAL the BEST - INVENT the REST
  Reply With Quote
Old 16th June 2005, 12:36 PM   #6
diyAudio Member
 
cocolino's Avatar
 
Join Date: May 2002
Location: Bavaria (south of veal sausage equator)
another pic from the front plate
Attached Images
File Type: jpg mikroohm_02.jpg (32.5 KB, 306 views)
__________________
Christoph
STEAL the BEST - INVENT the REST
  Reply With Quote
Old 19th June 2005, 04:02 PM   #7
cpemma is offline cpemma  United Kingdom
diyAudio Member
 
Join Date: Jul 2003
Location: S Yorkshire OK
I've used a Kelvin Bridge (a Tinsley, but much older model than the one shown) for very low resistance measurement (microhms or less). Ran off a small lead-acid battery, so I guess current was fairly high compared to modern ones.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
FS: Resistors, LM3886, speaker terminal, variable resistors, switches and rectifiers chris-man Swap Meet 1 28th May 2009 11:47 AM
how to measure and match source resistors 0,22-1ohm? elviukai Pass Labs 14 7th May 2006 04:15 PM
Speaker Workshop - using "Measure -> Passive Components" to measure ESR ? percy Multi-Way 0 12th March 2006 09:18 PM
SMD resistors measure badly after soldering? motherone Parts 18 4th March 2005 03:57 AM


New To Site? Need Help?

All times are GMT. The time now is 07:10 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2