DMM with Nanoamp Current Resolution - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

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 29th September 2014, 09:31 PM   #1
diyAudio Member
 
Join Date: Feb 2014
Question DMM with Nanoamp Current Resolution

I am working on guitar effect boxes and would like a DMM that has resolution to the nanoamp for measuring base and collector current being fed to transistors. I am often finding current values in the 100 to 200 nanoamp range and need to be able to evaluate them to something finer than .1 microamp in order to determine proper gain values. Would prefer something not out of hobbyist's price range. Bench or hand held is not an important factor.

If anyone knows of any particular meters that would fit this bill or can point me to source material your help is greatly appreciated.
  Reply With Quote
Old 29th September 2014, 10:30 PM   #2
diyAudio Member
 
Kiriakos's Avatar
 
Join Date: Jul 2014
Location: In from of my workbench
Just of curiosity I need to ask, what are you using today in such measurements?
No one can offer a suggestion about a better meter with out been aware of what you use now.
  Reply With Quote
Old 29th September 2014, 10:47 PM   #3
diyAudio Member
 
Join Date: Feb 2014
I currently use a pair of handheld Extech MN36 meters, one tied into the base current and one tied into the collector current. The best resolution I get is to 0.1uA. Unfortunately, that is not fine grained enough for the very low current values I am encountering, i.e. between 0.1uA and 0.2uA.
  Reply With Quote
Old 29th September 2014, 11:18 PM   #4
diyAudio Member
 
Join Date: Nov 2005
Resolution below .1uA is not available in common handheld meters because it requires either too high of a shunt resistance to be practical or an extra DC precise amplifier with tons of gain. If you want to make a nanoammeter yourself, those are still the options.
  Reply With Quote
Old 29th September 2014, 11:54 PM   #5
diyAudio Member
 
PedroDaGr8's Avatar
 
Join Date: Dec 2009
Location: San Diego, CA
You don't need a new multimeter, you just need this:

The uCurrent Gold. It's designed and sold by Dave Jones at EEVBlog and is a current to voltage converter. It has a nA, uA and mA range. Not only will it allow you to measure nA currents, it also has a much lower burden voltage than pretty much all multimeters. This is especially important with dealing with nA currents. You basically use this in conjunction with your regular multimeter on the mV range and the reading in mV is the current in mA.
  Reply With Quote
Old 30th September 2014, 07:02 AM   #6
diyAudio Member
 
Kiriakos's Avatar
 
Join Date: Jul 2014
Location: In from of my workbench
Quote:
Originally Posted by PedroDaGr8 View Post
You don't need a new multimeter, you just need this:
The pile of complains is large by the ones who got it.
I do not have to offer an alternative solution, by neither I would trust, something which is not accepted for verification by any calibration lab.
  Reply With Quote
Old 30th September 2014, 07:14 AM   #7
nr12 is offline nr12  Germany
diyAudio Member
 
Join Date: Mar 2011
Location: Schwaben
Try a Keithley 2001.
Range Resolution
200 uA 10 pA
2 mA 100 pA
20 mA 1 nA
200 mA 10 nA
2 A 100 nA

Maybe a Keithley 2000 will be ok also?
  Reply With Quote
Old 30th September 2014, 07:54 AM   #8
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Measuring low currents? -- read up on the application notes at Linear Tech, and Bob Pease (RIP) "What's all this fempto-Ampere stuff anyway?" which is archived on the Texas Instruments site.

My Fluke 177 has a DC millivolt range, but below 5mv it gets a bit wonky. You'll need a very low noise, low bias current instrumentation amplifier, perhaps an OPA4140 arranged as an inamp with a gain of 10,000, perhaps you can get away with a shunt resistor of as much as 100R -- then 10nA will read 10mV. For this low current, low noise measurement you will need to use shielded twisted pair, run the INAMP off 9V batteries which are decoupled with 100nF ceramic caps, etc., etc. It can be done for less than $10.

EDIT - specifically look for application note #105 of Linear's website.

Last edited by jackinnj; 30th September 2014 at 07:59 AM.
  Reply With Quote
Old 30th September 2014, 07:59 AM   #9
nr12 is offline nr12  Germany
diyAudio Member
 
Join Date: Mar 2011
Location: Schwaben
A Fluke 8050a will give you a resolution of 0.01 A (range 200 A).
  Reply With Quote
Old 30th September 2014, 12:47 PM   #10
oshifis is offline oshifis  Hungary
diyAudio Member
 
Join Date: Mar 2004
Location: Budapest, Hungary
The gain of a properly designed transistor circuit is determined by external components. You can measure the health and approximate current amplification factor of a transistor by a Beta-tester, part of most hand held DMMs.
  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
dmm hfe back Solid State 5 29th October 2012 08:07 AM
Cheap DMM that does L and C? AudioLapDance Equipment & Tools 15 6th August 2012 04:29 PM
Looking for a Decent DMM quickbrownfox Parts 4 18th October 2007 07:41 PM
DMM's jleaman Parts 13 15th August 2006 05:14 AM
DMM, what accuracy should i be looking for waben Everything Else 14 23rd March 2004 07:04 PM


New To Site? Need Help?

All times are GMT. The time now is 03:17 PM.


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