[ARC5] Low Low Ohmeter

[Tom Lee]

...and if you drive with a current source (e.g., with a power supply in 
current-limited mode), then the source resistance will approach 
infinity. Remember: A Buick in series with a current source is still a 
current source.

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/21/2020 03:35, Tom Lee wrote:
> The source resistance doesn't matter. You only need to know what 
> current you're applying. You measure the voltage, and Ohm's law does 
> the rest.
>
> Draw the circuit and you should be able to see it.
>
> --Tom
> -- 
> Prof. Thomas H. Lee
> Allen Ctr., Rm. 205
> 350 Jane Stanford Way
> Stanford University
> Stanford, CA 94305-4070
> http://www-smirc.stanford.edu
> On 1/21/2020 03:10, Bry Carling wrote:
>> What about "internal resistance of the source?"
>>
>> Sincerely,
>>
>> 73 - Brian "Bry" Carling, AF4K
>>
>>
>>
>>
>>
>> ------------------------------------------------------------------------
>> *From:* arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> 
>> on behalf of Dennis Monticelli <dennis.monticelli at gmail.com>
>> *Sent:* Thursday, January 16, 2020 13:06
>> *To:* Robert Eleazer <releazer at earthlink.net>
>> *Cc:* ARC-5 Maillist <arc5 at mailman.qth.net>
>> *Subject:* Re: [ARC5] Low Low Ohmeter
>> Just make your own Kelvin four-point ohmmeter.  Pass some serious 
>> current (say 1A) through the thing you're measuring and connect a 
>> voltmeter _inside of_ the atttached points of entry and exit of the 
>> current.  If 1A then each mV equals one milliohm.
>>
>> Dennis AE6C
>>
>> On Thu, Jan 16, 2020 at 9:56 AM Robert Eleazer 
>> <releazer at earthlink.net <mailto:releazer at earthlink.net>> wrote:
>>
>>     Recently I did some work on my airplane and struggled with
>>     measuring some resistances.  For example, a max of 0.1 ohms is
>>     Okay for one test while 3 ohms is not.
>>     I recall an article I think was in a ham magazine many years ago
>>     about how to build a Low Low Ohmmeter, designed to measure very
>>     low resistances.  Any of y'all recall that?
>>     Thanks!
>>     Wayne
>>     WB5WSV
>>     ______________________________________________________________
>>     ARC5 mailing list
>>     Home: http://mailman.qth.net/mailman/listinfo/arc5
>>     <http://mailman.qth.net/mailman/listinfo/arc5>
>>     Help: http://mailman.qth.net/mmfaq.htm
>>     <http://mailman.qth.net/mmfaq.htm>
>>     Post: mailto:ARC5 at mailman.qth.net <mailto:ARC5 at mailman.qth.net>
>>
>>     This list hosted by: http://www.qsl.net <http://www.qsl.net>
>>     Please help support this email list:
>>     https://www.qsl.net/donate.html <https://www.qsl.net/donate.html>
>>
>>
>> ______________________________________________________________
>> ARC5 mailing list
>> Home:http://mailman.qth.net/mailman/listinfo/arc5
>> Help:http://mailman.qth.net/mmfaq.htm
>> Post:mailto:ARC5 at mailman.qth.net
>>
>> This list hosted by:http://www.qsl.net
>> Please help support this email list:https://www.qsl.net/donate.html
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20200121/98e4cc72/attachment-0001.html>