[ARC5] Low Low Ohmeter

[Tom Lee]

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
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