[TriEmbed] Measure uA

[John Wettroth]

Yes- you are correct Brian, I didn't understand Paul's question.  All a shunt is a resistor that drops a voltage across it that you measure- V/R is amps.  This is what ammeters do.  If you have a sufficiently sensitive meter, the R can be pretty small.  The EEVBLOG uCurrent gadget, has a tiny resistance - a tenth of an ohm and a very low offset amp with a gain of 100 amp IIRC. (A Maxim Op-Amp that I helped define in my time there).  This keeps the "burden voltage", the portion of the voltage dropped across the shunt in order to measure current very low.  Dave Jones is really big on low burden voltage measurement because it does get in the way in some cases.  He even makes a nice little multimeter with his microcurrent built in to minimize burden voltage

I have remind myself that not everyone is an analog guy- its one of my main skills.  I don't do FPGA's and a lot of other facets that others find easy to do.


Regards,
John M. Wettroth
(984) 329-5420 (home)
(919) 349-9875 (cell) 
-----Original Message-----
From: TriEmbed <triembed-bounces at triembed.org> On Behalf Of Brian via TriEmbed
Sent: Thursday, August 26, 2021 10:55 AM
To: triembed at triembed.org
Subject: Re: [TriEmbed] Measure uA

> *From:*The MacDougals <paulmacd at acm.org>
> *Sent:* Thursday, August 26, 2021 9:25 AM
> *To:* jwet at mindspring.com
> *Subject:* RE: [TriEmbed] Measure uA
> 
> I assume you mean using a 330 ohm as a shunt resistor in series with the 
> load (not across the load).
> 
> Measure the voltage between the R and the load and use Ohm’s law to 
> calculate the resistance of the load and then calculate amps.

Just measure the voltage across the resistor and calculate the current 
through it with Ohm's law; no need to calculate the load's equivalent 
resistance.

-B

_______________________________________________
Triangle, NC Embedded Computing mailing list

To post message: TriEmbed at triembed.org
List info: http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
TriEmbed web site: http://TriEmbed.org
To unsubscribe, click link and send a blank message: mailto:unsubscribe-TriEmbed at bitser.net?subject=unsubscribe