In article <35b9a4f0.90061240@news.giganews.com>,
  none@this.address (Cyber Bandit ¥ßûÿ) wrote:
> Probelm:
>
> I am trying to sense a current in an AC line (which is run through a
> circuit board)  The current is from 20ma > 8A, 120VAC @ 60Hz.
>
> To make matters worse, it is on a different phase of power than the
> circuit board is running on.  Any help would be appreciated, oh, BTW,
> I must keep the cost at about $1.50 for all parts, so that rules out
> the current Xfmr.
>

Hi,
May be you can try this circuit :

  Rs  I  ----------- Power line
-----+----/\/\/\/\-+------------<---------------  |  |	R1  |/	| 
+------------+-----/\/\/\------|/  ---------------------------------  |  |/ 
\  +  -  /  |  \  /  \	\  /  /  R2  \	/  \  \  /  /  \/  |  |  | 
+---------------------	Vo  |  <----------------------|

You can calculate Rs, R1, R2 according to your current and your Amp-Op.

Regards,
--------
Michael A. Purwoadi
Group for Instrumentation and Control Technology

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