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From: ron@brl-tgr.ARPA (Ron Natalie <ron>)
Newsgroups: net.analog
Subject: Re: AC current monitor
Message-ID: <9482@brl-tgr.ARPA>
Date: Mon, 25-Mar-85 16:12:43 EST
Article-I.D.: brl-tgr.9482
Posted: Mon Mar 25 16:12:43 1985
Date-Received: Fri, 29-Mar-85 01:39:19 EST
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Organization: Ballistic Research Lab
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>      I have a tough question here.  I need a circuit to indicate
> the presence of a load on an AC line. Wait, it gets more difficult.
> The load can vary from 100 watts to 1000 watts, and the output 
> signal must be a TTL level.  Also, it cannot drop the 110 volt
> AC line by very much.  One more thing: the ground of whatever 
> circuit is used will be tied to the neutral line of the AC, so complete 
> isolation is not possible.
> 
How about building a current sensor by running (one side of) the cord
through a coil.  You could then sample the output with a comparator
circuit.  This is how my PDU in the computer room works.

-Ron