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From: dsi@unccvax.UUCP (Dataspan Inc)
Newsgroups: net.analog
Subject: Re: AC current monitor
Message-ID: <167@unccvax.UUCP>
Date: Sun, 24-Mar-85 12:26:16 EST
Article-I.D.: unccvax.167
Posted: Sun Mar 24 12:26:16 1985
Date-Received: Thu, 28-Mar-85 00:53:35 EST
References: <5139@fortune.UUCP>
Organization: UNC-Charlotte
Lines: 14


     Use a current transformer * AROUND * the conductor in question, and
an op-amp with a diode connected in the feedback loop for the required
impedance transformation and rectification. If you want to get terribly
fancy, a comparator at the output of said integrated and rectified current
transformer will allow you to set the TTL "load trippage" level or whatever.

    The design of such transformers at AUDIO frequencies should be available
from any decent textbook on AC machines, etc. These kinds of current sampling
devices are often used at radio frequencies for sampling the magnitude and
phase of antenna current; etc. Of course, be sure to put whatever transformer
you make around just ONE conductor.

dya