At 10:08 AM 7/29/01 -0400, you wrote:

> The output will actually be
>proportional to the current and its frequency

Actually a current transformer (CT), if you terminate it in a low enough
resistance will be independent of the frequency over a wide range.

----   ||(----------------x-----------> input
 1t    ||) 500t         [Rl]
----   ||(------0v        |
                          0V

The single-turn primary is just a loop through the core (say a tape-wound
toroidal core). With a 500t secondary and a 10 ohm load resistor you
will have a 1V output for 50A input. By putting a back to back diodes
in there with the 10.0 Ohm in series with one to ground, you will get
a DC output of 1V at the cost of a slightly larger core.

To CT
(other lead to 0V)

-x-----|<|----- 0V
 |
 x-----|>|----x---------> low pass filter, 0-1V for 0-50A in the primary.
              |
             10.0
              |
             0V

The core material is determined by the upper frequency, the core size by
the lowest frequency of interest, required output burden, and the
required accuracy. Probably a 1" O.D. tape wound toroid would do it.

Best regards,

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