On Sun, 29 Jul 2001, Olin Lathrop wrote:

> One way is to float a regular amp with one end of the current sense
> resistor.  This would require a separate small power transformer to make the
> floating supply voltages.  This floating section would digitize the signal
> and pass back the result to the rest of the world via opto isolators.

Agree ! But you don't need to digitize the signal, there are some simple
methods of using a pair of optocouplers and one or two operational
amplifiers (both in the same package ) so what you've got is a floated
analogic signal proportinal with the input current, ready to be measured
with an AD tehnique ( sigma-delta, comparator or standard ad ) from
microcontroller ( if you have one...)
But the second method Olin proposed is better and is well known in
switching power supplies world. ( using a curent sense transformer )
Vasile

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