A firm I consult for makes current transformers for metering applications,
give me the spec. and I will see if they can do anything.

----- Original Message -----
From: Alan B. Pearce <A.B.Pearce@RL.AC.UK>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, July 31, 2001 9:49 AM
Subject: Re: [EE]: (Followup) Having difficulty interfacing a current
senseresistor to create a proportional voltage


> >1. Use a 1:1 transformer to isolate the voltage across
> >the low-ohm resistor (current sensor), from the
> >interfacing analog circuitry. On the secondary side,
> >the voltage can be referenced to ground, making it
> >quite easy to get reasonable accuracy out of an
> >inverting op-amp circuit with .1% resistors.
> > This will work, since I am only concerned with AC
> >current. The problem is finding a 1:1 transformer with
> >truly accurate winding ratios (within 1%). Or else, I
> >will have to perform some type of testing in each unit
> >during manufacturing and come up with a normalization
> >look-up table in software.
>
> Use a Bifilar wound transformer. I would also put the resistor on the
> secondary, but that decision would also depend on getting a transformer
with
> suitable core and windings.
>
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