Resend.....to the list this time, sorry Luis

> Have you looked at Magnetoresitive products either as a complete current
> monitoring product or as a device strapped to wire carrying the current
>
> http://www.zetex.com/
>
> click on Semiconductor Products
> then either
>
> Power Management Discrete Components - Magnetic Sensors
> or
> Application Specific Standard Products - Current Monitors
>
> Regards
>
> Chris Carr
>
> > >
> > > I have an application where I need to monitor and
> > > digitize the current waveform output of an audio power
> > > amplifier into a subwoofer (speaker).
> > > Previously, I used a hall-effect based sensor, but for
> > > cost purposes (consumer product), it is impractical.
> > > So instead, I have decided to use a 1 milli-ohm
> > > current sense resistor. The problem now is creating an
> > > electrical interface to convert the instantaneous
> > > current (0 - 50 amps) into a proportional
> > > instantaneous voltage (0-2.5v). Since the audio output
> > > is not referrenced to ground, some type of
> > > differential circuit must be used. But although the
> > > voltage across the resistor will always be small, the
> > > voltage at each of the 2 resistor taps, with respect
> > > to ground can swing as high as much as +/-100 volts.
> > > Unfortunately most instrumentation op-amps that can
> > > handle such a high common-mode input voltage, are also
> > > quite expensive. In addition, a textbook differential
> > > op-amp circuit doesn't provide the needed accuracy,
> > > even with .1% resistors, since any component
> > > tollerance is multiplied by the gain of the circuit
> > > (50). I though it would be easy finding an interface
> > > circuit that would solve my problem, especially since
> > > almost every DMM must use something similar for DC
> > > current measurement. But I have had no luck. I would
> > > appreciate some advice, even better a schematic.
> > > Thanks
> > >
>
>

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