Hi Sanjay, sorry I don't know where you were trained,
but I was taught that to get good reliable measurements
of "active" signals you need to allow 2% to 5% of the
total for the measurement equipment. You mention a
sense resistor of 1 milliohm, this is ridiculous. I have
a good milliohm meter, and any electrical connnection will
give you a few milliohms resistance. Your sense resistor
will have two of these connections.

My suggestion for good accuracy is to sacrifice 5% of
your total power to the subwoofer load and use that
to measure the current waveform, then of course allow
for that 5% in your calcs. Don't ever expect accurate
results from a 1 milliohm resistor!!
:o)
-Roman



> ----- Original Message -----
> From: "Sanjay Punjab" <piclistguy@YAHOO.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Sunday, July 29, 2001 7:07 AM
> Subject: [EE]: Having difficulty interfacing a current sense resistor to
> create a proportional voltage
>
> > 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...

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