Seems complicated to me! I'd be concerned about the stability of the
differential amplifier (if you're trying to build the diff amp yourself),
stability of the PWM output, ripple of the PWM output, etc. IF the
transducer indeed has the resolution and accuracy you're seeking, it seems
a simpler approach is to use an external A/D that has more resolution. I
did a precision thermometer using a Data Acquisition System chip from
Maxim. It, as I recall, has a 16 bit delta sigma A/D, a 10 bit D/A, and a
real time clock. Simple to interface to the PIC with SPI.

Harold
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