>
> This seems a good application for an old fashioned dual-slope A-D
> converter.  They can have pretty good resolution and they naturally
> integrate the signal.
>
> Has anyone built one with a PIC?
>


A PIC based dual slope A/D was used in the precision thermometer I just
redesigned. That design was maybe 10 years old. It used a quad op-amp and
a fair number of other parts. I replaced all that with the Maxim DAS part
to get 16 bit A/D, 10 bit D/A (which I use to vary display brightness),
and a real time clock. My previous dual slope experience has been using
the MC14433 in a design about 30 years ago. Worked great! Also used the
Intersil 7109 in another project. That one was interesting in that the A/D
circuitry was floating. I passed the busy AND clock, busy, and polarity
back through opto couplers. The counter in a 6522 counted the busy AND
clock to get the conversion. That also worked nicely.

Harold



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