Maybe not really answering your question, but have you thought of
using some of the temp sensors with digital output ?

Like the TC77 from Microchip. -55 -- +125 deg C range with
1/16 degree resolution and +-1 deg C accuracy between +25 and +65
deg C. Serial interface interface with a 13-bit temp value.

You'll only get the analog "problems" in one place. The PIC side of it
is all digital.

Regards
Jan-Erik Svderhom.
S:t Anna Data
Sweden

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