AVR-Chat

One real simple test to isolate the problem: Swap CPUs between a working
board and a failing board.

My money is on the board, not the CPU, as the source of the problem.

-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Jim Wagner

When you say that this is a mature system, does that mean
that it used to work properly and isn't now?

One of the potential problems with differential measurement
is keeping the common-mode voltage within allowable limits.
Normally, however, you would expect lower sensitivity
rather than greater if this were violated. But... do you
have a ground reference connection in addition to the two
signal connections?