Pioneer Microsystems wrote:

>   I would not expect to pay this
> much attention to ground layout unless I were doing a 12 bit A/D.  But
> we
> had to here.  We did try raising the reference to 4V, which did not
> appear
> to change anything.  So we are tempting fate and sticking with the
> 2.5Vref.

That's probably not a good idea. There's a reason for the spec. You
should always try to understand why the rules were made before breaking
them.

Thermocouples produce extremely low voltages. I would expect this
circuit to be sensitive, regardless of the number of bits you have; the
resolution per bit is probably not much different than you would have in
a 12 bit system, and so the sensitivity should be the same.

Tom Rogers  VP-R&D  Time Tech Inc.