On Tue, 07 Dec 2010 13:34:46 -0500, you wrote:

>Olin Lathrop wrote:
>> Sean Breheny wrote:
>> > Is there really one reference junction, though? I am under the
>> > impression that any joint of dis-similar metals in the thermocouple
>> > circuit will cause a voltage difference which is temperature
>> > dependent. This includes even things like bond wire connections inside
>> > the IC used to read the thermocouple.
>>=20
>> Temperature differences don't matter anymore when both conductors are
>> made of the same material, like both become copper traces on a PC board.
>
>Sean is right. You have many different junctions throughout the circuit, a=
nd
>you need to make sure that corresponding junctions are at the same tempera=
ture
>throughout. It never becomes a "don't care". However, in most cases,
>corresponding junctions are pretty much implicitly at the same temperature
>because of the physical constraints of building the circuit.

...and if your required accuracy is such  that these things matter, you prob=
ably should be  using
PT100s instead of thermocouples  anyway!

--=20
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