I too have used copper wire to connect TC's, and not had a problem,
the cold junction was always in the instrument providing the
measurement incidentally. I would not used copper for a serious long
term measurement strategy though, hence my lack of experience with
this type of setup.

I do recollect having problems with damp connections on more
conventional connectors in a similar application that seemed to be
exacerbated by the use of aluminium bootlace ferrules, so the
reactivity is the item of concern. Anything else can be quantified and
rectified.


AB

Back when Ford built a brand new factory near Valencia for the new
Fiesta, I went out there to commission the paintshop bake ovens. The
electrical contractor had no idea about the importance of the correct
use of Thermocouple compensating cable, and the long runs were
connected randomly. The effect of this was that some zone burners were
running flat out, while others were idling, and there was a total lack
of control of oven temperature. Once this was sorted out, it worked
properly. Until then, it was chaos.

--
Davey.