On Sun, 09 Sep 2007 02:56:39 GMT, "Pete C."
wrote:

RoyJ wrote:

Yeah, but Karl's son is one of those TIG welder guys that practices on
beer cans. For what he wants to do, welding his own seems like the best
choice.

Certainly an option. Save a few $ in TC connectors.


I didn't find the TC wire in McMaster, used the Omega site since it had
a good writeup.

McMaster page 541, bottom.


I've always used 'K' wire, you mentioned 'J'. Why/Comments?

No particular reason, just first in the list of supported TC types for
the controller.


snip

J t/c's come on a lot of stuff because they're cheaper. They work
fine, but don't use one around moisture or corrosive environments. The
iron (J = iron/constantan) will corrode and fail. Actually, when I
need as much accuracy as I can get, I use RTD's. Most temp
controllers support them, and the signal is much more robust than the
t/c millivolt signal. I have them assembled with Brad Harrison
Nanochange connectors by Sandelius in Houston. That makes it easy to
swap in a spare. The normal four prong connector made from two t/c
connectors of copper is too big and clunky.

I still use J's when they come installed by the OEM. But when I use
them, I calibrate the entire loop with a dry block tester at least
once per year. I have found that J's will drift significantly over a
period of years in a temperature cycling application, like an oven or
an extruder that doesn't run continuously.

Pete Keillor