Hi David;
A really good and quick intro to Thermocouple info can be found here
http://www.omega.com/thermocouples.html
If after reading that you're ready for more then follow some of the
thermocouple technical info links that are in the left sidebar. Good info
and a pretty good supplier for materials if you want to make some of your
own (easy to do). Some years back I wrote a write up on how to make your own
"K" type thermocouples for EGT probes. It can probably be found in the
archives or IIRC, someone may have posted it on the WIKI site. You can make
your own "J" type probes using some portions of this info, but much simpler
as they do not need to be as robust.
S. Todd Bartrim
C-FSTB
Turbo13B RV9
http://members.cox.net/rogersda/rotary/configs.htm#C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm