Rockwell Automation 1746-NT4 Series B,D17466.6.1 SLC 500 4-Channel Thermocouple/mV Input Module User Manual - Manual (Page 115)

1 Publication 1746-UM007C-EN-P - July 2004
Appendix
D
Thermocouple Types
This appendix describes the three types of thermocouple junctions.
They are
•
Grounded Junction - The measuring junction is physically
connected to the protective metal sheath providing electrical
continuity between junction and sheath.
•
Ungrounded Junction – The measuring junction is electrically
isolated from the protective metal sheath. (Also called Insulated
Junction.)
•
Exposed Junction – Does not have a protective metal sheath so
the measuring junction is exposed.
The illustration that follows shows each of the 3 thermocouple types.
Extension Wire
Metal Sheath
Grounded Junction Measuring Junction is
connected to sheath.
Measuring Junction is
isolated from sheath.
Measuring Junction
has no sheath.
Ungrounded (Insulated) Junction
Exposed Junction