Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 123)

1 Publication 1762-UM002A-EN-P - July 2002
Appendix
D
Using Thermocouple Junctions
This appendix describes the types of thermocouple junctions
available, and explains the trade-offs in using them with the 1762-IT4
thermocouple/mV analog input module.
Available thermocouple junctions are:
•
grounded
•
ungrounded (isolated)
•
exposed
Using a Grounded Junction
Thermocouple With a grounded junction thermocouple, the measuring junction is
physically connected to the protective sheath, forming a completely
sealed integral junction. If the sheath is metal (or electrically
conductive), there is electrical continuity between the junction and
sheath. The junction is protected from corrosive or erosive conditions.
The response time approaches that of the exposed junction type
described in Using an Exposed Junction Thermocouple on page D-3.
ATTENTION
!
Take care when choosing a thermocouple junction,
and connecting it from the environment to the
module. If you do not take adequate precautions for
a given thermocouple type, the electrical isolation of
the module might be compromised.
Extension Wire
Metal Sheath
Measuring Junction
Connected to Sheath