Rockwell Automation 1746-NT8 SLC 500 Thermocouple/mV Analog Input Module User Manual - Manual (Page 96)

Publication 1746-UM022B-EN-P - January 2005
B-4 Using Grounded Junction, Ungrounded Junction, and Exposed Junction Thermocouples
Exposed Junction Thermocouples
Recommended wiring for exposed junction thermocouples is shown
in the following illustration. Using exposed junction thermocouples
may result in removal of channel-to-channel isolation. This may occur
if multiple exposed thermocouples are in direct contact with
electrically conductive process material. To prevent violation of
channel-to-channel isolation:
•
For multiple exposed thermocouples, do not allow the
measuring junction of the thermocouple to make direct contact
with electrically conductive process material.
•
Use all ungrounded junction thermocouple instead of the
exposed junction type.
+
-
+
-
1746-NT8
CH0
MUXES
CH3
Grounded junction with
nonconductive protective sheath
Metal sheath with electrical continuity
to thermocouple signal wires.
(floating ground connection)