Rockwell Automation 1790P-T4T0 CompactBlock LDX I/O Thermocouple Modules - Manual (Page 87)

Publication 1790-UM003A-EN-P
Using Thermocouple Junctions D-3
Using an Exposed
Junction Thermocouple An exposed junction thermocouple uses a measuring junction that does
not have a protective metal sheath. A thermocouple with this junction
type provides the fastest response time but leaves thermocouple wires
unprotected against corrosive or mechanical damage.
As shown in the next illustration, using an exposed junction
thermocouple can result in removal of channel-to-channel isolation.
Isolation is removed if multiple exposed thermocouples are in direct
contact with electrically conductive process material.
Measuring Junction Isolated from Sheath
Measuring Junction with No Sheath
+
-
IN 0
+
-
IN 3
Module
Exposed Junction with Shielded Cable
Multiplexer Conductive Material
CH 0
CH 1