Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 125)

Publication 1762-UM002A-EN-P - July 2002
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
1762-IT4
Exposed Junction with Shielded Cable
Multiplexer Conductive Material