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Thermocouple junctions – Rockwell Automation 1746-NT4 SLC 500 Thermocouple/mV Input Module Installation Instructions User Manual

Page 12

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12 SLC™ 500 4-Channel Thermocouple/mV Input Module

Publication 1746-IN010D-EN-P - June 2004

Thermocouple Junctions

There are three types of thermocouple junctions:

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 three thermocouple types.

Extension Wire

Metal Sheath

Measuring Junction is connected to sheath.

Measuring Junction is isolated from sheath.

Measuring Junction has no sheath.

Grounded Junction

Ungrounded (Insulated)
Junction

Exposed Junction