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Wiring of Thermocouple I/O modules to thermocouple in field.

Created by: Arunabha at: 8/8/2007 3:09 PM (4 Replies)

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8/8/2007 3:09 PM	Rate (0)
Arunabha Member Joined: 5/25/2007 Last visit: 9/5/2007 Posts: 6 Rating: (0)	Please help Me!!! What is the best procedure to wire up a thermocouple in the field and the Analog thermocouple I/O module? Should we use the compensating cable inside the panel also? From I/O Module to Terminal inside the Panel what should be the connecting wire and what should be the terminal type? a normal terminal or a compensating terminal (if any!!). Please help me with a standard practice. Regards Arunabha

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8/8/2007 10:42 PM	Rate (0)
Dorftrottel? Silver Member Joined: 8/10/2006 Last visit: 3/15/2023 Posts: 297 Rating: (29)	It depends on whether you need to be able to have the T/C's plugged in (quick replacement of throw-away modules, movable thermocouples, etc.) For permanent installations, I recommend wiring from the thermocouple head directly to the thermocouple module channel terminials. (No input blocks in between). This minimizes corrosion problems, helps simplify calibration Each terminal block, even the correct type, is a possible source of noise. If you do use terminal blocks, they must be the same type or composition as your thermocouples. Otherwise, each termination becomse a cold-junction point, and creates an offset to the actual temperature. (I have seen errors >40° C)

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8/9/2007 2:26 AM	Rate (1)
GJohn Posts: 112 Rating: (10)	I would also recommend wiring from the thermocouple head directly to the cold junction. (Noterminals in between). You should always use compensating cable between the thermocouple cable and the cold junction. The cold junction can be at your panel with the Analog thermocouple I/O module or it could be a seperate panel in the field with copper conductors wiredto the Analog thermocouple I/O module. Wire another thermocouple or RTD and locate this inside the cold junction panel to compensate for the cold junction temperature. If I have only a few thermocouples I would wire each of them to a 4-20mA converter which also compensates for the cold junction temperature. I would then use an analog current input module. This saves having to wire a sensor to compensate for thecold junctiontemperature.
GJohn Posts: 112 Rating: (10)
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8/9/2007 6:26 AM	Rate (0)
Arunabha Member Joined: 5/25/2007 Last visit: 9/5/2007 Posts: 6 Rating: (0)	Thanks for your views. I shall use direct termination of compensating cables from thermocouple ton I/O module other than using any third material with more cold junctions. eventhough it will give little difficulties for panel engineering when the nos. of thermocouples are 650. Thanks once more.

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8/10/2007 10:39 AM	Rate (0)
CS Moderator Moderator Joined: 9/1/2005 Last visit: 3/23/2023 Posts: 4099 Rating: (192)	closed cause question posted twice. The second thread with the topic Wiring of Thermocouple module to Thermocouple in fieldis published within the conference Process Instrumentation / Analytics. I copied the replies to this topic. Best regards CS Moderator
	My Forum is the place to personalize your profile, track your topics, and maintain content that interests you. Best regards CS Moderator
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