[?]: Thermocouple module

[VINESH KUMAR]

Dear all

i am using themocouple moduel 6es7-331-7kf02-0ab0 with s7314 cpu.
i connect k-type thermocouple and configured and hardware.
when i connect thrermocouple installed our burner kettle no value is read although mv are present.
I connect an other thermocouple kept beside plc it works.
finally when i use isolation amplifier with outside(burner kettle) thermocouple it wokrs can you please help what interferance is coming and how to eliminate

[ThermoNuclear]

Hi ,

do you have the proper cold- and hot- junction compensation in place . These parasitic "measurements " could eliminate your actual measurement.

Regards ,

ThermoNuclear.

[VINESH KUMAR]

hi i use thermocouple directly into input module no any compensation please reply

[krsh]

Hello friend,
For a more accurate answer please provide more info such as:

How long is the cable between the PLC module and the thermocouple itself?

Are there any high or medium voltage cables near the thermocouple cable or the furnace?

Did the program ever worked before? If yes what did you change in it?
And more details..

[manus_a]

If you connect thermocouple directly to module
do you try with TC_IL ( thermocouple internal linear ) in Hw config.
for me it work ok

[VINESH KUMAR]

thanks for reply. i am using first time.the length of cable is around 25meter from our control room.yes with thermocouple cable there is power cables.can you help me to understand b/w isolated thermocouple and unisolated thermocouple.becuause i think there is grounding problem ? i saw a example to ground -ve terminal of thermocouple with ground have you any experiance of this please help

[krsh]

VINESH KUMAR,
Your problem could be that the data transmission cable that is going from PLC to termocouple senzor is influenced from electromagnetic interference from external sources such as high or medium voltage power lines. These phenomena occur especially when data cables run ALONG power transmission cables, even for low-voltage power lines. You may check this possible cause by using a different route for your data cable.
About the isolated/unisolated thermocouple question you should consult the installation manual because i am sure there you will find more answers for you problem.