Hi All,

      I am using K-type underground Thermocouple with  SM331 [6ES7 331-7KF02-0AB0]. I am facing accurate reading problem. If actual reading is 78 deg c then it shows 120 deg. Difference  between reading is almost 25 to 30 deg. I hardware setting I have selected Thermocouple Internal compensation [TC-I]. I have insert a bridge between Comp+ and MANA also.

Please guide me to resolve this problem.

Regards,

Yogendra K

What do you mean by "underground"? That TCs are grounded?

Where is your cold junction? Are TCs leads connected directly to the module? Or are there any terminals, connectors, other leads on the way?

How about showing us the exact electrical diagram?

jacek d

What do you mean by "underground"? That TCs are grounded?

Where is your cold junction? Are TCs leads connected directly to the module? Or are there any terminals, connectors, other leads on the way?

How about showing us the exact electrical diagram?

 Hi,

Sorry for delay reply.

What do you mean by "underground"? Its not underground its ungrounded type TC.

Where is your cold junction?. I am using internal cold junction. Please explain me little more.  Do i need additional hardware for this? 

Are TCs leads connected directly to the module? --Yes 

How about showing us the exact electrical diagram? M0+ and M0- [CH0]

Regards,

Yogendra 

YogendraK

Where is your cold junction?. I am using internal cold junction. Please explain me little more.  Do i need additional hardware for this? 

Are TCs leads connected directly to the module? --Yes 

A cold junction is a place where a cold side of a TC is. I.e. where original leads of a thermocouple end unless properly extended with terminals, pins, wires made of the same materials as the thermocouple.

So, if your description is 100% correct, then everything is fine and should work properly. The only problem I can think of is a short circuit of the thermocouple leads somewhere on their way.

Hi must (its better) connect TC directly to module . Because the thermocouple is made of two identical metals, if you use another metal on the sensor-to-module path, the voltage difference that comes to the module is wrong and causes an error.

what is your module type ?  

Alex_BHP

the thermocouple is made of two identical metals,

 Hello,

A thermocouple consists of a pair of electrical conductors of different materials joined together at one point. This junction is conventionally called a hot joint or hot junction, and is the point at which the temperature to be measured is applied.

and if you want there is also this terminal:

Alex_BHP

what is your module type ?  

Read from the beginning.