I have a k-type thermocouple.
Thermocuple wire I have are small & have to place at relatively large distance away from measurement IC.

Can I connect two equal length copper wires at thermocouple to increase the size or will it create another copper wire-thermocuple junction in between & will lead to wrong readings??

 

You need type K extension wire to avoid creating another junction
http://www.omega.com/toc_asp/subsectionSC.asp?subsection=H07&book=Temperature

 

Any connection you make to the existing thermocouple will create an additional thermocouple.

If you use the same type of wire as the thermocouple to connect to it, i.e. chromel to chromel and alumel to alumel then you will not create additional junctions.

If you use extension wires that are different from the original thermocouple you will introduce errors if the additional junctions are at different temperatures.

 

I disagree. Extension wire has the same junction properties, but is not made of the same material. Platinum/Platinum Rhodium wire would be very expensive.

Yes, you should use the proper connectors. They are isothermal and also use the proper extension wire. The extension wire is NOT made of the same material as the thermocouple.

I had extensive experience with K, R, T and C thermocouples.

 

Your experience trumps mine.