Interfacing TC directly with arduino without any extra circuitary involved.

[hrh1818]

Which device are you referring to that has a price of US$1,000.00?

An op amp is a much better method for amplifying the output of a TC than a transistor.  For example:

<http://circuits.linear.com/26>

If you use this circuit in a room with constant temperature you could eliminate the cold junction compensation.  And if required you could use a programmable gain op amp.

Most IC TC amplifiers designed for industrial applications provide cold junction compensation for only one type of TC for cost and accuracy reasons.  For example: 

<http://www.analog.com/en/press-release/5_26_10_Precision_Thermocouple_Amplifiers_with_Int/press.html>

These units even compensate for TC non linearities.  Single unit price is US$5.00.

The MAX31855 will work with both type K and type J thermocouples.  See:

<http://www.adafruit.com/datasheets/MAX31855.pdf>

An op amp provides the cost method for amplifying the output of a TC.  But it has the lowest accuracy of the three approaches listed above.

hrh1818

[hrh1818]

Wen using an op amp in your application software cold junction compensation may be substituted for hard ware cold junction compensation. One could use a temperature sensor like a TMP36 to measure the cold junction temperature and then use software to compensate for variations in ambient temperature. See:

<https://www.sparkfun.com/products/10988?gclid=CP3Kq6XTgroCFZFFMgod3WgA1Q>

<http://paginas.fe.up.pt/saic/Docencia/ci_lem/Ficheiros/an043.pdf>

hrh1818

[Ranjeet_Singh]

Thanks a lot all. Will get bac kto you if any other problem