One way to measure thermocouple temperature is to:

This short & less processor intensive

1. Measure hot junction voltage
2. Convert it into equivalent temp from lookup table
3. Measure cold junction temp
4. Add the two

Other is hell of processor intensive include double math from NIST:

1. Measure hot junction voltage
2. Measure cold junction temp
3. Calculate the cold junction equivalent thermocouple voltage using the NIST temperature-to-voltage coefficients
4. Add the cold junction equivalent thermocouple voltage calculated in step 3 to the thermocouple voltage calculated in step 1.
5. Use the result of step 4 and the NIST voltage-to-temperature coefficients (the “inverse” coefficients) to calculate the cold-junction-compensated, linearized temperature value.

Why people prefer method 2. Is there better accuracy?
Or method 1 is wrong correc method is second?
I have on many small processor people usually apply method 1?

 

I use an AD595 precision amp and set the gain resistor on pins 8-9, to suit your thermocouple output, it will give 10mV per deg C. Just put the output into an A/D pin and display it.

 

Hello aamirali

Linearization thermocouple necessary or not?
Depends:

If we want to see in the Display millivolts that are giving us the thermocouple when subjected to a temperature X, would not even linearize these thermocouple outputs.

But if we want to read, in the Display, the temperature at which the thermocouple is subjected, necessarily have to linearize the output of the thermocouple, and convert it to either: Degrees Celsius or Kelvin or Fahrenheit.

Note that there are two things:
Linearización.
And
Convert millivolt to readings in degrees (Celsius,Farenheith, Kelvin)

Since the Thermocouples not give us a linear output we must linearize its output.
This happens with any type of thermocouple. Its output, in millivolts, is not linear.

Therefore we have to linearize the output of thermocouples and we have to do a converter millivolts to temperature in degrees Celsius or any: Farenheith, Kelvin.

In your original message you mentioned two methods for linearization.
For me, the second method is better, but it takes longer to perform that procedure to the processor.

You can find here almost everything related to these devices called thermocouples.
http://www.omega.com/thermocouples.html

 

How important is how intensive processing is?

Timing-wise, processes involving thermocouples, are they really demanding?

 

...
Why people prefer method 2. Is there better accuracy?
...

Why not choose a 3rd method and use a lookup table? You have to calibrate it in testing but after that it is very fast processing.