Hello!
I am a newbie at arduino and fresh at this forum, so i hope i am posting in the right forumpart.
I am trying to build a kiln controller and the temperature sensor is a type k thermocouple, and i am usning the adafruit MAX31855 amp to be able to read the temperature with arduino. The thing is that is is somewhat off the correct temperature and i would like to know if it is possible to do an interpolated correctiontable for this. My ide is that i can determine some temperature correctly, for instance 0 degrees C, 100 deg C, 680 deg C, 1180 deg C and 1380 deg C or simular.
Can i do a correctiontable for this? You might call it a calibration or likewise of course.
How should i do this? I suspect that the thermocoulpe is a bit old and therefore i have this problem, but i still belive that the thermocouple is linjear in itś readings, just off like 50-200 deg or so.
Sorry again if i am posting in the wrong forumpart
/Parkeringskungen
You are on the right track. If you have access to another means of accurately measuring the temperature (at least temporarily) it is straightforward to calibrate your thermocouple. If you have enough reference temperatures, you can even fit a nonlinear correction curve that could produce more accurate measurements.
Adafruit has a pretty good tutorial that gives an overview of the process, and then goes into some detail, with specific application to your thermocouple.
Thanks for the reply, i really feel a bit :-[ because i really should know how to use google and such before posting 
I will read up on the subject and return if i have further questions on the subject.
/Parkereingskungen
A few people , including myself, have run into stability issues with the MAX31855. The chip, when attached to an arduino, seems to be subject to power line noise that throws off the digital readout. For me, this happened when the temperature of the kiln got to around 1600 F. Why it should be temperature dependent is a real question. I have posted this problem here before and gotten no resolution. I use the AD 595 with an op amp to get the temperature into the correct analog range for the Arduino. This has worked well for me. I use a trim pot to zero in on the correct temperature, once I have the circuit wired.
Here is a java app in development for a kiln controller. I do not use PID, just on/off. PID for a ceramic kiln is like using a micro tome to slice lunch meat... At least in my opinion.
The app just looks for a temperature out and uses "T" and "C" to turn the kiln on and off... works like a champ. I had done this befor in VB6, but the a**holes at MS pulled the plug, so no more MS anything for this lad. My sketch uses the AD595, but all you would need to do is plug in the code to get the temp from the MAX31855.
Hope you have better luck than me this chip. code and app at http://raventreestudios.com/kiln_wiz.zip
(somehow it would not link as a url )