Thermocouple amplifier circuit question

[ec911]

Hi!

I've drawn a schematic of a temperature sensing circuit of an Aoyue hot air station (852A++).  I'm not a pro about circuit designing and I'd like to know what you guys think of the circuit and if I could improve it mabye? I find that temperature of the device is inaccurate even after calibrating with the trimmer pot. The display is also slow to react to temperature change and don't know if it's because something's wrong with the T° sensing circuit.

Note that the output goes to pin PC4(ADC4) of an Atmega8a AU µC.

Also I'm doing this not only to see if I could improve things but also to learn more about electronics..

I've been reading on cold-junction compensation when using a thermocouple with ADC, I don't think this circuit have this???

[charlespax]

I think R9 might be a thermistor, which is a resistor that changes resistance based on its temperature.

R7 is for open circuit detection. When the thermocouple is disconnected R7 will pull that side of the connection toward 5 V. The microcontroller will try to read the thermocouple voltage and see that it is very high and know the thermocouple is not there.