I am Trying to read in a K-Type Thermocouple to a 0-5V Arduino Uno.
I Can read my Thermocouple directly using a Fluke meter on temperature setting giving me the correct value of 21°C, but when I switch to mV setting I read 0 mV on my Fluke. Similarly on my Arduino I am reading 0mV or some garbage hits (0.3xx mV, 1.9xx mV) every 10 readings or so that I assume is noise. My room is 70°F or 21°C so I expect to see 0.838mV according to the K-Type Thermocouple table
I have made a test load that produces 0-54mV
The INA121P Instrumentation Op-Amp works as expected giving a 50x gain on my test load when I use Rg = 1 kΩ resistor between pins 1 & 8.
So as stated before when I replace my test load with my K-Type Thermocouple, I read 0mV on Vo (expected should be 0.838 mV x 50 = 41.9 mV)
I have not included my Cold-Junction Tref in the Circuit yet, but I have my thermistor reading properly using the Steinhart-Hart equation in other tests.
In my code I will be dividing off the gain to get back to Vtc in mV. I am using the K-Type Coefficients to curve fit my thermocouple.
My overall questions are:
- Until I add my cold junction should I expect to be reading 0mV on my TC?
Answer: Yes since TC and Tref are at the same Temp no differential occurs. Thanks @TimWescott
- How can I get rid of the "noise" is 0.01 μF in the ballpark or should I change that value?
- Would you recommend any changes to my approach?