I am trying to calibrate a measurement system for temperatures between (-200C to 100C). I am using thermocouple type K.
Currently I am using the table3 from AN-1087 to convert the voltage to temperature.
I use 10V supply. Attached the design.
I use R7 to adjust the offset for negative temperatures and R9 to adjust the span of the output to the microcontroller ADC (0 to 3.3V).
I have an error above 20C when measuring cryogenic temperatures.
Would I need a new table if the Trf is not at 25 degrees? How could recalculated do that?
Currently Trf is around 10C, but since the system is outdoors temperature fluctuates.
I would truly appreaciate your help.