dave-in-nj:
<...> MAX31855K seems to be the chip of the dayas for the 'accuracy' of a thermocouple. getting a number to decimal places is resolution, having it return to the exact same output with the exact same input is repeatability, then there is hysteresys....
I accept that you can be 2 deg off, but have great sensitivity and repeatability. What did you find as regards these things ?
if your sensitivity and repeatability are great, then you can just shift the reading in software.Dave
Agreed with s/w fine-tuning. But, in all honesty, I did not have anything in my lab accurate enough to qualify the build... Slushly ice water showed 0C and boiling water was 99C but my GPS shows my elevation at 1045 feet. However, I used tap-water so there were impurities. Since this need is EGT, decimal accuracy was not required.
I observed no detectable hysteresis.
The stainless EGT sensor (eBay sourced) are rather heavy (mass) so it does take a couple of seconds to stablize.
Ray
Crazy talk: for anyone using the internal 1.1V AD reference, you can achieve aroundv5% to 6% temp reading from a "T" thermocouple without an amplifier! See here