Hi Ville and Jim,
Here is the spreadsheet Jim provided, but with an extra column of K type thermocouple calculation according to Omega’s formula.
Jim – I am sorry to report that I think the thermocouple was not properly connected during this experiment… it looks like the aux input voltage didn’t rise in a way that matches your description of temperature change. If you provide more details on the setup I am happy to try and help.
Feel free to use this spreadsheet as a template, I also gave commenting permissions to anybody who sees the link.