RIMU Calibration

I turned the freezer up to 7. I’m sure yours goes to 11, but I am not so lucky. After being turned up to 7, the resulting mean temperature is still too high at 18.8°F. And with that, we bid adieu to our refrigerator. It is around 20 years old—no way to be sure, and it has had a good life. I suppose the EPA would frown on a Viking funeral?


As a final check, I tested the thermometer by running it from a stirred ice bath up to a rolling boil. The ice bath temperature, averaged over about 1 minute, is about 33.1°F. A 1°F error does not present any problems.


Calibration in an ice bath is quite easy, but calibration at boiling is not. The pressure estimated from the RIMU predicts a temperature below the measurement, while the local airport’s barometric pressure predicts one above. In any case, the error is a few percent or less.


2 thoughts on “RIMU Calibration

  1. Hey Park- The airport barometric pressure isn’t the actual barometric pressure at the airport. Rather, it’s the reference pressure you set your altimeter to that will make your altimeter read the correct altitude at the airport. 826 mb is much closer to correct. – Robert

    • Ah, well that is a lot more useful for the kinds of people who go to airports. That also suggests my thermistor measurement is biased slightly high. This could be due to errors in the reference temperature, or in the thermistor-to-temperature conversion, or most likely in both. Thanks for the note!

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