Strange temperature stepping effect

I am getting a strange stepping effect with the temperature readings on my new BrewPi Spark 3. It looks to be stepping by around 0.06 degrees C each time I did not see this with my old BrewPi with Arduino.

Is this normal? If not, what could be the cause?


This shows the interface with the temperature plat and the profile.

This shows a zoomed in section of the plot:

That’s quantization error. Perfectly normal. Those steps are just the steps between the most accurate values the sensor can read. Think of it like if you could only use whole numbers. If you got 0.2, you might round down to 0. If you had 0.8, you might round up to 1.

Sure, that makes sense. But why did I not see this with the Arduino? The plots were smooth.

Because the readings were averaged in old Arduino code. Only the room temperature was the raw value from the sensor. Now averaging is only used as the input to PID. Logged data is raw sensor data (@elco correct me if I’m wrong).

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Yes, this is correct. The old version showed the filtered temperature and the current version shows the actual measured temperature. The filtered temperature has a delay, so showing the actual temperature is fairer. The filtering is now done inside the PID class, not at the input.

OK, thanks for the confirmation. If this is how it should look, then that is fine. I just found it confusing to go from one to the other.