Improving Temperature accuracy

In the past month i’ve spent almost all of my time to test temperature offsets of the different enclosures. Sadly i didn’t spend it earlier so now some workarounds are needed, after some customers noted this

  • Temperature deviation based on sensor type
    • It turned out each type of sensor has a slight (0.5) deviation.
    • BME280 (temp/hum/pressure) is ~0.5 degrees above SI7021 (temp/hum), and +/- 0.5º between readings from same sensors
    • BMP180 (temp/pressure) is ~0.5 degrees below (SI7021), and again ±0.5º between same sensors
    • SI7021 – has < ±0.2º difference between same sensors, and sits in the middle therefore i took it as base
    • The latest versions of the FW (after build 20161205) store the raw temperature in variable %TEMPR% and apply a correction so that the %TEMP% is either increased or decreased by 0.5 (or kept)
  • Temperature offset from enclosures
    • I have underestimated the power consumption of some modules
    • Temperature offset from the enclosure can reach up to 2º-3º
    • This is quite consistent and doesn’t matter from ambient temperature
    • It can be measured by taking the sensor out of the box, measuring the offset and then either storing it into the firmware via the Configuration tool (Settings -> Temperature Offset), or applying it to the software or service that stores the data. Or leaving the sensor out.
    • Temperature adjustment is also applied on the TEMP variable after the adjustment from the sensor type is applied (so if you have a BME280 (+0.5) and apply +0.5 in addition – then TEMP will be 1 degree more than TEMPR

I have redesigned all boxes and now for all devices that ship after 20.Dec – this is resolved.

If you do not want to apply temperature adjustments and do not want to keep the temperature sensor out, you can order a new enclosure from here:

Currently it’s price is just the price for the PLA used to print it.


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