BME280 wrong readings above 30ºC

[Kneg]

Hi! I'm using a few BME280 sensors to measure temperature, but the readings are getting wrong after 30ºC.

In a 32ºC afternoon the sensors are measuring 40ºC, this  is very strange as the sensors are doing a good job with temperatures whitin 10 - 25ºC.

Does anyone ever experienced something like this? tks

[o_o]

I would look at 2 things here:

1- In your datalog, do you see discontinuities in the temperature signal ? That could indicate an error in the compensation formula
2- Temperature is a very localized measurement. Is it possible that the temperature reached 40C due to heating from the sun ? How did you validate the reference temperature, with a separate thermometer next to BME280, or with the weather forecast?

[Kneg]

1 - The first graphic has 6 sensors togheter during a hour, look likes linear for me

2 - The second one shows the bme vs a professional wheather station, which is a few centimeters away

[o_o]

I didn't think to mention that, but are you using the official sensor API ? https://github.com/BoschSensortec/BME280_driver/

Please log the value of the trimming registers (constant per sensor) and the raw data. You can use the excel spreadsheet found here to validate the output of your compensation formula.