I am running many BME280s in a moderate humidity environment (between 50% and 80%, at around 20C) and am seeing around 10% of the units reporting more than 5% off of what our reference sensor reports in the same environment. We use a hand held sensor like this as our reference. Since these devices have been deployed for less than a year, there is concern that this drift is outside of what is characterized in the data sheet. Is there a more detailed aging reference available?
It would be great to confirm that temperature output of all the devices are close together since relative humidity is temperature dependant. Would you be able to confirm if the reconditionning process has any impact on the output of new and older devices?
This difference should not belong to the long term drift which is considered by year. Our humidity sensor absolute accuracy achieve +-3RH% and you should consider the reference device accuracy error. So 5% is acceptable.
I didn't express my experiment clearly:
I measured the difference between reference and BME280 about a year ago, and measured an average over 20 units of approximately 3% well within the accuracy limits of both devices. Now, I measure the same units it and its coming in around 13%.