BME280 humidity offset

[buja]

Dear Team,

We are using BME280 to monitor humidity and temperature. Temperature is working as expected but humidity has got an offset always.

We have bought a couple of humidity sensors, which will be the reference humidity value. You can see from the above graph that all the BME280s (green lines) are having a negative offset on the humidity value (RED is the reference). We are using the APIs from the Bosch sensortec github. Why do you think there is an offset ?

The datasheet says the reconditioning procedure is mandatory after soldering process. We haven't done the reconditioning. Could that be the reason for the offset ? Also, could you please suggest us the best way to do the reconditioning ? Are there any standard device which can do the reconditioning in the production ? 

[BSTRobin]

Hi buja,

Could we know more detailed information about your test:
1.Is this tested in a standard test device?
2.How does the test device adjust the temperature and humidity?
3.What is the temperature curve like?
4.Do you have more detailed log data? It includes time stamp, temperature value and humidity value.

[buja]

1.Is this tested in a standard test device?

5 devices are taken for testing. In these, 4 devices are assembled by us. 1 device is an evaluation board from adafruit (BME280_eval_board).

All the devices are kept near to the window, at the same place.

3.What is the temperature curve like?

Please see the attached graph. Black lines show temperature

[BSTRobin]

Hi buja,

For "All the devices are kept near to the window, at the same place."， it seemed you didn't test them in test box? Is it correct?

[buja]

That's correct, we didnt test in test box. Is that the picture of test box ?