BME688 Development board (Adafruit + 8xBME688) - Temperature sensor - offset of 5 degrees+

[fpineau]

Hello, 

On my project, we would to use the BME688 4 in 1 sensor. I already test the COV, humidity and pressuee part.
And now I work on the temperature sensor BME688. So, I'm posting here because I want to have more information about the data of this temperature sensor.
I see that in the datasheet the accuracy of this sensor is +/-0.5°C between 0-65°C.

So for my tests, I did some run with the development board ( Adafruit + 8 BME688) and I put the board in a fidge at 15°C (with a variation of 0.3°C).
You can see below a 4 days run with the heater profile HP-322 / RDC-3-12. 

We can see that we have an offset of 5°C. We are far that the accuracy of  +/-0.5°C between 0-65°C.
Also I see that this offset change with the heater profile.

So my questions are : Where come from the offset of 5°C ? And I how I can fix it ?

Thank you for your precision.

Florian

[BSTRobin]

Hi fpineau,

Sorry for the delay reply.
For your test environment "I put the board in a fidge at 15°C (with a variation of 0.3°C).", can your test environment ensure accurate temperature control at about 15 °?

[BSTRobin]

Hi fpineau,

Could you give feedback?

[fpineau]

Hello,

Sorry for the late feedback. 
So for this test I used the "ST 1 P SMART PRO" for m POL-EKO APARATURA.
We have a quality control certificate dated of 04.02.2022.

And the accurence at every temperature is 0.1°C. (please see an excerpt of the incubator datasheet ).

So that's why I don't understand the 5 degree offset

Best regards.
Mister Pineau Florian

[BSTRobin · Accepted solution]

Hi fpineau,

If you want to fix it, you can modify the offset which located in function 'ProcessData()' of Bsec2.cpp as following: