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    BME680 BSEC Accuray output drops infrequently to 0

    BME680 BSEC Accuray output drops infrequently to 0

    New Poster

    Using BME680 with the BSEC library on an ESP8266.

    As expected it takes some time during startup when accuray is 0, then moves to 1. Exposure to clean outside air and aftwards breathing leads to 2 or 3.

    As also explained in the forum, I can see switching between 3 and 2 indicating a new re-calibration happening.

    However, as shown below, there are also instances where the accuracy indicator drops to 0, and without intervention becomes 3 again after some time.


    Please see also the corresponding equivalent CO2 output:


    As well as the IAQ output:


    Any explanation of this issue?

    Thank you


    6 REPLIES 6

    Occasional Contributor

    Hi Sir:

    What mode did you choose currently?

    The accuracy droped to 0, according to besc algorithm, in general it means supply voltage changed suddenly and recover or it is wrong for timestamp(it means that the polling interval time is abnormal occasionally), besc will re-startup to calcuate with your configuration mode.

    Could you get constant IAQ value before and after accuracy drop to 0 suddenly?



    Good morning,

    IAQ versus accuracy looks as follows:


    I'm running in 3d / 3 second mode.

    No, power is not dropping, I have other sensors, which behave properly over time.

    I also can confirm, that I looked into the timing issue. Datasheet says, that you have to be in 50% of the timing, so maximum with a 3second cycle time is 4.5 seconds. I have put in checking code, that ensures, that this timing is kept and it has not shown any violation.


    Occasional Contributor

    Hi Sir:

           Regarding your results, I will ask for internal experts help.

          if any update, I will keep you informed.


    Occasional Contributor

    Hi Sir:

        Could you offer the complete log including timestamp, raw temperature, raw humidity, raw gas resistance, IAQ, IAQ accuracy?

       We need these information to analyze and look for the reason.

       Thank you.