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    BME680 & BSEC - Changing between LP & ULP while sensor is Active

    New Poster

    BME680 & BSEC - Changing between LP & ULP while sensor is Active

    Hi,

    I'm currently evaluating using BME680 + BSEC software and was wondering what the optimum way was to switch between LP & ULP (and vice versa) while the sensor & library is running. 

    1. Can I simply call "updateSubscription" with the new "BSEC_SAMPLE_RATE_..."? or...
    2. Do I need to reinitialize as if it's turned on for the first time? i.e. with "begin(...)" & "bsec_virtual_sensor_t" & "updateSubscription" commands? or...
    3. Do I need to soft-reset the BME680 before doing the above?

    Ideally, I would like to keep the calibration data when switching e.g. calibrate quickly using the 3s mode then switch to the 5min mode after IAQ accuracy >1 is achieved.

    I had some concerns as the integration guide mentions: "To achieve best gas sensor performance, the user shall not switch between LP and ULP modes during the life-time of a given sensor" 

    Any advice would be great.Thanks!

    4 REPLIES 4
    Occasional Contributor

    Re: BME680 & BSEC - Changing between LP & ULP while sensor is Active

    Hi Sir:

        We will talk to our internal experts to check the integration guide mentions what means.

       

     

    Occasional Contributor

    Re: BME680 & BSEC - Changing between LP & ULP while sensor is Active

    Hi Sir:

          Recommend you to have a test to verify your idea, but maybe the result will be got after a long time.

          "To achieve best gas sensor performance, the user shall not switch between LP and ULP modes during the life-time of a given sensor" , this means sensor mode cannot be changed during a particular measurement cycle, try to follow is that the sensor/sensor array should be running with a particular mode throughout to achieve a good performance.It does not mean that we cannot change it-but it is ideal to maintain a constant mode of operation.

         So actually the sample rate can be changed between LP/ULP/DC when we use BME680, but still recommend the customer use one mode for use to achieve good performance. If the mode is changed, it needs a long time to get a stable performance, and the standard of good/bad air quality is different under different sample rate.

    New Poster

    Re: BME680 & BSEC - Changing between LP & ULP while sensor is Active

    Hi Jet,

    Thanks for checking and apologies for my late reply.

    I understand, I’ll keep switching to a minimum to overall reduce the time the sensor is stabilising - I’ll assume this also means switching eliminates any existing ‘baselines’ and needs to ‘calibrate’ again in the new mode.

    I just have 2 follow up questions:

    1) In the event that I do need to switch, what is the procedure in the code to do so – should I:

    • Simply call "updateSubscription" with the new "BSEC_SAMPLE_RATE_..."?
    • Or before this do I need to reinitialize as if it's turned on for the first time? i.e. with "begin(...)" & "bsec_virtual_sensor_t" & then "updateSubscription" commands? or...
    • Do I need to soft-reset the BME680 before doing the above?

    2) Are you able to expand on why the standard of good/bad air quality changed with the measurement frequency?

    Thanks a lot!

    Occasional Contributor

    Re: BME680 & BSEC - Changing between LP & ULP while sensor is Active

    Hi Sir:

          Please see my comments:

         1.  Before this do I need to reinitialize as if it's turned on for the first time and it is better not to load the previous state file which is not helpful, if load it, mabye you will get the odd results.

         2. When the environment are changed, the standard of good/bad air quality will be defined, because IAQ 25 is the standard of good air and 250 is the standard of bad air, even if change into better or worse environment, IAQ is larger than 250 or smaller than 25, after a long time, the IAQ value will scale to 25 or 250. Vice versa.

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