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    BME680 bVOC value very off

    BME680 bVOC value very off

    mhoff87
    New Poster

    I have been experimenting with the BME680's gas sensing using 5 BME680 breakout boards inside a small gas chamber. I am using an ESP32, BSEC2 library, and sampling every 3 seconds on LP mode. Here is one test I ran a few times:

    - Ran the BME680's for multiple days until IAQ accuracy reached 3

    - Flush chamber with ultra zero air until readings stabilize (https://www.calgasdirect.com/gasco-105l-1-zero-air-calibration-gas-20-9-o2-balance-nitrogen-a-105-li...)

    - Fill chamber with 1ppm isobutylene in Nitrogen calibrated gas until readings stabilize (https://www.calgasdirect.com/isobutylene-calibration-gas-c4h8-1-ppm-balance-nitrogen-in-a-103-liter-...)

    The BME680's bVOC values immediately get pinned at 1000ppm when the gas enters the chamber. I understand it is calibrated to a different gas mixture, but there isn't anything that can explain a 1000x difference. Isobutylene has a molecular weight of 56.1 g/mol and I calculated the bVOC gas mixture to have a molecular weight of 51.29 g/mol. I would appreciate any help or thoughts people have.

    Thanks!

     

    9 REPLIES 9

    BSTRobin
    Community Moderator
    Community Moderator

    Hi mhoff87,

    Did you have further feedback?

    Hi BSTRobin,

    I will run this test when I get the chance and get back to you.

    Thank you,

    Mark

    I ran air>Isobutylene>air. Attached are graphs of the results. Tests were run at 4800ft (1463m) above sea level.

    Screenshot 2024-03-25 at 11.24.56 AM.png

     

    Screenshot 2024-03-25 at 11.25.20 AM.png

    Screenshot 2024-03-25 at 12.58.26 PM.png

    Screenshot 2024-03-25 at 11.25.31 AM.png

    Screenshot 2024-03-25 at 11.25.09 AM.png

    BSTRobin
    Community Moderator
    Community Moderator

    Hi mhoff87,

    Thank fo your feedback.
    We think you didn't get the point,
    when testing 'Isobutene', you should mix filed air with isobutene, not all isobutene.
    As we mentioned before, our sensor can not operate without oxygen.

    BSTRobin
    Community Moderator
    Community Moderator

    Hi mhoff87,

    Did you have further feedback?

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