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    BME 680 IAQ accuracy abnormal operation

    BME 680 IAQ accuracy abnormal operation

    adam_smith
    New Poster

    Hi,

    I am working with a BME680 VOC sensor on a project and I have detected some abnormal performance while reading values for a long time.

    My setup is as follows:

    - BSEC 1.4.8.0 Normal Version

    - generic_18v_300s_4d config operation

    - I have a sensor calibrated as indicated in the manual: about 30 minutes exposed to fresh air and another 30 minutes in a box with exhaled breath. During this calibration process I was able to see how the IAQ accuray went from  index 0 to index 3.

    - Location: Indoor office

    After that, I was reading some values that were more or less correlated with measurements taken from other VOC sensors that we were using as a reference. However, at some point in time, BME680 took some wrong value and started a recalibration (index 2) until new calibrated values were obtained.

    Here you can find a snapshot of the logs:

    [05:23:17.046] T, 24.52, rH, 30.85, Pa, 93866.99, IAQ, 128.94 (3), Static IAQ, 110.07, CO2e, 1100.71 (3), bVOC, 1.80 (3)
    [05:23:20.052] T, 24.51, rH, 30.93, Pa, 93863.14, IAQ, 129.27 (3), Static IAQ, 110.33, CO2e, 1103.35 (3), bVOC, 1.81 (3)
    [05:23:23.058] T, 24.52, rH, 30.90, Pa, 93866.49, IAQ, 128.77 (3), Static IAQ, 109.92, CO2e, 1099.20 (3), bVOC, 1.80 (3)
    [05:23:26.064] T, 24.52, rH, 30.94, Pa, 93865.57, IAQ, 128.38 (3), Static IAQ, 109.60, CO2e, 1096.01 (3), bVOC, 1.79 (3)
    [05:23:29.070] T, 24.52, rH, 30.95, Pa, 93866.09, IAQ, 132.40 (3), Static IAQ, 112.89, CO2e, 1128.92 (3), bVOC, 1.88 (3)
    [05:23:32.076] T, 24.51, rH, 30.95, Pa, 93862.64, IAQ, 153.91 (3), Static IAQ, 130.48, CO2e, 1304.86 (3), bVOC, 2.46 (3)
    [05:23:35.082] T, 24.52, rH, 30.93, Pa, 93866.60, IAQ, 174.60 (3), Static IAQ, 147.41, CO2e, 1474.13 (3), bVOC, 3.18 (3)
    [05:23:38.088] T, 24.52, rH, 30.97, Pa, 93864.11, IAQ, 189.91 (3), Static IAQ, 159.93, CO2e, 1599.35 (3), bVOC, 3.84 (3)
    [05:23:41.094] T, 24.52, rH, 30.96, Pa, 93865.80, IAQ, 212.69 (3), Static IAQ, 178.56, CO2e, 1785.64 (3), bVOC, 5.09 (3)
    [05:23:44.100] T, 24.52, rH, 30.95, Pa, 93865.80, IAQ, 236.98 (3), Static IAQ, 198.43, CO2e, 1984.37 (3), bVOC, 6.87 (3)


    [05:23:47.106] T, 24.52, rH, 30.95, Pa, 93865.85, IAQ, 264.75 (2), Static IAQ, 221.86, CO2e, 2218.62 (2), bVOC, 9.80 (2)
    [05:23:50.112] T, 24.52, rH, 30.95, Pa, 93865.07, IAQ, 312.35 (2), Static IAQ, 261.79, CO2e, 2617.94 (2), bVOC, 17.92 (2)
    [05:23:53.118] T, 24.52, rH, 30.97, Pa, 93865.98, IAQ, 369.26 (2), Static IAQ, 309.70, CO2e, 3097.06 (2), bVOC, 36.98 (2)
    [05:23:56.124] T, 24.53, rH, 30.98, Pa, 93866.55, IAQ, 427.10 (2), Static IAQ, 358.71, CO2e, 3587.18 (2), bVOC, 77.59 (2)
    [05:23:59.130] T, 24.52, rH, 31.03, Pa, 93865.92, IAQ, 471.39 (2), Static IAQ, 396.78, CO2e, 3967.88 (2), bVOC, 137.96 (2)
    [05:24:02.136] T, 24.53, rH, 31.02, Pa, 93865.97, IAQ, 489.92 (2), Static IAQ, 413.58, CO2e, 4135.87 (2), bVOC, 177.84 (2)
    [05:24:05.142] T, 24.52, rH, 30.98, Pa, 93864.74, IAQ, 491.81 (2), Static IAQ, 416.52, CO2e, 4165.27 (2), bVOC, 185.92 (2)

    [05:24:29.190] T, 24.53, rH, 30.87, Pa, 93868.17, IAQ, 500.00 (2), Static IAQ, 441.76, CO2e, 4417.66 (2), bVOC, 272.29 (2)
    [05:24:32.196] T, 24.54, rH, 30.88, Pa, 93869.30, IAQ, 500.00 (2), Static IAQ, 451.84, CO2e, 4518.46 (2), bVOC, 317.11 (2)
    [05:24:35.202] T, 24.53, rH, 30.87, Pa, 93869.53, IAQ, 500.00 (2), Static IAQ, 455.42, CO2e, 4554.22 (2), bVOC, 334.72 (2)

    .............
    [05:31:02.976] T, 24.54, rH, 30.83, Pa, 93864.33, IAQ, 243.24 (2), Static IAQ, 285.56, CO2e, 2855.62 (2), bVOC, 25.67 (2)
    [05:31:05.982] T, 24.55, rH, 30.86, Pa, 93865.46, IAQ, 242.80 (2), Static IAQ, 285.03, CO2e, 2850.32 (2), bVOC, 25.47 (2)
    [05:31:08.988] T, 24.55, rH, 30.84, Pa, 93865.01, IAQ, 243.85 (2), Static IAQ, 286.27, CO2e, 2862.78 (2), bVOC, 25.95 (2)
    [05:31:11.994] T, 24.55, rH, 30.85, Pa, 93863.44, IAQ, 243.36 (2), Static IAQ, 285.67, CO2e, 2856.76 (2), bVOC, 25.72 (2)
    [05:31:15.000] T, 24.55, rH, 30.83, Pa, 93863.95, IAQ, 242.47 (2), Static IAQ, 284.61, CO2e, 2846.14 (2), bVOC, 25.31 (2)
    [05:31:18.006] T, 24.55, rH, 30.81, Pa, 93864.39, IAQ, 241.47 (2), Static IAQ, 283.40, CO2e, 2834.03 (2), bVOC, 24.85 (2)
    [05:31:21.012] T, 24.55, rH, 30.78, Pa, 93865.75, IAQ, 241.06 (3), Static IAQ, 282.90, CO2e, 2829.09 (3), bVOC, 24.66 (3)
    [05:31:24.018] T, 24.55, rH, 30.78, Pa, 93864.90, IAQ, 240.78 (3), Static IAQ, 282.57, CO2e, 2825.71 (3), bVOC, 24.54 (3)
    [05:31:27.024] T, 24.55, rH, 30.78, Pa, 93865.99, IAQ, 240.46 (3), Static IAQ, 282.17, CO2e, 2821.70 (3), bVOC, 24.39 (3)
    [05:31:30.030] T, 24.55, rH, 30.81, Pa, 93863.61, IAQ, 241.72 (3), Static IAQ, 283.66, CO2e, 2836.67 (3), bVOC, 24.95 (3)
    [05:31:33.036] T, 24.55, rH, 30.84, Pa, 93864.17, IAQ, 241.62 (3), Static IAQ, 283.54, CO2e, 2835.40 (3), bVOC, 24.90 (3)
    [05:31:36.042] T, 24.55, rH, 30.86, Pa, 93864.39, IAQ, 241.94 (3), Static IAQ, 283.91, CO2e, 2839.14 (3), bVOC, 25.04 (3)
    [05:31:39.048] T, 24.55, rH, 30.88, Pa, 93864.28, IAQ, 242.02 (3), Static IAQ, 283.99, CO2e, 2839.94 (3), bVOC, 25.07 (3)
    [05:31:42.054] T, 24.55, rH, 30.91, Pa, 93864.06, IAQ, 242.32 (3), Static IAQ, 284.34, CO2e, 2843.48 (3), bVOC, 25.21 (3)
    [05:31:45.060] T, 24.56, rH, 30.91, Pa, 93865.12, IAQ, 242.10 (3), Static IAQ, 284.07, CO2e, 2840.73 (3), bVOC, 25.10 (3)
    [05:31:48.066] T, 24.55, rH, 30.92, Pa, 93864.23, IAQ, 241.52 (3), Static IAQ, 283.37, CO2e, 2833.76 (3), bVOC, 24.84 (3)
    [05:31:51.072] T, 24.56, rH, 30.90, Pa, 93866.09, IAQ, 241.65 (3), Static IAQ, 283.52, CO2e, 2835.21 (3), bVOC, 24.89 (3)
    [05:31:54.078] T, 24.56, rH, 30.90, Pa, 93865.29, IAQ, 240.92 (3), Static IAQ, 282.63, CO2e, 2826.39 (3), bVOC, 24.56 (3)

    As you can see, we are working in a controlled area with around 1000ppm CO2 values. This concentration values did not change throughout the test (we know this because other VOC sensors gave us CO2 concentration values around 1000ppm throughout the test). However, as you can see, the BME680 started to provide some abnormally high CO2 values (it even hit an IAQ of 500!), began a recalibration, and after that it provided abnormal unrealistically high IAQ, CO2e, and bVOC values.

    We don't undertand why the sensor suddenly started showing these strange values. We are planning to use this sensor to monitor Air Quality in critical areas and we can't afford to provide erroneous values.

    Have you experienced something like this? Could it be a bug within BSEC library? Do you have any suggestions on what may be going on?

    Regards

     

    10 REPLIES 10

    BSTRobin
    Community Moderator
    Community Moderator

    Hello adam_smith,

    The CO2 is estimated from VOC output (SIAQ), so it can not be used as an reference of CO2 concentration and it does not have accuracy.

    Hello,

    I can understand that the CO2 values are estimated and they are not quiet accuracy. However, any other value is also wrong. 

    You can see an IAQ value around 130 but it suddenly starts to show values around 300, but the envoronmental conditions have not changed.

    Can you provide some guideline on why the sensor suddenly starts to recalibrate if there has been no change in the environment?

    Thanks

    Hello again,

    any update about this?

    Thanks

    BSTRobin
    Community Moderator
    Community Moderator

    Hello adam_smith,

    We couldn't give comment on limited log data, since we do not know the actually test environment.
    If you needed, you could provide the raw data to us, we can do simulation for them. The log data needs to be recorded in the format of attachment.

    BSTRobin
    Community Moderator
    Community Moderator

    Hello adam_smith,

    Do you have further feedback?

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