[BME688 and BSEC 2.0] IAQ accuracy 3 but IAQ value bouncing between 25 to 150

[amessner]

I am using the BME688 with BSEC 2.0 on a nRF52840 (Cortex M4F).

I ported the example provided in the BSEC library package (bsec_2-0-6-1_generic_release_04302021), only difference is that I subscribe to a few additional sensor outputs:

BSEC_OUTPUT_RAW_TEMPERATURE,
BSEC_OUTPUT_RAW_PRESSURE,
BSEC_OUTPUT_RAW_HUMIDITY,
BSEC_OUTPUT_RAW_GAS,
BSEC_OUTPUT_RAW_GAS_INDEX,
BSEC_OUTPUT_IAQ,
BSEC_OUTPUT_STATIC_IAQ,
BSEC_OUTPUT_CO2_EQUIVALENT,
BSEC_OUTPUT_BREATH_VOC_EQUIVALENT,
BSEC_OUTPUT_SENSOR_HEAT_COMPENSATED_TEMPERATURE,
BSEC_OUTPUT_SENSOR_HEAT_COMPENSATED_HUMIDITY,
BSEC_OUTPUT_GAS_ESTIMATE_1,
BSEC_OUTPUT_GAS_ESTIMATE_2,
BSEC_OUTPUT_GAS_ESTIMATE_3,
BSEC_OUTPUT_GAS_ESTIMATE_4

If I let the code run for a while the system reaches IAQ accuracy 3, however the IAQ measurements are not stable. The IAQ value bounces between ~25 and ~150, I expected it to be much more stable.

I'm using the provided configuration "bsec_sel_iaq_33v_4d" and each 5 scanning cycles look like the example log below (please note: IAQ is only updated once per scanning cycle, but I store it in a variable so that each print statement prints its last known value): 

<info> app: gas index 0
<info> app: BME688 - T: 24.44 degC, P: 940.70 hPa, H 40.40 %rH, G: 271474.03 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 1
<info> app: BME688 - T: 24.56 degC, P: 940.75 hPa, H 40.34 %rH, G: 40292652.00 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 2
<info> app: BME688 - T: 24.70 degC, P: 940.73 hPa, H 39.56 %rH, G: 37491992.00 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 3
<info> app: BME688 - T: 25.08 degC, P: 940.74 hPa, H 37.17 %rH, G: 34420168.00 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 4
<info> app: BME688 - T: 25.69 degC, P: 940.74 hPa, H 36.90 %rH, G: 2014756.50 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 5
<info> app: BME688 - T: 25.96 degC, P: 940.75 hPa, H 36.55 %rH, G: 1951405.37 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 6
<info> app: BME688 - T: 26.09 degC, P: 940.78 hPa, H 36.21 %rH, G: 1885385.50 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 7
<info> app: BME688 - T: 26.51 degC, P: 940.75 hPa, H 35.90 %rH, G: 286513.71 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 8
<info> app: BME688 - T: 26.74 degC, P: 940.75 hPa, H 35.49 %rH, G: 335188.21 ohm
<info> app: IAQ: 41.80, IAQ Acc: 3, Stat IAQ: 41.75, CO2e: 566.99, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 9
<info> app: BME688 - T: 26.88 degC, P: 940.78 hPa, H 35.11 %rH, G: 380033.40 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 0
<info> app: BME688 - T: 26.97 degC, P: 940.73 hPa, H 34.72 %rH, G: 410174.25 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 1
<info> app: BME688 - T: 26.60 degC, P: 940.80 hPa, H 34.52 %rH, G: 79703256.00 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 2
<info> app: BME688 - T: 25.73 degC, P: 940.77 hPa, H 33.86 %rH, G: 74599888.00 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 3
<info> app: BME688 - T: 25.50 degC, P: 940.74 hPa, H 33.26 %rH, G: 65437844.00 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 4
<info> app: BME688 - T: 26.09 degC, P: 940.76 hPa, H 33.26 %rH, G: 3366344.75 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 5
<info> app: BME688 - T: 26.32 degC, P: 940.79 hPa, H 33.22 %rH, G: 3219493.00 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 6
<info> app: BME688 - T: 26.43 degC, P: 940.76 hPa, H 33.09 %rH, G: 3102442.75 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 7
<info> app: BME688 - T: 26.83 degC, P: 940.77 hPa, H 33.02 %rH, G: 377302.87 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 8
<info> app: BME688 - T: 27.05 degC, P: 940.75 hPa, H 32.85 %rH, G: 416683.62 ohm
<info> app: IAQ: 140.20, IAQ Acc: 3, Stat IAQ: 139.84, CO2e: 1398.36, bVOC: 2.84, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 9
<info> app: BME688 - T: 27.16 degC, P: 940.74 hPa, H 32.66 %rH, G: 444637.43 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 0
<info> app: BME688 - T: 27.25 degC, P: 940.74 hPa, H 32.47 %rH, G: 464609.81 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 1
<info> app: BME688 - T: 26.88 degC, P: 940.82 hPa, H 32.37 %rH, G: 100863408.00 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 2
<info> app: BME688 - T: 25.99 degC, P: 940.78 hPa, H 32.02 %rH, G: 91948088.00 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 3
<info> app: BME688 - T: 25.72 degC, P: 940.77 hPa, H 31.96 %rH, G: 81868832.00 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 4
<info> app: BME688 - T: 26.31 degC, P: 940.75 hPa, H 32.05 %rH, G: 4000000.00 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 5
<info> app: BME688 - T: 26.52 degC, P: 940.75 hPa, H 32.05 %rH, G: 3815556.50 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 6
<info> app: BME688 - T: 26.63 degC, P: 940.73 hPa, H 32.02 %rH, G: 3666965.00 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 7
<info> app: BME688 - T: 27.03 degC, P: 940.72 hPa, H 31.97 %rH, G: 415668.75 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 8
<info> app: BME688 - T: 27.24 degC, P: 940.74 hPa, H 31.88 %rH, G: 452296.81 ohm
<info> app: IAQ: 104.87, IAQ Acc: 3, Stat IAQ: 104.60, CO2e: 1046.01, bVOC: 1.67, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 9
<info> app: BME688 - T: 27.36 degC, P: 940.73 hPa, H 31.78 %rH, G: 476944.56 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 0
<info> app: BME688 - T: 27.45 degC, P: 940.74 hPa, H 31.63 %rH, G: 493850.96 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 1
<info> app: BME688 - T: 27.04 degC, P: 940.76 hPa, H 31.52 %rH, G: 102400000.00 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 2
<info> app: BME688 - T: 26.16 degC, P: 940.78 hPa, H 31.27 %rH, G: 101331272.00 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 3
<info> app: BME688 - T: 25.88 degC, P: 940.77 hPa, H 31.43 %rH, G: 90707264.00 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 4
<info> app: BME688 - T: 26.45 degC, P: 940.72 hPa, H 31.53 %rH, G: 4295752.50 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 5
<info> app: BME688 - T: 26.67 degC, P: 940.75 hPa, H 31.56 %rH, G: 4126952.25 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 6
<info> app: BME688 - T: 26.78 degC, P: 940.74 hPa, H 31.54 %rH, G: 3950807.75 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 7
<info> app: BME688 - T: 27.18 degC, P: 940.75 hPa, H 31.52 %rH, G: 438074.87 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 8
<info> app: BME688 - T: 27.37 degC, P: 940.71 hPa, H 31.46 %rH, G: 473635.53 ohm
<info> app: IAQ: 74.00, IAQ Acc: 3, Stat IAQ: 73.83, CO2e: 738.27, bVOC: 1.05, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 9
<info> app: BME688 - T: 27.49 degC, P: 940.71 hPa, H 31.36 %rH, G: 493850.96 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 0
<info> app: BME688 - T: 27.57 degC, P: 940.74 hPa, H 31.23 %rH, G: 516649.84 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 1
<info> app: BME688 - T: 27.17 degC, P: 940.76 hPa, H 31.11 %rH, G: 102400000.00 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 2
<info> app: BME688 - T: 26.28 degC, P: 940.73 hPa, H 30.86 %rH, G: 102400000.00 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 3
<info> app: BME688 - T: 25.98 degC, P: 940.76 hPa, H 31.11 %rH, G: 96093840.00 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 4
<info> app: BME688 - T: 26.56 degC, P: 940.73 hPa, H 31.21 %rH, G: 4493691.50 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 5
<info> app: BME688 - T: 26.78 degC, P: 940.74 hPa, H 31.24 %rH, G: 4309311.00 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 6
<info> app: BME688 - T: 26.88 degC, P: 940.73 hPa, H 31.19 %rH, G: 4171079.50 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 7
<info> app: BME688 - T: 27.27 degC, P: 940.73 hPa, H 31.20 %rH, G: 452596.68 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 8
<info> app: BME688 - T: 27.47 degC, P: 940.71 hPa, H 31.11 %rH, G: 486114.40 ohm
<info> app: IAQ: 56.46, IAQ Acc: 3, Stat IAQ: 56.34, CO2e: 625.36, bVOC: 0.80, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 9
<info> app: BME688 - T: 27.59 degC, P: 940.73 hPa, H 31.01 %rH, G: 511233.15 ohm
<info> app: IAQ: 41.63, IAQ Acc: 3, Stat IAQ: 41.56, CO2e: 566.25, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: cur->54529 next->54637 (seconds)
<info> app: gas index 0
<info> app: BME688 - T: 24.46 degC, P: 940.67 hPa, H 40.59 %rH, G: 270613.09 ohm
<info> app: IAQ: 41.63, IAQ Acc: 3, Stat IAQ: 41.56, CO2e: 566.25, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 1
<info> app: BME688 - T: 24.58 degC, P: 940.72 hPa, H 40.51 %rH, G: 40107712.00 ohm
<info> app: IAQ: 41.63, IAQ Acc: 3, Stat IAQ: 41.56, CO2e: 566.25, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3
<info> app: gas index 2
<info> app: BME688 - T: 24.73 degC, P: 940.70 hPa, H 39.74 %rH, G: 37524192.00 ohm
<info> app: IAQ: 41.63, IAQ Acc: 3, Stat IAQ: 41.56, CO2e: 566.25, bVOC: 0.64, H2S: 0.00, H2S Acc: 3, non-H2S: 1.00, H2S Acc: 3

Has anybody seen this before? Any help is much appreciated.

[BSTRobin · Accepted solution]

Hello amessner,

From the log you provided, there is no data loss, and the IAQ is not obvious abnormal.
Could you try to test with your target gas to see if the gas can be distinguished or not?

[BSTRobin]

Hello amessner,

Could you give further feedback?

[BSTRobin]

Since there was no further feedback for a long time, we close this topic first. You could update feedback in the future if you have.