BME688 gas resistance reading stuck, but only with bsec

[Remyhx]

Hi,

I use BSEC 1.6.1480 with Arduino 1.8.16 on an esp32 board / BME688 SDO tied to GND. I am interested in the IAQ index, seems to work. But strange thing: if i use the basic example, unchanged, the gas resistance reading seems not ok (stuck at 12917167 ohm). For example:

4170038, 23.09, 99831.00, 48.16, 12917167.00, 81.06, 1, 23.03, 48.33, 49.49, 597.95, 0.72
4173039, 23.10, 99833.00, 48.13, 12917167.00, 81.09, 1, 23.04, 48.28, 49.50, 598.00, 0.72
4176038, 23.08, 99831.00, 48.13, 12917167.00, 81.16, 1, 23.02, 48.34, 49.53, 598.13, 0.72
4179039, 23.09, 99831.00, 48.16, 12917167.00, 81.19, 1, 23.03, 48.33, 49.55, 598.18, 0.72
4182038, 23.09, 99833.00, 48.17, 12917167.00, 81.20, 1, 23.03, 48.36, 49.55, 598.20, 0.72
4185039, 23.09, 99831.00, 48.11, 12917167.00, 81.27, 1, 23.03, 48.29, 49.58, 598.32, 0.72
4188038, 23.08, 99831.00, 48.13, 12917167.00, 81.33, 1, 23.02, 48.34, 49.61, 598.43, 0.73
4191039, 23.09, 99833.00, 48.15, 12917167.00, 81.36, 1, 23.03, 48.32, 49.62, 598.48, 0.73
4194038, 23.09, 99831.00, 48.13, 12917167.00, 81.40, 1, 23.03, 48.31, 49.64, 598.55, 0.73
4197038, 23.09, 99829.00, 48.17, 12917167.00, 81.41, 1, 23.03, 48.35, 49.64, 598.56, 0.73
4200038, 23.10, 99831.00, 48.14, 12917167.00, 81.42, 1, 23.04, 48.30, 49.64, 598.58, 0.73
4203039, 23.09, 99833.00, 48.13, 12917167.00, 81.45, 1, 23.03, 48.32, 49.66, 598.64, 0.73
4206038, 23.09, 99833.00, 48.11, 12917167.00, 81.51, 1, 23.03, 48.30, 49.68, 598.73, 0.73
4209039, 23.09, 99831.00, 48.12, 12917167.00, 81.55, 1, 23.03, 48.31, 49.70, 598.81, 0.73
4212038, 23.10, 99829.00, 48.13, 12917167.00, 81.56, 1, 23.04, 48.29, 49.71, 598.83, 0.73
4215039, 23.10, 99833.00, 48.12, 12917167.00, 81.58, 1, 23.04, 48.29, 49.71, 598.86, 0.73
4218038, 23.11, 99829.00, 48.13, 12917167.00, 81.56, 1, 23.05, 48.28, 49.71, 598.83, 0.73
4221039, 23.11, 99833.00, 48.13, 12917167.00, 81.55, 1, 23.05, 48.29, 49.70, 598.81, 0.73
4224038, 23.10, 99831.00, 48.08, 12917167.00, 81.59, 1, 23.04, 48.27, 49.72, 598.89, 0.73
4227039, 23.10, 99831.00, 48.02, 12917167.00, 81.69, 1, 23.04, 48.21, 49.76, 599.05, 0.73
4230038, 23.10, 99831.00, 48.02, 12917167.00, 81.78, 1, 23.04, 48.21, 49.80, 599.21, 0.73

Strange thing is, if i use the Adafruit library gas resistance reading appears to be normal, at least dynamic. But no IAQ reading.

I could only use the IAQ reading and ignore gas resistance, but i worrie about a faulty IAQ reading. Compared to the Sensirion vocindex buildup a fake index could be appearing. When i test with alcohol spray (not directly applied of course) in the room, the voc index drops by 5, instead of climbing...

Do you have a suggestion?

NB: Adafruit BME680 version 2.0.1(!) / look at the ohm change...

Temperature = 23.41 *C
Pressure = 998.68 hPa
Humidity = 48.96 %
Gas = 23.78 KOhms
Approx. Altitude = 122.02 m

Gas kOhms changes, with alcoholspray aerosol drops.

Zanshin library for BME680:

Loop Temp°C Humid% Press hPa Alt m Air mΩ
==== ====== ====== ========= ======= ======
1 23.51 51.088 998.52 123.48-1901.67
2 23.74 51.132 998.52 123.48-1901.67
3 23.52 51.074 998.56 123.14-1901.67
4 23.36 51.199 998.54 123.31-1901.67

Gas resistance seems faulty too. Strange!

[Ciprian]

Hey there,

A bit late, but have you been able to find a solution?

I am running a 688 on a Nicle Sense ME board, and my Gas Resistance is stuck at:  12946859.00 and my comp_g (compensated gas resistance in ohms) is 7.

These values seem extremely weird, although the IAQ,  VOC_EQ and CO2_EQ seem correct.

Any advice?

[bastler67]

I'm facing kind of the same issue:

The Hardware I use is the

- Adafruit BME688 board

- Arduino Nano IOT 33.

 software I'm usingThe is the

- BSEC library v1.6.1480

- the "basic" arduino sample provided for that lib (only change made is to change the I2C adress to "secondary")

- Arduino IDE v 1.8.13 

after some days of calibration I see the following output:

8:52:49.818 -> 244371027, 21.34, 99526.00, 43.63, 12976914.00, 147.29, 3, 21.28, 43.83, 117.42, 1174.20, 2.02
18:52:52.811 -> 244374027, 21.35, 99534.00, 43.66, 12976914.00, 147.31, 3, 21.29, 43.83, 117.43, 1174.27, 2.02
18:52:55.819 -> 244377027, 21.35, 99524.00, 43.69, 12976914.00, 147.30, 3, 21.29, 43.86, 117.42, 1174.21, 2.02
18:52:58.789 -> 244380027, 21.35, 99524.00, 43.77, 12976914.00, 147.26, 3, 21.29, 43.94, 117.39, 1173.85, 2.02
18:53:01.782 -> 244383027, 21.35, 99520.00, 43.84, 12976914.00, 147.18, 3, 21.29, 44.01, 117.32, 1173.21, 2.02
18:53:04.788 -> 244386027, 21.35, 99518.00, 43.90, 12976914.00, 147.07, 3, 21.29, 44.07, 117.24, 1172.36, 2.02
18:53:07.803 -> 244389027, 21.35, 99516.00, 43.93, 12976914.00, 146.95, 3, 21.29, 44.10, 117.14, 1171.43, 2.01
18:53:10.801 -> 244392027, 21.35, 99514.00, 43.90, 12976914.00, 146.86, 3, 21.29, 44.07, 117.07, 1170.66, 2.01
18:53:13.825 -> 244395027, 21.36, 99514.00, 43.82, 12976914.00, 146.79, 3, 21.30, 43.97, 117.01, 1170.15, 2.01
18:53:16.819 -> 244398027, 21.35, 99510.00, 43.72, 12976914.00, 146.80, 3, 21.29, 43.90, 117.01, 1170.15, 2.01
18:53:19.782 -> 244401027, 21.35, 99514.00, 43.63, 12976914.00, 146.85, 3, 21.29, 43.80, 117.05, 1170.51, 2.01
18:53:22.792 -> 244404027, 21.36, 99520.00, 43.55, 12976914.00, 146.93, 3, 21.30, 43.71, 117.11, 1171.06, 2.01
18:53:25.802 -> 244407027, 21.36, 99516.00, 43.47, 12976914.00, 147.04, 3, 21.30, 43.63, 117.19, 1171.89, 2.01
18:53:28.812 -> 244410027, 21.36, 99514.00, 43.44, 12976914.00, 147.17, 3, 21.30, 43.60, 117.28, 1172.83, 2.02
18:53:31.821 -> 244413027, 21.32, 99516.00, 43.50, 12976914.00, 147.31, 3, 21.26, 43.75, 117.39, 1173.87, 2.02

Here I sprayed some desinfection spray (includes a lot of alcohole and obviously some water) in the room ONCE:
18:53:34.832 -> 244416027, 21.05, 99524.00, 46.74, 12976914.00, 146.10, 3, 20.99, 47.60, 116.47, 1164.71, 1.99
18:53:37.808 -> 244419027, 20.97, 99524.00, 55.02, 12976914.00, 140.74, 3, 20.91, 56.09, 112.42, 1124.18, 1.87
18:53:40.819 -> 244422027, 20.95, 99522.00, 62.17, 12976914.00, 132.06, 3, 20.89, 63.23, 105.86, 1058.56, 1.70
18:53:43.783 -> 244425027, 20.95, 99522.00, 67.29, 12976914.00, 121.36, 3, 20.89, 68.25, 97.78, 977.75, 1.50
18:53:46.793 -> 244428026, 20.90, 99524.00, 70.06, 12976914.00, 110.10, 3, 20.84, 71.08, 89.27, 892.68, 1.32
18:53:49.804 -> 244431027, 20.90, 99524.00, 70.67, 12976914.00, 99.32, 3, 20.84, 71.54, 81.12, 811.25, 1.17
18:53:52.814 -> 244434027, 20.87, 99530.00, 70.94, 12976914.00, 89.18, 3, 20.81, 71.79, 73.47, 734.67, 1.04
18:53:55.824 -> 244437027, 20.85, 99530.00, 70.90, 12976914.00, 79.76, 3, 20.79, 71.70, 66.35, 665.40, 0.93
18:53:58.781 -> 244440026, 20.80, 99526.00, 70.11, 12976914.00, 71.37, 3, 20.74, 70.96, 60.02, 640.06, 0.85
18:54:01.792 -> 244443027, 20.78, 99522.00, 67.82, 12976914.00, 64.55, 3, 20.72, 68.60, 54.87, 619.47, 0.79
18:54:04.802 -> 244446026, 20.78, 99522.00, 65.02, 12976914.00, 59.38, 3, 20.72, 65.66, 50.96, 603.82, 0.74
18:54:07.813 -> 244449026, 20.76, 99520.00, 61.97, 12976914.00, 55.84, 3, 20.70, 62.57, 48.29, 593.15, 0.71
18:54:10.823 -> 244452027, 20.78, 99524.00, 59.09, 12976914.00, 53.72, 3, 20.72, 59.53, 46.68, 586.73, 0.69
18:54:13.787 -> 244455027, 20.79, 99526.00, 56.61, 12976914.00, 52.76, 3, 20.73, 56.96, 45.96, 583.83, 0.69
18:54:16.797 -> 244458027, 20.80, 99524.00, 54.46, 12976914.00, 52.76, 3, 20.74, 54.75, 45.96, 583.83, 0.69
18:54:19.808 -> 244461027, 20.81, 99524.00, 52.89, 12976914.00, 53.42, 3, 20.75, 53.13, 46.46, 585.83, 0.69
18:54:22.818 -> 244464027, 20.83, 99524.00, 51.60, 12976914.00, 54.59, 3, 20.77, 51.77, 47.34, 589.34, 0.70
18:54:25.827 -> 244467027, 20.84, 99526.00, 50.43, 12976914.00, 56.19, 3, 20.78, 50.58, 48.55, 594.19, 0.71
18:54:28.784 -> 244470027, 20.85, 99524.00, 49.47, 12976914.00, 58.13, 3, 20.79, 49.61, 50.01, 600.03, 0.73
18:54:31.794 -> 244473026, 20.87, 99526.00, 48.76, 12976914.00, 60.26, 3, 20.81, 48.86, 51.62, 606.47, 0.75
18:54:34.805 -> 244476027, 20.88, 99524.00, 48.39, 12976914.00, 62.45, 3, 20.82, 48.48, 53.27, 613.08, 0.77
18:54:37.816 -> 244479026, 20.89, 99526.00, 48.10, 12976914.00, 64.66, 3, 20.83, 48.19, 54.94, 619.75, 0.79
18:54:40.826 -> 244482027, 20.91, 99524.00, 48.00, 12976914.00, 66.80, 3, 20.85, 48.06, 56.55, 626.19, 0.81
18:54:43.790 -> 244485027, 20.92, 99528.00, 47.83, 12976914.00, 68.90, 3, 20.86, 47.90, 58.14, 632.54, 0.83
18:54:46.800 -> 244488027, 20.93, 99530.00, 47.64, 12976914.00, 70.99, 3, 20.87, 47.71, 59.71, 638.84, 0.84
18:54:49.810 -> 244491027, 20.94, 99530.00, 47.38, 12976914.00, 73.09, 3, 20.88, 47.45, 61.29, 645.18, 0.87

As you can see the gas resistance does not change (stuck at 12976914.00) and the IAQ values drop down instead of rising as I expected.

You can also see that the values recover after a while (but it is still some kind of smelly... so I should stop writing soon... :-))

for your reference, output is:

unsigned long time_trigger = millis();
if (iaqSensor.run()) { // If new data is available
output = String(time_trigger);
output += ", " + String(iaqSensor.rawTemperature);
output += ", " + String(iaqSensor.pressure);
output += ", " + String(iaqSensor.rawHumidity);
output += ", " + String(iaqSensor.gasResistance);
output += ", " + String(iaqSensor.iaq);
output += ", " + String(iaqSensor.iaqAccuracy);
output += ", " + String(iaqSensor.temperature);
output += ", " + String(iaqSensor.humidity);
output += ", " + String(iaqSensor.staticIaq);
output += ", " + String(iaqSensor.co2Equivalent);
output += ", " + String(iaqSensor.breathVocEquivalent);

I tried the same with applying the calibation file "config/generic_33v_3s_4d/bsec_iaq.txt" as provided with the "config_state" example but the result seems to be the same...

Can one of you please help?

Many thanks in advance!