BME680: IAQ accuracy going from 3 o 1

[micha_pr]

Hello,

using the BME680 as indoor sensor in office room I can see red marked IAQ accuracy

18:57:52.693 -> 164814095, 24.24, 101317.00, 54.56, 731373.00, 38.85, 3, 24.18, 54.75, 32.37, 529.50, 0.56
18:57:55.732 -> 164817096, 24.24, 101321.00, 54.58, 721204.00, 39.58, 3, 24.18, 54.77, 32.77, 531.06, 0.56
18:57:58.729 -> 164820096, 24.25, 101319.00, 54.62, 729001.00, 36.84, 1, 24.19, 54.79, 31.31, 525.23, 0.55
18:58:01.735 -> 164823096, 24.24, 101319.00, 54.63, 721976.00, 37.78, 1, 24.18, 54.84, 31.81, 527.22, 0.55
18:58:04.726 -> 164826095, 24.25, 101317.00, 54.64, 712818.00, 42.12, 1, 24.19, 54.82, 34.12, 536.47, 0.57

There was no reason for changing the accuracy to 1, I think...
I understand that after a while in little changing environmental conditions the accuracy may fall down to value 2 until it can come back to value 3, but why to value 1?

Value 1 will be there for at least 14 hours, as I can see.

(BTW: it was taking 3 days until the IAQ accuracy was set to 3 - in office room. I know... stable environment ...)

And - does it make sense to (auto-)save this config state (with value 1) and overwrite the existing state 3?
Or can it help to save the old config state and reload it if there are no changes in environmental conditions?

Thanks!

Michael

[BSTRobin]

Hello micha_pr,

Default BSEC output values every 3 second. You should check your timestamp and ensure get_timestamp_us() function is correct. And try your test again.

[micha_pr]

Hi,

do not understand.... every sensor is reporting values every 3 seconds as you can see in log, right?
(there are two sensors in log)

And every sensor have the same issue - that is going to accuracy "1" after some time and is not going back a long time again.

This was the question... 😉

Thanks!

[BSTRobin]

Hello micha_pr,

If you use default BSEC config in you program, BSEC output data about every 3S.

Yes, BSEC output data every 3 second in my following log, time stamp unit is nanoseconds.

If time stamp has wrong value, IAQ accuracy has posibillity to drop down.

[micha_pr]

Hi,

ok, but do not understand what problem may be..

I use "if (iaqSensor1.run()) ... "  and "if (iaqSensor2.run()).." and read the values.
same code as in sample (basic_config_state_multi)

You think it maybe better to use an own delay of 4 seconds as sample to read values?

[BSTRobin]

Hello micha_pr,

IAQ accuracy indicator will notify the user when she/he should initiate a calibration process. Calibration is performed automatically in the background if the sensor is exposed to clean and polluted air for approximately 30 minutes each.

From you log data, There was no big difference for IAQ value output. Do you have log data for more time?