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,

How long has your BME680 been running since it was powered on? Are there any specific changes in the environment?

[micha_pr]

Hi
164814 seconds - so 45 hours. Before it was running 4 days (powered on again)

And - as I wrote, no changes in environment.

Michael

[micha_pr]

Same today - I use the sketch with 2 sensors:

14:06:24.608 -> 1, 88107148, 25.16, 102053.00, 49.86, 86078.00, 57.86, 3, 25.10, 50.06, 41.91, 567.63, 0.65
14:06:24.983 -> 2, 88107531, 26.22, 102059.00, 50.07, 85901.00, 64.09, 3, 26.16, 50.26, 45.67, 582.66, 0.68
14:06:27.585 -> 1, 88110148, 25.15, 102053.00, 49.83, 85813.00, 58.27, 3, 25.09, 50.05, 42.12, 568.47, 0.65
14:06:27.995 -> 2, 88110531, 26.21, 102059.00, 50.04, 86256.00, 63.38, 3, 26.15, 50.26, 45.29, 581.16, 0.68
14:06:30.610 -> 1, 88113148, 25.16, 102051.00, 49.82, 85990.00, 57.90, 3, 25.10, 50.01, 41.93, 567.72, 0.65
14:06:30.987 -> 2, 88113530, 26.22, 102057.00, 50.03, 86256.00, 62.86, 3, 26.16, 50.22, 45.02, 580.07, 0.68
14:06:33.608 -> 1, 88116147, 25.16, 102053.00, 49.78, 85813.00, 58.29, 3, 25.10, 49.97, 42.13, 568.50, 0.65
14:06:33.979 -> 2, 88116531, 26.21, 102057.00, 49.99, 86167.00, 62.84, 3, 26.15, 50.20, 45.01, 580.03, 0.68
14:06:36.601 -> 1, 88119148, 25.16, 102053.00, 49.77, 86525.00, 56.03, 1, 25.10, 49.96, 40.97, 563.86, 0.64
14:06:36.974 -> 2, 88119531, 26.22, 102057.00, 49.97, 86167.00, 62.82, 3, 26.16, 50.16, 44.99, 579.98, 0.68
14:06:39.578 -> 1, 88122148, 25.17, 102053.00, 49.78, 86078.00, 56.02, 1, 25.11, 49.95, 40.96, 563.85, 0.64
14:06:39.999 -> 2, 88122531, 26.23, 102061.00, 49.96, 86256.00, 62.48, 3, 26.17, 50.12, 44.81, 579.26, 0.67
14:06:42.614 -> 1, 88125148, 25.16, 102055.00, 49.74, 86078.00, 56.05, 1, 25.10, 49.94, 40.98, 563.91, 0.64
14:06:42.987 -> 2, 88125531, 26.22, 102059.00, 49.95, 86346.00, 61.96, 3, 26.16, 50.14, 44.54, 578.14, 0.67
............

15:45:48.552 -> 1, 94071148, 25.03, 102002.00, 51.14, 82667.00, 82.48, 1, 24.97, 51.33, 52.60, 610.39, 0.76
15:45:48.922 -> 2, 94071531, 26.08, 102002.00, 51.35, 82422.00, 89.74, 3, 26.02, 51.54, 56.98, 627.92, 0.81
15:45:51.573 -> 1, 94074148, 25.03, 102000.00, 51.11, 82422.00, 82.98, 1, 24.97, 51.30, 52.84, 611.34, 0.76
15:45:51.946 -> 2, 94074530, 26.09, 102006.00, 51.31, 82913.00, 88.44, 3, 26.03, 51.48, 56.33, 625.34, 0.80
15:45:54.562 -> 1, 94077148, 25.03, 101998.00, 51.13, 82585.00, 82.66, 1, 24.97, 51.32, 52.68, 610.73, 0.76
15:45:54.934 -> 2, 94077530, 26.09, 102006.00, 51.33, 83161.00, 86.57, 1, 26.03, 51.50, 55.41, 621.66, 0.79
15:45:57.547 -> 1, 94080148, 25.04, 102000.00, 51.11, 82913.00, 81.14, 1, 24.98, 51.28, 51.95, 607.81, 0.75
15:45:57.966 -> 2, 94080531, 26.08, 102008.00, 51.32, 83079.00, 85.63, 1, 26.02, 51.53, 54.94, 619.78, 0.79
15:46:00.582 -> 1, 94083148, 25.02, 102000.00, 51.11, 82585.00, 81.42, 1, 24.96, 51.34, 52.09, 608.34, 0.75
15:46:00.955 -> 2, 94083531, 26.09, 102010.00, 51.30, 82504.00, 87.18, 1, 26.03, 51.48, 55.71, 622.84, 0.80
15:46:03.566 -> 1, 94086148, 25.03, 102000.00, 51.10, 82422.00, 82.25, 1, 24.97, 51.30, 52.48, 609.94, 0.76

No changes in environment, no open window or something else - after 88000 / 94000 seconds.

Change from 3 -> 1, if recalibration needed should chgange from 3-> 2, right ?
(this I have seen after opening window in the morning at 7:30 for about 20 minutes)...

(EDIT: today in the morning (08:00 - after 17hours - still at accuracy 1 ...)

Michael

[micha_pr]

Nobody have an idea?

Can the values with accuracy "1" be used for checking air in room? I think yes, because CCS811 I use as reference show comparable values...
(both sensors are still again at accuracy "1" - since more as 24 hours after they were at "3" before. I cannot move the sensor every 2 days in bad environment, right? 😉 )

Would like to give my customer an answer, use the BMP sensor, or not...

@ BSTRobin - nothing?