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## BME680: IAQ accuracy definition

Established Member

Would be nice to get some better understanding about the internal definition of the IAQ accuracy.

Following will happen:

1) starting sensor - IAQ=0, accuracy=0
2)  some later - IAQ=50, accuracy=0  (as sample)
3)  some later - IAQ=55, accuracy=1  (as sample)
4)  some later - IAQ=87, accuracy=1  (as sample)
.....
1000)  some later - IAQ=76, accuracy=2  (as sample)
......
2000)  some later - IAQ=155, accuracy=2  (as sample)
......
3000) some later - IAQ=125, accuracy=3  (as sample)
THEN
3000) some later - IAQ=87, accuracy=2  (as sample)
3005) some later - IAQ=25, accuracy=2  (as sample)
3010) some later - IAQ=5, accuracy=2  (as sample)
3020) some later - IAQ=0, accuracy=2  (as sample)
3021) some later - IAQ=0, accuracy=2  (as sample)
3022) some later - IAQ=0, accuracy=2  (as sample)
.......for long time
xxxx) some later - IAQ=0, accuracy=2  (as sample)

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As far as I understand the sensor is collecting data and after was decided that enough data available the accuracy will be set to 1/2/3.

So the questions:

1) how long this process should be going on, and what kind of data needed?
(one senor here is already collecting data since >10 hours (every 3 seconds) and still have accuracy=1)
2) what is the condition for accuracy=2 and accuracy=3? Can somebody describe the internal workflow?
3) How can it be correct that accuracy=2 -> but IAQ=0 for a long time?
I think in such a case there could be an internal "reset" of collected data (or recalculation/shift) and accuracy should be set back to "0", right?

Current accuracy=2 means - not trust these values, they can be wrong at all, right?
But if this is right - after what time we can expect an accuracy=3 then???

Maybe somebody from development can tell us a bit more about this?

Thanks!
Michael

10 REPLIES 10
Occasional Visitor

Hi

I finally found a good topic to bring up my questions.

There are good questions for the accuracy, when this sensor is intended to be used in final product. The customer may not be interested in relatively complicated calibration. I see there is no other way to use it properly rather than adding the instruction to the final user about the proper calibration, like: after each power up: 1. wait 5min till sensor stalibize, 2: breathe air/place ethanol soaked cloth near the sensor.

Is there any way to save / restart the accuracy settings after power up (state_load, state_save in bsec)?

"If I turn the sensor on in the office I'm in, it normally sits just above 50 IAQ. However if I turn the sensor on outside for 10mins it gets a baseline of good air quality, so when I bring it back inside it goes up towards 150 IAQ. "

I made similar tests and noticed quite similar behaviour