@Isarvation wrote:
1. You wrote: "It seems that almost all the devices were reset at the same time at the very beginning of graph 1, while BSEC was already running previously for some." What does this mean? The sensors and the BSEC where resetted before (this is what we are aware of). But how do you mean "BSEC was already running ... for for some"`? What impact does this have and how can we mitigate this?
There are two things here, mainly that each BME680 will stabilize to its surrounding environment (hardware effect of the BME680's sensing technology) and that BSEC will self-calibrate based on the air quality history it has observed (software effect of the BSEC library). There are no specific mitigation procedure expected, but due to these effects it is expected that the sensor-to-sensor deviation (in the standard IAQ output) will improve over time.
@Isarvation wrote:
2. How can you see that BSEC ran prior?
This came simply from the fact that the some of the logs show longer history than others (with timestamps prior to the time window in your snippets). It is possible to guess when a specific sensor (technically BSEC, not the BME680) was reset from its IAQ accuracy.
@Isarvation wrote:
3. How can we reset a BME680 device connected via I²C to complete new state without cutting power from the I²C bus and the ESP8266 device? NOt sure if we forget something here.
Not sure what is meant here. If it has to do with question #1, then no such procedure is expected. If you mean a reset of the sensor's configuration including register map, then it is possible to issue a "soft-reset" command, by writing the value 0xB6 to register address 0xE0 (in I²C mode).
@Isarvation wrote:
4. Regarding the time constant 4d and 28d: Can you give a guidline to choose which one would be be best for a use case and what the main difference in the resulting measurement will look like?
In short, the longer the time constant, the longer events detected by BSEC will influence its outputs and self-calibration. This means a typ. rule of thumb would be that shorter time constants (4d) are nicely suited for highly dynamic environments (e.g. carry-on device/portable air quality tracker), while longer time constants (28d) are nicely suited for stationary applications (e.g. device in a fixed location inside a home).
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