@BASER wrote:
There seems to be no absolute zero point in the sensor and so the measurements are worthless. What is wrong here ?
The BME680 can track tVOC levels, but is not selective to specific compounds, and as other sensors working on a similar MOX sensing technology, such devices cannot output an absolute tVOC level. Therefore this sounds like the expected behavior. Each BME680 needs to stabilize to some equilibrium based on the envrionment it has been operating in.
@BASER wrote:
I need the same values in same environment.
It seems like you are currently using the raw resistance output. I believe it would be good to evaluate the BSEC library. Among other things, BSEC will keep track of this background history to self-calibrate. By using BSEC, two fully stabilized and calibrated sensors sharing the same BSEC history will show the same IAQ outputs in the same environment. Alternatively if the devices are sitting in a fixed location, we would recommend to use the sIAQ (static IAQ) output instead.
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