I’m trying to build my own office weather station, meant to monitor bad working conditions.
I have been observing the bare readings for a few weeks now and I came to some conclusions regarding the gas resistance which may be interesting for the community:
- The gas resistance seems to have an exponential dependency on the humidity. When you plot the logarithm of the gas readings over the humidity you may notice parallel streaks in the scattered values, indicating a constant slope with varying offset.
- The offset observed varies over long timespans (several days) and seems to originate from the sensor drift. I think it could be compensating by just fitting a linear function to the measurements of the past days.
- I tried around with different heating profiles. There I observed, that a new profile is not immidiately loaded but after the next reading. So you have to set a new profile, thean read sensor values and after that you can read values using the new profile. I am not sure if this is due to the bme itself or the python library. In general I observed that the risistance decreases for longer heating (ant hence interaction) time and higher heating temperatures. In the response to air pollution I was not albe to find any difference aside from different scalings, but maybe I was just not probing the right substances.
Currently I am trying out different algorithms for compensating the sensor drift but I think I am pretty close to obtain stable results.