I've been measuring the resistance of an MQ2 sensor, trying to get something like the tempco results shown in the DS.
This is a sensitive device, and something like a breeze (eg from a hairdryer) massively alters results. I can't be sure, but I think the net effect of the hairdryer (no cold setting!) is to lower the surface temperature of the ZnO sensor. However, also tried holding sensor over a convection heater, and similar results - hard to believe that is lowering surface temperature - though still, admittedly, there are convection currents.
What I see is an initial slow, large rise in resistance, then (whilst trying to keep conditions steady) a slow fall. This is similar to the power-up results: A cold sensor has huge resistance (maybe the ZnO is not a semiconductor when cold?), then the resistance falls quite fast, then rises a bit: Hard to sepasrate from room conditions though.
What are the top contributions to widely varying/wobbling sensor resistance in "stable/normal" room conditions: temperature, pollutants...moisture?
Another thing is DS indicates a burn-in of up to 48 hours (for stock not used for a long time) - why so long? If I actually do this, will the thing stabilise, and what takes so long?