I’ve recently purchased a few of the BME680 sensors for a thermostat project. I can see that I need to calibrate the temperature by using the offset function. On the one I’m working with right now it looks to be reading about 4.5degC high but easily fixed with said function. However, humidity is reading around 32%RH from the BME680 (using example temp-press-humidity.py after 2 hour burn in with read-all.py), where the temperature/humidity monitor I’m calibrating against shows 40%, (which also matches a cheap analog gauge I picked up this afternoon).
So can I apply a similar offset in my code for the humidity? Would it be linear? Why is it such a big difference to begin with? I could actually believe either reading as it does get quite dry in our house, but as of yet we haven’t noticed much in the way of tell-tale static electricity this winter. I’m looking to eventually control a humidifier so I want to have confidence that my readings are reasonably accurate, but 8% variation is way too much. (Or even worse 20% if you take it as the ratio of one reading to the other!)
I have read other posts regarding temperature variations and sensor mounting considerations. My BME680 is in the same plane as the Pi Zero so when they’re laid flat it’s off to one side away from the CPU. When installed in its case they’ll be vertical with the BME680 below the Pi. So I believe that the temperature measurement isn’t unduly effected by the Pi.