I have been searching for a simple equation to reduce the effect of humidity on particle concentration readings.
I have found this Developing a Relative Humidity Correction for Low-Cost Sensors Measuring Ambient Particulate Matter - PMC
which is a long article but does reference another paper which seems to have a simple equation which may be of some use.
Equation is C=1+(κ/1.65)/(−1+1/aw)
PM(Corrected)=PM(Raw) / C
aw = 100/humidity%
where k is about 0.4 and seems to be very variable with location
aw is the relative humidity in %
In my case it reduced a reading of 47 to about 14 which seems more reasonable given my location
I am also finding that the temperature as recorded by my sensor is about 4 deg C higher that that showing on my Davis weather station and the humidity is a lot lower possibly for this reason
I assume the temperature variation is due to a combination of the following:
a) inherent inaccuracy of the sensor
b) Lack of a solar shield
c) Self heating.
I would seem that the absolute readings from the sensor can be quite variable and in particular humidity is an important factor.
Any comments and corrections welcome
Tim