I’m reading local data from two different PurpleAir units (a PA-II and a PA-II-FLEX) which are placed directly next to each other. The PA-II unit’s values seem to be consistently a lot lower than the PA-II-FLEX (details below).
Is this due to the laser getting old or dirty?
If so, can I clean it to fix it, or do I need to replace the lasers?
Or can I recalibrate the units somehow?
The p_0_3_um* values differ between the two units. The A and B channels on each unit agree with each other, and both units show the same relative movements over time, but the PA-II unit’s values (cyan/purple) are significantly offset lower compared to the PA-II-FLEX unit’s values (orange/magenta).
The p_0_5_um* values have the same issue as the >0.3um count.
For the p_1_0_um* values, the PA-II unit (cyan/magenta) is almost always zero, and shows almost no movement. The PA-II-FLEX unit’s values (purple/orange) have a relatively low magnitude, so maybe the PA-II unit would show non-zero values if there were a lot more dust? I tried generating some dust, but didn’t notice much change, though.
The higher particle size counts (2.5, 5.0, 10.0) have the same issue as the >1.0um count.