@MallocArray did you get or find any clarification to your questions about the custom calibration methods in the end? I am trying to use them but just like you, am finding the terminologies and explanations slightly confusing.
I did not. Right now I’m assuming applying the PM2.5 calibration based on the PM 0.3 count first and then applying the EPA correction after that, but I haven’t dug deep enough to know if that is exactly the same as what the stock firmware is doing
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According to the Knowledge Base → Calibration Algorithms page on the AirGradient website:
if PM_Countraw < 100, then PM2.5 (calib) = 0
else if PM_Countraw >= 100: PM2.5 (calib) = PM_Countraw x scaling_factor + offset
Does the above if-else condition only apply to custom formulas or also the special PMS5003 calibration formulas? Why set PM2.5 (calib) to 0 when PM_Countraw < 100, if the purpose of the PMS5003 calibration factors is to correct low PM counts? Or is the calibrations page not up to date? I can’t find this if-else condition anywhere in the Github code. Thank you.