Hi Everyone
Is it normal for there to be such a big difference between the PM readings and the Particle Count/dL readings? I am a bit concerned my sensor is not reading correctly.
Thank you
The Plantower sensors used in the PA products employ a proprietary algorithm to convert the sensor output into PM concentration and particle counts.
The Plantower sensors act as nephelometers. The particle count displayed is not an actual count. In addition, as PM2.5 is a weight measurement (in μg/m3), an assumption about particle weight and density is made.
Researcher Lance Wallace determined the conversion factors used in the Plantower sensors in his paper.
If you’re not sure about the accuracy of your sensor, first compare the outputs of the two channels – they should be close (within 10-15%). The PA map charts can help with this. Second, compare your readings to readings of nearby sensors, ideally on a day where the air quality in your area is uniform throughout. They should generally be the same.
PurpleAir has some FAQ entries posted around the board that provide more information about determining the quality of your sensor’s observations and maintenance you can perform to address any issues.
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Hello @dwhitemv
Thank you for this information.
I checked my sensors confidence score which is sitting at 100%.
I also checked it against my closest sensors (7-10km away) and the reading were very close.
Thank you so much for your help! 
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