Weather Station Hardware > Air Quality Sensors

Ecowitt WH41 - Calculations to take the humidity out

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I have mounted my PMS5003 in my  garage having drilled a couple of holes for it to poke through and used a cowling to protect it.

I also added code to correct for humidity

//Correction algorithm thanks to help of Zbyszek Kiliański (Krakow Zdroj)
pm2p5 = pm2p5/(1.0+0.48756*pow((humidity/100.0), 8.60068));

pm10 = pm10/(1.0+0.81559*pow((humidity/100.0), 5.83411));

Probably not really required since the units are low end but made me feel good !

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@watsonm love this installation, very professional.

Very interested in how to factor humidity into the ecowitt WH41 results, which is what I'm using now. I'm in the pacific northwest where humidity does sometimes get off the charts. My unit actually says that it's the WH41B, but I have no idea what they changed.

As far as calibration goes, I'm using home assistant as a "middleman" to present easy graphs for the family before ingesting from that to a time series database (I'm using prometheus and grafana). I'm using home assistant's template object, which lets you take one datasource, transform it, and expose it as a new one, for other metrics as a way to apply formulas (for example to calculate AQI) and calibration offsets where they aren't supported.

My installation is one that is using my own software so I can easily add the correction code.  This is then sent to a broker where it is read by
another software package for integration into my weather data.


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