There are two reasons these can differ.  One, the PurpleAir map you are showing is a 2m average while the weewx-purple loop packets are the most recent reading.  Also, the EPA has updated the AQI calculation (see: https://www.epa.gov/system/files/documents/2024-02/pm-naaqs-air-quality-index-fact-sheet.pdf ).  Weewx-purple has been updated with the new AQI calculation while the PurpleAir map has not been.

A third reason could be if the PurpleAir map is not using the EPA correction (which corrects pm2_5)—see https://www.epa.gov/sites/default/files/2021-05/documents/toolsresourceswebinar_purpleairsmoke_210519b.pdf .  I cannot tell if this is so from your screenshot.

On Jan 10, 2025, at 6:40 AM, Dan Hinckley <d...@suiattle.org> wrote:

When I access my PA unit directly, the readings I see are different from the one generated by the John Kline extension.

When I check right after WeeWx has generated new files on each loop, direct access to the PA shows this:

<Screen Shot 2025-01-10 at 09.37.37.png>

And the WeeWx-Purple displays this:

<Screen Shot 2025-01-10 at 09.37.56.png>

I don't know enough about how the AQI is calculated to know if this discrepancy is normal or is something else.

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