Author Topic: Calibration  (Read 385 times)

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Offline zippm

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Calibration
« on: September 14, 2023, 01:32:43 PM »
I'm using the ecowitt WH41B (outdoors), WH45 (indoors), and a awair unit (indoors) to try and get a comprehensive view of PM2.5 on my property. I live with someone who is very sensitive to smoke, and so I'm trying to get solid charts and graphs to show whether we are a good job of filtering it inside.

I'm really interested in what others have done for calibration. The awair claims to be calibrated out of the box, but the WH41B and WH45 seem to suggest you calibrate it from the nearest legit sensor outside.

Should I pack them all up with a battery backup and drive to the nearest government sensor? It wouldn't be that hard. But outside of smoke season, normally PM2.5 values are so low that it feels like the offset would be really low.

Separately, I have the same question for my various humidity sensors, which appear to vary about 10% in the same room. Anybody have good strategies for finding the right offset?

Many thanks.

Offline Wooks61

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Re: Calibration
« Reply #1 on: October 04, 2023, 07:34:20 PM »
It depends on whether you want an accurate PM2.5 measurement or just a relative one.

I have four WH41 (outdoor types) and one WH45.
I use two to monitor outside areas: Street side of building and rear side of building.
The other two are indoors in different areas I want to monitor.
I " calibrated" them by sitting them all together and monitoring their values.
Then made any offsets as required. In my case this was none. All four WH41s and the WH45 were all reading near enough the same.

Now knowing what my min values are, it is easy to  see any variation in reading around the property and take steps to reduce internal "pollution" eg not opening windows at peak traffic times, using extractors in the kitchen etc.

Whilst my monitors are not calibrated to a known official value, they allow sufficient indications for my needs..

 

anything