Question: Should the Purple Air be co-located with a weather station?

stevie asked on January 11, 2019 16:50
164 views | 2 answers | #18102


I know the Purple Air collects data on temperature, pressure and humidity, but we're also wondering if wind speed, and direction might also be important data to collect?

Wondering what people think about this? If wind data is important, what devices might be useful to pair with the Purple Air. Or, where else could we gather wind data?



2 Comments

Normally, in an open location, the national weather service (NWS) wind direction would be ok. But as you get into more urban locations, where buildings could change the direction, there is cause for concern. Don't know the answer to this one.

Now for weather stations. There are services available, such as NWS,weather underground, and weather channel, that have stations around that can provide info. More and more of these are charging, instead of being free.

Another option is buying a weather station. These typically run about $150. Some are solar charged. Regardless, they should be put in a high clear location. And regardless of the "solar charging", it's not uncommon for them to need new batteries every couple of trade-off so make sure they are accessable. They usually contact the display by RF ( 433 mhz or 915 mhz are common). Many can also directly access the internet with their data.

There is another option. Check locations near where you plan to put the particle counter. Check for any private weather stations in the area. If it is a school, the data may already be available. But, the other way is to use your computer and an rtlsdr dongle (cost about $20). Using freeware ( with Windows it's sdr# and rtl_433, but there are equivalent versions for linux), you can decode the signals.

See rtl-sdr.com for more details. You will need to spend a fair amount of time getting used to the software. There is also an rtl_433 forum, for more info on that program.

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It all depends on what your objectives are. You'll notice that most air quality monitoring stations (the regulatory ones) have wind measurements with them and that's because the purpose of the measurements are not just "how much" but "where from" and "where to". So, in principle, it is very useful to have wind information next to air quality sites. Now, in practice that's much more tricky as the representativeness of a meteorological site is quite different to that of an air quality measurement. In general, you'll want to know where did the air that ended up in your sensor come from and that might be better served by data from a site further away. Ultimately, there is no "right" answer for all cases so what I'd suggest it to try to identify what your objectives are (what are you going to do with your data) and then think about what else you might need.

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