Davis AirLink Professional Air Quality Sensor (7210UK)

[HansR]

I would like to know whether the numbers delivered by the AirLink are updated every minute or only at the whole hour defined by their frequency. Because I don't have the equipment I can't see for myself and I can't find this. But as the device is polled on a minute basis I assume minute updating resulting in a moving average. What does the AirLink do in reality?

So, first case, updates on their defined frequency:

• Minute values are updated every minute;
• 1 hour averages are updated every hour;
• 3 hour averages are updated every 3 hours;
• 24 hour averages are updated every 24 hour;
• nowcast is updated every hour

Second case:

• All averages, including the nowcast, are updated every minute which would make the parameters moving averages (imho easier to implement).

This is not clear from the specs of the calculations (especially for the nowcast) nor from the nowcast wiki.
Or maybe I am missing something

[mcrossley]

From what I have seen they are all rolling averages.

Look at the Davis map - https://www.weatherlink.com/map - and select the Air Quality overlay. Then pick a station and you can see the current values updated every minute, and a graph of the nowcast.

[HansR]

OK, thnx

[HansR]

And what is the invalid NowCast value if we have less than 2 hrs of data (the required minimum to give an estimate for NowCast) after a reset/restart? 0 (zero) or -1 (invalid)?

[beteljuice]

@Hans ...

Thanks for the AirNow link

"Nowcast" isn't quite what I thought it was - hmm, may have to rethink presentation - but then again mx is now doing it for me, my coding experiment is / will be redundant !

[mcrossley]

The data still needs a presentation layer though

[HansR]

Thanks for the AirNow link

you're welcome

"Nowcast" isn't quite what I thought it was - hmm, may have to rethink presentation - but then again mx is now doing it for me, my coding experiment is / will be redundant !

Yes, it surprised me as well. They make it - I humbly think - needlessly complex. Both in calculation as in interpretation.

The data still needs a presentation layer though

Yes, good, keeps us occupied in lockdown situations (like they just announced again here in NL).
Anyway, but how to present if we don't know valid from invalid after a restart?

[PaulMy]

Hoping soon I can catch up with all the newness... just order mine along with WLL

Enjoy,
Paul

[beteljuice]

The beteljuice plaything (Davis version) now correctly labels "Nowcast" and uses that value for the "widget"

zip link at bottom of page for the adventurous ...

Edit: Link modified

[Mapantz]

Handy having the live data eh betejuice?

[HansR]

@beteljuice:
Really nice. Though I saw it more than an hour ago and now the plaything disappeared giving me some 'Heart Internet' provider homepage.
I have the following remark: I don't think NowCast should be shown anywhere but the USA choice. It really is something only for the US and I think it causes confusion of shown e.g. in the UK. It has no meaning there.

@Mapantz:
Could you reset the device and report on the values of the averages while they have not reached their minimal required data (e.g. NowCast requires at least 2 hours of data so what is reported before that)? The same question for the normal averages. I would highly appreciate that.

[beteljuice]

some 'Heart Internet' provider homepage

At 06:00 some new billing system decided I was in arrears and closed me down.

Much apologising, but still not available ATM

Edit:

I don't think NowCast should be shown anywhere but the USA choice. It really is something only for the US and I think it causes confusion of shown e.g. in the UK. It has no meaning there.

Yes and no ...
It is site owner choice what is displayed (but not at classification type level).
If we are to be 'strict' then only 24hr pm2.5 should be shown, and also used for the 'widget'
I have mentioned elsewhere that if any level starts rising rapidly and you live next to a chemical factory you may want to go visit Aunty Mary before you see the 24hr value

[HansR]

Much apologising, but still not available ATM

That's life. Hope you did not lose anything.

Edit:

I don't think NowCast should be shown anywhere but the USA choice. It really is something only for the US and I think it causes confusion of shown e.g. in the UK. It has no meaning there.

Yes and no ...
It is site owner choice what is displayed (but not at classification type level).

Well, we disagree apparently about the responsibility of the application builder to keep things together which belong together.
imnsho: Avoid confusion and garbage. The user makes the choice to display USA data or UK data or whatever... OK. But not NL data plus some nowcast of which nobody in NL knows what it is: it should not be displayed to avoid confusion. Let the Americans make life complicated.... we can live a simple life? Yes?

If we are to be 'strict' then only 24hr pm2.5 should be shown, and also used for the 'widget'

Why is 24 hr average 'strict' truth? Who says?

I have mentioned elsewhere that if any level starts rising rapidly and you live next to a chemical factory you may want to go visit Aunty Mary before you see the 24hr value

Yes.
That is why realtime (minute data) and 'an' average is useful (not necessarily a 24 hr average).

Graphing the data btw makes even more clear what is going on in the air.
But anyway, minor differences between display layers

------

Does anybody already know what values are given by the AirLink at startup when there are no valid averages?
If not I think I'll go for a -1.

[mcrossley]

Why is 24 hr average 'strict' truth? Who says?

Most the AQIs are defined for a 24 hour average value. Some of them do define different scales for 1 hour average data, but not many. Most also provide PM 10 scales as well.

Cumulus uses separate PM 10 scales for all but one of the current AQIs - US EPA, UK COMEAP, EU AQI, EU CAQI, AU NE, NL LKI, and BE BelAQI (Canada AQHI is the exception)

Cumulus also uses different scales for 1 hour data (I also apply it to the 3 hour and "current") for the following - EU AQI and EU CAQI,

[HansR]

@mcrossley: OK, lots to read apparently.