Welcome to the Cumulus Support forum.

Latest Cumulus MX release 3.13.8 (build 3154) - 09 November 2021

Legacy Cumulus 1 release v1.9.4 (build 1099) - 28 November 2014 (a patch is available for 1.9.4 build 1099 that extends the date range of drop-down menus to 2030)

Download the Software (Cumulus MX / Cumulus 1 and other related items) from the Wiki

If you are interested in supporting Cumulus then maybe you would like to contribute to the maintenance of the Wiki? This need not take hours of your time - just a half hour here and there can make a big difference, particularly if many people are doing this. Any contributions are very welcome, whether they involve new content or editing of existing content. It will be very helpful to current and future users of Cumulus software if the Wiki is kept well-maintained and current. If you are interested then please contact forum user saratogaWX and ask for a Wiki account.

Air Quality - Segal's Law adaptation

Talk about the weather
User avatar
HansR
Posts: 2620
Joined: Sat 20 Oct 2012 6:53 am
Weather Station: Davis Vantage Pro 2+ / GW1100
Operating System: Raspberry OS/Linux 10 (Buster)
Location: Wagenborgen (NL)
Contact:

Re: Air Quality - Segal's Law adaptation

Post by HansR »

water01 wrote:
Thu 23 Sep 2021 9:26 am
I took your advice after my neighbour had a particularly smoky chimera running a week or two ago and I was getting strange high readings afterwards. Blew it through with compressed air cleaner and hey presto readings returned to reality!!
Good 👍
Hans

https://meteo-wagenborgen.nl
https://meteo-wagenborgen.nl/CMX4/index.html
https://meteo-wagenborgen.nl/CMX4/index.htm
Cumulus build 3149 ● Davis Vantage Pro 2+ ● RPi 3B+ ● Raspbian 5.10.52-v7+ ● Mono 6.12.0.122

User avatar
HansR
Posts: 2620
Joined: Sat 20 Oct 2012 6:53 am
Weather Station: Davis Vantage Pro 2+ / GW1100
Operating System: Raspberry OS/Linux 10 (Buster)
Location: Wagenborgen (NL)
Contact:

Re: Air Quality - Segal's Law adaptation

Post by HansR »

HansR wrote:
Tue 21 Sep 2021 3:36 pm
They must be pulling is or sensor.community is pushing every sensor forward because the API of air-net is different from the sensor.community.

Another minor thing is that air-net is only using the AQI of the USA for pm2.5 without any reference to the actual concentration.
I have communicated with sensor.community and they claim air-net is pulling the data. Just the sensors and the location.

Note that address information is presented on the sensor page which I think is unwanted. I thought that it was info from the sensor.community database, but I have been sworn that is not the case, they claim the Chinese do a reverse mapping of the position to get the address (using openstreetmap or Google Maps etc...) and if the position is exact that may no0t be what you want.

Still it is not a good situation so I asked them
1) do they have conditions of data use which forbid this (no answer yet)
2) I am experimenting with the position of the sensor to see how the Chinese site reacts. This may take some time as there is no knowledge of the refresh rate of aqicn.org
Hans

https://meteo-wagenborgen.nl
https://meteo-wagenborgen.nl/CMX4/index.html
https://meteo-wagenborgen.nl/CMX4/index.htm
Cumulus build 3149 ● Davis Vantage Pro 2+ ● RPi 3B+ ● Raspbian 5.10.52-v7+ ● Mono 6.12.0.122

User avatar
HansR
Posts: 2620
Joined: Sat 20 Oct 2012 6:53 am
Weather Station: Davis Vantage Pro 2+ / GW1100
Operating System: Raspberry OS/Linux 10 (Buster)
Location: Wagenborgen (NL)
Contact:

Re: Air Quality - Segal's Law adaptation

Post by HansR »

1) The experiment i mention above is still running but as this is probably a bit too fas from the subject (and the forums subject) i'll skip this further and only maybe take it to the sensor.community forum.

2) Coming back to the subject of this thread however - I mean the variable measurements caused by the humidity factor - it may be nice to mention that the AQM-III has an implicit compensation for humidity for all supported sensors. The compensation is based on this article (pdf). Note that the placement of the temperature sensors then becomes important (close to the air inlet). The seller might emphasize it a bit more (both the compensation as the sensor placement).

[Edit:]
2a) Note that as a result of that correction on measurement the sensor does not give values when the T/H sensor is not connected.

[Edit 2:]
2b) Reading the article more accurate I find that the correction is only regarded as valid up to 70% humidity. Humidity correction seems to be the holy grail of PM measurement. I don't know about everybody else, but I live in a corner of the world where humidity may not fall below 70% for a whole year. Afaik the tropics will be problematic as well.

3) Another effort for humidity compensation is made by the NETIGO PRO - see above - kit which I bought as well. This one has an air inlet heater. I am very curious how those different efforts behave and compare.

Not sure what guys like DAVIS and Purple Air do with humidity.
Last edited by HansR on Tue 28 Sep 2021 9:13 am, edited 1 time in total.
Hans

https://meteo-wagenborgen.nl
https://meteo-wagenborgen.nl/CMX4/index.html
https://meteo-wagenborgen.nl/CMX4/index.htm
Cumulus build 3149 ● Davis Vantage Pro 2+ ● RPi 3B+ ● Raspbian 5.10.52-v7+ ● Mono 6.12.0.122

Cortmalaw
Posts: 49
Joined: Sat 26 Dec 2020 2:21 pm
Weather Station: Davis
Operating System: Raspbian
Location: Near Glasgow, Scotland, UK

Re: Air Quality - Segal's Law adaptation

Post by Cortmalaw »

PaulMy wrote:
Sat 11 Sep 2021 5:53 pm
My Davis AirLink Weatherlink.com says: AQI = 0.06; PM1 = 1.8 µg/m³; PM2.5 = 1.3 µg/m³; PM10 = 1.3 µg/m³
Paul
Going back to Paul's original post, there's another issue no-one has yet mentioned.

Those (Davis) results are impossible.
PM1 is the mass per cubic meter of all particles with a size less than 1 µm
PM2.5 is the mass per cubic meter of all particles with a size less than 2.5 µm
PM10 is the mass per cubic meter of all particles with a size less than 10 µm

They are cumulative totals if you like, not a measure of quantity or mass of particles of a particular size.
It follows that PM10 must be >= PM2.5, and PM2.5 must be >= PM1.
You cannot have PM1 being larger than PM2.5 or PM10!

Typo? Or software fault? Or hardware fault?

User avatar
PaulMy
Posts: 2815
Joined: Sun 28 Sep 2008 11:54 pm
Weather Station: Davis VP2+ Cumulus1 / CummulusMX
Operating System: Windows8 / Windows10
Location: Komoka, ON Canada
Contact:

Re: Air Quality - Segal's Law adaptation

Post by PaulMy »

Hi Cortmalaw,
Typo? Or software fault? Or hardware fault?
Good catch... and a typo on my part :oops: I have attached the page from Sep 11

Now:
AirLink AQI = 0.32 PM1 = 6.3 PM2.5 = 6.8 PM10 = 7.4
Ecowit433 AQI =57 PM2.5 = 15
Ecowitt915 AQI=57 PM2.5 = 15

Enjoy,
Paul
You do not have the required permissions to view the files attached to this post.

User avatar
mcrossley
Posts: 9155
Joined: Thu 07 Jan 2010 9:44 pm
Weather Station: Davis VP2/WLL
Operating System: Buster Lite rPi
Location: Wilmslow, Cheshire, UK
Contact:

Re: Air Quality - Segal's Law adaptation

Post by mcrossley »

After my AirLink was approaching the 1 year continuous uptime mark, I took it down for a clean.

It looked pristine inside TBH. I blew it out using a pump-up garden sprayer (empty!) whilst stopping the fan from spinning to avoid over speeding it.
(I'm not a fan of "canned air" blowers - I have seen what it can do when some of the propellant 'liquid' sprays out of them onto optics. It makes a mess that is hard to clean off :(

Afterwards - there was no discernible difference in the numbers.
Anyway at least I know it's clean!

User avatar
HansR
Posts: 2620
Joined: Sat 20 Oct 2012 6:53 am
Weather Station: Davis Vantage Pro 2+ / GW1100
Operating System: Raspberry OS/Linux 10 (Buster)
Location: Wagenborgen (NL)
Contact:

Re: Air Quality - Segal's Law adaptation

Post by HansR »

@mcrossley: You must live in a clean air environment!
Hans

https://meteo-wagenborgen.nl
https://meteo-wagenborgen.nl/CMX4/index.html
https://meteo-wagenborgen.nl/CMX4/index.htm
Cumulus build 3149 ● Davis Vantage Pro 2+ ● RPi 3B+ ● Raspbian 5.10.52-v7+ ● Mono 6.12.0.122

Post Reply