Particle matter

Questions about the Waspmote board and its modules
dprestor
Posts: 45
Joined: Mon Dec 12, 2016 2:19 pm

Particle matter

Post by dprestor » Tue Feb 14, 2017 11:57 am

Hello,

we were comparing Libelium PM10 data with our national agency's data and the discrepancies seem very high. For example, if their values are at around 60µg/m3, Libelium values are over 120 and sometimes even over 200µg/m3. Any idea what could be the cause of that? The systems are stationed basically next to each other.

Kind regards,

Domen

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: Particle matter

Post by libelium-dev » Wed Feb 15, 2017 9:16 am

Hi,

Dust, dirt or pollen may be accumulated inside the dust sensor structure. Make sure the sensor has their air holes clean and the area around them is cleared.

Regards

dprestor
Posts: 45
Joined: Mon Dec 12, 2016 2:19 pm

Re: Particle matter

Post by dprestor » Thu Feb 16, 2017 1:10 pm

Thanks for your response,

we tried clearing it. It didn't help. Could it be that air humidity (mist for instance) also influences the readings in a way so that they skytop. Also; how come all three PM values are so similar to each other; I'm enclosing a screenshot of yesterday's data.

https://postimg.org/image/tru62kic7/

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: Particle matter

Post by libelium-dev » Mon Feb 20, 2017 4:03 pm

Hi,

Do you know which sensor is used by the national agency of your country?

We're not experts on the values PM pollution but normally the values are quite similar between them.

Regards

dprestor
Posts: 45
Joined: Mon Dec 12, 2016 2:19 pm

Re: Particle matter

Post by dprestor » Tue Feb 21, 2017 1:38 pm

Our agency is allegedly using Leckel sensors.

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: Particle matter

Post by libelium-dev » Wed Feb 22, 2017 3:30 pm

Hi,

Are the PM1 and PM2.5 similar between the two sensor?

Regards

dprestor
Posts: 45
Joined: Mon Dec 12, 2016 2:19 pm

Re: Particle matter

Post by dprestor » Thu Feb 23, 2017 8:36 am

No, they're not. They seem very different.

dprestor
Posts: 45
Joined: Mon Dec 12, 2016 2:19 pm

Re: Particle matter

Post by dprestor » Thu Feb 23, 2017 8:43 am

Also; can you help me determining the accuracy of individual sensors? I can't seem to find it in technical specs.

libelium-dev
Posts: 27967
Joined: Mon Sep 28, 2009 1:06 pm

Re: Particle matter

Post by libelium-dev » Fri Feb 24, 2017 10:47 am

Hi,

First of all, sorry for the delay to answer.

You can check the characteristics of the particle matter sensor here, libelium_files/OPC_N2.pdf

Regards

TomoPNosaka
Posts: 1
Joined: Fri Feb 24, 2017 10:25 am

Re: Particle matter

Post by TomoPNosaka » Fri Feb 24, 2017 11:10 am

Greetings,

I would like to further corroborate what dprestor is asking and will post some data and our findings. First of all, RH, temperature and pressure sensors seem to work as intended, but PM and most gas sensors could be either malfunctioning (PM) or are miscalibrated (gas).

Our national agency uses Leckel and TEOM sensors, and we placed Libelium sensors close to the location where national agency takes their measurements (approx. 100-150m air distance). We expected that most if not all values would be a little higher due to proximity of roads but the measurements were not reliable as far as some gases and PM goes.

NO2 (nitrogen dioxide) is said to be at 0 at all times during our test run (11th to 19th feb 2017). CO (carbon monoxide) and O3 (ozone) are around 8 to 11 times higher than what our national agency publishes.

PM10 (and PM2.5, PM1) readings are fine in general, but whenever RH (relative humidity) rises and/or temperature drops to around 0 C or lower, readings go off the charts. On a foggy morning (15th of Feb, 5:00 to 7:00 AM) Libelium measured an extraordinary high amount of PM10, going as high as 4000 ug/m^3. On the next day, readings were higher from 1:00 AM till 9:00 AM (200 to 300 ug/m^3 while agency showed 50-100 ug/m^3), when the system started to measure correctly again. On both days, Libelium started to measure fine right after fog dissipated. A similar problem occured when the rain started to fall (from 18:00 to 22:30 on 17th of feb), rising the values while our national agency didn't notice an uptick of PM (values of Libelium were six times higher than those of our agency, 50 to 300 ug/m^3). Could it be that some condensation within the device offsets the readings? On a sunny day, PM10 (and other PM) measurements appear to be correct and similar to those of our national agency without any of us cleaning or touching the devices.

We would like to hear your opinion and are looking forward to your response! Best regards.

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