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This thread was split, from this thread: https://www.meteocercal.info/forum/Threa...2-readings


Hello,

Thanks for the explanation, now I understand why the Sharp I got was pretty fancy.
I will mount another SDS011 without a t° sensor to understand its correction (if correction is made).
Another SDS011 with a t° sensor in a normalized shelter to measure the quality of its correction. 
I don't have the knowledge to dig into the codes.
My solar installation should support the 3.
I am posting the links to the graphs of the three?

I have to find an excuse for my dear wife....

Have a nice day.

(27-04-2021, 06:37)tobyportugal Wrote: [ -> ]I will mount another SDS011 without a t° sensor to understand its correction (if correction is made).
Another SDS011 with a t° sensor in a normalized shelter to measure the quality of its correction. 

I don't know to which system you will connect your SDS011, nor the software it uses, however from the following document, things are clear.

MASS CALIBRATION AND RELATIVE HUMIDITY COMPENSATION REQUIREMENTS FOR OPTICAL PORTABLE PARTICULATE MATTER MONITORS

[attachment=2728]


Some DIY systems doesn't apply any correction on the software, that is why, specially on sensors installed in rural zones, you can see substantial changes on the readings along a day / night.
As in the case, observed on first post (regarding CO2 readings), without correction, the changes on the PM readings are in many cases caused by the natural changes of %RH along the day / night.

In the case of the WeatherDuino AQM, the software was designed in a way, that without the readings from the T / H sensor the system will not work properly. In other words, installing the T / H sensor is mandatory.

I do not question your words or your system!
I was simply going to study the ones (you know which ones) I use to see how the correction is done and done well,
I think I am able to analyse data according to t°/HUM drifts.
No big deal, I'll continue for my information.

Good evening

(27-04-2021, 21:31)tobyportugal Wrote: [ -> ]I do not question your words or your system!
I was simply going to study the ones (you know which ones) I use to see how the correction is done and done well,
I think I am able to analyse data according to t°/HUM drifts.
No big deal, I'll continue for my information.

Good evening

Hi Toby,
If the ones you have are using the sensor.community software, from what I think I know, their software also applies correction for humidity.


The problem is more notorious on homebuilt systems where people just buy the sensors, connect them to the microcontroller, use a library to read the data, and believe their data is right by just doing that.

Somewhere in the sensor.community forum there is a discussion about their concern on allowing the use of other sensors which may not be applying the required data corrections (they are aware that some are doing even more exotic things like adding heaters on the air intake, trying to keep %RH near 50%).
All this, simply could cause inconsistency between the sensors listed on their map. So their concern is quite reasonable.

Good morning

I am aware of this, but they have little means to act (there is a privacy issue with German law).
Your post simply gave me an idea to get people's attention.
Why: there is an action with technical schools in Portugal (good news) but they also use: https://pm.chillibits.com/
which is very fancy.
I notice that a school in Viseu shows a pressure of 960mb in this application. (email not answered).
I have a contact with ASPEA, I raise this problem which concerns several Portuguese schools: the discussion stops!
Two solutions: either I give up and it's a pity for their reputation, or I go through another way.
End of off-topic.

(28-04-2021, 06:44)tobyportugal Wrote: [ -> ]...
Why: there is an action with technical schools in Portugal (good news) but they also use: https://pm.chillibits.com/
which is very fancy.
I notice that a school in Viseu shows a pressure of 960mb in this application. (email not answered).
I have a contact with ASPEA, I raise this problem which concerns several Portuguese schools: the discussion stops!
Two solutions: either I give up and it's a pity for their reputation, or I go through another way.
End of off-topic.

Toby, isn't a problem specific to a school in Viseu - Portugal. Hundreds of stations on that map, in several countries, report a pressure of 960mB, I think that happen because they don't have a pressure sensor installed (and it isn't required).
People are still learning on this field... is better be doing something than nothing.

No , there is a sensor that gives a correct measurement on sensor.community.



I don't know why schools (Portuguese or other countries) want this application https://pm.chillibits.com/ which is a ....



I know, I'm a pain in the ass... but high school kids going to see 960mb with a nice sunshine is making the youth stupid. (personal opinion)

You don't know (nor I) if for their purposes, they are sending the Ambient Pressure instead of the Equivalent Sea Level Pressure. Maybe its better not be so critical...

By the way, what your sensors are sending for sensor.community is also Ambient Pressure, but what is show on their maps is the Equivalent Sea Level Pressure. Their servers do the calculation, they have the data needed for it!

[attachment=2729]

So, the "correct measurement" is also a question of what the purposes! We don't know the purposes of the "chillibits"

We are going a bit off topic.

Hello

I don't want to have the last word, in a common application comparing apples and pears, the pedagogical interest disappears,
it's like if on a t° map point A is in chill t° and point B in real t°.
Look at the school in Valença on this application.
I'm not criticizing, I've been kindly alerting for consistency, the proof of my positive approach: I had asked for the exact names of the schools for my template https://portugal.aqi.eco/en (they are all there!), because I have difficulty to find the correct names, and motivating for the schools to find their names.
Have a great day.
PS: you can delete the off-topic.  
PS2: When I was young, I was in aviation, so I know the pressures

Today I find this text, on a webpage...

Quote:The design suggested by the community was not applicable for my environment by using such gray PVC elbows. Our flat has only a South – South-West view and using such housing for the sensor would lead to incorrect and elevated temperature readings because of the direct sunlight during the day.

Almost everywhere, I find this misunderstood about the role of the Temp / Hum sensors on air quality measurement devices. They aren't there to provide precise readings of the outdoor temperature / humidity. They are there to provide Temp / Hum data as seen by the Dust Sensor, and to allow the software to do the required corrections, specially against the %RH. That's why the T/H sensor should be placed near to the dust sensor, ideally in the air intake path.