This device measures fine dust and NO2 concentration in the air while on the move and adds GPS coordinates to each measurement location.
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Please send me your mail address, because I am not going to post this on this forum.
Hello Harald, I admit that the NO2-sensor (which was added to the mobile meter recently) is still not functioning properly. It is a SnO2 based metal oxide sensor which has to be heated to 220°C. Once that temperature is reached the resistance of the sensorstrip changes with NO2 concentration and this is shown in the datasheet of SGX Sensortech, but the single diagram they show holds only for 25°C and 40% humidity. Unfortunately I could not find further information for other ranges of temperature and humidity. Also, in the datasheet is spoken of cross-sensitivity with ozone, but no details are given how to cope for this.
I've chosen for the 4541 because this was the only sensor available at AliExpress which was mounted on a small breakout board. However, it houses two sensors: one for NO2 and another for CO measurement. Since I am not interested in CO measurement I only use the NOX and not the RED output pin. The board also houses a MOSFET for preheating and a corresponding pin to enable this. I did not intend to use this, but since I experience a rather slow stabilization of nearly 20 minutes before the NO2 concentration gets realistic, I am going to test with a preheating time of 30 seconds and hope that this will considerably shorten the stabilization time. Also, I am going to remove the feeding resistor of 82 ohm for the heating of the CO-sensorstrip to save on battery capacity.
Thanks for informing me about the existence of Breeze technologies, but on their site I could not find any relevant technical info, which seems normal to me because they commercialize their meters which are highly probable patented.
If you order the SDS011 finedust sensor, you also get a flat cable with two connectors attached to it and a serial2USB convertor module. When you connect the sensor to this module with the flat cable, then you can plug the serial2USB module into a USB-port of your laptop or notebook. Of course, you always need some software to read the serial messages which the SDS011 sensor sends every second and decode these into readable format on the screen. I recommend to install Python and the CH341 serial2usb driver on your computer (you can get a free download of both on the internet). By running a small Python program (which I can always post to you) you can read the current PM10 and PM2.5 values on the screen and with a small extension, you can also log all measurements into a file for later consultation.
This is to my opinion the cheapest and simplest solution to measure finedust concentration on a fixed location.
The measurement of NO2-concentration is a bit more difficult, since the sensor which I use and most sensors of this kind on the market provide an analogue output, so you need a microcontroller which can perform A/D-conversion and after that, some calculations have to be made to determine the exact NO2-concentration for which you also need temperature, humidity and barometric pressure as input.
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