I’m interested in obtaining a multichannel gas sensor v2 for environmental monitoring. However, it is not clear to me how should I calibrate the sensor.
The wiki contains some general calibration curves, and shows the effect of humidity and temperature, but this is not enough.
Therefore I’d like to ask the following questions:
Is the software already takes into account the calibration curves?
Regarding temperature/humidity curves, does the software is ready to accept temperature/humidity data in order to better calibrate the sensors? In that regard, could one just simply add a temperature/humidity sensor (e.g. BME680) to obtain more precise readings? (e.g. via the WIO terminal?)
If there is no embedded calibration software, do you have the data from the calibration curves in a table?
We also consulted sensor manufacturers about calibration.There is no specific calibration table for the sensor, only a curve of temperature and results obtained from multiple experiments.The manufacturer told me that this curve is linear.But I can’t give you the exact slope, because it depends on the pressure and altitude in different regions. If you want to use it in real products, please do many experiments and do calibration yourself.
This is not for a commercial product, it is for educational purposes.
I don’t have the means to do the experiments, I really needed that chart, because if it is going to change with temperature and humidity, as seen in the figures, you need to include that in the calibration so you have a decent offset of the bias.
Can you explain me how are you calibrating the sensor in the software?
What is this voltage number that the program outputs? I need to know how it correlates with the calibration plots from the wiki…the ppm numbers are too high!
No. I’m taking my measurements in a very low pollution area. I just need to know what to do to calibrate the sensor, if anything. And I need to know the meaning of the voltage.
I had a discussion with SEEED. Unfortunately, in the case of the multichannel sensor they don’t know what they produce. Their sketch means nothing, except the voltage values. These big readings are NOT ppm or ppb. There was absolutely unadequate email conversation between me and the SEEED service engineer (for example he said, that these “ppm” of hundreds are normal LOL! It is not normal! It is deadly! I had a conversation with WINSON, the company which produces the four sensors of the multichannel sensor. Because the WIKI of the SEEED is not full (NO2 calibration curve is missing), and they said nothing about that, I asked WINSON to send me the curve. After that I wrote a sketch which reads the CO and NO2 sensors and I have made the calibration of the sensors. Actually, the sensors are enough accurate (more than I expected before the tests). If someone is interested about how to read REAL ppm from the sensors, please write me to vcoder(at)abv.bg. SEEED, take this on mind! You sell not so cheap sensor! Please inform yourself, correct your WIKI and show to your customers how to operate with that sensor!
