Are Chinese PM2.5 Sensors Reliable?
The smog in Bangkok has got pretty bad in the past month. Luckily, I’ve bought myself an air purifier before it got sold out everywhere. Wanting to know how well it works, I got myself some cheap sensors from Aliexpress — PMS5003 and PMS7003 and I was pretty satisfied with the readings they gave. Outside was polluted (with numbers being similar to the official numbers) and inside is clean with the air purifier on. If you’re interested, I have a Chrome App and an Android App to give you readings.
All was fine and dandy, until I got access to an SDS011 and it was giving very different reading from my sensors! Thus, to find out how their readings differed, I’ve performed an experiment. In a room with dirty air from outside, I’ve connected all sensors and turned on my Sharp FP-J30TA air purifier.
At first, I thought that the difference was only during low concentration, but the actual result was mind-boggling.
You can see that the PMS5003 and PMS7003 gave consistent result but the SDS011 almost all the time gave half the reading of the other sensors. I’ve checked and checked and it wasn’t a programming error. You can find the raw data here.
One final test is the next morning, when pollution was pretty bad, I’ve tried all three sensors again and the result is as follows:
It looks like at higher concentration, the difference is now 1.5 times instead of 2 times. So go figure.
Conclusion: The exact readings may not be reliable, but they’re good enough for seeing the ups and downs of the pollution level.
