SDS 011 sensor not reliable?

1

Hi there,

I use the SDS 011 sensor as part of the Sensor.Community network. Setup is identical to Sensor Community, without temperature or humidity meter.

So far everything is going well. For the sake of interest, I took the device with me on the go (via a USB power bank).
At two measuring stations of the Lower Saxony air quality measurement network (Göttinger Straße, Lindener Berg in Hanover), the values ​​on my SDS011 deviated by an average of 40% over several days in December from the officially measured values ​​there. The values ​​I have measured are lower than the officially measured values. The values ​​for PM2.5 differ. The values ​​for PM10 were halfway comparable.

In the meantime, I had ordered another SDS011 for a colleague and then let both sensors run in parallel against the two measuring stations of the Lower Saxony air quality measurement network. Same result, the two SDS011 deviate almost identically from the values ​​of the official station. Again my measurement results are lower.

What could be the problem? I tested the power supply. Operation on the power bank at home does not differ from operation of the SDS011 via a USB cable in the socket.

2

Please send me the sensor ID and the location of the station.

The SDS011 is reliable like a low cost sensor. I can send you some papers.

3

I will check the sensor ID, please send some papers if you have more information.

4

Two things that may affect the values:
On mobile use the battery power may be a problem. The SDS011 may show high values if it can’t get more than 100mA. With a USB port limited to 100mA (some older computers have such ports) the values were up to 10 times higher.
Humidity above 90% may affect the values also (some people say this happens above 70% …). The humidity may condense on the particles making them bigger. The optical detection can’t “see” this and will show higher values.

5

You say in both cases the SDS011 would show higher values, right? In my case it shows smaller values than the official government station in my hometown.