Values of PM and ranges

[georgekalantzis4]

Hello. I am using the code from /examples/sps30/sps30.ino to test the quality of the measurements of the sps30. Also I have multiple sensors from different brands to test them at the same time. The sps30 is attached to Arduino Yun rev2. I have a question for the values of PM of sps30. You can see the following example.

sps30_pm1.0 | sps30_pm2.5 | reference_sensor_pm2.5 18.28 | 19.33 | 38.33 18.72 | 19.80 | 38.72 17.81 | 18.84 | 38.11

As you can see the pm2.5 of sps30 are much lower than the reference sensor. But the sum of sps30_pm1.0 and of sps30_2.5 is very close to the pm2.5 of the reference_sensor.

The value of the m.mc_2p5 is in range of 1μm-2.5μm or in range 0.3μm-2.5μm?

Also at the end of README you are providing a screenshot that explains the ranges. But I tested the sps30 with a cigarette and I found out something strange:

sps30_pm1.0 | sps30_pm2.5 | sps30_pm4.0 | sps30_pm10.0 111.22 | 118.99 | 120.10 | 120.32

With the explanation of the screenshot the μg/m3 of the range 4.0 to 10.0 μm is 0.22μg/m3 and this is not logical. Because with a cigarette the value of pm10.0 should be around 500μg/m3. But if I add all the values of the pm the result is logical.

So my question again is: m.mc_1p0 -> 0.3 to 1.0 μm m.mc_2p5 -> 1.0 to 2.5 μm m.mc_4p0 -> 2.5 to 4.0 μm m.mc_10p0 -> 4.0 to 10.0 μm

OR

m.mc_1p0 -> 0.3 to 1.0 μm m.mc_2p5 -> 0.3 to 2.5 μm m.mc_4p0 -> 0.3 to 4.0 μm m.mc_10p0 -> 0.3 to 10.0 μm

Thank you.

[winkj]

Hi George,

For any product support - i.e. anything not related to the driver - it's best to contact Sensirion's product support team via https://sensirion.com/contact; the github issues are followed closely by our software teams, but as far as I can tell your question is mostly about the product, and not the arduino-sps driver.

I'd be happy to clarify the implementation of the arduino-sps library though: The values in m.mc_* are not modified after reading them from the bus (see https://github.com/Sensirion/arduino-sps/blob/master/sps30.cpp#L135), so the data available in the Arduino example will be whatever the sensor is transmitting.

According to the datasheet, the ranges are specified as follows

PM1   (mc_1p0):  0.3 to 1.0 μm
PM2.5 (mc_2p5):  0.3 to 2.5 μm
PM4   (mc_4p0):  0.3 to 4.0 μm
PM10  (mc_10p0): 0.3 to 10.0 μm

If you have any further question on the arduino-sps library, feel free to reopen this issue. For any other questions not related to the driver itself, please reach out to the Sensirion support team as mentioned above.

[georgekalantzis4]

Thank you for your time and for your explanation, I will contact Sensirion's product support for this issue.