A little compare with other sensors

I am comparing one of my sensors SDS011 with an Ecowitt WH41.

Some notes:

  • I limit my compare to PM 2.5 only and omit AQI.
  • both sensors are located on the roof of a house over 2 meters high from the peak without obstacles
  • 12m height from the ground
  • there are no official ARPA tracking stations nearby to extende may compare
  • the Wcowitt WH45 sensor is not significant (inside an house at 50 meters), it’s only informative
  • As soon as I solve the power problems, I will make comparisons over longer times

In all tests and in this example, there is an average difference between the two sensors (WH41 gives 50% higher data on average).
I do not have a certain reference that allows us to understand if WH41 overestimates or SDS underestimates.
What do you think?

da gif a jpg

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Extending the comparison to 5 consecutive days, WH41 measures on average 52% above what the SDS detects.
I don’t look at the peaks, but I didn’t expect such a significant difference.
(Humidity: grey line and scale on the right)


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have any of you updated the scaling factor of your sensor?
Most probably didn’t… correct?