[HansR]

I don't think it's all that important to mention that aspect. As much as I think I know, all commercial Air Quality sensors implement humidity compensation, that's the main reason why they all have T/H sensors included.

You mean the AirLink and PurpleAir etc... I don't know that, they don't publish that, I think they should and would.

The purpose isn't provide accurate T/H readings, but instead measure the air humidity as close to the dust sensor air intake as possible. Brands don't reveal their algorithm, the AQM-III uses the one which source of study is clearly identified on the code.

Yes.

One user here in Portugal is running the AQM III (with a PMS7003), side by side with an AirLink and a Purple Air since several months, and the results of the 1H, 3H, 12H and 24H averages are consistent between them, which leads us to believe that the humidity compensation method that we use is valid.

OK... good

The Sensirion SPS30 readings seems to be less sensible to humidity changes than the PMS7003 or the SD011, that's why on the current firmware, the humidity compensation isn't applied for the SPS30.

Now that is something I dislike a bit, an inconsistency. As this T/H correction is apparently a non-documented feature, everywhere it becomes very difficult to say something about it and measure the correctness of the output. Comparison becomes difficult. A lot has been written about this T/H correction but no specification mentions it. I find that difficult. Fortunately with the AQM there is the code, I may start trying some things.

I think you have an original AirLink, try putting both running outside side by side, and let them work for some days. On the AQM III preferably use a PMS7003, as it is from the same brand and similar to the ones used by the Davis Airlink.

No I don't have a real airlink, it is my own emulator with an PMS1003. I may start using a PMS7003 and compare that with my other sensors. I am currently starting a test examining exactly that: T/H compensation (where I live humidity can be a whole year 70% and up).

Anyway... interesting feature that compensation. I think it should be mentioned just as it should with an AirLink.

Regards, Hans