Re: DHT11 versus DHT22
The data all looks reasonable from my test with a fan. I found that all sensors respond very quickly to temperature changes. Going from ~68°F air inside to ~33°F air outside, all 6 DHT11 sensors reported constant temperatures 33 in 90 seconds (±offset error of course). The humidity was a bit different. Of my 6 sensors, 4 reached steady values within 6 minutes. However, the last 2 were still slowly climbing after 13 minutes. As a guestimate, I'd say another 10-15 minutes would be required for those to reach a steady value.
I know the first 3 or 4 sensors used resistors from one package. The last 2 or maybe 3 were from a different package (the outliers). I don't remember off the top of my head if these were the same resistance, but I don't see why it would matter. The last 2 sensors were also from a different order a month or so later. I don't mind just using the first sensors that work correctly, but I'm curious if there's something that could explain the different response? If I have a sensor fail in service, I don't want to have to remove all of them and perform this calibration test again. I'd prefer to just install everything and build a calibration routine into the setup function.