How to prevent outdoor temperature/humidity sensors from having wildly incorrect humidity readings?

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Hey folks,

I’ve been using DHT-22 sensors for yonks but noticed that the humidity readings always ended up being wildly wrong after a while, reading 100% humidity even though it’s nothing close to that (I’ve always been carefully to actually shield them from the rain and they’re not getting physically wet). If it got warm enough the humidity readings would drop, it’s not that it was permanently at 100%, but it was definitely enough to make it a fairly useless reading.

I discovered the Core Electronics BME-280 sensors late last year and bought a handful and they’ve been doing well, but I’ve noticed that the one I’m using outdoors has now succumbed to the same issue… the humidity readings are 100% even though the BoM reckoned it was 65% humidity and I can feel that it’s definitely not crazy-humid.

Has anyone else run into this? Is there some way to avoid it?

Thanks!

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Have experienced the same problem with the BME280. It is suitable for measuring humidity indoors but not outdoors. When it rains and the humidity reaches 100% the dielectric saturates so when the humidity lowers it continues to read 100% until it dries. I am not aware of any solution but if the BME280 is mounted where there is good airflow it helps.

The Adafruit SHT30 overcomes this problem by having an internal heater to dry out the dielectric but I have not tried it.

Good luck

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Oooh, that’s very interesting, thanks so much! I’ll definitely have to take a look at the SHT-30, I see there’s a fully weather-proof mesh-protected one which might be the go, save me having to worry about if it’s going to get wet or not!

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@Fractal,

Thanks for the great explanation.
Basically how I thought it happened :slight_smile: