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DHT11 Humidity Readings

I’ve purchased a number of the DHT11 sensors to monitor the basement temp and humidity of a house I own in Wisconsin. The sensor is connected to a SeeedStudio XBee shield on an Arduino Uno board.

I have two dehumidifiers in the basement, an older one my mom owned and a new one (hopefully using less power). The new one shows a humidity of 55 – 65% when running. The older one shows a higher humidity, but does respond when the new dehumidifier is running.

The first sensor registered 39%humidity and never changed. The local weather stations (WUnderground) indicate the humidity in the area is above 50% and the new dehumidifier shows the humidity between 55 and 65% when it is running. I then tried two more sensors that I just ordered. One indicated the same 39% and never changed. The other registered 48 – 49%, but still did not change, even after I turned the dehumidifier off and the humidity definitely rose. If I blow on the sensors, they do increase in both temp and humidity, but reset back to the previous values.

Does this sensor need air flow to accurately record humidity? Would the DHT22 do better? The accuracy says +/- 5%, but I’m not seeing that.

Any suggestions, as I really need to know what the accurate humidity so I can determine if the dehumidifier should be running or not.

Thanks.

Greg Walters

2 Answers

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The DHT22 will definitely give you better performance, but either way some airflow is generally recommended. Humidity tends to build up low as well so you may want to put your sensors closer to the ground, and play with different angles.

I have also had good luck with putting the devices in a box with pinholes in it since that eliminates some of the air circulation sensitivity you can see in certain environments.

Another step you can take is to try the Bake method for re-conditioning your DHT11 as outlined in .

Either way let me know how things go, I look forward to hearing more about your progress.

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Joseph,

You said “Bake method for re-conditioning your DHT11 as outlined in .” Outlined in what? I could not find anything describing this method.

Greg

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