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Topic: DHT11 - temp ok, but RH values wildly off (Read 3 times) previous topic - next topic

naladka

Looks like sensor resetting procedure helps me. I think it happens when sensor is used in extreme conditions like when breathing on it or placing straight under vapor stream or ultrasonic humidifier.

all you need to do:

Step one: Keep the DHT sensor at the condition of Temperature 50~60Celsius, humidity <10%RH for 2 hours;
Step two:K keep the DHT sensor at the condition of Temperature 20~30Celsius, humidity >70%RH for 5 hours.


In my case it wasn't hard to get that environment: first one can be achieved just placing sensor in air heater (water or electric), second- just cover sensor with something wet in room temperature. After resetting i have checked measurements and surprisingly humidity was both equal on DHT11 and expensive, calibrated hygrometer.

Willian

Hello, I tested the DHT11 sensor in extreme conditions (under rain hehehe).
After it get water on it the sensor reading freezes on 60ÂșC temperature and 75% Humidity.
I waited a few days to dry the sensor properly, put him in the sun and heater for no more than 2 hours and the Temperature reading get back to the right reading (I compare with the sensor DS18B20 which also get in the rain and doesn't get any problems in the readings). But the humidity is stuck in about 35-40%, same problem of our friend jbishop129 . =\
I will try to make this resetting routine.
Thanks for the tip!

Willian

I tried the re-calibration procedure about 5 times, but the humidity still stuck in about 35 ~ 40%, any tip why?  =)
If I breath on it, the reading goes up to 60% normaly.

mrbig

Hi!


In my case it wasn't hard to get that environment: first one can be achieved just placing sensor in air heater (water or electric), second- just cover sensor with something wet in room temperature.


Those who had success with this process, did you do this with the device powered on, or did you disconnect it before?
(Trying to guess whether the recalibration is an active, or a passive process)

naladka

Power was off while recalibrating. After few days of running in normal conditions (i even didn`t breath on it), it resumes to show abnormal humidity. I was running room humidifier until real humidity rises to 55%, while DHT11 sensor still shows 14%. Maybe you can use sensor to read changes in humidity, but not the actual value. I my case i didn`t find it usefull at all.

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