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We're running an old Raspberry Pi B512 with a DHT11 humidity sensor on an i2c. Although the DHT11 claims the accuracy is +/-2C for the temperature and +/-5% for humidity, we're seeing more inaccurate readings.

Does anyone know how to calibrate this? I've looked rather extensively, but all I'm finding is that it's factory calibrated...

Thank you for your help.

ProfRose
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3 Answers3

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I think this could not be calibrated. The only option, from my experience, is to use DHT22, which is more accurate.

Gerard Taub
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  • For future reference, this sort of response would be better as a comment to the original question. – Rajesh Apr 20 '15 at 15:45
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You can buy another DHT22 or DHT11 device and compare the results with your original sensor.

Try to capture several samples, e.g. log data from both sensors every 2 seconds for 10 minutes. This way you obtain 300 samples. You can blow several times on both sensors or open the window. Then plot the diagrams and see how they differ.

Then you might be able to build your calibration model.

Viliam Simko
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Regarding to the documentation/data sheet here you can accelerate the calibration process like this:

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

thomasb
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