I have the DHT11 up and running on an Uno. When I compare the values to two other thermometers (one infrared and one digital) I’m getting a 5 deg F difference (higher) on the DHT11. The others are within 0.5F.
What is the anticipated accuracy of the device? Is calibration through software recommended?
The DHT11 is expected to be within +-2 degrees accuracy throughout it’s reading range. For calibrated reading accuracy it is recommended that you use one of the following methods:
1.) The Delta Method is a simple calibration that is centered at a particular temperature. The advantage of this method is it’s simplicity and ease of implementation.
The Delta Method is employed by taking the temperature reading of your DHT11 and of another device (let’s say your infrared thermometer) and subtracting the DHT11 reading from the infrared reading. The number you get would then be added to the readings from your board.
This method is most accurate when you do not expect a large range of temperatures, and will still be +- 2 degrees at it’s worst as you get further and further from your calibration point.
2.) The Array Method involves measuring the read temperature and the actual temperature for each temperature of interest in the operational range of the DHT11 and inputting the calibrated values into a look-up array whose index corresponds to each individual temperature.
This method has the advantage of being extremely accurate, but the disadvantage of being tedious, and a little more difficult to implement.
3.) For much greater accuracy try the Virtuabotix DHT22 (https://www.virtuabotix.com/?page_id=3117&productid=0609224531774) which provides a lot more resolution and accuracy.
Hopefully that answers your question, let me know if there is anything else I can do to help!