The DHT22 is a basic, low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed). Its fairly simple to use, but requires careful timing to grab data. The only real downside of this sensor is you can only get new data from it once every 2 seconds, so when using our library, sensor readings can be up to 2 seconds old.

• Size: 28.2 mm (length) * 13.1 mm (width) * 10 mm (high)
• Weight: 6 g
• Working voltage: 3 V - 5.5 V
• The sensor models: the loose AM2302 temperature and humidity sensor
• Signal output form: digital signal
• Temperature measurement range: - 40°c to 80°c
• Measuring accuracy: 0.5°c
• The humidity measuring range: 0-100% RH
• Measuring accuracy: 2% RH
• Resolution: 16
• With fixed screw holes, convenient installation and fixation. Diameter of 2.6 mm
• Module interface description:
• "+" : positive
• "-" : the power of anode
• "Out" : the microcontroller IO port

Downloads:

DHT22 datasheet

Arduino library and example code

Detailed usage tutorial