Now offered in "brand name" and "generic", please see our generic product FAQ for more information. PLEASE NOTE: the generic version of this product DOES NOT include the resistor
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.
Simply connect the first pin on the left to 3-5V power, the second pin to your data input pin and the right most pin to ground. Although it uses a single-wire to send data it is not Dallas One Wire compatible! If you want multiple sensors, each one must have its own data pin! Adafruit has written an Arduino library with example code
Compared to the DHT11, this sensor is more precise, more accurate and works in a bigger range of temperature/humidity, but its larger and more expensive
The Adafruit version comes with a 4.7K - 10K resistor, which you will want to use as a pullup from the data pin to VCC. The generic version does not come with a 4.7K resistor.