DHT21 is a high performance temperature and humidity sensor, providing accurate measurement, low power consumption, long distance data transmission, automatic calibration and long life. 

It is perfect for projects that require measurement of temperature and humidity such as greenhouse and portable weather station that provides precise information about the environment. The sensor has small size making it to be easily integrated into the project.

Specifications:

• Humidity sensing range: 0 to 99.9% RH
• Humidity measurement accuracy: ±3% RH
• Temperature measurement range: -40 to 80 °C
• Temperature measurement accuracy: ±0.5 °C
• Supply voltage: 3.3 to 5.2 V

Connection Diagram

• Sensor :  Arduino
• Red: 5 V
• Black : GND
• Yellow: Digital I/O pin

Useful links:

• Example Code:  http://arduinolearning.com/code/am2301-example.php
• Library "DHT"  https://github.com/adafruit/DHT-sensor-library