DHT21 is a low-cost capacitive humidity & temperature sensor. It uses the same protocol as the DHT11.Ultra-low power: 300uA Average, 15uA when sleepExcellent long-term stabilityAll calibration, digital outputCompletely interchangeableLong distance signal transmission: up to 20mSpecifications:Power Supply: 3.3-5.2V DCResolution: 0.1Temperature measurement range: -40 ~ +80 @0.5Humidity measurement range: 0-99.9%RH @3%RHDHT21 DatasheetArduino library and example code