Description:The HTU21D is a cost-effective, easy to use, high-precision, digital humidity and temperature sensor. this sensor is ideal for environmental sensing and data acquisition and is perfect for a weather station or humidor control system. All you need is two lines for I2C communication and you'll have relative air humidity readings and very accurate temperature readings as a bonus!There are only four pins, must be connected to start with this sensor in a project. for VCC, for GND, and two data lines for I2C communication. this breakout board has in 4,7 karat pull up resistors for I2C communication. if they hook several I2C devices on the same bus, they can disable these resistors.dimensions: 0.6x0.6 "Package Included:1 * HTU21D Temperature and humidity Sensor Module Breakout Board