Description:The HTU21D is a low-cost, easy to use, highly accurate, digital humidity and temperature sensor. This sensor is ideal for environmental sensing and data logging and perfect for a weather stations or humidor control systems. All you need is two lines for I2C communication and you'll have relative humidity readings and very accurate temperature readings as a bonus! There are only four pins that need to be hooked up in order to start using this sensor in a project. One for VCC, one for GND, and two data lines for I2C communication. This breakout board has built in 4.7k pull up resistors for I2C communications. If you're hooking up multiple I2C devices on the same bus, you may want to disable these resistors.The new generation HTU21D temperature and humidity sensor sets a new standard in terms of size and intelligence: it is embedded in a reflow friendly dual row flat pin-less DFN package with a base of 3x3mm and a height of 1.1mm. The sensor outputs a calibrated digital signal in standard I2C format. Diversified output modes, wide operating voltage range, and high temperature accuracy and humidity accuracy. HTU21 series module is designed for low power and small volume applications, with good quality, fast response speed, strong anti-interference ability, high cost performance advantages, small size (3x3mm), very low power consumptionSpecifications:Power supply voltage: 1.5V-3.6Humidity measurement range: 0-100%RHTemperature measurement range :-40C -105 CPower consumption :2.7uWCommunication mode :I2CHumidity accuracy range (10%RH to 95%RH) :HTU21D2%RHHumidity lag: 1%RHMeasurement time: 50msAnnual drift: -0.5%RH/yearResponse time: 5 sAt the same time, the HTU21D can be fully compatible with the Swiss SHT20 and SHT21, and the hardware Pin can be Pin to Pin without modifying the circuit board.