Features: The HTU21D is a low cost, easy to use, highly accurate, digital humidity and temperature sensory. This sensory is ideal for environmental and data logging and perfect for a weather stations or humidor control. All you need is two lines for I2C communication and you’ll have relative humidity readings and very accurate temperature readings. There are only four pin that need to be hook up in order to start using this sensory in a project. and two data lines for I2C communication. This board have with 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 Engineered as a direct replacement for SHT20/SHT21 sensory, this module maintains identical while offering enhances durability against electromagnetic interference. Specifications: Size: Approx.15x15mm/0.59x0.59inch Color: Red Operating: 1.5V to 3.6V Package Includes: 1Pc Temperature and Humidity sensory Module note: 1.Please allow 1-2cm errors due to manual measurement, making sure that you not mind before order. 2.Due to the differences between different monitors, the picture may not reflect the actual of the item.