The humidity and temperature sensor board that carries a digital SHT21 humidity and temperature sensor from Sensirion. The SHT21 uses a capacitive sensor elements to measure humidity, while temperature is measured by a band space sensor. Both sensors are perfectly coupled to a 14-bit ADC, which then transmits the digital data via the I2C protocol. It has a 4-pin interface that can communicate directly with the analog pins Bidirectional communication over a single pin on I2C protocol Board is 5V tolerant, allowing sensor to run from a 5V supply on I/O pins colour:Blue Material:Electronic component size:Approximately 1.3 x 1cm Package Contents: 5 x HTU21D Temperature & Humidity Sensor Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.