Fangrui Product Details 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 Mits 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.