Datasheet

Download Adafruit Si7021 Library

https://adafru.it/rAx

Rename the uncompressed folder Adafruit_Si7021 and check that the Adafruit_Si7021 folder contains

Adafruit_Si7021.cpp and Adafruit_Si7021.h

Place the Adafruit_Si7021 library folder your arduinosketchfolder/libraries/ folder.

You may need to create the libraries subfolder if its your first library. Restart the IDE.

We also have a great tutorial on Arduino library installation at:

http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use

Load Demo

Open up File->Examples->Adafruit_Si7021->si7021 and upload to your Arduino wired up to the sensor

Thats it! Now open up the serial terminal window at 115200 speed to begin the test.