The WEATHERmeter includes an internal compass (magnetometer). It is calibrated at the factory and should work reasonably well out of the box. However, since the magnetic field of the earth varies quite a bit, it may need to be re-calibrated periodically. If you believe your WEATHERmeter is not providing an accurate wind direction, follow this procedure to calibrate the internal compass on your WEATHERmeter:
1) Find an open, outdoor space away from electronics, large metal objects and any other source of magnetic interference.
2) With the app running and the WEATHERmeter connected, go to Menu > Settings > Calibrate Compass (you will see a dialog box)
3) Hold the meter vertically and blow gently into the meter - just enough to spin the blades.
4) With the impeller blades still spinning, rotate your body slowly through a full 360 degree rotation. It doesn't hurt to complete more than one rotation.
5) Tap "ok"
Even with calibration, the compass in the meter will probably not be as accurate as your smart phone. Smart phones have more sensors (GPS, accelerometer) and can often auto-calibrate.
In cases where you want or need a more accurate direction reading, the Wind & Weather Meter app has an option to use your phone's compass. In that case, you will need to point the phone in the same direction as the meter.
To enable the phone's compass:
From the Menu, go to Settings > Use WEATHERmeter Compass > check No
If the Battery is removed the compass will need to be re-calibrated