Measurement of Magetic Field and Compass Direction
The sensor is located at the red rectangle position. Press keypad "6" to measure the variation of magnetic field (and compass direction, if appropriate) within 10s.

Remarks:
The mobile logger reports the magnetic field H along its three (X, Y and Z) axes in unit of mG (milligauss). Note that 1 G = 1000 mG = 10^-4 T (tesla). If there is no other magnetic substance nearby, the logger also will give the compass direction for its X axis. Otherwise, the compass direction should be interpreted as the angle between the resultant magnetic field (from Earth and nearby magnetic substances) on the XY plane and the X axis. The X and Y axes are shown in the above diagram while the Z axis is pointing vertically upwards from the surface of the logger.