Now the computer can tell what the fingers are doing. The next thing it needs to know is the position of the hand relative to a fixed point. VPL has incorporated the Polhemus Navigation Sciences' 3Space Tracker into the DataGlove. The Tracker measures magnetic interference in three dimensions. Users of Exos's Dexterous Hand Master typically employ the Tracker, too.
Any coil charged with an electrical current generates an electromagnetic field.
The field is strong in the direction of the coil's radius, and it is relatively weak in the perpendicular direction. Similarly, a magnetic field passing through a coil of wire generates an electric current proportional to the field's strength. The Tracker uses a transmitter with three coils of wire, each perpendicular to the other two. The Tracker's controller pulses each of the transmitter's coils in turn and reads the current generated in each of the three receiving coils, for a total of nine readings. The system works amazingly well.