Posted on Mar 7, 2013 4945
The TL3103 linear Hall-effect device can be used as a compass. By definition, the north pole of a magnet is the pole that is attracted by the magnetic north pole of the earth. The north pole of a magnet repels the north-seeking pole of a compass. By convention, lines of flux emanate from the north pole of a magnet and enter the south pole. The circuit of the compass is shown. By using two TL3103 devices instead of one, we achieve twice the sensitivity.
With each device facing the opposite direction, device A would have a position output while the output of device B would be negative with respect to the zero magnetic field level. This gives a differential signal to apply to the TLC251 op amp. The op amp is connected as a difference amplifier with a gain of 20. Its output is applied to a null meter or a bridge balance indicator circuit.