Hall-effect-compass

  
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.
Hall-effect-compass - schematic

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.




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