Magnetic sensor coil is simple, can detect the change of the magnetic flux density.
When a magnet near the coil, the coil in the magnetic flux density increases.
Then, in the coil produces in place on the direction of the magnetic flux density increase magnetic flux of the induction electromotive force/induced current.
Instead, keep magnets away from moving coil will reduce coil in the magnetic flux density, so will produce inductive electromotive force and inductive current in coil, to increase the magnetic flux density.
Also, since when the magnet is not moving magnetic flux density did not change, so will not produce inductive electromotive force and inductive current.
By measuring the induced electromotive force direction and size, can detect the change of the magnetic flux density.
Due to its simple structure, the coil is not easy to damage.
However, the output voltage depends on the change rate of flux.
May not be able to use the coil to detect slowly changing permanent magnet or magnetic flux.
Reed switch is a kind of sensor, which extend from the left and right pieces of metal sealed in a glass tube, overlapping location in the reed has a gap.
When the external magnetic field, the reeds were magnetized.
When reed was magnetized, overlap each other to attract and contact, and then the switch.
Even in the case of static magnetic field, the magnetic core of sensors can also detect the magnetic field, the magnetic flux density did not change.
Therefore, components used in many applications, such as magnets, Angle sensor and current sensor combined use of non-contact switch.
Use components of geomagnetic sensors for mobile phones and other applications.