A Hall effect sensor is a transducer that varies its output voltage in response to a magnetic field. Hall effect sensors are used for proximity switching, positioning, speed detection, and current sensing applications.
Fig : A wheel containing two magnets passing by a Hall effect sensor
In its simplest form, the sensor operates as an analog transducer, directly returning a voltage. With a known magnetic field, its distance from the Hall plate can be determined. Using groups of sensors, the relative position of the magnet can be deduced.
Frequently, a Hall sensor is combined with circuitry that allows the device to act in a digital (on/off) mode, and may be called a switch in this configuration.
WORKING PRINCIPLE
A Hall probe contains an indium compound semiconductor crystal such as indium antimonide, mounted on an aluminum backing plate, and encapsulated in the probe head.
When the Hall probe is held so that the magnetic field lines are passing at right angles through the sensor of the probe, the sensor gives a reading of the value of magnetic flux density (B). A current is passed through the crystal which, when placed in a magnetic field has a “Hall effect” voltage developed across it. The Hall effect is seen when a conductor is passed through a uniform magnetic field. The hall effect voltage produced is an indication of magnetic object passed around it. Hence the Hall effect voltage is the signal output and used to sense an object near it.
Also Read: Proximity Switch Animation
ADVANTAGES
A Hall effect sensor may operate as an electronic switch.
In the case of linear sensor (for the magnetic field strength measurements), a Hall effect sensor:
DISADVANTGAES
Hall effect sensors provide much lower measuring accuracy than fluxgate magnetometers or magnetoresistance-based sensors. Moreover, Hall effect sensors drift significantly, requiring compensation.
APPLICATIONS
Sensing the presence of magnetic objects (connected with the position sensing) is the most common industrial application of Hall effect sensors, especially those operating in the switch mode (on/off mode). The Hall effect sensors are also used in the brushless DC motor to sense the position of the rotor and to switch the transistors in the right sequence.
Smartphones use hall sensors to determine if the Flip Cover accessory is closed.
Hall effect sensors may be utilized for contactless measurements of DC current in current transformers. In such a case the Hall effect sensor is mounted in the gap in magnetic core around the current conductor. As a result, the DC magnetic flux can be measured, and the DC current in the conductor can be calculated. The Hall effect was used to detect DC current in a superconducting DC transformer also.
The Hall sensor is used in some automotive fuel level indicators. The main principle of operation of such indicator is position sensing of a floating element. This can either be done by using a vertical float magnet or a rotating lever sensor.
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I think that hall effect sensor can used as a string based musical instruments .we can get audio signal(ac) by hall effect output