Hall effect and sensor

The Hall effect was discovered in 1879 by American scientist Edwin Herbert Hall. Its essence is as follows (see Fig. 1). If through the conductive plate to pass current, and perpendicular to the plate to direct the magnetic field in the direction of the transverse current (and the direction of the magnetic field) on the plate voltage will appear: Uh = (RhHIsinw) / d, where Rh – Hall coefficient, which depends on the material of the conductor; H – magnetic field strength; I – current in the conductor; w – the angle between the current and the magnetic field vector (if w = 90 °, sinw = 1); d – the material thickness.

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Figure 1 – Hall effect




Imagine that on the table in front of you is a piece of the lead wire and the magnetic field perpendicular to the plane of the table. If the wire by passing a current, the magnetic field will cause the charges inside the wire deflected in one direction (right or left of the current direction depending upon the orientation of the magnetic field and the polarity of the charges). Shifting the direction of the rectilinear motion inside the conductor, the charges will be accumulated in the border zone, while the forces of mutual electrostatic repulsion between them arising under the action of Coulomb’s law, does not counterbalance the deflecting force of the magnetic field by the current. After that, the current again flows in a straight line, but on the conductor electrical potential difference occurs in the plane perpendicular to the direction of the current as well as directly to the lines of force of the magnetic field caused by the redistribution of electric charges in the plane of the cross section of the conductor, and the magnitude of this potential difference is proportional to the voltage and current magnetic field.
Due to the fact that the output effect is determined by the product of two variables (H and I), Hall-effect sensors are used quite widely.
Contactless key switches based on the Hall effect were used abroad quite extensively since the early 70s. The advantages of this switch – high reliability and long life, small size, and the disadvantages – the constant energy consumption and relatively high cost.
Hall sensor
Hall Sensor – Magnetic field sensor or Hall sensor working on the Hall effect, the essence of which is that when placed in a magnetic field of a conductor with a constant current in the conductor a transverse potential difference. Also called the Hall voltage.

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Figure 2 – Hall sensor

Application
For example, non-contact limit switches. Moreover, in contrast to the reed switches, Hall sensors are almost timeless – there is no one moving part.
And if connect sensor magnet gear and slip it to be closed through a magnetic flux, it is possible to easily obtain the rotational speed sensor. When a tooth would be closer to the sensor, the resistance of the magnetic flux is lower, and hence its power will be greater. And mizhzubtsovih intervals all the way around. As a result, the sensor’s output pulses are similar to the shape of gear teeth and have to find them is not difficult.

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Figure 3 – Using of Hall sensor



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