Hall Sensor

The Hall effect is the basis for using a common technology for contactless phase detection from the approach, displacement, and rotation speeds of ferromagnetic objects.

What is a Hall sensor can be understood by understanding the essence of the processes occurring in it. At the time when the current passes through the body of the plate in the longitudinal direction, when a magnetic field occurs on the extreme parts of the plate in the direction transverse to the current, a potential difference is formed. It is due to the law of Lorentz, which establishes the fact that due to the influence of the magnetic field, the feeders tend to shift toward the edges of the plate. The resulting potential difference is in direct proportion to the magnitude of the product of the field strength and current vectors H • I.

In the absence of a magnetic field, there is no distortion in the electron beam. When a magnetic field occurs , the Lorentz forces participate in the deflection of the electrons and lead to a curvature of their trajectories. These trajectories cause the accumulation of negative charges on one side of the plate. The opposite side of the plate serves as a place for accumulating an uncompensated positive charge. The concentration of charges on the surface of the opposite faces of the plate causes the appearance of an electric field in the transverse direction, which was called the Hall field. The process of accumulation of charges continues until the appearing transverse EMF compensates the forces created by the magnetic field. Then, the steady-state process is established, in which the electrons move in parallel with the faces of the plate, just as in the absence of a magnetic field.

Hall sensor, materials for manufacturing

The semiconductor material from which the Hall sensor is to be manufactured should be the carrier of not only high, but also as low as possible temperature-dependent values of the coefficient known as the Hall constant and the mobile capabilities of the current carriers. To implement the choice of semiconductor material (the goal - to make a Hall sensor) should be guided by the scope of its use.

The Hall constant is determined by the need to measure the induction of the magnetic field, the current through the sample with its installed thickness. Having knowledge of the value of the Hall constant, it is possible to establish the concentration of charge carriers in the body of the plate, which is inversely proportional to the product of the Hall constant with the electron charge.

Usually, semiconductors with electronic conduction are used because they have a much higher mobility of charge carriers than those that have p-type conductivity. It is necessary to know that the physical properties of semiconductor materials can be subject to significant changes, depending on what kind and how many impurities will be introduced into them.

Hall sensor, manufacturing technology

To produce a semiconductor plate for use in the Hall sensor, it is possible to do the following:

1. Saw a crystalline Hall plate of the desired shape from a single crystal bar.

2. Obtain a Hall plate by the method of depositing on the substrate the thinnest layers of materials from semiconductors.

The scope of Hall sensors

The use of linear Hall sensors is widely distributed in the form of:

- current sensors;

- Variable speed drives;

- schemes of control and protection of electric motors;

- position sensors;

- flow sensors;

- brushless DC motors ;

- contactless potentiometers;

- rotation angle sensors;

- detectors of ferromagnetic bodies;

- vibration sensors;

- tachometers.

The information presented in the article will be useful to the reader in the event of a discussion about what a Hall sensor is.