Hall sensor: principle of operation and application

The Hall effect got its name thanks to the scholar E.G. Holl, who opened it in 1879 when working with thin gold plates. The effect consists in the appearance of a voltage when a conducting plate is placed in a magnetic field. This tension is called - Hall voltage. The industrial application of this effect became possible only 75 years after the discovery, when semiconductor films with certain properties began to be produced. So there was a Hall sensor, the principle of which is based on the same effect. This sensor is a device for measuring the strength of a magnetic field. On its basis, many other devices are created: sensors for angular and linear displacement, magnetic field, current, flow, etc. The Hall sensor has a number of advantages due to which it has become widespread. First, non-contact operation excludes mechanical wear. Secondly, it is easy to use at a fairly low cost. Thirdly, the device is small in size. Fourthly, a change in the response frequency does not lead to a displacement of the very moment of measurement. Fifthly, the electrical signal of the sensor does not have the character of a burst, and when switched on it immediately acquires a constant value. Other advantages are: transmission of a signal without a hiccup, contactless character of the signal transmission itself, practically unlimited lifetime, a large frequency range, etc. However, it has its own disadvantages, the main ones being the sensitivity to electromagnetic interference in the power circuit and temperature changes.

The principle of the Hall sensor. The Hall sensor is a slotted design with a semiconductor on one side and a permanent magnet on the other. When a current flows in a magnetic field , a force acts on the electrons, the vector of which is perpendicular to the current and to the field. At the same time, a potential difference appears on the sides of the plate. In the sensor gap, there is a screen through which the lines of force close. It prevents the formation of a potential difference on the plate. If there is no screen in the gap, then under the influence of the magnetic field, the potential difference will be removed from the semiconductor plate. When the screen (rotor blade) passes through the gap, the induction on the integrated microcircuit will be zero, and the output will appear voltage.

The Hall sensor and devices based on it are very widely used in the aviation, automotive, instrument engineering and many other industries. They are produced by such famous companies as Siemens, Micronas Intermetall, Honeywell, Melexis, Analog Device and many others.

The most common so-called key Hall sensor, output Which changes the logical state in the case when the magnetic field exceeds a certain value. These sensors are particularly widely used in brushless electric motors as rotor position sensors (DPRs). Logical Hall sensors are used in synchronization devices, ignition systems, magnetic card readers, keys, in contactless relays, etc. Widely used integral linear sensors, which are used to measure linear or angular displacement and electric current.