The Hall effect got its name from the scientist E. G. Hall, who discovered it in 1879 while working with thin gold plates. The effect is the appearance of a voltage when a conductive plate is placed in a magnetic field. This voltage is called the 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. This is how the Hall sensor appeared, the principle of operation of which is based on the effect of the same name. This sensor is a device for measuring the strength of the magnetic field. Many other devices are also created on its basis: sensors of angular and linear displacement, magnetic field, current, flow, etc. The Hall sensor has a number of advantages, thanks to which it has become widespread. First, non-contact actuation eliminates mechanical wear. Secondly, it is easy to use at a fairly low cost. Thirdly, the device has a small size. Fourth, a change in the response frequency does not lead to a shift in the very moment of measurement. Fifthly, the electrical signal of the sensor does not have a burst character, and when turned on immediatelygains a constant value. Its other advantages: signal transmission without distortion, non-contact nature of the signal transmission itself, practically unlimited service life, large frequency range, etc. However, it also has its drawbacks, the main of which are sensitivity to electromagnetic interference in the power circuit and temperature changes.
The principle of operation of the Hall sensor. The Hall sensor is a slot-hole structure 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 both the current and the field. In this case, a potential difference appears on the sides of the plate. In the gap of the sensor there is a screen through which the lines of force are closed. It prevents the formation of a potential difference on the plate. If there is no screen in the gap, then under the action of a magnetic field, a potential difference will be removed from the semiconductor plate. When the screen (rotor blade) passes through the gap, the induction on the integrated circuit will be zero, and a voltage will appear at the output.
The Hall sensor and devices based on it are very widely used in the aviation, automotive, instrumentation and many other industries. They are produced by such well-known companies as Siemens, Micronas Intermetall, Honeywell, Melexis, Analog Device and many others.
The most common is the so-called keyHall sensor, the output of which changes the logical state if the magnetic field exceeds a certain value. These sensors are especially widely used in brushless electric motors as rotor position sensors (RPS). Hall logic sensors are used in synchronization devices, ignition systems, readers of magnetic cards, keys, contactless relays, etc. Integral linear sensors are widely used, which are used to measure linear or angular displacement and electric current.
