Hall sensor - a device designed to measure the strength of a magnetic field. Its work is based on the Hall effect, which is the phenomenon of a potential difference in a magnetic field when a direct current conductor is placed in it. This device has found wide application in various devices and mechanisms.
Content
- The history of the creation of the device
- Design features
- Operating principle
- Types of devices
- Sensor Application
- Using sensors in smartphones
The history of the creation of the device
At the end of the 19th century, an American scientist from Baltimore, Edwin Herbert Hall, placed a semiconductor plate in a magnetic field and connected an electric current to it. This action created stress on the wide sides of the plate.
This phenomenon is called the Hall effect and has attracted public attention. 75 years later, when the industry began to produce semiconductor films, this discovery has found wide application in the field of technology. Today sensors are used:
- Electronic ignition in cars.
- In computer drive and fan motors.
- As the basis for the electronic compass in smartphones.
- In non-contact electrical devices for measuring current and voltage.
- In some models of ion jet engines.
The first types of sensors began to be produced in the middle of the 20th century. In 1965, American specialists created a solid-state device that greatly improved the performance of equipment. Sensors are considered practically eternal, since they do not have interacting and rubbing elements.
Design features
Semiconductors of gallium and indium arsenides are considered the most effective materials for the manufacture of the sensor. Most often, the device is a film, the thickness of which does not exceed 10 microns. The sensor has three terminals:
- power supply with an input voltage of 6V;
- zero contact;
- the output from which the signal goes to the switch.
The terminal to which the power supply fits is wide and occupies the entire side of the rectangle. The output terminal has a point electrode. A common point acts as a zero contact. Since a small signal remains at the contacts in the absence of a magnetic field, a differential amplifier is used to correct the output data.
The microcircuit is applied to the substrate by lithography, which improves the accuracy of the readings. Usually in various devices this is used to check the position of the elements of the mechanism.
Operating principle
The principle of operation of a Hall sensor is based on a galvanomagnetic phenomenon, which shows the result of the interaction of a magnetic field with a semiconductor. A semiconductor is connected to an electrical circuit that changes its properties.
As soon as transverse stress appears, the Hall effect immediately occurs. At this moment, the charge is directed perpendicular to the field vector. This phenomenon is explained by the effect on electrons or holes of the Lorentz force, which leads to their deflection.
Under the influence of this force, particles in a semiconductor move in different directions, in accordance with their sign. Electrons (negative charge) are collected on one side of the plate, and particles with a positive sign on the other.
As the charges accumulate between them, an electric flow arises, which prevents them from moving under the influence of the Lorentz force. Upon reaching the equality of this force and the magnetic field, the semiconductor enters the equilibrium phase. This is how a Hall sensor works.
Types of devices
The main task of this device is to determine the strength of the magnetic flux. In practice, it is a sensor for determining the values of the magnetic field. There are two types of sensors:
- digital;
- analog.
Digital instruments are bipolar and unipolar. Bipolar elements work depending on the polarity of the magnetic field, that is, one turns on the sensor, and the other turns it off.
Unipolar devices turn on when any polarity appears and turn off when it decreases. Digital sensors measure induction and the occurrence of a corresponding voltage, that is, the presence or absence of a magnetic field.
The instrument displays one when the field induction reaches the threshold value. Until this moment, the sensor will show zero. Such a sensor will not be able to detect the presence of a magnetic field with weak induction. In addition, the distance to the measured object will affect the accuracy of the readings.
Sensor Application
Hall converters are widely used in modern household appliances. With their help, the laundry is weighed in washing machines. When the unit is started, things first get wet, and then the drum begins to rotate. According to its rotation speed, the total weight is determined and the machine is programmed for the consumption of powder, water and rinse aid.
In serial production, sensors were first used in computer keyboards. Here the interaction of the sensing element on the board and the magnet on the keys takes place. Elasticity is provided by a polymer material that has a long service life.
The only thing that can break in the keyboard is the controller. Hall sensors are used very often by electricians.when measuring the current strength in the wires with a contactless clamp. The Meter reacts to changes in the electromagnetic field around cables and wires.
Due to the inductance of the copper wire in the clamp, excitation is generated and an electromagnetic wave is generated. Part of its value is estimated by the sensor, which transmits data to the controller. According to the formulas embedded in it, the calculation is made, and the result is displayed.
Sensors are used in cell phones to monitor the battery charge and its consumption. But such a moment is considered very important in the operation of electric vehicles, since the presence of energy in them occupies a special place. Hall transducers are used in electronic compasses and as an image stabilizer in mobile cameras.
But these devices are especially widely used in the automotive industry. In cars, they are used to determine the engine speed, throttle position, vehicle speed, and so on. A sensor is used in the electronic ignition system. It is located in the distributor and replaces the contacts to form a spark.
Using sensors in smartphones
Due to their small size, Hall sensors are widely used in modern electronic gadgets. In smartphones, they help to return the screen to its original position, provide a quick start of GPS search, extend the battery life, and so on.
The ability to react to magnetic fields is used in folding phones and laptops. Due to the presence of a sensor, devices are turned on when opened and turned off when the screen is closed. In smartphones, the same function is performed by a sensor that interacts with a magnet built into the cover of the book. When the cover is opened, the effect of the field is weakened and the sensor turns on the backlight of the screen. The Hall transformer in gadgets performs the following useful functions:
- provides orientation in relation to the horizon of the earth;
- works as a compass of a mobile device;
- performs screen orientation.
The sensor is of no small importance in the device of the video camera. Together with a special microcircuit, it allows you to adjust the image quality. This is especially true when filming in the evening.
