The principle and application of the Hall effect
The Hall effect is a kind of electromagnetic effect, which was discovered by American physicist Hall (A.H.Hall, 1855-1938) in 1879 when he studied the conduction mechanism of metals. When the current passes through the conductor perpendicular to the external magnetic field, an additional electric field will be generated in the direction perpendicular to the current and the magnetic field, resulting in a potential difference between the two ends of the conductor. This phenomenon is the Hall effect. This potential difference is also called the Hall potential difference. The Hall effect should be judged using the left-hand rule.
principle:
In 1879, Hall (A.H.Hall) found in the experiment: put a plate-shaped metal conductor in the uniform strong magnetic field B, and it is perpendicular to the direction of the magnetic field B as shown in Figure 1, in the metal plate along the direction perpendicular to the magnetic field B, the When the current is I, there will be a lateral potential difference UH between the upper and lower surfaces of the metal plate. This phenomenon is called the Hall effect, and the potential difference UH is called the Hall potential difference. Further observation experiments also pointed out that the size of the Hall potential difference UH is proportional to the magnitude of the magnetic induction intensity B and the current intensity I, and is inversely proportional to the thickness d of the metal plate. That is, UH =RHIB/d (V); in the formula, RH——(m^3*C^-1) is only related to the conductor material, which is called the Hall coefficient.
application:
The Hall effect is particularly important in applied technology. Hall found that if a current (Iv) is applied to a conductor (d) in a magnetic field (B) whose direction is perpendicular to the direction of the applied voltage, then at both the magnetic field and the applied current direction perpendicular In the direction of , another voltage (UH) will be generated, which is called the Hall voltage, and this phenomenon is called the Hall effect. It is like a road. Originally, everyone was evenly distributed on the road and moved forward. When there is a magnetic field, people may be pushed to the right side of the road. On both sides of the old circuit (conductor), there will be a voltage difference. This is called the "Hall Effect". The Hall device made according to the Hall effect is to use the magnetic field as the working medium to convert the motion parameters of the object into the form of digital voltage output, so that it has the functions of sensing and switching.
So far, Hall devices that have been widely used in modern automobiles include: signal sensors on distributors, speed sensors in ABS systems, automobile speedometers and odometers, liquid physical quantity detectors, and currents of various electrical loads. Detection and working status diagnosis, engine speed and crankshaft angle sensors, various switches, etc.
For example, in automotive ignition systems, designers place Hall sensors in distributors to replace mechanical circuit breakers and act as ignition pulse generators. This Hall-type ignition pulse generator generates a pulsed voltage in the charged semiconductor layer with the rotating magnetic field, which controls the primary current of the electronic control unit (ECU). Compared with mechanical circuit breakers, Hall-type ignition pulse generators are wear-free and maintenance-free, can adapt to harsh working environments, and can precisely control ignition timing, which can greatly improve engine performance and have obvious advantages.
Used as a power Hall circuit on a car switch circuit, it has the effect of suppressing electromagnetic interference. Many people know that the higher the degree of automation in the car, the more microelectronic circuits, the more afraid of electromagnetic interference. In the car, there are many lamps and electrical devices, especially the high-power headlights, air conditioner motors and wiper motors will generate inrush current when switching, which will cause arcing of the mechanical switch contacts, resulting in large electromagnetic interference. Signal. These phenomena can be reduced by using a power Hall switch circuit.
By detecting changes in the magnetic field, the Hall device converts it into an electrical signal output, which can be used to monitor and measure the changes in the operating parameters of various parts of the car. For example, position, displacement, angle, angular velocity, rotational speed, etc., and these variables can be transformed twice; pressure, mass, liquid level, flow rate, flow rate, etc. can be measured. The output of the Hall device is directly interfaced with the electronic control unit, which can realize automatic detection. Today's Hall devices can withstand a certain degree of vibration, and can work in the range of minus 40 degrees Celsius to 150 degrees Celsius above zero.
