Hall sensor product knowledge spread
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According to the Hall effect, a component made of a semiconductor material is called a Hall element. It has the advantages of being sensitive to magnetic fields, simple structure, small size, wide frequency response, large output voltage change, long service life, etc. Therefore, it has been widely used in measurement, automation, computer and information technology.
Second, Hall sensor characteristics (A) linear Hall sensor characteristics Output voltage and applied magnetic field strength is linear, as shown in Figure 3, visible, in the B1 ~ B2 magnetic [1] within the range of sensing intensity Good linearity, when the magnetic induction exceeds this range, it is saturated.
(II) Characteristics of Switch Hall Sensors
Assume that the BOP is the magnetic induction intensity of the "open" working point, and BRP is the magnetic induction intensity of the release point "off."
When the external magnetic induction exceeds the operating point Bop, the sensor outputs a low level. When the magnetic induction intensity drops below the operating point Bop, the sensor output level does not change, and the sensor is always down to the release point BRP. Jumps high. The lag between Bop and BRP makes switching more reliable.
Third, Hall sensor application (a) Linear Hall sensor is mainly used for the measurement of some physical quantities.
1. Current sensor Since there is a magnetic field inside the energizing solenoid, its size is proportional to the current in the conductor, so the Hall sensor can be used to measure the magnetic field and determine the current in the conductor. Using this principle, a Hall current sensor can be designed. The advantage is that it does not make electrical contact with the circuit under test, does not affect the circuit under test, does not consume the power of the tested power supply, and is particularly suitable for large current sensing. The working principle of the Hall current sensor is shown in Fig. 6. The standard ring core has a notch. The Hall sensor is inserted into the notch. The ring is wound with a coil. When the current passes through the coil, a magnetic field is generated. The Hall sensor has a signal. Output.
2. Displacement measurement Two permanent magnets are placed opposite to each other. The linear Hall sensor is placed in the middle. Its magnetic induction intensity is zero. This point can be used as the zero point of the displacement. When the Hall sensor is used for the â–³Z displacement on the Z axis, The sensor has a voltage output, and the voltage is proportional to the size of the displacement.
If the tension, pressure and other parameters into displacement, you can measure the size of tension and pressure, as shown in Figure 8, is a force sensor made according to this principle.
(b) Hall-type sensors are mainly used to switch the number of revolutions, speed, speed, flow rate, proximity switches, door closing informers, alarms, automatic control circuits.
1. Measure the number of revolutions or the number of revolutions on the side of the non-magnetic material stick a piece of magnet, the Hall sensor is placed near the edge of the disc, the disc rotates one revolution, the Hall sensor will output a pulse, which can measure the number of revolutions ( Counter), if you access the frequency meter, you can measure the speed.
If the switch type Hall sensor is regularly arranged on the track at a predetermined position, a pulse signal can be measured from the measurement circuit when a permanent magnet mounted on the moving vehicle passes through it. The speed of the vehicle can be measured based on the distribution of the pulse signal.
Fourth, Hall sensor use matters needing attention
(2) When large DC current flows through the primary winding of the sensor, and the secondary circuit is not connected to the power supply | regulator or secondary open circuit, the magnetic circuit is magnetized and remanence occurs, affecting the measurement accuracy ( Therefore, it is necessary to turn on the power supply and the measurement terminal before use. When this happens, demagnetization must be performed first. The method is that the secondary circuit does not add power, but in the primary coil, an alternating current of the same level is passed and its value is gradually reduced.
(3) In most cases, Hall sensors have a strong resistance to external magnetic fields. Generally, a magnetic field generated by a current twice the operating current Ip between 5-10cm of the distance module is negligible. However, when there is a stronger magnetic field interference, appropriate measures must be taken to solve it. The usual methods are:
1 Adjust the direction of the module to minimize the influence of the external magnetic field on the module;
2 Put a metal shield against the magnetic field on the module;
3 Select module power supply with double Hall elements or multiple Hall elements;
(4) The best measurement accuracy is obtained under the rated value. When the measured current is much lower than the rated value, the best accuracy can be obtained. The primary side can use multiple turns, namely: IpNp = rated ampere turns. In addition, the temperature of the primary feeder should not exceed 80°C.
Hall sensor features (compared to common transformers)
Hall sensors can measure arbitrary waveform currents and voltages, such as DC, AC, pulse waveforms, and even transient peak measurements. The secondary current faithfully reflects the waveform of the primary current. The common transformer is not comparable to it, it is generally only suitable for measuring 50Hz sine wave.
2. The electrical insulation between the primary circuit and the secondary circuit is completely insulated. The insulation voltage is generally 2KV to 12KV, and the special requirement is up to 20KV to 50KV.
3, high precision: in the working temperature area accuracy is better than 1%, the accuracy is suitable for any waveform measurement. The common transformer is generally 3% to 5% accurate and suitable for 50Hz sinusoidal waveforms.
4, good linearity: better than 0.1%
5, dynamic performance is good: response time is less than 1μs tracking speed di/dt is higher than 50A/μs
6, Hall sensor module This excellent dynamic performance provides a key foundation for improving the performance of modern control systems. Compared with the common transformer response time is 10-12ms, it can not meet the needs of the development of the work control system.
7. Work frequency bandwidth: The accuracy is 1% in the frequency range of 0-100kHz. Accuracy is 0.5% in the 0-5kHz frequency range.
8, measuring range: Hall sensor module for the system product, current measurement up to 50KA, voltage measurement up to 6400V.
9, strong overload: When the primary current overload, the module reaches saturation, can automatically protect, even if the overload current is 20 times the rated value, the module will not be damaged.
10. The module is small in size, light in weight and easy to install. It will not cause any loss in the system.
11. The “capacitance†between the primary and the secondary of the module is very weak. In many applications, the various effects of the common-mode voltage are usually negligible. When the high voltage changes of several kV/μs are reached, the module has its own Shielding function X-ray machine maintenance. 12. The module's high sensitivity makes it possible to distinguish weak signals on "high components", for example, to distinguish a few milliamperes of AC components from a few hundred amps of dc components.
13, high reliability: failure rate: λ = 0.43 ╳ 10-6 / hour 14, the ability to resist external magnetic field interference: a magnetic field generated by a current at twice the operating current (2Ip) at 5-10cm from the module The error caused by interference is less than 0.5%, which is sufficient for most applications against external magnetic field interference, but appropriate measures should be taken for strong magnetic field interference. [
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