Magnetic Sensor Overview
Magnetic sensors have basic characteristics such as non-contact measurement, high reliability, durability, and high measurement sensitivity. Magnetic fields are able to penetrate many non-metallic materials, triggering the exchange process without the need for direct contact with the target object. By using a magnetic conductor such as iron, magnetic fields can be conducted over longer distances and signals can be transmitted from areas of higher temperature. People convert the changes in the magnetic properties of sensitive components caused by magnetic field, current, stress and strain, temperature, light, etc. into electrical signals, and devices that detect corresponding physical quantities in this way are called magnetic sensors. They are not only used to detect the magnitude and direction of the magnetic field, but also combined with permanent magnets for non-contact detection of various non-magnetic quantities such as position, speed, angle, temperature, and current.
Applications of Magnetic Sensors
1. Application in industry
In industrial applications, the most popular types of magnetic sensors are current sensors, including shunt resistors, Hall-effect integrated circuits, current-sensing transformers, open-loop and closed-loop Hall devices, and fluxgate sensors.
Motor: In brushless motors, magnetic sensors are used for rotor pole position sensing and stator armature current commutator. Many magnetic sensors, Hall devices, Wigand devices, reluctance devices, etc. can be used, but currently the ones that are used in large quantities are mainly Hall devices.
In addition, the magnetic sensor can also perform overload protection and torque detection for the motor; the AC frequency converter is used for motor speed regulation, and the energy-saving effect is excellent. As the use of magnetic encoders shows more and more advantages, it is gradually replacing optical encoders to detect and control the rotational speed of the motor.
Power electronics technology: Power electronics technology is a combination of power technology and electronic technology, which can realize the mutual conversion of AC and DC current, and can realize the free adjustment of current, voltage and frequency within the required range.
Using these technologies and products, it can be made into various special power supplies (such as switching power supplies, arc welding machine inverter power supplies, etc.) and AC frequency converters and other products. The core of these frequency conversion devices is high-power semiconductor devices.
Various current sensors based on magnetic sensors are used to monitor, control and protect these high-power devices. The Hall current sensor has a fast response speed, and relies on the magnetic field to couple with the controlled circuit, and is not connected to the main circuit, so it has low power consumption, strong overload resistance, good linearity, and high reliability. It can be used as overcurrent protection for high-power devices. The driver can also be used as a feedback device and become a control link of the self-control loop.
Energy management: The automatic detection system of the power grid needs to collect a large amount of data. After computer processing, it monitors the operation status of the power grid, and performs load distribution adjustment and safety protection. All control links of the automatic monitoring system can be realized by current sensors and transformers based on magnetic sensors. Hall current sensors have long been used in power grid systems. The watt-hour meter made of Hall devices has also turned from research to practical use. They can automatically bill and display power factor, so that they can be adjusted at any time to ensure efficient power consumption.
Magnetic information recording devices: In addition to magnetic tapes and magnetic disks, magnetic information recording devices also include magnetic cards, magnetic ink recording books, magnetic recording of banknotes, etc., which have a huge demand for magnetic information storage and readout sensors. At present, inductive magnetic heads, thin-film magneto resistive magnetic heads, and amorphous magnetic heads have all been used in large quantities. As recording density increases, magnetic heads with higher sensitivity and spatial resolution are required. Giant magneto resistive magnetic heads based on multilayer metal films, amorphous alloy magnetic heads made of amorphous alloy wires, giant magnetoresistance magnetic heads, etc. are in fierce competition.
Traffic Control: Traffic accidents and traffic jams are a big problem in urban and inter-city transportation. At present, both at home and abroad are strengthening the development and construction of driving support road systems, intelligent transportation systems and road traffic information systems. In these new systems, high-sensitivity, high-speed response miniature magnetic sensors are of great use.
2. Application in the medical field
The application of magnetic sensors in the medical field, although on a smaller scale than in the industrial field, can assist patient care and monitoring in various ways in various settings: ambulance, hospital and home care, etc. Whether it is during surgery, in the intensive care unit, or in home care, it provides an effective way to control movement, air flow, detect blood pressure, and administer medication to save or improve the quality of life. It is mainly used for motor control in medical equipment that commutes sensors, such as ventilators, infusions, insulin and kidney dialysis machines.
3. The application in the car
In automobiles, it is mainly used for speed, inclination, angle, distance, proximity, position and other parameter detection as well as navigation and positioning applications, such as vehicle speed measurement, pedal position, gearbox position, motor rotation, power torque measurement, crankshaft position, inclination angle Surveying, electronic navigation, anti-lock brake detection, parking positioning, defect detection in airbags and solar panels, seat position memory, improved heading resolution for navigation systems.
In saving energy and reducing consumption, the application of magnetic sensors can make motor control or commutation more precise. In addition, automotive electronic wire-controlled throttle systems, battery monitoring, and smart fans all have magnetic sensors.
4. Application in the field of consumer electronics
With the popularity of consumer electronics in the world, the application performance of magnetic sensors in consumer electronics is also very strong. For example, mobile phones, notebook computers, electronic toys, electronic compasses, etc. have a very wide range of applications.
Magnetic sensors play an important role in multi-axis measurement electronic compass. At present, mobile phones and tablet computers with GPS systems will adopt multi-axis measurement electronic compass as standard equipment, which also makes magnetic sensors catch the express train of consumer electronics invisibly. At present, the application of magnetic sensors in consumer electronics also enables game controllers, notebooks, digital cameras, etc. to have geo-tagging functions.
5. Application in the fields of aviation, spaceflight, satellite communication and military industry
Sensors with high sensitivity and low magnetic field can be used in aviation, spaceflight and satellite communication technology. As we all know, in the military industry, with the development of absorbing technology, military objects can be concealed by covering with a layer of absorbing material, but they will generate a magnetic field anyway, so the concealed objects can be found out through the magnetic field sensor. Magnetic field sensors can also be used on satellites to detect objects on the Earth's surface and the distribution of mineral deposits underneath. Electronic compasses play an important role in weapon/missile navigation, high-performance navigation equipment for navigation and aviation.
6. Application in environmental monitoring
The premise of environmental protection is the monitoring of various environmental parameters, where a large number of sensors are required. Using strong magneto strictive amorphous magnetoelastic miniature magnetic sensor and inductive magnetic sensor, it can measure the temperature and air pressure in vacuum or closed space at the same time, and it can be telemetered and accessed remotely without connectors.
7. In other industrial applications
In other industrial applications, magnetic sensors can be used in uninterruptible power supplies for machines such as computer servers, and welding systems. In higher current applications such as large variable frequency motors, open-loop and closed-loop Hall sensors use a Hall-effect IC in a small package; it is also possible to increase the level of integration by including an ASIC in the package. Hall ICs are also used in industrial washing machine inverter control applications. In addition to current sensors, there is also a sizeable market for standalone Hall-effect ICs or magnetoresistive sensor switches. These devices are used in motor commutation to reduce ripples and improve performance, or for position measurement, etc.
The development trend of magnetic sensor
High sensitivity: The strength of the detected signal is getting weaker and weaker, which requires the sensitivity of the magnetic sensor to be greatly improved. Applications include current sensors, angle sensors, gear sensors, and space environment measurements.
Temperature stability: More application fields require the working environment of magnetic sensors to be more and more severe, which requires that magnetic sensors must have good temperature stability, and the application fields are mainly in the automotive electronics industry.
Anti-interference: Sensors and instruments are subjected to various interferences in the field operation, such as: electrostatic induction, electromagnetic induction, leakage current induction, radio frequency interference, etc., which requires the magnetic sensor itself to have good anti-interference. The application fields are mainly automotive electronics, water meters and so on.
Multifunctional, integrated, and intelligent: Multifunctional can not only reduce production costs and volume, but also effectively improve performance indicators such as stability and reliability of sensors. The combination of sensors and microprocessors not only has detection functions, but also has artificial intelligence such as information processing, logical judgment, self-diagnosis, and thinking, which is called the intelligence of sensors. This type of sensor has the advantages of multi-function, high performance, small size, suitable for mass production and easy to use. To achieve multi-functionality, integration, and intelligence, this requires chip-level integration, module-level integration, and product-level integration. There are many integrated magnetic sensors, such as electron spin resonance current sensors.
High-frequency characteristics: With the expansion of application fields, the operating frequency of magnetic sensors is required to be higher and higher. The application fields are mainly water meters, automotive electronics industries, and information recording industries.
Low power consumption: In many fields, the power consumption of the magnetic sensor itself is required to be extremely low, which can prolong the service life of the magnetic sensor. The main application fields are implanting magnetic biochips and compass in the body.
Magnetic sensor is the primary link to realize automatic detection and automatic control. If there is no sensor for accurate and reliable measurement of raw data, no matter whether it is signal conversion, information processing, display and control of data, it will be impossible to talk about it. Without accurate and reliable sensors, there is no automatic detection and control system. It can be seen that the magnetic sensor plays a huge role.