I. Magnetic Sensor
The detector of a magnetic sensor is a magnetic probe. When the magnetic probe is working, it creates a static magnetic field around it. When an object made of ferromagnetic metal, such as a rifle or vehicle, enters this static magnetic field, it will induce a new magnetic field, which will interfere with the original static magnetic field. The interference caused by the movement of the target will change the magnetic field, causing the magnetometer pointer to deflect and swing, generating an electrical signal, thereby enabling the detection of people and vehicles carrying weapons.
Magnetic sensors possess a strong ability to distinguish target characteristics, differentiating between unarmed personnel, armed personnel, and various vehicles. They also exhibit a relatively fast target detection reaction speed, typically around 2.5 seconds, enabling real-time detection of rapidly moving targets. Compared to other sensors, magnetic sensors have a significant advantage: they can adapt to various battlefield conditions, making them particularly suitable for areas where vibration sensors struggle, such as swamps, beaches, and waterways, thus compensating for the limitations of vibration sensors. However, magnetic sensors have limited energy resources, resulting in a relatively short detection range: typically 3-4 meters for personnel, less than 15 meters for wheeled vehicles, and less than 25 meters for tracked vehicles.
II. Applications of Magnetic Sensors
1. Industrial Use
In industrial applications, the most popular type of magnetic sensor is the current sensor, which includes shunt resistors, Hall effect integrated circuits, current sensing transformers, open-loop and closed-loop Hall devices, and fluxgate sensors.
2. Automotive Industry Applications
In automobiles, these sensors are primarily used for detecting parameters such as vehicle speed, tilt angle, distance, proximity, and position, as well as for navigation and positioning applications. Examples include speed measurement, pedal position measurement, gearbox position measurement, motor rotation measurement, power steering torque measurement, crankshaft position measurement, tilt angle measurement, electronic navigation, anti-lock braking system (ABS) detection, parking positioning, defect detection in airbags and solar panels, seat position memory, and improving the heading resolution of navigation systems. In energy conservation and emission reduction, especially given the current pressure on manufacturers to reduce even a drop of carbon emissions or other pollutants, a key area is motors. Motors are transitioning from friction-based, constantly operating pulley systems to electric motors, which can be controlled on demand. Simultaneously, electric motors are shifting towards more efficient and reliable brushed DC motors, while the application of magnetic sensors allows for more precise motor control or commutation.
3. Medical Applications
While smaller in scale than in industry, the application of magnetic sensors in the medical field assists patient care and monitoring in various settings and in diverse ways: ambulances, hospitals, and home care. Whether during surgery, in intensive care units, or in home care, they provide effective methods for controlling movement, airflow, detecting blood pressure, and administering medication—all crucial for saving lives or improving quality of life. They are primarily used in motor control within medical devices employing commutation sensors, such as ventilators, infusion machines, insulin pumps, and kidney dialysis machines.
4. Consumer electronics
With the global popularity of consumer electronics, magnetic sensors have also seen strong applications in these devices. They are widely used in mobile phones, laptops, and electronic compasses. MEMS sensors and magnetic sensors mutually reinforce each other in their applications, contributing to the gradual growth of magnetic sensors in the consumer electronics market. Although magnetoresistive sensors have a long history and relatively mature technology, their standalone application in electronic compasses was not previously highly regarded. However, their combination with MEMS is poised to become a highlight in the navigation market. Because MEMS and magnetoresistive sensors complement each other functionally, their combination makes navigation products more accurate. Integrating gyroscopes, accelerometers, and magnetic sensors together, with their complementary functions, creates even more powerful inertial navigation products.
5. Aerospace and military industry
High-sensitivity, low-magnetic-field sensors are used in aviation, aerospace, and satellite communication technologies. As is known in the military industry, with the development of radar-absorbing technology, military objects can be concealed by covering them with a layer of radar-absorbing material. However, they will still generate magnetic fields regardless, so GMR (Ground Magnetic Resonance) magnetic field sensors can be used to locate concealed objects. GMR magnetic field sensors can be used on satellites to detect objects on the Earth's surface and the distribution of mineral deposits underground. Electronic compasses play an indispensable role in high-performance navigation equipment for weapons/missiles, and in maritime and aviation applications.
6. Environmentally friendly and energy-saving
Environmental protection hinges on monitoring various environmental parameters, which necessitates the use of numerous and diverse sensors. Employing strong magnetostrictive amorphous magnetoelastic miniature magnetic sensors and inductive magnetic sensors, it is possible to simultaneously measure temperature and pressure in a vacuum or confined space, without the need for connectors, enabling remote measurement and long-distance access.
7. 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 high-current applications such as large variable frequency motors, open-loop and closed-loop Hall effect sensors use Hall effect ICs in a small package; integration can also be increased by including a dedicated integrated circuit within the package. Hall effect ICs are also used in the control of inverters for industrial washing machines. Besides current sensors, there is also a considerable market for stand-alone Hall effect ICs or magnetoresistive sensor switches. These devices are used for motor rectification to reduce ripple and improve performance, or for position measurement, etc.
