Introduction: However, as modern sensors , magnetic sensors need to convert magnetic signals into electrical signals for easier signal processing. The earliest applications were magnetoelectric sensors based on the principle of electromagnetic induction. These magnetoelectric sensors made outstanding contributions to industrial control, but today they have been replaced by new magnetic sensors based on high-performance magnetically sensitive materials.
Electromagnetic sensors are the oldest type of sensor, and the compass is one of the earliest applications of magnetic sensors. However, as modern sensors, for ease of signal processing, magnetic sensors need to convert magnetic signals into electrical signals. The earliest applications were magnetoelectric sensors based on the principle of electromagnetic induction. These magnetoelectric sensors made outstanding contributions to industrial control, but today they have been replaced by new magnetic sensors based on high-performance magnetically sensitive materials.
Basic definition
What is a magnetic sensor? It's a device that converts changes in the magnetic properties of a sensitive element caused by magnetic fields, current, stress, strain, temperature, light, etc., into electrical signals to detect corresponding physical quantities. What generates a magnetic field? The Earth generates a magnetic field. If you can measure the Earth's surface magnetic field, you can make a compass. Any electric current can generate a magnetic field; a current sensor is also a magnetic field sensor. Current sensors can be used in household appliances, smart grids, electric vehicles, wind power generation, and so on. The third type of sensor is called a position sensor. If there is a change in position between a magnet and a magnetic sensor, and this change is linear, it's a linear sensor; if it involves rotation, it's a rotation sensor. We use many magnetic sensors in our daily lives, such as in computer hard drives, compasses, and household appliances.
Overview
Among the electromagnetic sensors used today, the magnetic rotation sensor is an important type. A magnetic rotation sensor mainly consists of several parts: a semiconductor magnetoresistive element, a permanent magnet, a fixture, and a housing. A typical structure involves mounting a pair of magnetoresistive elements on the stimulus of a permanent magnet, connecting the input and output terminals of the elements to the fixture, then mounting them in a metal box, and finally sealing them with engineering plastic to form a hermetically sealed structure, which provides excellent reliability. Magnetic rotation sensors have many advantages that semiconductor magnetoresistive elements cannot match. Besides possessing high sensitivity and a large output signal, they also have a wide rotational speed detection range, a result of advancements in electronic technology. Furthermore, this type of sensor can be used over a wide temperature range, has a long operating life, and is highly resistant to dust, water, and oil, thus tolerating various environmental conditions and external noise. Therefore, this type of sensor is widely valued in industrial applications.
Magnetic rotary sensors have wide applications in factory automation systems because of their satisfactory characteristics and maintenance-free operation. Their main applications include detecting the rotation of machine tool servo motors, positioning of robotic arms in factory automation, detecting hydraulic strokes, position detection of related equipment in factory automation, detection units for rotary encoders, and various rotation detection units.
Working principle
The electromagnetic flow sensor is designed based on Faraday's law of electromagnetic induction. A pair of detection electrodes are installed on the pipe wall, perpendicular to the axis of the measuring tube and the magnetic field lines. When a conductive liquid moves along the measuring tube in an alternating magnetic field perpendicular to the magnetic field lines, the liquid cuts the magnetic field lines, generating an induced electromotive force (EMF). This EMF is detected by the two detection electrodes on the measuring tube, as shown in Figure 1. This can be expressed by the following formula:
E = BVD(V)
Where: E – induced electromotive force V
B – Magnetic flux density T of the magnetic field
V – Average flow velocity of the conductive liquid (m/s)
D - Inner diameter of the catheter (m)
