According to different current measurement principles, current sensors generally have five technologies: resistance shunt detection, Hall effect, flux gate, electromagnetic induction, and Roche coil (electromagnetic induction principle and Ampere's loop law). According to the different measuring principles, current sensors mainly include shunt, Hall current sensor, current transformer, fluxgate current sensor, Roche coil, Giant Magneto Resistance current sensor and optical fiber current sensor.

1、 Diverter

The shunt is made according to the principle that the voltage is generated at both ends of the resistance when the DC current passes through the resistance. The shunt is actually a resistance with very low resistance. When the DC current passes through, the voltage drop is generated, which is displayed by the DC ammeter. The DC ammeter is actually a voltmeter. Generally, the range of this voltmeter is 75mV, 150mV, 300mV. Use a voltmeter to measure the voltage, and then convert the voltage into current, We have completed the measurement of high current. In low frequency anᩚᩚᩚᩚᩚᩚ⁤⁤⁤⁤ᩚ⁤⁤⁤⁤ᩚ⁤⁤⁤⁤ᩚ𒀱ᩚᩚᩚd small amplitude current measurement, it exhibits high accuracy and fast response speed. In the industrial field, in situations where there is no electrical isolation between the measurement circuit and the measured current, a shunt is a low-cost solution to convert the current signal into a voltage signal.

2、 Current transformer

The principle of current transformers is based on the principle of electromagnetic induction. A current transforꦑmer is composed of a closed iron core and winding. The function of a current transformer is to convert a primary current with a larger value into a secondary current with a smaller value through a certain transformation ratio, for protection, measurement, an🍬d other purposes. Current transformer technology is mature and has very high accuracy in power frequency measurement. Due to its principle limitations, it cannot measure direct current.

3、 Hall current sensor

Hall current sensors ꦑinclude two types: open-loop and closed-loop. The open-loop Hall current sensor adopts the Hall direct amplifi😼er principle, while the closed-loop Hall current sensor adopts the magnetic balance principle. Most high-precision Hall current sensors belong to the closed-loop type.

4、 Fluxgate current sensor

The fluxgate sensor measures a weak magnetic field by utilizing the nonlinear relationship between the magnetic induction 📖intensity and the magnetic field intensity of a high permeability magnetic core in the measured magnetic field under the saturation excitation of an alternating magnetic field. This physical phenomenon appears as a "gate" to the measured environmental magnetic field, through which the corresponding magnetic flux is modulated and induced electromotive force is generated. Using this phenomenon to measure the magnetic field generated by current indirectly achieves the purpose of measuring current. The fluxgate sensor has the characteristics of high resolution, wide measurement range of weak magnetic fields, reliability, direct measurement of m💦agnetic field components, and suitability for use in high-speed motion systems.

5、 Roche coil

Roche coil is a circular coil uniformly wound on a non-ferromagnetic material. The output signal is the differential of current over time. By integrating the output voltage signal into a circuit, the input current can be truly restored. This coil has the characteristics of real-time measurement of current, fast response speed, and non saturation, making it suitable for AC, especially high-frequency high current measurement. Roche coil is a circular coil uniformly wound on a non-ferromagnetic material. The output signal is the differential of current over time. By integrating the output voltage signal into a circuit, the input current can be truly restored. This coil has the characteristics of real-time measurement of current, fast response speed, and non saturation, mak🅰ing it suitable for AC, especially high-frequency high current measuremen🧸t.

6、 Giant Magneto Resistance current sensor

The resistivity of a substance may undergo slight changes in a magnetic field. This phenomenon is called magnetoresistive effect (AMR). Under certain conditions, the material resistivity will change greatly with the magnetic﷽ field, which is called Giant Magneto Resistance effect (GMR). GMR can have an order of magnitude greater sensitivity than AMR. The Giant Magneto Resistance effect is a phenomenon of quantum mechanics and condensed matter physics. It refers to the phenomenon that the resistivity of magnetic materials changes greatly with the effect of external magnetic field compared with that without the effect of external magnetic field. The sensor based on this effect is the Giant Magneto Resistance sensoﷺr.

7、 Fiber optic current sensor

Fiber optic current sensor is a new type of current sensor based on Faraday magneto optical effect and using optical fibers as the medium. The laser beam passes through an optical fiber and generates polarized light through a polarizer. It is then projected onto a magneto optical crystal through a self focusing lens. Under the external magnetic field generated by the current, the polarization plane rotates θ F angle; After passing through a polarizer, optical fiber, and entering the signal detection syste🐼m θ The measurement of F yields the current value. Fiber optic current sensors are mainly used for measuring current in power systems; In addition, in combination with motor manufacturers and measurement instrument manufacturers, a series of measurement and diagnostic devices for power systems can also be developed, including calibration devices for line accident points and fault interval determination devices.