How is Magnet Strength Measured?

Magnetic measurement refers to the measurement of magnetic fields and magnetic materials, and other physical quantities are measured by magnetic measurement. Basic measurements include magnetic flux , magnetic induction intensity B, magnetic field intensity H, magnetization intensity M, and the like. In 1785, Coulomb discovered the Coulomb's law and the magnetic Coulomb's law of forces acting between charges and magnetic poles, which opened the prelude to the history of magnetic measurement. From 1819 to 1820, Oster discovered the magnetic effect of electric current and Ampere s law of ampere force on the magnetic interaction force between electric currents. Faraday discovered the law of electromagnetic induction on induced electromotive force of changing magnetic flux in 1831, which made human A comprehensive and essential understanding of macroscopic magnetic phenomena led to the formation of the Gaussian unit system in 1832, and true magnetic measurement was realized.

Magnetic measurement refers to the measurement of magnetic fields and magnetic materials, and other physical quantities are measured by magnetic measurement. Basic measurements include magnetic flux , magnetic induction intensity B, magnetic field intensity H, magnetization intensity M, and the like.

It is an ancient thing for humans to come into contact with magnetic phenomena. As early as the third century BC, our ancestors discovered that natural magnets could attract iron, and then successfully used the magnet's directivity on a compass. However, the history of measuring magnetic quantities is only two hundred years. In 1785, Coulomb discovered the Coulomb's law and the magnetic Coulomb's law of forces acting between charges and magnetic poles, which opened the prelude to the history of magnetic measurement. From 1819 to 1820, Oster discovered the magnetic effect of electric current and Ampere s law of ampere force on the magnetic interaction force between electric currents. Faraday discovered the law of electromagnetic induction on induced electromotive force of changing magnetic flux in 1831, which made human A comprehensive and essential understanding of macroscopic magnetic phenomena led to the formation of the Gaussian unit system in 1832, and true magnetic measurement was realized.

The measuring instruments used at first were of course very crude. As these basic magnetic laws were affirmed, various well-designed magnetic measuring instruments appeared one after another. The earliest magnetic measuring instruments were solenoids and electromagnets. By 1846, Faraday used the magnetic scales he had invented to sense the extremely weak magnetism (paramagnetic and diamagnetic) of weakly magnetic substances. The flowmeter measures and studies the technical magnetization behavior of iron. Over the next 100 years, magnetic measuring instruments, methods and technologies will continue to develop with the development of magnetism, magnetic materials, magnetic devices, and other science and technology related to magnetism, and they will promote each other. Today, there are a large number of magnetic measurement items and instruments, and the sensitivity and accuracy of measurement have been greatly improved. Therefore, magnetic measurement has become an important modern physical measurement technology in the scientific and technical wood collar city.

Magnetic law is the relationship between various magnetic quantities in space, matter, materials and objects or between magnetic quantities and other physical quantities. Some relationships are qualitative, some are quantitative, and some of the more basic ones can often be accurately expressed using simple mathematical formulas.

The range of magnetic laws has been expanding with people s understanding of magnetic phenomena, and has been developed around different aspects of magnetic laws. These magnetic laws include the basic macroscopic magnetic laws and magnetic units, the laws of material magnetism, the laws of magnetization of ferromagnetic materials, the laws of sample magnetization, and the magnetic effects of substances.

The magnetic law is the physical basis for magnetic measurements to be performed correctly and effectively. First of all, basic magnetic quantities such as magnetic field strength, magnetic moment, magnetization and magnetic induction can only be measured after the basic macroscopic magnetic laws are found and their definitions and units are given. Only by mastering the corresponding specific magnetic laws, and thus defining the magnetic quantities that reflect their characteristics, can they be measured. That is to say, the definition of the magnetic measurement object and the measured magnetic quantity both come from the magnetic law, which should be the basis of magnetic measurement. Secondly, in order to achieve the correct measurement of the measured magnetic quantity, the principles of the measurement methods used must be correct, and these principles are basic or relatively basic magnetic laws. For example, the principles of two major types of magnetic measurement methods, magnetic force method and induction method, are the aforementioned magnetic Coulomb's law, ampere force law, and Faraday's law of electromagnetic induction. They are basic magnetic laws.

The instruments used for various magnetic measurements must be able to measure the magnetic quantity defined by the magnetic law with the specified accuracy. The various operating regulations for implementing magnetic measurement are also constrained by various magnetic laws, which must meet the requirements put forward by the magnetic laws. Some basic magnetic laws have long been established, but the level of magnetic measurement, even for basic magnetic quantities, is still constantly improving. This is a comprehensive result of the continuous development of science and technology, including the ability to apply basic magnetic laws. Of improvement. The role of basic magnetic laws in specific magnetic measurement is often gradually recognized, and some more specific magnetic laws need to be discovered through practice. This recognition and discovery will play an important role in the development of magnetic measurement technology. .

When a sample is placed in a single magnetic field, a magnetic moment is induced. When the sample is placed in the pickup coil of a vibrating sample magnetometer, a voltage signal is induced in the detection coil due to a change in the magnetic flux passing through the sample. This signal is proportional to the magnetic moment, so a vibrating sample magnetometer can be used to measure the magnetic properties of the material. The magnetic field can be generated by an electromagnet or a superconducting magnet, so magnetic moment and magnetization can be measured as parameters of the magnetic field. As a parameter of temperature, when the temperature is lower than normal temperature, a sample with a superconducting magnet placed in a single magnetic field will induce a magnetic moment. When the sample is placed in the pickup coil of a vibrating sample magnetometer, a voltage signal is induced in the detection coil due to a change in the magnetic flux passing through the sample. This signal is proportional to the magnetic moment, so a vibrating sample magnetometer can be used to measure the magnetic properties of the material. The magnetic field can be generated by an electromagnet or a superconducting magnet, so magnetic moment and magnetization can be measured as parameters of the magnetic field. As a temperature parameter, when it is lower than normal temperature, a VSM system with a superconducting magnet or a system with a low temperature Dewar electromagnet or a VSM system with a low temperature Dewar electromagnet can be used. Above normal temperature, a system with a heating furnace can be used. Above normal temperature, a VSM system with a heating furnace can be used. Because the selection of ferromagnetic materials is mainly determined by their magnetization and hysteresis loops, so the system. Because the selection of ferromagnetic materials is mainly determined by their magnetization and hysteresis loops, the common function of VSM systems is to measure the magnetic characteristics of ferromagnetic materials.

Static magnetism refers to the magnetic properties of magnetic materials in a stable magnetic field, including the basic magnetization ^[1] curve, hysteresis loops, and various defined parameters, such as saturation magnetization M; or saturation magnetization and residual magnetization Or residual magnetic induction, various susceptibility or permeability. Basically, the above parameters are determined by measuring the magnetization or magnetic induction in a certain magnetic field. Dynamic magnetic properties refer to the magnetic properties of magnetic materials in an alternating magnetic field.

The magnetic characteristics of a magnetic material in an alternating magnetic field are called AC magnetization characteristics. Different from static magnetic characteristics. The dynamic magnetic properties of a substance are not only related to the magnetism of the substance itself, but also to factors such as the frequency, amplitude, and waveform of the excitation current.

The area of the static hysteresis loop is the static hysteresis loss, and the area of the dynamic hysteresis loop is the total loss, including three parts: Hysteresis loss: refers to the inherent loss of ferromagnetic materials as a magnetic medium under a certain excitation magnetic field (Loss generated in the process of converting electric energy to magnetic energy); eddy current loss: when the magnetic flux changes, the core generates induced electromotive force and then generates an induced current, the induced current is vortex-shaped, and the induced current loss on the core resistance is Eddy current loss; Residual loss: Loss other than hysteresis loss and eddy current loss, so the area of the dynamic hysteresis loop is always larger than the area of the static hysteresis loop.