Helmholtz coil measurement system measurement principle, main use and case sharing

According to the shape of the coil, the helmholtz coil can be divided into circular helmholtz coil and square Helmholtz coil. According to the direction of magnetic field, helmholtz coil can be divided into one-dimensional helmholtz coil, two-dimensional Helmholtz coil and three-dimensional Helmholtz coil. Helmholtz coil can be divided into DC helmholtz coil and AC Helmholtz coil according to coil current properties.

Helmholtz coil, uniform area of large volume, open space, easy to operate, with it can produce a very weak magnetic field to hundreds of gauss magnetic field; Can realize one-dimensional, two-dimensional, three-dimensional combined magnetic field, can provide the coil current proportional to the AC magnetic field or DC magnetic field; Its internal space can be fitted with a suitable non-magnetic support platform, which is convenient for users to place the measured instruments or experimental equipment. It is very suitable for various research institutes, universities and enterprises to do material magnetic or detection experiments, and applied to various disciplines such as materials, electronics, biology, medical treatment, aerospace, chemistry, applied physics and so on.

Helmholtz coil main uses:
Generate standard magnetic field (magnetic field generating device);
Cancellation and compensation of the Earth's magnetic field;
Geomagnetic environment simulation;
Judgment of magnetic shielding effect;
Electromagnetic interference simulation experiment;
Calibration of Hall probe and various magnetometers;
Mobile phone magnetic compass algorithm calibration;
Research on biological magnetic field and magnetic properties of material.

Helmholtz coil magnetic field use and role in industry, national defense, scientific research need to measure the magnetic field, there are many methods to measure the magnetic field, such as impact galvanometer method, Hall effect method, nuclear magnetic resonance method, balance method, electromagnetic induction method and so on
Because of the open nature of the Helmholtz coil, it is easy to put other instruments in and out, as well as to make direct visual observations. Therefore, it is a commonly used device in experiments. Helmholtz coil can be used to measure the change of magnetic flux caused by the rotation of permanent magnet, and the magnetic parameters of permanent magnet can be obtained, including magnetization direction, remanent magnetic Br and coercivity Hc.

Measurement principle of Helmholtz coil measurement system
Helmholtz coils are formed by a pair of coils whose axial distance is equal to the radius of the coils. When the coils are connected in series with stable direct current, a more uniform axial magnetic field can be generated in the center area of the coil. Conversely, helmholtz coils can also be used to measure the parameters of permanent magnets placed inside them.

Figure 1 is a schematic diagram of helmholtz coil. The natural coordinate system is adopted to approximate the permanent magnet located at the center of the coil. Its magnetic moment is M and its spatial components are mx, my and Mz respectively. Mr In the front column coordinates corresponds to my in the natural coordinates, and Mz corresponds to MX, mz. When the permanent magnet rotates around the center of the coil and in the horizontal plane, a periodic magnetic signal is excited in the coil

Reference: Measurement principle and program design of Helmholtz coil measurement system in Institute of High Energy Physics, Chinese Academy of Sciences
Keywords Helmholtz coil permanent magnet magnetic moment remanent magnetic coercivity
A typical case of helmholtz coil system
Fe-3hm140 3D Helmholtz coil
1. Coil adopts electric board, aluminum profile and PVC as the skeleton material of coil
2, X coil: winding wire diameter 1.0, physical diameter of about 140mm, coil turns number of 616, coil resistance of about 12.35 ohm, 2A corresponds to 150GS
3, Y coil: winding wire diameter 1.0, physical diameter 235mm, coil turns 1024, coil resistance about 34.8 ohms, 2A corresponds to 150Gs
4, Z coil: winding wire diameter 1.2, physical diameter about 380mm, coil turns 1672, coil resistance about 62 ohm, 2A corresponds to 150Gs
5. Schematic diagram of coil placement: The minimum coil is placed horizontally