Helmholtz Coil

In the laboratory, Helmholtz coils can be used to measure the properties of magnetic materials such as magnetization and hysteresis loops. In medical devices, Helmholtz coils can be used to generate magnetic fields to help treat diseases such as cancer and neurological disorders. In geophysics and astronomy, Helmholtz coils are used to measure the magnetic fields of the Earth and planets. In engineering, Helmholtz coils are also used to manufacture high-precision sensors. These sensors can accurately measure the magnetic flux in the ambient magnetic field, and through this quantitative level of magnetic field data, various other physical quantities can be analyzed in a variable manner. Helmholtz coils are therefore an integral part of the engineering world.

Place the microscope between the Helmholtz coils and watch the movement of magnetic ions in the alternating magnetic field.

The conductor piece rotates in a three-dimensional Helmholtz coil.

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Dexinmag is a world-renowned manufacturer specializing in the production of Helmholtz coils.

Working Principle of the Helmholtz Coil

When two coils are passed current in the same direction, they generate a magnetic field. This magnetic field can be described by Maxwell's equations. Since a Helmholtz coil is symmetrical, the magnetic field it produces is uniform along its axis.
When the two coils are supplied with reverse current, the superposition weakens the magnetic field, so that a region where the magnetic field is zero appears.

What does a Helmholtz coil do?

A Helmholtz coil is commonly used to generate a static DC or AC uniform magnetic field.

A Helmholtz coil usually consists of two parallel circular coils of exactly the same radius and number of turns, which are fixed on a common axis and whose radius is equal to the distance between them. 

Applications of Helmholtz Coils

1.  Generate a standard magnetic field;
2.  Offset and compensation of the earth's magnetic field;
3.  Geomagnetic environment simulation;
4.  Judgment of magnetic shielding effect;
5.  Electromagnetic interference simulation experiment;
6.  Calibration of Hall probes and various magnetometers;
7.  Research on biomagnetic fields;
8.  The study of the magnetic properties of matter.

Magnetic field simulation

Precautions of Helmholtz coils

The design of a Helmholtz coil requires consideration of the size and current of the coil, as well as the distance of the circular coil. According to the empirical formula, two coils with a radius of R and a distance of 2R, if their current is I, the magnetic field strength generated is B=0.9μ0I/R, where μ0 is the vacuum permeability.


The frame and support system of the coil must be non-metallic and the radius of the coil should be at least 2.5 times the largest specimen to be tested. This confinement allows all samples to be within the homogeneous area of the coil, making measurements mindful of distant electromagnetic interference. Such as other magnets, transformers or fluorescent sources, etc.

Uni-directional Helmholtz Coil

Two-dimensional Helmholtz Coil

3 Axis Helmholtz Coil

1D, 2D, 3D Helmholtz coil magnetic field

Connection and calibration of Helmholtz coils

The connecting of the power supply.
The Amphenol connector of Helmholtz coil generally adopts an aviation socket, binding post, line bank, banana socket, etc. The user just needs to connect the Amphenol connector to the output end of the constant current power supply. Usually, a three-dimensional coil has 3 units of Amphenol connector and it is controlled by 3 sets of power supply respectively.

 

Turn on the power supply to calibrate
Before turning the power supply, please zero the current and voltage (some specified power supply does not need to adjust voltage). 
a.    Turn on the power supply, and increase the voltage of the power supply from the lowest to the state which shows the power supply is in constant. (Some specified power supply does not need to do this process). 
b.    Adjust the current from the lowest to higher, and place the probe of the Gauss meter to the center of the coil. At this time, if you see the magnetic field strength is increased with the increase of current, it shows the connection is correct and you could normally use the coil.

Trouble removal

Trouble Possible cause Check method Solution
No magnetic field strength after power connecting The coil is open circuit. Check the connecting of coil and power supply. Connect cables
Power is out of work Test the output of current Contact the power supply manufacturer.
The disconnection of winding inside coil. Test the DC resistance of coil. Inform the manufacturer to solve
The fault of meter or wrong test method. Check the direction and range of meter or change a new meter. Note the direction of probe whether the same as the test magnetic field direction.
Magnetic field /current constant has a large difference or is not linear. The coil is out of shape. Check the dimension of coil Recover the structure after calibration.
The direction of serial connection or parallel connection is opposite. Change the direction of coil tap and then test the magnetic field. Correct connection.
The output current of power supply is not correct. Test the output current of power supply. Inform the manufacturer to maintain.
The short-circuit inside of inner coil Test the DC resistance of coil. Inform the manufacturer to maintain.
There is ferromagnetic substance in the magnetic field.   Remove the ferromagnetic substance.
When in high magnetic field work, the current could be adjusted to set value. The working time is long, the coil is heat and the resistance is high. Test the surface temperature of coil and the DC resistance of coil. Stop the usage and cool the coil.
The heat of coil is not symmetrical The heat coil would short circuit. Test single coil DC resistance. Inform the manufacturer to maintain.
Note: If the trouble is not mentioned as above, please contact Dexing Magnet Company.

Helmholtz coil magnetic field control system