The 2 axis helmholtz coil manufacturer tells you that a Helmholtz coil is a pair of coaxial circular (square) coils that are parallel and connected to each other. The currents in the two coils have the same direction and the same size. When the 2 axis helmholtz coil manufacturer tells you that the distance between the coils is exactly equal to the radius of the circular coil, this circular current-carrying coil is called a Helmholtz coil. The characteristic of this coil is that it can generate a wide uniform magnetic field near the midpoint of its common axis. There is a good linear relationship between current and magnetic field.

2 axis helmholtz coil manufacturers tell you that Helmholtz coils are classified into DC Helmholtz coils and AC Helmholtz coils according to the magnetic field.
Helmholtz coils are classified into one-axis Helmholtz coils, two-axis Helmholtz coils, three-axis Helmholtz coils and multi-axis combined Helmholtz coils according to the number of axes of the generated magnetic field. 2 axis helmholtz coil manufacturers tell you that it is suitable for various research institutes, universities and enterprises to do material magnetic or detection experiments, and is used in materials, electronics, biology, medical, aviation and other industries.