Both the Teslameter and the fluxmeter can measure the residual magnetic induction of the magnet, but when measuring small magnets, the distance between the probe and the surface of the sample must be accurately removed when measuring small magnets, otherwise the measurement error Very big. The use of Helmholtz coils with flux meters effectively solves this problem. Helmholtz coils are used to generate a uniform magnetic field, and vice versa, they can also be used to measure the magnetic flux of open-circuit samples. Remove the measured magnet from the center of the coil, the magnetic flux in the Helmholtz coil changes and induces a voltage and transmits it to the fluxmeter, which obtains the flux change through data processing. The flux coil can be customized according to the coil constant of different types of flux meters.