A reconstruction approach to determining the magnetic field around an electromagnetic velocity probe

A novel approach to determining the magnetic field around an electromagnetic velocity probe is introduced. This is a measurement and calculation joint approach. Based on the characteristic that there are no exciting currents in the measuring volume out of the probe, a magnetic scalar potential is introduced to calculate the magnetic field around the probe. The potential obeys Laplace's equation in the volume. A magnetic scanning device is designed to measure the contribution of the normal component of the magnetic field on the surface of the probe, which provides boundary conditions necessary for solving Laplace's equation. Thus, the magnetic field around the probe can be numerically reconstructed by solving Laplace's equation with a finite-element method. Compared with traditional measuring approaches, directly measuring the distribution of the 3D magnetic field in the whole measuring volume out of the probe, the novel approach only needs to measure the distribution of the normal component of the magnetic field on the surface of the probe. Compared with traditional calculating approaches, calculating the magnetic field from the inner exciting unit of the probe based on Maxwell's equations, the novel method has overwhelming advantages of avoiding modeling of the inner complex structure of the probe and solving only one Laplace's equation. All the above advantages together lead to a good, efficient and accurate determination of the magnetic field, which is experimentally verified and is very useful for studying the performance of an electromagnetic velocity probe, especially in dry calibration of the probe.