Numerical calibration of a Lorentz force particle analyzer

A Lorentz force particle analyzer (LFPA) is a device for the contactless measurement of micron-sized particles in an electrical conductor. Calibration is vital for the successful application of an LFPA. In this article, we first show that the presence of particles that possess the same size but are located at different positions will lead to variations of their measured quantity; therefore, the LFPA requires calibration. Then, two numerical models are developed to solve this problem. For the case of a wire, a I Ialbach-array magnetic system with 24 segments replaces the cubic permanent magnet (PM) to generate a homogeneous magnetic field in the working area. Three identical sensors are arranged around the wire at azimuthal intervals of 2 pi/3 and at certain distances (double the size of the magnetic system) in the axial direction, and the resultant values of the calibration deviation coefficient (eta) smaller than 6% except for the case of edge. For the case of a thin sheet, we create an arc-like boundary at the front of the cubic PM to reduce the gradient of the magnetic flux density along the through-thickness direction. Two sensors arc placed at the two sides of the thin sheet, and eta <= 10% is obtained. These results imply that the numerical models presented here are simple, robust and reliable methods for the numerical calibration of an LFPA and may become a low-cost alternative to the expensive full-scale calibration achieved by the experiment.