A Micro-Force Measurement System Based on Lorentz Force Particle Analyzer for the Cleanliness Inspection of Metal Materials

In this paper, a MEMS micro-force measurement system based on Lorentz force particle analyzer (LFPA) principle is developed for the inspection of micro defects in or near the surface of metal materials. This system mainly consists of a small permanent magnet, a capacitive MEMS sensor and an interface circuit. The three parts convert a defect first into a force pulse, then a capacitive variance, and finally a voltage output. Experimental results show that this sensor system is capable to measure forces up to
$\sim 10~\mu \text{N}$
with a resolution down to
$\sim 0.2~\mu \text{N}$
, corresponding to defects with size of
$0.5~\sim $
2 mm. The amplitude of the obtained pulse signal increases with the enlargement of the defects volume, and the actual pulse waveform is consistent with the simulated pulse waveform. It demonstrates that the MEMS sensor can be the loadcell of LFPA to inspect micro defects in or near the surface of solid metals. This system is expected to be applied to the cleanliness inspection in metal sheet or foil. [2021-0116]