Abstract:In order to identify non-contact measurement of micro-hole diameter and depth, this paper proposes a measurement method utilizing eddy current effect. The measuring coil, composed of a single-layer multi-turn coil, traverses evenly over the target body during the micro-hole measurement process. The time variation of the coil’ s inductance correlates directly with the micro-hole’ s diameter. A linear relationship exists between the peak value of the coil’s inductance and the square of the micro-hole’s diameter, where the slope of this linear relationship is proportional to the depth of the micro-hole. According to the equivalent eddy current ring model, a mathematical model was established between the coil’s inductance value and the micro-hole’s diameter and depth. The influence law of the micro-hole diameter and depth on the coil’ s inductance value during the measurement process was analyzed by COMSOL finite element simulation. The simulation results were consistent with the analysis of the equivalent eddy current ring model. The eddy current measurement system for micro-hole diameter and depth was established, achieving measurements for diameters of 1. 5~ 5 mm and depths of 0. 1~ 0. 5 mm. When the micro-hole diameter is larger than 3 mm and depth greater than 0. 3 mm, the relative error in the diameter measurement stays within ±2%. The resolution of the depth measurement is 0. 01 mm. When the diameter of the micro-hole exceeds 2. 5 mm, the measurement error of depth is less than 0. 02 mm.