<p>Parameters of ECP designs.</p>

A method is proposed for suppressing uncontrollable noise factors in the form of local variations in the electrophysical properties of the weakly magnetic substrate material of tested objects during eddy current measurements of the thickness of dielectric coatings in the medium frequency range up to 100 kHz. As opposed to methods focused on complicating measuring instruments, in particular the use of multi-frequency techniques, swept-frequencies, resource-intensive numerical techniques for computer-based solution of inverse problems, etc., the new approach to solving this problem involves the use of the Taguchi method for robust parameter design of optimal eddy current probes in terms of improving signal-to-noise ratios, which ultimately ensures minimal variability of the useful signal without actually eliminating uncontrollable interference inherent in the tested objects. This made the medium frequency ECPs competitive for the specified measurements compared to high frequency ones due to the simplification of the hardware part of the gauges, the removal of the problem of equipping them with special sensors, and the reduction of their cost. Because of conducting a variance ANOVA analysis, the statistical influence of the design parameters of thickness gauge probes on the characteristics of the output signal was determined. This enabled the establishment of technical requirements for the accuracy of measuring devices in the manufacturing process, as well as the maintenance of operating parameters, specifically frequency and excitation current, within acceptable limits without significantly compromising the optimal signal-to-noise ratio.

针对最高100kHz的中频频段下介质涂层厚度的涡流检测（eddy current measurement），本研究提出一种抑制非可控噪声因素的方法，该类噪声以被测对象弱磁性基材材料的电物理性能局部变化形式存在。与以复杂化检测仪器为目标的现有方法（例如采用多频技术、扫频技术、基于计算机求解逆问题的高资源消耗数值计算方法等）不同，本方案采用田口方法（Taguchi method）开展最优涡流探头（eddy current probe，简称ECP）的鲁棒参数设计以提升信噪比，最终可在无需实际消除被测对象固有非可控干扰的前提下，将有用信号的变异性降至最低。得益于厚度检测仪硬件部分的简化、无需配备专用传感器的问题解决以及成本降低，相较于高频ECP，中频ECP在上述检测场景中更具竞争力。通过开展方差分析（analysis of variance, ANOVA），本研究明确了厚度检测探头的设计参数对输出信号特性的统计影响。据此可确立制造过程中测量设备精度的技术要求，并可在不显著损害最优信噪比的前提下，将运行参数（具体为频率与激励电流）维持在可接受范围内。