Introduction: The XAU-4CS spectrum analyzer is a spectrum analyzer with a compact design and a high degree of module precision. It uses a down-illuminated C-shaped cavity design and is a multi-purpose spectrometer. Using the core EFP algorithm and low-light concentration technology, it not only retains the performance of the special thickness gauge to detect tiny samples and grooves, but also meets the micro-area RoHS detection and composition analysis. XAU-4CS spectrum analyzer is widely used in quality control of various products, incoming inspection and measurement of production process control.