Abstract: Embedded devices in power systems are demanding ever-higher overall accuracy, thereby imposing increasingly stringent requirements on the design and manufacturing of both hardware and software. Focusing on the critical AC sampling module, this work describes the characteristics of current transformers, analyzes errors in the AC sampling module, and provides theoretical support for transformer screening and selection. Considering the practical requirement of interoperability between AC sampling boards and various sampling DSP boards, a matching circuit for the sampling DSP in the calibration instrument was designed. Test results show that the compensation coefficients obtained using this approach enable high-precision system-level sampling.