Electronic measuring instruments are based on analog circuit technology and digital circuit technology, covering signal processing technology, communication technology, software technology, bus technology and other multi-disciplinary integration of high-precision measuring equipment or systems. Its purpose is to qualitatively or quantitatively measure electrical properties, and it has been widely used in various fields of the national economy. There are many kinds of electronic measuring instruments, which can be generally divided into two categories: special instruments and general instruments: special instruments are designed for one or several special purposes, such as TV color signal generators; general instruments are used to measure It is designed for one or several electrical parameters and can be used for various electronic measurements.