With the rapid development of China's socialist revolution and construction, automatic control technology has been more and more widely developed and used in industrial production. As one of the means of industrial automatic control, automatic control instruments have also been updated and developed accordingly. At present, automation instruments are widely used in chemical, petroleum, electric power, metallurgy, light industry and other industrial sectors. In recent years, it has also been applied in the production of medical equipment industry, and achieved good results. Industrial automatic control is the use of various types of instruments or industrial control machines in the production process to automatically control and regulate the controlled objects according to the specified operating rules. This can improve labor productivity, reduce costs, ensure product quality, and facilitate the safe and economic operation of production equipment. At present, the unit combination instrument is widely used and mature in various industrial automation systems in China.