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 industrial automatic control methods, automatic control instruments have also been updated accordingly. At present, automation instruments in the chemical industry, petroleum, power, metallurgy, light industry and other industrial sectors are widely used. In recent years, it has also been applied in the production of medical devices and achieved good results. Industrial automatic control is to use various types of instruments or industrial control machines in the production process to automatically control and adjust the controlled objects according to the specified operating rules. It can improve labor productivity, reduce costs, ensure product quality, and facilitate the safe and economic operation of production equipment. At present, unit combination meters are widely used and mature in various industrial automation systems in China.