— plc input modules, a method of low-cost expansion of output module

analog output plc, a method of low-cost expansion of output module programmable controller (hereinafter referred to as PLC) because of its high reliability, simple programming, versatility, small size, compact structure, easy installation and maintenance features, in the industrial control has been widely used. PLC modules are generally divided into the following categories: digital input modules, digital output modules, analog input modules, analog output plc. In industrial control especially in the field of process control analog acquisition and control needs a relatively large amount, so the PLC analog input and output modules require more, and analog input and output modules are more expensive, increasing the analog input, output module increases the cost and reduces the cost of the entire system, limit the application of PLC. This paper presents a method based on extended analog input and output modules of communication trying to solve this problem.