附录Abstract: Programmable controller in the field of industrial control applications, and PLC in the application process, to ensure normal operation should be noted that a series of questions, and give some reasonable suggestions.Key words: PLC Industrial Control Interference Wiring Ground Proposal DescriptionOver the years, programmable logic controller (hereinafter referred to as PLC) from its production to the present, to achieve a connection to the storage logical leap of logic; its function from weak to strong, to achieve a logic control to digital control of progress; its applications from small to large, simple controls to achieve a single device to qualified motion control, process control and distributed control across the various tasks. PLC today in dealing with analog, digital computing, human-machine interface and the network have been a substantial increase in the capacity to become the mainstream of the field of control of industrial control equipment, in all walks of life playing an increasingly important role.ⅡPLC application areasCurrently, PLC has been widely used in domestic and foreign steel, petroleum, chemical, power, building materials, machinery manufacturing, automobile, textile, transportation, environmental and cultural entertainment and other industries, the use of mainly divided into the following categories:1. Binary logic controlReplace traditional relay circuit, logic control, sequential control, can be used to control a single device can also be used for multi-cluster control and automation lines. Such as injection molding machine, printing machine, stapler machine, lathe, grinding machines, packaging lines, plating lines and so on.2. Industrial Process ControlIn the industrial production process, there are some, such as temperature, pressure, flow, level and speed, the amount of continuous change (ie, analog), PLC using the appropriate A / D and D / A converter module, and a variety of control algorithm program to handle analog, complete closed-loop control. PID closed loop control system adjustment is generally used as a conditioning method was more. Process control in metallurgy, chemical industry, heat treatment, boiler control and so forth have a very wide range of applications3. Motion ControlPLC can be used in a circular motion or linear motion control. Generally use a dedicated motion control module, for example a stepper motor or servo motor driven single-axis or multi-axis position control module, used in a variety of machinery, machine tools, robots, elevators and other occasions.4. Data ProcessingPLC with mathematics (including matrix operations, functions, operation, logic operation), data transfer, data conversion, sorting, look-up table, bit manipulation functions, you can complete the data collection, analysis and processing. Dataprocessing is generally used, such as paper making, metallurgy, food industry, some of the major control system5. Communications and networkingPLC communication with the communication between PLC and the PLC and other communications between intelligent devices. Along with the development of factory automation network, the PLC now has communication interface, communication is very convenient.ⅢApplication features of PLC1. High reliability, strong anti-interferenceHigh reliability is the key to performance of electrical control equipment. PLC as the use of modern large scale integrated circuit technology, using the strict production process, the internal circuits to the advanced anti-jamming technology, with high reliability. Constitute a control system using PLC, and the same size compared to relay contactor system, electrical wiring and switch contacts have been reduced to hundreds or even thousands of times, fault also greatly reduced. In addition, PLC hardware failure with self-detection, failure alarm timely information. In the application software, application are also incorporated into the peripheral device fault diagnosis procedure, the system is in addition to PLC circuits and devices other than the access protection fault diagnosis. In this way, the whole system extremely high reliability.2. Fully furnished, fully functional, applicabilityPLC to today, has formed a series products of various sizes, can be used for occasions of all sizes of industrial control. In addition to processing other than logic, PLC data, most of computing power has improved, can be used for a variety of digital control in the field. A wide variety of functional units in large numbers, so that penetration to the position of PLC control, temperature control, CNC and other industrial control. Enhanced communication capabilities with PLC and human-machine interface technology, using the PLC control system composed of a variety of very easily.3. Easy to learn, well engineering and technical personnel welcomePLC is facing the industrial and mining enterprises in the industrial equipment. It interfaces easily, programming language easily acceptable for engineering and technical personnel. Ladder language, graphic symbols and expressions and relay circuit very close to are not familiar with electronic circuits, computer principles and assembly language do not understand people who engage in industrial control to open the door.4. System design, the workload is small, easy maintenance, easy to transformPLC logic with memory logic instead of wiring, greatly reducing the control equipment external wiring, make the control system design and construction of the much shorter period, while routine maintenance is also easier up, even more important is to change the procedures of the same equipment has been changed production process possible. This is particularly suitable for many varieties, small batch production situations.(1)Installation and wiring●Power lines, control lines and power lines and PLC I / O lines should be split wiring, isolation transformer and PLC and I / O should be used between the cable connection Shuangjiao. The PLC's IO lines and power lines go separate lines, such as to be in the same groove, the separation of bundled communication lines, DC lines, if conditions allow, the best sub-groove alignment, not only will it have the greatest possible distance and can reduce the noise to a minimum.●PLC should stay away from strong interference sources such as welding, high-power silicon rectifier devices and large power equipment, not with the high-voltage electrical switch installed in the same cabinet. PLC in the cabinet should stay away from power lines (the distance between the two should be more than 200mm). And PLC cabinets installed within the same inductive load, such as large power relay, contactor coil, arc should be parallel RC circuit.●PLC input and output separately from the best alignment, switch and analog should be laid separately. The transmission of analog signals should be shielded cable, one end or both ends of the shield should be grounding resistance should be less than the shielding layer 1 / 10.●AC output line and DC output lines do not use the same cable, the output line should be far from power lines and power lines, to avoid parallel.(2)I / O wiring terminalInput Connection●Input wiring generally not too long. But if the environment interfere with small, small voltage drop, the input terminal can be properly longer.●Input / output lines can not be used with a cable, input / output lines should be separated.●The extent possible, normally open contact form to connect to the input in the establishment of the ladder and relay the same schematic, easy to read。