【正文】 le, one end or both ends of the shield should be grounding resistance should be less than the shielding layer 1 / 10. 4. PLC basic unit and expansion modules and functional modules, connecting cables 8 should be installed separately, to prevent interference from outside signals. 5. 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. Third, I/O wiring terminal 1. Input Connection (1) Input connection generally should not exceed 30 meters. But if the environment interfere with small, small voltage drop, the input terminal Longer be appropriate. (2) Input / output lines can not be used with a cable, input / output lines should be separated. (3) The extent possible, normally open contact form connected to the input in the establishment of the ladder and relay the same schematic 2. Output connection (1) Output terminal is divided into separate output and public output. In different groups, using different types and voltage levels of output voltage. However, output in the same group can only use the same type, the same voltage level of power. (2) Since the PLC39。 switch cabi, the lower should be a ventilation shutters, to prevent too much direct sunlight。 the input register reflecting the input signal status, output point reflects the state of the output latch. Input module will transform electrical signals into digital signals into the PLC system, the output module opposite. I/O into digital input (DI), digital outputs (DO), analog input (AI), analog output (AO) modules. Common I/O as follow Switching capacity: voltage level by points, with 220VAC, 110VAC, 24VDC, by Way of isolation, there is isolation and transistor isolation relays. Analog: by type of signal, a current type (420mA ,020mA), voltage (010V ,05V,1010V) and so on, by the precision points are 12bit, 14bit, 16bit, etc. . In addition to these generalpurpose IO, there are special IO modules, such as thermal resistance, thermocouple, pulse and other modules. 6 By I/O module specifications and to determine the number of points, I/O modules can be more or less, but the maximum number of CPU can be the basic configuration management capabilities, which by the largest floor or rack slot limit. Power Modules PLC power supply modules for the PLC to provide the power supply integrated circuits. Meanwhile, some of them for the work input circuit to provide 24V power supply. Power input types are: AC power (220VAC or 110VAC), DC power supply (monly used to 24VDC). Most modular PLC to use floor or rack, its role is to: electrical, the realization of the modules, so that the CPU can access all the modules on the floor, machinery and realize the connection between each module, so that each module constitutes a overall. 3 Installation and debugging Of PLC control system Programming device: development and application programmer is the PLC to monitor the operation, inspection, maintenance indispensable device for programming, some system settings, monitor the PLC and the PLC control system working conditions, but it is not directly involved in field control run. PLC programmers are generally small handheld programmer, the current general by the puter (running programming software) as programmer. That is, our system PC. Human Machine Interface is the simplest indicators and buttons, the current LCD screen (or touch screen) typeone operator terminal has been widely applied by the puter (running the configuration software) as a very popular manmachine interface. PLC munication work rely on advanced industrial work technology can quickly and efficiently collect, transfer of production and management of data. Therefore, the work automation system integration projects in the importance of more and more significant, even been suggested that the work is the controller39。s internal circuitry, but the working mechanism of the various parts, or should have sufficient understanding. CPU and the control work, which will read the instructions, directives and executive orders to explain. However, the pace of work from the vibration signals. Computing devices used for digital or logic operation, under the mand of the controller work. CPU speed and memory capacity are important parameters for PLC, which determines the pace of work PLC, I/O number and software capacity, etc., thereby limiting the control of the scale. I/O modules PLC interface with the electrical circuit is through the input and output section ( I/O) pletion. I/O module integrates the PLC39。 these elements bine not a dismountable whole. Module type PLC including the CPU module, the I/O module, the memory, the power source module, the ledger wall or the rack, these modules may defer to certain rule bination disposition. CPU constitution CPU is the PLC core, plays nerve center39。 for example, 4 aircraft flight controls. Programmable controllers are widely used in motion control, positioning control and torque control. Some manufacturers produce motion control units to be integrated with PLC so that Gcode (involving a CNC machine) can be used to instruct machine movements. PLC may include logic for singlevariable feedback analog control loop, a proportional, integral, derivative or PID controller. A PID loop could be used to control the temperature of a manufacturing process, for example. Historically PLC was usually configured with only a few analog control loops。 little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLC is low pared to the cost of a specific custombuilt controller design. On the other hand, in the case of massproduced goods, customized control s