英文翻译原文PLC SynopsisPLC Introduction Programmable controller is the first in the late 1960s in the United States, and then called PLC programmable logic controller (Programmable Logic Controller) is used to replace relays. For the implementation of the logical judgment, timing, sequence number, and other control functions. The concept is presented PLC General Motors Corporation. PLC and the basic design is the computer functional improvements, flexible, generic and other advantages and relay control system simple and easy to operate, such as the advantages of cheap prices combined controller hardware is standard and overall. According to the practical application of target software in order to control the content of the user procedures memory controller, the controller and connecting the accused convenient target. In the mid-1970s, the PLC has been widely used as a central processing unit microprocessor, import export module and the external circuits are used, large-scale integrated circuits even when the PLC is no longer the only logical (IC) judgment functions also have data processing, PID conditioning and data communications functions. International Electro technical Commission (IEC) standards promulgated programmable controller for programmable controller draft made the following definition: programmable controller is a digital electronic computers operating system, specifically for applications in the industrial design environment. It used programmable memory, used to implement logic in their internal storage operations, sequence control, timing, counting and arithmetic operations, such as operating instructions, and through digital and analog input and output, the control of various types of machinery or production processes. Programmable controller and related peripherals, and industrial control systems easily linked to form a whole, to expand its functional design. Programmable controller for the user, is non-contact equipment, the procedures can be changed to change production processes. The programmable controller has become a powerful tool for factory automation, widely popular replication. Programmable controller is user-oriented industries dedicated control computer, with many distinctive features. First, it is high reliability, anti-interference capability; Second, programming visual, simple; Third, adaptability good; Fourth, functional improvements, strong functional interface.1. PLC CharacteristicPLC is one kind of digital operation electronic system, specially for applies under the industry environment designs, it has used the programmable foreword memory, uses for to carry out the logic operation, the sequential control in its internal memory, fixed time, counts with operation the and so on arithmetic operation instruction, and through digital and simulation -like input and output, controls each kind of type the machinery or the production process. It is specially, has face the industry control bright characteristic that designs for the industry environment under application.The PLC reliability high, the ant jamming ability is strong. It is specially, besides to the component which designs for the industry control carries on strict screening, the hardware and software have also used measure and so on shield, filter, photo electricity isolation, breakdown diagnosis and self-recovery. General nimble, the function complete, the connection function is strong. The programmable controller is through the procedure realization control, nearly may satisfy all controls situation the demand. When the control request has the change, so long as the revision procedure may realize the control mode transformation, and because the programmable controller product has standardized, the serration, the universalization, therefore can nimbly conveniently carry on the system disposition, the composition scale is different, the function different control system, has the greatly strengthened compatibility. Programming simply, is direct viewing, the easy to operate. The programmable controller face the user, faces the scene, it uses is different with the computer assembly language trapezoidal chart language. The trapezoidal chart language face the process control, is similar, the form succinctly with the black-white control circuit diagram, direct viewing is strong. The computer technology and between the tradition black-white control technology barrier completely does not exist on the programmable controller. Between the PLC trapezoidal charts, the flow chart, the sentence table may conveniently carry on the transformation, sped up its promoted speed.The modular structure, the installment simple, the debugging is convenient. PLC each part, including CPU, the power source, I/O and so on uses the modular design, the system function and the scale may voluntarily dispose according to users actual demand, thus realizes the best natural price ratio. Clearly installs the line to be simple, the LED demonst