| lijiujia |
2009-02-18 14:36 |
考博复试面试英语
Good morning everyone, I am very glad to have this opportunity to take my report on PLC. The PLC, his full name is programmable logic controller. It is a computer with a single mission. Most commonly used in industrial applications, it usually lacks a monitor, keyboard, and a mouse, as it is normally programmed to operate a machine or system using but one program. Factory assembly line machinery is activated and monitored by a single PLC, but in the past hundreds of times and relays would have been required to do the task. The machine and system user rarely, if ever, interacts with the PLC’s program. When it is necessary to either edit or create the PLC program, a personal computer is usually (but not always) connected to it. xlwsZ
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In the 1960s, the American automobile industry was searching for a way to do business better. The process of sequencing control and interlock logic needed for automobile manufactory was a time consuming and arduous task. These processes required manual updating of relays timers and dedicated closed-loop controllers. When a new year’s model was coming off the drawing board, skilled electricians were called on to reset the production line. GM Hydramatic specifically requested proposal for a replacement for the old system for speeding up the process and keep costs down. \
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Bedford Associates, out of Bedford, Massachusetts, came up with the winning proposal , designated the 084. The 084 became the first PLC, and a new industry was born. @ [FFYV ru
Programmable logic controllers sometime referred to simply as programmable controllers. They are microprocessor based on units and in essence monitor external sensory activity from additional devices. They take in the date and these dates report on a wide variety of activity, suchPOST http://www.freekaobo.com/post.php? HTTP/1.0 . >|'6J!Op
Prompediment. They also control attached motor starters, pilot lights, valves and many other devices. Both functions respond to a custom, user-created program. RyhR#
Programmable logic controllers contain a variable number of input/output ports, and are typically Reduced Instruction Set Computer (RISC) based. They are designed for real-time use, and often must withstand harsh environments on the shop floor. The programmable logic controller circuitry monitors the status of multiple sensor input and control output actuators as like motor starters, solenoids, lights and displays, or valves. PR'FSTg
Most PLCs are programmed in a special language called Ladder logic. Ladder logic is essentially a Boolean logic-solving program with a graphical user interface, which is designed to look like an elementary wiring diagram, familiar to all industrial electricians. A modern programmable logic controller is usually programmed in any one of several languages, ranging from Ladder logic to Basic or C. Typically, the program is written in a development environment on a personal computer, and then is download onto programmable logic controller directly through a cable connection. The program is stored in the programmable logic controller in non-volatile memory. E1C8yIF
Well, I think this might be a good place for me to wind up my talk. Thank you.
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