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　　隨著我國企業發展，現代化的企業規模不斷擴大，PLC維修工业自化控制应用也越来越广泛，PLC的简述就是可编程逻辑控制器，它采用一类可编程的存储器，用于其内部存储程序，执行逻辑运算、顺序控制、定时、计数与算术操作等面向用户的指令，并通过数字或模拟式输入/输出控制各种类型的机械或生产过程。对于PLC維修人员来说在PLC維修过程中都会遇到哪些故障现象呢?

　　一、CPU反常：

　　CPU反常報警時，應查看CPU單元銜接于內部總線上的一切器材。具體方法是順次替換可能發作毛病的單元，找出毛病單元，並作相應處理。

　　二、存儲器反常：

　　存儲器反常報警時，如果是程序存儲器的問題，經過從頭編程後還會再現毛病。這種狀況可能是噪聲的攪擾引起程序的改變，否則應替換存儲器。

　　三、輸入/輸出單元反常、擴展單元反常：

　　發作這類報警時，應首要查看輸入/輸出單元和擴展單元銜接器的刺進狀況、電纜銜接狀況，斷定毛病發作的某單元之後，再替換單元。

　　四、不履行程序：

　　一般状况下可依照输入---程序履行---输出的过程进行查看(1)输入查看是运用输入LED指示灯辨认，或用写入器构成的输入监视器查看。当输入LED不亮时，可开始断定是外部输入体系毛病，再合作万用表查看。如果输出电压不正常，就可断定是输入单元毛病。当LED亮而内部监视器无显现时，则可认为是输入单元、CPU单元或扩展单元的毛病。(2) 程序履行查看是经过写入器上的监视器查看。当梯形图的接点状况与成果不一致时，则是程序错误(例如内部继电器两层运用等),或是运算部分呈现毛病。(3)输出查看可用输出LED指示灯辨认。当运算成果正确而输出LED指示错误时，则可认为是CPU单元、1/0接口单元的毛病。当输出LED是亮的而无输出，则可判别是输出单元毛病，或是外部负载体系呈现了毛病。

　　PLC維修发展到现在有了极大的进步，在各种领域也有了越来越大的应用，所以在PLC維修的问题上我们应该认真对待，解决好每个在维修过程中出现的故障问题。

For an Oriental city Tokio has remarkably wide streets, and some of them are laid out with all the care of Western engineering. In the course of their morning ride the party came to Sakuradu Avenue, which Fred recognized from a drawing by a native artist, who had taken pains to preserve the architecture of the buildings on each side with complete fidelity. The foundations of the houses were of irregular stones cut in the form of lozenges, but not with mathematical accuracy. The boys had already noticed this form of hewing stone in the walls of the castles, where some very large blocks were piled. They were reported to have been brought from distant parts of the empire, and the cost of their transportation must have been very great. Few of the houses were of more than two stories, and the great majority were of only one. Along Sakuradu Avenue they were of two stories, and had long and low windows with paper screens, so that it was impossible for a person in the street to see what was going on inside. The eaves projected far over the upright sides, and thus formed a shelter that was very acceptable in the heat of summer, while in rainy weather it had many advantages. These yashikis were formerly the property of Daimios, but are now occupied by the Foreign Office and the War Department. Inside the enclosure there are many shade-trees, and they make a cooling contrast to the plain walls of the buildings. The Japanese rarely paint the interior or the exterior of their buildings. Nearly everything is finished in the natural color of the wood, and very pretty the wood is too. It is something like oak in appearance, but a trifle darker, and is[Pg 120] susceptible of a high polish. It admits of a great variety of uses, and is very easily wrought. It is known as keyaki-wood; and, in spite of the immense quantity that is annually used, it is cheap and abundant. "Shut it," said Charlotte, with a sigh like that which had risen when the lead first struck her. "If I could be moved ever so little,--" she said. "That's his look-out, madam. If the sick lady isn't Charlotte Oli'--" The truth is that Doctor Allingham had not been able to summon the courage to make a further examination of the Clockwork man; and he had permitted himself to assume that there would be no immediate developments. So far as was possible he had allowed himself that very necessary relaxation, and he had insisted upon Gregg sharing it with him. The Clockwork man was not quite what either of them had, alternatively, hoped or feared. From Allingham's point of view, in particular, he was not that bogey of the inhuman fear which his original conduct had suggested. True, he was still an unthinkable monstrosity, an awful revelation; but since the discovery of the printed instructions it had been possible to regard him with a little more equanimity. The Clockwork man was a figment of the future, but he was not the whole future. Skip this postscript if you don't want your sensibilities all Larry took a swift, sharp look around the enclosure. His railroad friend again came up with some hot coffee and broiled meat, and explained that after the train had reached a station some miles out it got orders to run back and clear the track for some trains of troops from the Army of the Potomac which were being rushed through. The Deacon's heart almost sank in despair, but he took the coffee and meat, and helped the boys to it. As they were all eating they heard a voice outside which struck on the chords of their memories: "Whose head'll you knock off?" said a burly man, thrusting himself in front of the lawyer, with his fist doubled. "Why," said Si, "I supposed that they was too tired to do anything but lay down and go to sleep. What'd they do?" "It isn't me. I only asked for a little time to think it over, and then you go and cool off." These tricks were never unkind, for David and William were the most benevolent little boys. They saw life through a golden mist, it smelt of milk and apples, it was full of soft lowings and bleatings and cheepings, of gentle noses to stroke and little downy things to hold. For the first time since it became Reuben's, Odiam made children happy. The farm which had been a galley and a prison to those before them, was an enchanted land of adventure to these two. Old Beatup, who remembered earlier things, would sometimes smile when he saw them trotting hand in hand about the yard, playing long hours in the orchard, and now and then[Pg 385] pleading as a special favour to be allowed to feed the chickens, or help fetch the cows home. He seemed to see the farm peopled by little ghosts who had never dared trot about aimlessly, or had time to play, and had fed the fowls and fetched the cows not as a treat and an adventure, but as a dreary part of the day's grind ... he reflected that "the m?aster had learned summat by the others, surelye." "My lord," said the intrepid yeoman, "I had a right to defend my dwelling against unlawful assault." Here Calverley's quick ear caught the sound of the tramping of a horse—his heart beat quick—it might be a traveller journeying to Gloucester, but it was more probable that it was the messenger. He threw the bridle of his horse over the branch of a tree, sprang to the end of the path, and, concealing himself behind the under-wood, discovered in a moment, by the dark medley hue of the rider's dress, that it was the man he expected. He hurried back, and, mounting his steed, waited till the echo of the horse's hoofs could no longer be distinguished; and then, giving the impulse to his own spirited animal, he was the next moment bounding at full speed after the messenger, followed at a distance by his accomplice. No reply was given, but the door was instantly unclosed by Holgrave. Black Jack stood in the shade, just beyond the light that streamed from within, but so close that Holgrave, without crossing the threshold, merely leant his head forward, and heard him say, "Stephen Holgrave, do you remember the cross-roads and Hailes church-yard?" HoME 欧美videosgratis浓毛ENTER NUMBET 002czhtmj.com.cn
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