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Automate programabile - PLC

May 20 2009 12:00 PM | donpetru in Automatizari

1. Introducere

Sistemele automate de control a proceselor sunt un conglomerat de dispozitive electronice care conferă stabilitate, acurateţe şi performanţă. Sistemele de operare pot avea diverse forme de implementare pornind de la surse de alimentare şi până la maşini. Fiind un rezultat rapid a progresului tehnologic, cele mai complexe operaţii au fost rezolvate prin conectarea în sistem a unor automate programabile şi unităţi centrale de proces. Aceste automate programabile (PLC - Programabille Logic Controller), aşa cum le vom denumi în continuoare, pe lângă conexiunile cu instrumentele de măsură şi senzorii din procesul de automatizare, va trebui să permită comanda intregului proces şi ceea ce este şi important, să comunice operatorului stările procesului prin semnale vizuale şi sunet şi/sau printr-o reţea de comunicaţie la un computer local. Aceste caracteristici permit exploatarea automatizări la un înalt grad de flexibilitate, prin schimbarea şi monitorizarea mult mai comodă a parametrilor de bază a procesului.

Fiecare componentă din sistemul de control a procesului joacă un anumit rol, în concordanţă cu importanţa sa. Spre exemplu, fără niciun senzor, PLC-urile nu ar putea ştii modul de variaţie în timp a parametrilor principali ai procesului (consideraţi parametri de intrare). În sistemele automate, PLC-urile sunt partea centrală a sistemului de control sau a automatizării.

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Prin executarea programului înregistrat în memorie, PLC-ul monitorizează în mod continuu stările sistemului prin ...
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