Logic DiagramsDOE-HDBK-1016/2-93ENGINEERING LOGIC DIAGRAMSRev. 0Page 1PR-05ENGINEERING LOGIC DIAGRAMSThis chapter will review the symbols and conventions used on logic diagrams.EO 1.1IDENTIFY the symbols used on logic diagrams to representthe following components:a.AND gateh.Adderb.NAND gatei.Time-delayc.COINCIDENCE gatej.Counterd.OR gatek.Shift registere.NOR gatel.Flip-flopf.EXCLUSIVE OR gatem.Logic memoriesg.NOT gate or inverterEO 1.2EXPLAIN the operation of the three types of time delaydevices.IntroductionLogic diagrams have many uses. In the solid state industry, they are used as the principaldiagram for the design of solid state components such as computer chips. They are used bymathematicians to help solve logical problems (called boolean algebra). However, their principleapplication at DOE facilities is their ability to present component and system operationalinformation. The use of logic symbology results in a diagram that allows the user to determinethe operation of a given component or system as the various input signals change.To read and interpret logic diagrams, the reader must understand what each of the specializedsymbols represent. This chapter discusses the common symbols used on logic diagrams. Whenmastered, this knowledge should enable the reader to understand most logic diagrams.Facility operators and technical staff personnel commonly see logic symbols on equipmentdiagrams. The logic symbols, called gates, depict the operation/start/stop circuits of componentsand systems. The following two figures, which use a common facility start/stop pump circuitas an example, clearly demonstrate the reasons for learning to read logic diagrams. Figure 1presents a schematic for a large pump, and Figure 2 shows the same pump circuit using onlylogic gates. It is obvious that when the basic logic symbols are understood, figuring out howthe pump operates and how it will respond to various combinations of inputs using the logicdiagram is fast and easy, as compared to laboriously tracing through the relays and contacts ofthe schematic diagram for the same information.

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