Programmable Logic Controller

Written by Jerry Ratzlaff on . Posted in Instrumentation & Controls

There are four primary types of signals that the programmable logic controller (PLC) generates.  On a P&ID, when referencing the type of signal for a particular instrument or installation, it should be in reference to the PLC.  The types of signals are analog output (AO), analog input (AI), discrete output (DO), and discrete Input (DI).

 

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