Programmable Logic Controller

Written by Jerry Ratzlaff on . Posted in Instrumentation

Programmable Logic Controller

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 ( \(DI\) ).