PLC Questions With All Correct & Verified
Answers
What is a programmable logic controller (PLC)? Correct answer-An industrial grade computer that
is capable of being programmed to perform control functions. It is basically a digital computer
designed for use in machine control.
Identify four tasks in addition to relay switching operations that PLCs are capable of performing.
Correct answer-Timing, counting, calculating, and the processing of analog signals.
List six distinct advantages that PLCs offer over conventional relay-based control systems. Correct
answer-Reliability, flexibility, lower cost, communication capability, faster response time, easier to
trouble shoot.
Explain the difference between open and proprietary PLC architecture. Correct answer-Open
architecture allows the use of parts from different manufacturers, while proprietary architecture
uses most parts from the PLC manufacturer.
State two ways in which I/O is incorporated into the PLC. Correct answer-Fixed and Modular.
Describe how the I/O modules connect to the processor in a modular-type PLC configuration.
Correct answer-Divided by compartments into which separate modules can be plugged.
Explain the main function of each of the following major components of a PLC:
Processor module (CPU)
I/O modules
Programming device
Power supply module Correct answer-CPU; Controls all PLC activity, designed to be programmed
with ladder logic.
I/O Module; Forms the interface by which field devices are connected to the controller.
Programming Device; Used to enter the desired program into the memory of the processor.
Power Supply; typically uses DC power to feed the modules plugged into the rack.
What are the two most common types of PLC programming devices? Correct answer-Hand-held
programming devices and PC's.
Explain the terms program and programming language as they apply to a PLC. Correct answer-
Program- A user-developed series of instructions that directs the PLC to execute actions.
Programming Language- Provides rules for combining the instructions so that they produce desired
actions.
What is the standard programming language used with PLCs? Correct answer-Ladder Logic.
The programmable controller operates in real time. What does this mean? Correct answer-Input
data is processed virtually immediately, firing its programmed output.
Answers
What is a programmable logic controller (PLC)? Correct answer-An industrial grade computer that
is capable of being programmed to perform control functions. It is basically a digital computer
designed for use in machine control.
Identify four tasks in addition to relay switching operations that PLCs are capable of performing.
Correct answer-Timing, counting, calculating, and the processing of analog signals.
List six distinct advantages that PLCs offer over conventional relay-based control systems. Correct
answer-Reliability, flexibility, lower cost, communication capability, faster response time, easier to
trouble shoot.
Explain the difference between open and proprietary PLC architecture. Correct answer-Open
architecture allows the use of parts from different manufacturers, while proprietary architecture
uses most parts from the PLC manufacturer.
State two ways in which I/O is incorporated into the PLC. Correct answer-Fixed and Modular.
Describe how the I/O modules connect to the processor in a modular-type PLC configuration.
Correct answer-Divided by compartments into which separate modules can be plugged.
Explain the main function of each of the following major components of a PLC:
Processor module (CPU)
I/O modules
Programming device
Power supply module Correct answer-CPU; Controls all PLC activity, designed to be programmed
with ladder logic.
I/O Module; Forms the interface by which field devices are connected to the controller.
Programming Device; Used to enter the desired program into the memory of the processor.
Power Supply; typically uses DC power to feed the modules plugged into the rack.
What are the two most common types of PLC programming devices? Correct answer-Hand-held
programming devices and PC's.
Explain the terms program and programming language as they apply to a PLC. Correct answer-
Program- A user-developed series of instructions that directs the PLC to execute actions.
Programming Language- Provides rules for combining the instructions so that they produce desired
actions.
What is the standard programming language used with PLCs? Correct answer-Ladder Logic.
The programmable controller operates in real time. What does this mean? Correct answer-Input
data is processed virtually immediately, firing its programmed output.
