PLC: 1 FINAL EXAM QUESTIONS AND
ANSWERS 2026/2027 UPDATE.
PLC stands for - Answer Programmable Logic Controller
Two types of PLC are: - Answer Fixed or modular
What is a fixed PLC - Answer Everything built in
Limited to the number of I/O
Found in small applications due to lower cost and physical size
What is a modular PLC - Answer Has separate components, can easily change to whatever
module needed.
Large applications due to flexibility and power.
What are the 4 main components of a plc - Answer Power supply
Central processing unit (CPU)
Input/output modules
Chassis
Common voltages of power supply (2) - Answer 115 VAC
24 VDC
Chassis: - Answer Aka backplane or rack
Provides connections and communications between modules, power supply and CPU
CPU (Central Processing Unit) - Answer - Brain of the PLC found in slot 0
- handles comms and interactions with other components of the system
- this operating cycle is called SCAN OR SWEEP
What state can a wired input be? - Answer Open/closed
What state can an input terminal be - Answer Energized/de-energized
What state can a bit address be? - Answer Set (1) / Reset (0)
, Instruction state is either: - Answer True/false
Rung state is either: - Answer True/false
Output terminal state is either: - Answer Energized / de-energized
Wired output state is either: - Answer On/off
Indication when an instruction is true? - Answer Address is highlighted yellow
Indication on PLC when an input or output terminal is energized. - Answer Red when
energized, black when not
Must the address of an output match the input terminal? Or can any input control any output? -
Answer Any can control any
What is an OTE? - Answer -( )- Output Energized: becomes true when entire rung of
instructions before become true. Once true, it will write a value of 1
What is an XIO? - Answer -]/[- Examine if opened: the instruction will go true when it reads a
bit value of 0 (ex: NO input, instruction remains true until PB is pressed)
What is an XIC? - Answer -] [- Examine if closed: Instruction will go true when it reads a bit
value of 1. (Ex NO input, stays false until PB is pressed)
What do input modules do? - Answer Carry data from the process to the controller
What do output modules do? - Answer Carry data from the controller to the process
Signals back to the I/O card can either be (2 types) - Answer Discrete or analog type
What is a discrete type signal? - Answer They behave as binary switches (on or off, 1 or 0,
true or false, respectively)
What is an analog type signal? - Answer Like volume controls, has a range of values. Usually
0-10V or 4-20 mA
ANSWERS 2026/2027 UPDATE.
PLC stands for - Answer Programmable Logic Controller
Two types of PLC are: - Answer Fixed or modular
What is a fixed PLC - Answer Everything built in
Limited to the number of I/O
Found in small applications due to lower cost and physical size
What is a modular PLC - Answer Has separate components, can easily change to whatever
module needed.
Large applications due to flexibility and power.
What are the 4 main components of a plc - Answer Power supply
Central processing unit (CPU)
Input/output modules
Chassis
Common voltages of power supply (2) - Answer 115 VAC
24 VDC
Chassis: - Answer Aka backplane or rack
Provides connections and communications between modules, power supply and CPU
CPU (Central Processing Unit) - Answer - Brain of the PLC found in slot 0
- handles comms and interactions with other components of the system
- this operating cycle is called SCAN OR SWEEP
What state can a wired input be? - Answer Open/closed
What state can an input terminal be - Answer Energized/de-energized
What state can a bit address be? - Answer Set (1) / Reset (0)
, Instruction state is either: - Answer True/false
Rung state is either: - Answer True/false
Output terminal state is either: - Answer Energized / de-energized
Wired output state is either: - Answer On/off
Indication when an instruction is true? - Answer Address is highlighted yellow
Indication on PLC when an input or output terminal is energized. - Answer Red when
energized, black when not
Must the address of an output match the input terminal? Or can any input control any output? -
Answer Any can control any
What is an OTE? - Answer -( )- Output Energized: becomes true when entire rung of
instructions before become true. Once true, it will write a value of 1
What is an XIO? - Answer -]/[- Examine if opened: the instruction will go true when it reads a
bit value of 0 (ex: NO input, instruction remains true until PB is pressed)
What is an XIC? - Answer -] [- Examine if closed: Instruction will go true when it reads a bit
value of 1. (Ex NO input, stays false until PB is pressed)
What do input modules do? - Answer Carry data from the process to the controller
What do output modules do? - Answer Carry data from the controller to the process
Signals back to the I/O card can either be (2 types) - Answer Discrete or analog type
What is a discrete type signal? - Answer They behave as binary switches (on or off, 1 or 0,
true or false, respectively)
What is an analog type signal? - Answer Like volume controls, has a range of values. Usually
0-10V or 4-20 mA
