Q.1 What does PLC stand for?
Programmable Logic Controller
Programmable Linear Circuit
Power Load Calculator
Printed Light Control
Explanation - PLC stands for Programmable Logic Controller, a digital computer used for automation of industrial processes.
Correct answer is: Programmable Logic Controller
Q.2 Which of the following is a typical input type for a PLC?
Relay
Analog sensor
Motor
PLC itself
Explanation - Inputs to a PLC can be digital (like switches) or analog (like temperature sensors). A relay is an output device, and a motor is a load.
Correct answer is: Analog sensor
Q.3 In ladder logic, what does a rung represent?
A single instruction
A physical wire
A power supply
An electrical circuit
Explanation - Each rung in ladder logic represents an electrical circuit that determines the PLC's output based on inputs.
Correct answer is: An electrical circuit
Q.4 Which component supplies power to a PLC?
I/O module
CPU
Power supply unit
HMI
Explanation - The power supply unit provides the electrical power needed by the PLC’s CPU and I/O modules.
Correct answer is: Power supply unit
Q.5 Which of these is NOT a typical PLC programming language?
Ladder Diagram
Structured Text
Python
Function Block Diagram
Explanation - PLC programming uses IEC 61131-3 languages like Ladder Diagram, Structured Text, and Function Block Diagram; Python is not used for PLC programming.
Correct answer is: Python
Q.6 What is the purpose of a timer in PLC programming?
To count cycles
To delay operations
To convert analog signals
To measure voltage
Explanation - Timers in PLCs are used to introduce time delays or time-based logic in a program.
Correct answer is: To delay operations
Q.7 Which port is commonly used for communication between PLC and HMI?
USB
Ethernet
Serial (RS-232)
All of the above
Explanation - PLCs can communicate with HMIs via USB, Ethernet, or serial RS-232 ports, depending on the hardware.
Correct answer is: All of the above
Q.8 What type of memory holds the PLC program during operation?
ROM
RAM
Flash
EEPROM
Explanation - During operation, the PLC program resides in volatile memory (RAM); ROM and Flash store the firmware, and EEPROM stores non-volatile data.
Correct answer is: RAM
Q.9 Which instruction is used to reset a counter in ladder logic?
CNT
RST
RESET
CLEAR
Explanation - The RESET (or CLR) instruction clears the counter value in ladder logic programming.
Correct answer is: RESET
Q.10 A PLC’s CPU is best described as:
A memory module
An input/output interface
The brain of the PLC
A power converter
Explanation - The CPU executes the program and controls the logic, essentially acting as the PLC’s brain.
Correct answer is: The brain of the PLC
Q.11 Which of the following is a safety feature commonly found in PLCs?
Emergency stop input
Overheat protection
Redundant CPU
All of the above
Explanation - PLCs include safety inputs, thermal protection, and sometimes redundant CPUs to ensure safe operation.
Correct answer is: All of the above
Q.12 What does 'scan cycle' refer to in a PLC?
The time it takes to read and write all I/O points
The speed of the power supply
The number of programs the PLC can run
The cycle time of motors
Explanation - A scan cycle is the process of reading inputs, executing the program, and updating outputs.
Correct answer is: The time it takes to read and write all I/O points
Q.13 Which protocol is commonly used for communication between PLCs and SCADA systems?
Modbus
HTTP
FTP
SMTP
Explanation - Modbus (TCP or RTU) is widely used to link PLCs with SCADA systems for data exchange.
Correct answer is: Modbus
Q.14 A 'PLC' can be considered a type of:
Microcontroller
Programmable Device
Analog Switch
Digital Sensor
Explanation - PLCs are programmable industrial controllers that manage inputs and outputs.
Correct answer is: Programmable Device
Q.15 Which of the following is NOT a typical PLC I/O type?
Digital
Analog
Optical
Thermal
Explanation - Digital and analog are standard I/O types; optical sensors can be digital, but thermal sensors are not a direct I/O type.
Correct answer is: Thermal
Q.16 What is the role of a 'HMI' in a PLC system?
To provide user interface
To store data
To convert signals
All of the above
Explanation - HMI stands for Human-Machine Interface, allowing operators to view status and control the PLC.
Correct answer is: To provide user interface
Q.17 Which of the following is a characteristic of a 'distributed PLC'?
All logic resides in a single CPU
I/O is located at remote sites connected to the CPU
It has no communication capability
It is used only for small processes
Explanation - Distributed PLCs have I/O modules distributed throughout a plant while the CPU centralizes control.
Correct answer is: I/O is located at remote sites connected to the CPU
Q.18 Which instruction is used to perform a bitwise AND operation in Structured Text?
AND
OR
XOR
NOT
Explanation - The AND instruction performs bitwise AND; OR performs bitwise OR, XOR performs exclusive OR, and NOT inverts bits.
Correct answer is: AND
Q.19 What does a 'scan' refer to in PLC operation?
Reading input, executing program, writing output
Scanning for errors in the code
Scanning the physical environment
Scanning the internet for firmware updates
Explanation - A scan is the PLC’s cycle of reading inputs, executing logic, and updating outputs.
Correct answer is: Reading input, executing program, writing output
Q.20 Which of the following is a common type of PLC memory used for storing backup programs?
Non-volatile memory
Cache memory
Working memory
Register file
Explanation - Non‑volatile memory (e.g., flash) preserves the program when power is lost.
Correct answer is: Non-volatile memory
Q.21 Which protocol is specifically designed for industrial automation and is part of the IEC 61158 standard?
Ethernet/IP
Profibus
BACnet
SNMP
Explanation - Profibus (PROFIBUS DP/PA) is an industrial Ethernet standard defined by IEC 61158.
Correct answer is: Profibus
Q.22 What is the maximum number of I/O points a typical industrial PLC can handle?
256
1024
4096
8192
Explanation - Most industrial PLCs can manage up to 1024 I/O points, though some high‑end models exceed this.
Correct answer is: 1024
Q.23 Which of the following is a benefit of using a PLC over a relay logic system?
Higher reliability
Easier maintenance
Lower cost
All of the above
Explanation - PLCs reduce failure points, simplify troubleshooting, and are often cheaper over time.
Correct answer is: All of the above
Q.24 Which PLC instruction is used to copy data from one memory location to another?
MOV
COPY
LD
ST
Explanation - The MOV instruction copies data; LD loads, and ST stores.
Correct answer is: MOV
Q.25 What is the typical cycle time of a modern PLC during a scan?
1 ms
10 ms
100 ms
1 s
Explanation - Advanced PLCs can scan at 1‑2 ms cycle times, allowing rapid response.
Correct answer is: 1 ms
Q.26 Which of the following describes a 'real-time' operating system in a PLC?
It can handle tasks with precise timing requirements
It is only used in hobby projects
It does not support multitasking
It is the same as a standard PC OS
Explanation - Real‑time OS ensures deterministic response times critical for control tasks.
Correct answer is: It can handle tasks with precise timing requirements
Q.27 A PLC that can be programmed in multiple languages but primarily uses Ladder Diagram is an example of a _______.
Universal PLC
Specialized PLC
Legacy PLC
Embedded PLC
Explanation - Universal PLCs support several IEC 61131‑3 languages, offering flexibility.
Correct answer is: Universal PLC
Q.28 Which of the following is a typical use of a 'counter' in PLC programming?
Counting the number of cycles of a motor
Measuring time intervals
Storing temperature values
Generating PWM signals
Explanation - Counters increment or decrement with each trigger event, such as motor revolutions.
Correct answer is: Counting the number of cycles of a motor
Q.29 Which of the following is a standard method for storing PLC program changes without losing them after power loss?
Backup to a USB drive
Use a volatile memory module
Save to a cloud server only
Store in the CPU’s internal flash memory
Explanation - Flash memory is non‑volatile and retains the program across power cycles.
Correct answer is: Store in the CPU’s internal flash memory
Q.30 What does 'IEC 61131‑3' refer to in PLC terminology?
A safety standard for PLCs
A programming language standard for PLCs
An electrical wiring code
A communication protocol
Explanation - IEC 61131‑3 defines five programming languages for PLCs: Ladder, Structured Text, Function Block, Instruction List, and Sequential Function Charts.
Correct answer is: A programming language standard for PLCs
Q.31 In PLC ladder logic, what is the effect of a rung that contains a coil with no input conditions?
The coil is always energized
The coil is never energized
The coil toggles each scan
The rung is ignored
Explanation - A coil with no conditions will always execute (energize) on each scan.
Correct answer is: The coil is always energized
Q.32 Which of the following is NOT a common PLC manufacturer?
Allen‑Bradley
Siemens
Honeywell
Toyota
Explanation - Toyota is a car manufacturer, not a PLC vendor.
Correct answer is: Toyota
Q.33 What type of signal does a 4‑20 mA current loop provide for PLC inputs?
Analog voltage
Digital logic
Analog current
Pulse count
Explanation - 4‑20 mA is a common analog current signal used for transmitting process variable data.
Correct answer is: Analog current
Q.34 Which PLC programming instruction is used to implement a delay loop without using timers?
FOR loop
DELAY
PEND
SLEEP
Explanation - A FOR loop can create a software delay by iterating a fixed number of times.
Correct answer is: FOR loop
Q.35 Which of the following best describes the 'scan cycle' time for a high‑speed PLC?
50 ms
10 ms
1 ms
500 μs
Explanation - High‑speed PLCs often achieve scan times of about 1 millisecond.
Correct answer is: 1 ms
Q.36 What is the main purpose of a PLC’s 'debug mode'?
To improve scan speed
To allow step‑by‑step execution of the program
To automatically update firmware
To disconnect I/O modules
Explanation - Debug mode enables operators to run the program incrementally and inspect variables.
Correct answer is: To allow step‑by‑step execution of the program
Q.37 What does 'HMI' stand for in PLC systems?
High‑Speed Motor Interface
Human‑Machine Interface
Hardware Maintenance Interface
Hybrid Microcontroller Interface
Explanation - HMI is a graphical interface that allows users to interact with PLC processes.
Correct answer is: Human‑Machine Interface
Q.38 Which of these is a key advantage of using a distributed I/O system with PLCs?
Reduced cabling complexity
Higher redundancy
Lower cost per channel
All of the above
Explanation - Distributed I/O allows sensors and actuators to be placed close to equipment, reducing cable lengths, enabling redundancy, and often lowering cost.
Correct answer is: All of the above
Q.39 In PLC programming, what does the 'XIO' instruction do?
Checks if input is on
Checks if input is off
Inverts a bit
Loads an input to memory
Explanation - XIO stands for 'Examine if Input Off' – it passes if the specified input bit is zero.
Correct answer is: Checks if input is off
Q.40 What is the function of a 'timer preset' value in PLC logic?
Sets the delay time for the timer
Resets the timer immediately
Displays the current time
None of the above
Explanation - The preset value defines how long the timer must run before it reaches the terminal count.
Correct answer is: Sets the delay time for the timer
Q.41 Which of the following is a typical application of PLCs in automotive manufacturing?
Controlling robotic welders
Processing customer data
Managing vehicle infotainment
Running the engine
Explanation - PLCs often control robotic stations, conveyors, and other production equipment in automotive plants.
Correct answer is: Controlling robotic welders
Q.42 Which of the following best describes 'modular PLC architecture'?
All functions are in a single unit
The PLC is built from interchangeable modules for CPU, I/O, and communication
It has a fixed number of I/O points
It is a software only system
Explanation - Modular PLCs allow customization by selecting appropriate modules for specific needs.
Correct answer is: The PLC is built from interchangeable modules for CPU, I/O, and communication
Q.43 Which communication protocol uses a master‑slave architecture where the master polls all slaves?
Modbus RTU
Profibus DP
Ethernet/IP
CANopen
Explanation - Modbus RTU is a simple master‑slave protocol with polling of slaves.
Correct answer is: Modbus RTU
Q.44 In PLC ladder logic, which instruction is used to create a 'pulse' of a fixed duration?
TON
TOFF
TONP
TOF
Explanation - TONP is the 'Timer On Pulse' instruction, generating a fixed‑duration pulse.
Correct answer is: TONP
Q.45 What is a 'scan time' in a PLC system?
The time it takes for the CPU to reboot
The time between consecutive I/O reads and writes
The time needed to download a program
The duration of a PLC’s power supply cycle
Explanation - Scan time is the period for the PLC to read inputs, execute logic, and write outputs.
Correct answer is: The time between consecutive I/O reads and writes
Q.46 Which type of memory in a PLC is used to store historical data for trending?
RAM
Non‑volatile memory
EEPROM
Internal data block
Explanation - Data blocks in PLCs can hold data for trending and history, often stored in non‑volatile memory.
Correct answer is: Internal data block
Q.47 What does the 'RESET' instruction do in a PLC?
Resets the PLC hardware
Clears a memory location to zero
Starts a timer
Switches to diagnostic mode
Explanation - RESET (or CLR) sets a specified memory bit or register to 0.
Correct answer is: Clears a memory location to zero
Q.48 Which of the following best describes 'soft PLC'?
A PLC that runs on a general‑purpose computer
A PLC that uses solid‑state relays only
A PLC that has no memory
A PLC that only controls lighting
Explanation - Soft PLCs are software programs that emulate PLC behavior on standard PCs.
Correct answer is: A PLC that runs on a general‑purpose computer
Q.49 Which communication standard is widely used for high‑speed Ethernet-based PLC communication?
PROFINET
CAN bus
RS-232
USB
Explanation - PROFINET provides deterministic, high‑speed Ethernet communication for industrial devices.
Correct answer is: PROFINET
Q.50 In a PLC program, what is a 'function block'?
A block of reusable code with inputs and outputs
A block that contains only the main program
A hardware component
A debugging tool
Explanation - Function blocks are modular code units that can be reused, encapsulating logic with defined interfaces.
Correct answer is: A block of reusable code with inputs and outputs
Q.51 Which PLC programming instruction would you use to set an output to ON when a start button is pressed and the motor is OFF?
AND
OR
XIO
LD
Explanation - An AND gate ensures both conditions (start pressed and motor OFF) must be true to energize the motor coil.
Correct answer is: AND
Q.52 What is a key feature of 'field‑bus' technology in PLC systems?
It uses analog signals only
It allows many devices to share a common communication line
It replaces all I/O modules
It requires a dedicated power supply per device
Explanation - Field‑bus networks (e.g., Profibus, DeviceNet) connect many devices over a single bus.
Correct answer is: It allows many devices to share a common communication line
Q.53 Which of the following is a typical safety function in PLC programming?
Emergency stop input
Overcurrent protection
Safety relay integration
All of the above
Explanation - Safety functions include emergency stop, overcurrent, and integration with safety relays.
Correct answer is: All of the above
Q.54 Which memory type in a PLC is used to store the current state of all program counters?
RAM
Flash
EEPROM
ROM
Explanation - RAM holds volatile data such as counters during operation.
Correct answer is: RAM
Q.55 What is the purpose of a 'scan counter' in a PLC?
To count the number of scan cycles performed
To measure temperature
To store program variables
To control motor speed
Explanation - A scan counter increments each scan cycle, useful for diagnostics.
Correct answer is: To count the number of scan cycles performed
Q.56 Which PLC manufacturer introduced the first 'PLC' in the 1960s?
Allen‑Bradley
Siemens
Omron
Rockwell Automation
Explanation - Allen‑Bradley developed the first PLC, the Model 5/05, in the 1960s.
Correct answer is: Allen‑Bradley
Q.57 In a PLC, what is a 'scan delay' used for?
To pause between scan cycles intentionally
To delay input reading
To delay program download
To delay output writing only
Explanation - A scan delay can introduce a deliberate pause between scans for synchronization.
Correct answer is: To pause between scan cycles intentionally
Q.58 Which of the following is a typical disadvantage of using a PLC?
Limited I/O points
Complex programming
High maintenance cost
None of the above
Explanation - PLCs generally have high I/O capability, manageable programming, and low maintenance costs.
Correct answer is: None of the above
Q.59 What does the 'TOF' instruction in PLC logic do?
Timer on first
Timer off function
Timer output fast
Timer off pulse
Explanation - TOF is the timer-off instruction, which starts counting when the input turns off.
Correct answer is: Timer off function
Q.60 In ladder logic, what does a 'contact' represent?
A logical gate
A physical switch
A coil
An output
Explanation - Contacts simulate real switches (normally open or normally closed) in the rung.
Correct answer is: A physical switch
Q.61 Which of the following is a primary benefit of using an Ethernet‑based PLC network?
Deterministic real‑time performance
High bandwidth for large data transfer
Low cost per device
Simple cabling
Explanation - Ethernet provides high data bandwidth and easy integration with IT networks.
Correct answer is: High bandwidth for large data transfer
Q.62 What is the typical maximum number of I/O points for a high‑end PLC with 16 modules?
512
1024
2048
4096
Explanation - With 16 modules each handling up to 256 I/O points, a high‑end PLC can manage up to 4096 points.
Correct answer is: 4096
Q.63 Which of the following PLC programming languages is best suited for complex mathematical calculations?
Instruction List
Structured Text
Ladder Diagram
Function Block Diagram
Explanation - Structured Text is a high‑level language ideal for mathematical operations.
Correct answer is: Structured Text
Q.64 In PLC control, what is a 'dead time'?
The time during which the PLC is not executing the program
The time between input changes and output response
The time the PLC stays idle
The time between power failures
Explanation - Dead time refers to the delay between a change in input and the corresponding output update.
Correct answer is: The time between input changes and output response
Q.65 Which of the following is a common method for PLC fault detection?
Self‑diagnosis routines
Manual inspection
Thermal imaging only
Visual inspection only
Explanation - Modern PLCs incorporate built‑in diagnostics to detect faults automatically.
Correct answer is: Self‑diagnosis routines
Q.66 What is the function of a 'PLC programmer'?
To develop the PLC program
To program the PLC’s firmware
To download the program to the PLC
All of the above
Explanation - A PLC programmer is used to write, edit, compile, and upload code to the PLC.
Correct answer is: All of the above
Q.67 Which PLC communication protocol uses a master‑slaves architecture with a fixed data format?
CANopen
Profinet
Modbus RTU
Ethernet/IP
Explanation - Modbus RTU is a simple master‑slave protocol with a fixed data format.
Correct answer is: Modbus RTU
Q.68 What does 'scan time' determine in a PLC system?
The speed of the CPU
The responsiveness of the controller
The memory capacity
The power consumption
Explanation - A shorter scan time means faster responsiveness.
Correct answer is: The responsiveness of the controller
Q.69 Which of the following is an example of a 'digital input' to a PLC?
Temperature sensor
Pressure transducer
Limit switch
Flow meter
Explanation - A limit switch provides a digital on/off signal.
Correct answer is: Limit switch
Q.70 Which of the following is NOT an advantage of using a PLC over a microcontroller?
Built‑in safety features
Ease of programming
High reliability
Unlimited I/O points
Explanation - While PLCs support many I/O points, there is always a limit based on hardware.
Correct answer is: Unlimited I/O points
Q.71 What is the role of 'communication modules' in a PLC system?
To provide additional I/O
To enable network connectivity
To increase the CPU speed
To serve as backup power
Explanation - Communication modules allow PLCs to connect to networks (Ethernet, CAN, etc.).
Correct answer is: To enable network connectivity
Q.72 Which of the following PLC programming functions is used to implement a 'count up' operation?
COUNTUP
INC
CNTUP
COUNTER
Explanation - CNTUP is an instruction that increments a counter.
Correct answer is: CNTUP
Q.73 In a PLC ladder diagram, what does a 'coil' represent?
A logic condition
An output device
A relay contact
An input device
Explanation - Coils are used to represent outputs in ladder logic.
Correct answer is: An output device
Q.74 Which of the following best describes a 'PLC program backup' strategy?
Storing the program on an external USB drive
Using a redundant PLC with mirrored memory
Both a and b
None of the above
Explanation - Backups can be stored externally or mirrored across redundant PLCs.
Correct answer is: Both a and b
Q.75 Which of the following is a key feature of the IEC 61131‑3 standard?
It defines safety standards for PLCs
It lists PLC hardware specifications
It specifies five programming languages for PLCs
It limits the number of I/O points
Explanation - IEC 61131‑3 covers Ladder Diagram, Structured Text, Function Block Diagram, Instruction List, and Sequential Function Charts.
Correct answer is: It specifies five programming languages for PLCs
Q.76 What does 'HMI' stand for in PLC terminology?
Human‑Machine Interface
Hardware Memory Interface
High‑Speed Motor Input
High‑Modulus Integrator
Explanation - HMI refers to the graphical interface used by operators.
Correct answer is: Human‑Machine Interface
Q.77 What is the purpose of a 'scan loop' in a PLC program?
To repeatedly read inputs, execute logic, and write outputs
To debug the program
To load firmware
To shut down the PLC
Explanation - The scan loop is the fundamental cycle of PLC operation.
Correct answer is: To repeatedly read inputs, execute logic, and write outputs
Q.78 Which of the following is an example of a 'programmable safety controller' (PSC) integrated into a PLC?
Siren
Emergency stop button
Safety relay
All of the above
Explanation - PSCs can monitor emergency stops, safety relays, and other safety inputs.
Correct answer is: All of the above
Q.79 Which PLC communication protocol is often used in automotive manufacturing for real‑time data exchange?
Ethernet/IP
Profinet
Modbus TCP
CAN bus
Explanation - Ethernet/IP offers high‑speed, real‑time communication suitable for automotive environments.
Correct answer is: Ethernet/IP
Q.80 What is the primary function of a 'timer preset' in a PLC?
To specify the delay time before a timer reaches its count
To reset the timer immediately
To display the current time
To load a program
Explanation - The preset sets the desired count value for the timer.
Correct answer is: To specify the delay time before a timer reaches its count
Q.81 Which of the following is a typical application of PLCs in the food and beverage industry?
Controlling conveyor belts
Processing recipes in software
Managing financial transactions
Designing packaging graphics
Explanation - PLCs automate machinery like conveyor belts, mixers, and packaging lines.
Correct answer is: Controlling conveyor belts
Q.82 Which of the following PLC programming tools is used to create graphical HMI screens?
TIA Portal
Step 7
Logix Designer
All of the above
Explanation - Each major PLC vendor provides tools for HMI design: TIA Portal (Siemens), Step 7 (Siemens), Logix Designer (Allen‑Bradley).
Correct answer is: All of the above
Q.83 In PLC ladder logic, which instruction would you use to toggle a coil on each input pulse?
XIO
XIC
TON
TOF
Explanation - TON (Timer On) can be used to generate a pulse, but the toggle function is typically implemented with a 'Toggle' instruction or by using a counter.
Correct answer is: TON
Q.84 Which of the following is an advantage of using a PLC with an 'Ethernet/IP' communication port?
Fast data exchange
High reliability over long distances
Low cost per port
Simplified cabling
Explanation - Ethernet/IP offers high‑speed data exchange suitable for real‑time control.
Correct answer is: Fast data exchange
Q.85 What is the role of the 'CPU' in a PLC?
To store memory
To execute the program
To provide input signals
To supply power
Explanation - The CPU runs the PLC program and manages logic.
Correct answer is: To execute the program
Q.86 Which of the following is NOT a typical PLC diagnostic feature?
Error logs
Fault codes
Live data monitoring
Automatic hardware replacement
Explanation - Diagnostics can report faults but cannot replace hardware automatically.
Correct answer is: Automatic hardware replacement
Q.87 Which of the following PLC programming languages uses a block‑based graphical representation?
Structured Text
Ladder Diagram
Function Block Diagram
Instruction List
Explanation - Function Block Diagram (FBD) uses graphical blocks connected by wires.
Correct answer is: Function Block Diagram
Q.88 What is the purpose of a 'redundant CPU' in a PLC system?
To increase processing speed
To provide backup in case of CPU failure
To reduce power consumption
To expand I/O capacity
Explanation - Redundant CPUs ensure continued operation if one CPU fails.
Correct answer is: To provide backup in case of CPU failure
Q.89 Which of the following best describes 'fieldbus' technology?
A bus connecting PLCs to the internet
A protocol for real‑time data exchange on a common bus
A method to connect sensors to a computer
A software framework for PLC programming
Explanation - Fieldbus enables multiple field devices to communicate over a shared bus.
Correct answer is: A protocol for real‑time data exchange on a common bus
Q.90 Which PLC programming instruction is used to implement a simple 'count up' operation?
CNTU
INCR
CNT
INC
Explanation - The CNT instruction increments a counter when triggered.
Correct answer is: CNT
Q.91 What does the 'TONP' instruction in a PLC do?
Starts a timer that counts while the input is on
Starts a timer that counts when the input is off
Generates a pulse of fixed duration
Resets a timer
Explanation - TONP creates a timer pulse that runs for a preset time.
Correct answer is: Generates a pulse of fixed duration
Q.92 Which of the following is a common way to provide safety functions in a PLC system?
Using dedicated safety I/O modules
Programming a safety routine in the main program
Installing a safety relay
All of the above
Explanation - Safety can be implemented using hardware modules, software routines, or safety relays.
Correct answer is: All of the above
Q.93 In ladder logic, what does an 'XIC' contact represent?
Examine if input is on
Examine if input is off
Set the coil
Reset the coil
Explanation - XIC is a normally open contact that passes current when the input is true.
Correct answer is: Examine if input is on
Q.94 Which PLC communication protocol is based on the IEC 61158 standard and supports real‑time data exchange over Ethernet?
Modbus TCP
Profinet
CANopen
Ethernet/IP
Explanation - Profinet is the IEC 61158‑3 Ethernet standard for industrial automation.
Correct answer is: Profinet
Q.95 What is the function of a 'scan counter' in a PLC program?
Counts the number of cycles completed
Counts the number of inputs
Keeps track of time
Counts the number of outputs
Explanation - The scan counter increments each time the PLC completes a scan cycle.
Correct answer is: Counts the number of cycles completed
Q.96 Which of the following is a typical method for extending the I/O range of a PLC?
Using a larger CPU
Adding I/O expansion modules
Increasing the scan time
Changing the programming language
Explanation - Expansion modules provide additional I/O points.
Correct answer is: Adding I/O expansion modules
Q.97 Which of the following PLC manufacturers is known for the Logix platform?
Siemens
Rockwell Automation
Mitsubishi
Schneider Electric
Explanation - Logix is Rockwell Automation’s PLC platform.
Correct answer is: Rockwell Automation
Q.98 What does 'PLC' stand for in industrial automation?
Programmable Logic Controller
Programmable Light Circuit
Power Load Computer
Printed Logic Converter
Explanation - PLC is a digital controller used to automate industrial processes.
Correct answer is: Programmable Logic Controller
Q.99 Which of the following is an example of an 'analog output' in a PLC?
Solenoid valve
Motor speed controller
Temperature probe
Pressure transmitter
Explanation - An analog output can drive a motor speed controller via voltage or current.
Correct answer is: Motor speed controller
Q.100 Which of the following PLC programming languages uses a graphical representation similar to a electrical circuit diagram?
Structured Text
Instruction List
Ladder Diagram
Sequential Function Charts
Explanation - Ladder Diagram looks like a ladder with rungs and contacts.
Correct answer is: Ladder Diagram
Q.101 What is the main advantage of using a 'distributed PLC' system?
Simpler programming
Reduced cabling distance
Lower cost per I/O point
All of the above
Explanation - Distributed PLCs allow remote I/O, reduce cabling, and can be cost‑effective.
Correct answer is: All of the above
Q.102 Which of the following PLC programming instructions would you use to create a countdown timer?
TON
TOF
TONP
CNT
Explanation - TOF (Timer Off) starts counting when the input turns off, creating a countdown.
Correct answer is: TOF
Q.103 Which of the following is a typical use of a PLC in the pharmaceutical industry?
Mixing chemicals
Processing paperwork
Managing inventory
Designing equipment
Explanation - PLCs control mixing, heating, and filtration processes.
Correct answer is: Mixing chemicals
Q.104 What is the primary purpose of a PLC 'diagnostic port'?
To allow debugging and error detection
To power the PLC
To provide I/O connectivity
To upgrade firmware
Explanation - Diagnostic ports give access to internal status and error codes.
Correct answer is: To allow debugging and error detection
Q.105 Which of the following PLC manufacturers uses the 'Simatic' brand?
Siemens
Mitsubishi
Omron
Allen‑Bradley
Explanation - Siemens Simatic is a family of PLCs.
Correct answer is: Siemens
Q.106 What is the function of a 'memory block' in a PLC program?
To store data variables
To store the program code
To store the firmware
To store I/O addresses
Explanation - Memory blocks hold data values used by the program.
Correct answer is: To store data variables
Q.107 Which of the following is a typical method to increase the reliability of a PLC system?
Use redundant power supplies
Add more I/O modules
Use a faster CPU
All of the above
Explanation - Redundant power supplies reduce the risk of power failure.
Correct answer is: Use redundant power supplies
Q.108 Which PLC communication protocol is commonly used in water treatment plants?
Modbus RTU
CANopen
Ethernet/IP
Profinet
Explanation - Modbus RTU is a simple serial protocol widely used in water treatment.
Correct answer is: Modbus RTU
Q.109 In PLC ladder logic, which instruction is used to create a 'debounce' filter for a button press?
TON
TOF
Rung
XIC
Explanation - TON can be used to debounce by requiring a button to be pressed for a set time.
Correct answer is: TON
Q.110 What is the role of a 'communication module' in a PLC system?
To add more I/O points
To connect the PLC to external networks
To increase CPU speed
To provide power to the PLC
Explanation - Communication modules enable the PLC to communicate over Ethernet, serial, or fieldbus.
Correct answer is: To connect the PLC to external networks
Q.111 Which of the following is an advantage of using a PLC over a traditional relay logic system?
Lower initial cost
Higher reliability
Simpler maintenance
All of the above
Explanation - PLCs typically reduce cost, improve reliability, and simplify maintenance.
Correct answer is: All of the above
Q.112 Which PLC programming instruction is used to implement a 'pulse counter'?
CNT
TON
TOF
XIO
Explanation - CNT counts pulses or events.
Correct answer is: CNT
Q.113 In a PLC system, which of the following is a common method to provide real‑time monitoring of the process?
Using an HMI display
Using a remote desktop
Using a handheld device
All of the above
Explanation - An HMI provides real‑time visualization of PLC data.
Correct answer is: Using an HMI display
Q.114 What does the 'TON' instruction in a PLC do?
Timer On
Timer Off
Timer One
Toggle Output
Explanation - TON starts a timer when the input becomes true.
Correct answer is: Timer On
Q.115 Which of the following is a typical use of a PLC in the automotive industry?
Controlling robotic welders
Processing sales data
Designing car models
Managing corporate HR
Explanation - PLCs automate welding stations and assembly lines.
Correct answer is: Controlling robotic welders
Q.116 Which of the following PLC communication protocols uses a master‑slave architecture with a fixed data format?
Modbus TCP
Ethernet/IP
Profinet
CANopen
Explanation - Modbus TCP is a master‑slave protocol with a simple, fixed data format.
Correct answer is: Modbus TCP
Q.117 Which of the following is a typical application of PLCs in food processing?
Automating conveyor belts
Designing packaging graphics
Managing payroll
Producing coffee beans
Explanation - PLCs control conveyor speeds, feeders, and packaging machinery.
Correct answer is: Automating conveyor belts
Q.118 What is the purpose of a 'reset' instruction in PLC programming?
To stop the PLC
To reset a counter or timer
To start the PLC
To clear all memory
Explanation - The reset instruction clears the value of a counter or timer.
Correct answer is: To reset a counter or timer
Q.119 Which of the following PLC manufacturers produces the 'ControlLogix' series?
Rockwell Automation
Siemens
Mitsubishi
Schneider Electric
Explanation - ControlLogix is a series of PLCs from Rockwell Automation.
Correct answer is: Rockwell Automation
Q.120 What does the 'TOF' instruction in PLC programming do?
Timer Off
Timer On First
Toggle Output Fast
Timer Output Function
Explanation - TOF counts while the input is false; it’s a countdown timer.
Correct answer is: Timer Off
Q.121 Which of the following is an example of an analog sensor input to a PLC?
Limit switch
Temperature sensor
Proximity sensor
Light switch
Explanation - A temperature sensor outputs an analog voltage or current.
Correct answer is: Temperature sensor
Q.122 Which of the following PLC programming languages is text‑based and resembles a high‑level language?
Ladder Diagram
Structured Text
Instruction List
Function Block Diagram
Explanation - Structured Text is a high‑level text language for PLCs.
Correct answer is: Structured Text
Q.123 Which of the following is a typical advantage of using a PLC over a microcontroller?
Higher reliability
Simpler programming
Built‑in safety features
All of the above
Explanation - PLCs offer reliability, easier programming, and integrated safety features.
Correct answer is: All of the above
Q.124 Which of the following PLC programming instructions is used to set a bit to '1'?
ST
LD
XIC
XIO
Explanation - ST (Store) writes a value to memory, setting a bit to 1.
Correct answer is: ST
Q.125 Which of the following is a typical use of PLCs in the oil and gas industry?
Automating valve control
Managing HR records
Designing pipelines
Producing marketing materials
Explanation - PLCs control valves, pumps, and safety interlocks in pipelines.
Correct answer is: Automating valve control
Q.126 Which of the following PLC components provides real‑time data access to a PC?
Ethernet/IP module
USB port
Serial port
All of the above
Explanation - Ethernet/IP, USB, and serial ports all allow data exchange with PCs.
Correct answer is: All of the above
Q.127 What does the 'XIC' instruction in ladder logic mean?
Examine If Condition
Examine if Input on
Examine if Input off
Execute If Condition
Explanation - XIC checks if an input is true.
Correct answer is: Examine if Input on
Q.128 What is the typical use of a 'scan counter' in a PLC program?
To count the number of times a particular event occurs
To count the number of scan cycles completed
To keep track of time in seconds
To measure temperature
Explanation - The scan counter increments each scan cycle.
Correct answer is: To count the number of scan cycles completed
Q.129 Which of the following PLC programming languages uses a text‑based syntax similar to Pascal?
Structured Text
Ladder Diagram
Instruction List
Function Block Diagram
Explanation - Structured Text resembles Pascal and C‑like syntax.
Correct answer is: Structured Text
Q.130 Which PLC communication protocol uses a 1000‑byte cyclic data exchange with low latency?
Modbus TCP
Ethernet/IP
Profinet
CANopen
Explanation - Ethernet/IP supports cyclic data exchange with low latency.
Correct answer is: Ethernet/IP
Q.131 What does the 'TONP' instruction in a PLC do?
Timer On Pulse
Timer On with Preset
Timer Off Pulse
Timer One Pulse
Explanation - TONP generates a pulse of a defined duration.
Correct answer is: Timer On Pulse
Q.132 What is the main advantage of using a PLC for controlling a conveyor system?
It reduces mechanical wear
It allows precise control of speed and stopping
It increases power consumption
It eliminates the need for sensors
Explanation - PLCs enable fine control of conveyor operations.
Correct answer is: It allows precise control of speed and stopping
Q.133 Which of the following PLC manufacturers uses the 'CompactLogix' series?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - CompactLogix is a compact PLC family from Rockwell.
Correct answer is: Rockwell Automation
Q.134 Which of the following PLC programming instructions is used to toggle an output on each trigger?
TON
TOF
Toggle
XIC
Explanation - The Toggle instruction flips the state of an output each time the rung is executed.
Correct answer is: Toggle
Q.135 What is the role of a 'diagnostic port' in a PLC?
To allow troubleshooting and monitoring
To provide power
To connect sensors
To upgrade firmware
Explanation - A diagnostic port gives access to internal status for troubleshooting.
Correct answer is: To allow troubleshooting and monitoring
Q.136 Which of the following is a typical use of PLCs in the chemical industry?
Automated tank level control
Designing chemical molecules
Marketing research
Customer support
Explanation - PLCs control valves and pumps to maintain tank levels.
Correct answer is: Automated tank level control
Q.137 What does the 'TON' instruction in ladder logic stand for?
Timer On
Timer Off
Timer One
Timed Output Normal
Explanation - TON is the Timer On instruction used to start a timer.
Correct answer is: Timer On
Q.138 Which of the following PLC manufacturers uses the 'MicroLogix' line?
Rockwell Automation
Siemens
Mitsubishi
Schneider Electric
Explanation - MicroLogix is a line of compact PLCs from Rockwell.
Correct answer is: Rockwell Automation
Q.139 In PLC ladder logic, what does a 'XIO' contact represent?
Examine if input off
Examine if input on
Set output
Reset output
Explanation - XIO is a normally closed contact that passes current when the input is false.
Correct answer is: Examine if input off
Q.140 Which PLC communication protocol is based on the CAN bus standard?
CANopen
Modbus RTU
Ethernet/IP
Profinet
Explanation - CANopen uses the CAN bus for communication.
Correct answer is: CANopen
Q.141 What is the typical advantage of using 'Profinet' for PLC communication?
High data bandwidth
Simple wiring
Low latency
All of the above
Explanation - Profinet supports high bandwidth, low latency, and standard Ethernet wiring.
Correct answer is: All of the above
Q.142 Which of the following PLC components stores the operating system and firmware?
CPU
ROM
RAM
I/O module
Explanation - ROM contains the firmware and operating system.
Correct answer is: ROM
Q.143 Which of the following is a typical use of PLCs in the paper manufacturing industry?
Controlling paper machine speed
Designing paper patterns
Managing sales
Producing office stationery
Explanation - PLCs manage conveyor belts, rollers, and machine speeds.
Correct answer is: Controlling paper machine speed
Q.144 What does the 'RUNG' instruction in a PLC program represent?
A line of code that executes on each scan
A memory block
An input device
An output device
Explanation - A rung is a logical chain that executes during each scan cycle.
Correct answer is: A line of code that executes on each scan
Q.145 Which PLC manufacturer uses the 'S7' series?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - The S7 series is from Siemens.
Correct answer is: Siemens
Q.146 Which of the following PLC programming instructions is used to implement a 'reset' operation?
RESET
CLR
XIO
XIC
Explanation - CLR clears a bit or register in PLC logic.
Correct answer is: CLR
Q.147 Which PLC communication protocol uses a master‑slave architecture with a serial interface?
Modbus RTU
Ethernet/IP
Profinet
CANopen
Explanation - Modbus RTU is a serial master‑slave protocol.
Correct answer is: Modbus RTU
Q.148 What is the purpose of a 'diagnostic port' on a PLC?
To debug and monitor status
To provide power
To connect I/O devices
To upgrade firmware
Explanation - A diagnostic port gives access to status and error codes.
Correct answer is: To debug and monitor status
Q.149 Which of the following PLC components is responsible for converting signals from sensors into digital form?
I/O module
CPU
Memory
Power supply
Explanation - I/O modules convert analog/digital signals for the CPU.
Correct answer is: I/O module
Q.150 What is the role of a 'scan counter' in a PLC program?
To count the number of scans performed
To count the number of inputs processed
To keep track of time
To measure output voltage
Explanation - The scan counter increments each time a scan completes.
Correct answer is: To count the number of scans performed
Q.151 Which of the following PLC manufacturers uses the 'Simatic S7-1200' series?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - Simatic S7-1200 is a Siemens PLC line.
Correct answer is: Siemens
Q.152 Which of the following PLC programming instructions is used to clear a counter?
RESET
CLEAR
CLR
RUNG
Explanation - The CLR instruction clears a counter or timer.
Correct answer is: CLR
Q.153 What does 'HMI' stand for in industrial automation?
Human‑Machine Interface
High‑speed Motor Input
Hardware Memory Interface
Hot‑Machine Identifier
Explanation - HMI refers to the interface between a human operator and a machine.
Correct answer is: Human‑Machine Interface
Q.154 Which of the following PLC communication protocols is often used in the building automation industry?
BACnet
Modbus
Ethernet/IP
CANopen
Explanation - BACnet is a standard for building automation and control networks.
Correct answer is: BACnet
Q.155 In PLC ladder logic, which instruction is used to set a bit to '0'?
RST
CLR
SET
ST
Explanation - CLR clears a bit or memory location.
Correct answer is: CLR
Q.156 Which of the following PLC manufacturers produces the 'CompactLogix 5000' series?
Rockwell Automation
Siemens
Mitsubishi
Schneider Electric
Explanation - CompactLogix 5000 is a Rockwell Automation PLC series.
Correct answer is: Rockwell Automation
Q.157 What does the 'TON' instruction in ladder logic do?
Timer On
Timer Off
Toggle Output
Set Output Normal
Explanation - TON starts a timer when the rung condition becomes true.
Correct answer is: Timer On
Q.158 Which PLC component provides the ability to read analog sensor signals?
Analog input module
Digital input module
Relay module
Power supply
Explanation - Analog input modules convert analog signals to digital values for the PLC.
Correct answer is: Analog input module
Q.159 What is the primary function of a PLC timer?
To count pulses
To introduce time delays
To store data
To provide power
Explanation - Timers generate delays or measure time intervals in PLC programs.
Correct answer is: To introduce time delays
Q.160 Which of the following PLC programming languages uses a block diagram style similar to electrical schematics?
Ladder Diagram
Function Block Diagram
Structured Text
Instruction List
Explanation - Function Block Diagram uses graphical blocks connected by wires.
Correct answer is: Function Block Diagram
Q.161 Which PLC communication protocol is commonly used for high‑speed real‑time control in the automotive sector?
Ethernet/IP
Modbus TCP
CANopen
Profinet
Explanation - Ethernet/IP offers low‑latency, real‑time communication.
Correct answer is: Ethernet/IP
Q.162 What does the 'TONP' instruction in a PLC do?
Timer On Pulse
Timer Off Pulse
Timer One Pulse
Timed Output Pulse
Explanation - TONP creates a pulse of a defined duration when triggered.
Correct answer is: Timer On Pulse
Q.163 Which of the following PLC manufacturers uses the 'Logix 5000' series?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - Logix 5000 is a Rockwell PLC family.
Correct answer is: Rockwell Automation
Q.164 Which PLC programming instruction is used to create a simple 'counter up' operation?
CNT
TON
TOF
XIO
Explanation - CNT increments a counter on each trigger event.
Correct answer is: CNT
Q.165 What does the 'RUNG' instruction in ladder logic represent?
A line of code that executes during a scan cycle
A memory block
An input device
An output device
Explanation - Each rung is a logical path in the ladder diagram.
Correct answer is: A line of code that executes during a scan cycle
Q.166 Which of the following is an advantage of using 'Ethernet/IP' for PLC communication?
Low latency
High bandwidth
Standard networking equipment
All of the above
Explanation - Ethernet/IP offers low latency, high bandwidth, and uses standard Ethernet equipment.
Correct answer is: All of the above
Q.167 Which PLC component provides a backup CPU for redundant operation?
Dual CPU module
I/O module
Power supply
HMI
Explanation - A dual CPU module provides redundancy for fault‑tolerant control.
Correct answer is: Dual CPU module
Q.168 What does the 'TON' instruction in a PLC do?
Start a timer when the input is true
Stop a timer when the input is false
Toggle an output
Reset a counter
Explanation - TON begins timing when the input condition is met.
Correct answer is: Start a timer when the input is true
Q.169 Which PLC manufacturer uses the 'CompactLogix 6000' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - CompactLogix 6000 is a Rockwell Automation product.
Correct answer is: Rockwell Automation
Q.170 Which of the following PLC programming instructions is used to set a bit to '1'?
ST
LD
XIC
XIO
Explanation - ST stores a value into memory, setting a bit to 1.
Correct answer is: ST
Q.171 In PLC ladder logic, which instruction is used to create a 'pulse counter'?
CNT
TON
TOF
XIO
Explanation - CNT counts the number of pulses or events.
Correct answer is: CNT
Q.172 Which of the following PLC manufacturers uses the 'Simatic S7-1500' series?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - Simatic S7-1500 is a Siemens PLC series.
Correct answer is: Siemens
Q.173 What is the primary advantage of using a PLC in a process control application?
Simpler wiring
Easier maintenance
Increased reliability
All of the above
Explanation - PLCs reduce wiring complexity, simplify maintenance, and enhance reliability.
Correct answer is: All of the above
Q.174 Which PLC programming instruction is used to reset a counter to zero?
CLR
RESET
RST
XIC
Explanation - CLR clears a counter or memory location to zero.
Correct answer is: CLR
Q.175 What does the 'RUNG' instruction in ladder logic represent?
A single logical path
A memory block
An input device
An output device
Explanation - Each rung is a logical chain that executes during each scan.
Correct answer is: A single logical path
Q.176 Which of the following PLC manufacturers uses the 'CompactLogix 5500' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - CompactLogix 5500 is a Rockwell PLC series.
Correct answer is: Rockwell Automation
Q.177 Which PLC communication protocol is known for its use in PLC‑to‑PLC networking and has a 100‑meter cable limit?
Ethernet/IP
Modbus RTU
PROFINET
CANopen
Explanation - Modbus RTU is a serial protocol with a typical 100‑meter limit.
Correct answer is: Modbus RTU
Q.178 In PLC ladder logic, what is the function of the 'XIC' contact?
Check if input is on
Check if input is off
Set output to 1
Reset output to 0
Explanation - XIC passes current if the input is true.
Correct answer is: Check if input is on
Q.179 What is the main purpose of a 'scan counter' in a PLC program?
Count the number of scan cycles
Count the number of inputs processed
Measure time in seconds
Measure temperature
Explanation - The scan counter increments each time a full scan cycle occurs.
Correct answer is: Count the number of scan cycles
Q.180 Which of the following PLC manufacturers uses the 'MicroLogix 1000' series?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - MicroLogix 1000 is a Rockwell Automation PLC.
Correct answer is: Rockwell Automation
Q.181 What does the 'TONP' instruction in PLC logic do?
Timer On Pulse
Timer On with Preset
Timer Off Pulse
Timed Output Pulse
Explanation - TONP generates a pulse of a specific duration.
Correct answer is: Timer On Pulse
Q.182 Which of the following PLC components provides a backup CPU in a dual‑CPU configuration?
Dual CPU module
I/O module
Power supply
HMI
Explanation - A dual CPU module provides redundancy for continuous operation.
Correct answer is: Dual CPU module
Q.183 Which of the following PLC manufacturers uses the 'CompactLogix 7000' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - CompactLogix 7000 is a Rockwell PLC family.
Correct answer is: Rockwell Automation
Q.184 In PLC ladder logic, which instruction sets a bit to 0?
CLR
SET
ST
LD
Explanation - CLR clears a bit or memory location.
Correct answer is: CLR
Q.185 What is the role of a 'communication module' in a PLC system?
Connect the PLC to external networks
Expand the I/O capacity
Provide power to the PLC
Store the PLC program
Explanation - Communication modules enable network connectivity.
Correct answer is: Connect the PLC to external networks
Q.186 Which of the following PLC manufacturers uses the 'S7-400' series?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - Simatic S7-400 is a Siemens PLC line.
Correct answer is: Siemens
Q.187 Which PLC programming instruction is used to generate a pulse of a fixed duration?
TONP
TOF
CNT
XIO
Explanation - TONP creates a timed pulse.
Correct answer is: TONP
Q.188 Which PLC communication protocol is used for high‑speed industrial Ethernet networking?
Ethernet/IP
Modbus TCP
CANopen
Profinet
Explanation - Ethernet/IP is designed for high‑speed industrial networks.
Correct answer is: Ethernet/IP
Q.189 What does the 'XIO' instruction in ladder logic do?
Examine if input is off
Examine if input is on
Set output to 1
Reset output to 0
Explanation - XIO passes current when the input is false.
Correct answer is: Examine if input is off
Q.190 What is a typical use of PLCs in the mining industry?
Automating conveyor belt speed
Managing payroll
Designing mining equipment
Producing marketing materials
Explanation - PLCs control conveyors, crushers, and safety interlocks.
Correct answer is: Automating conveyor belt speed
Q.191 Which PLC manufacturer uses the 'CompactLogix 4000' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - CompactLogix 4000 is a Rockwell product.
Correct answer is: Rockwell Automation
Q.192 Which PLC instruction is used to increment a counter?
CNT
TON
TOF
XIO
Explanation - CNT increments a counter each time it is triggered.
Correct answer is: CNT
Q.193 What does the 'RUNG' instruction in ladder logic represent?
A single logical path in the ladder diagram
A memory block
An input device
An output device
Explanation - Each rung is a logical chain executed during a scan.
Correct answer is: A single logical path in the ladder diagram
Q.194 Which PLC manufacturer uses the 'MicroLogix 1100' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - MicroLogix 1100 is a Rockwell Automation PLC.
Correct answer is: Rockwell Automation
Q.195 What is the main advantage of using a PLC in a high‑volume production environment?
Reduced wiring
Easier troubleshooting
Higher reliability
All of the above
Explanation - PLCs simplify wiring, allow easy troubleshooting, and increase reliability.
Correct answer is: All of the above
Q.196 Which PLC manufacturer uses the 'Simatic S7-1200' series?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - Simatic S7-1200 is a Siemens PLC line.
Correct answer is: Siemens
Q.197 Which PLC instruction is used to set a bit to '1'?
ST
LD
XIC
XIO
Explanation - ST writes a value to memory, setting a bit to 1.
Correct answer is: ST
Q.198 In PLC ladder logic, which instruction is used to reset a counter to zero?
CLR
RST
RESET
XIO
Explanation - CLR clears a counter or timer to zero.
Correct answer is: CLR
Q.199 Which PLC manufacturer uses the 'CompactLogix 9000' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - CompactLogix 9000 is a Rockwell PLC family.
Correct answer is: Rockwell Automation
Q.200 What does the 'TON' instruction in PLC programming stand for?
Timer On
Timer Off
Timed Output
Toggle On
Explanation - TON starts a timer when the rung condition becomes true.
Correct answer is: Timer On
Q.201 What is the primary function of a PLC timer?
To create time delays
To store data
To convert analog signals
To provide power
Explanation - Timers generate delays or measure time intervals in PLC programs.
Correct answer is: To create time delays
Q.202 Which PLC manufacturer uses the 'Simatic S7-400' series?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - Simatic S7-400 is a Siemens PLC family.
Correct answer is: Siemens
Q.203 What does the 'XIC' instruction in ladder logic do?
Check if input is on
Check if input is off
Set output to 1
Reset output to 0
Explanation - XIC passes current if the input is true.
Correct answer is: Check if input is on
Q.204 Which PLC communication protocol is best suited for low‑speed serial communication?
Modbus RTU
Ethernet/IP
Profinet
CANopen
Explanation - Modbus RTU is a low‑speed serial protocol.
Correct answer is: Modbus RTU
Q.205 Which PLC manufacturer uses the 'CompactLogix 7000' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - CompactLogix 7000 is a Rockwell Automation product.
Correct answer is: Rockwell Automation
Q.206 What is the main benefit of using a PLC in an automation system?
Reduced wiring complexity
Simplified maintenance
Improved reliability
All of the above
Explanation - PLCs reduce wiring, simplify maintenance, and improve reliability.
Correct answer is: All of the above
Q.207 Which of the following PLC manufacturers uses the 'MicroLogix 1200' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - MicroLogix 1200 is a Rockwell PLC.
Correct answer is: Rockwell Automation
Q.208 In PLC ladder logic, which instruction is used to generate a pulse when an input condition becomes true?
TONP
TOF
CNT
XIO
Explanation - TONP generates a pulse of specified duration when triggered.
Correct answer is: TONP
Q.209 Which PLC communication protocol uses a master‑slave architecture over Ethernet?
Ethernet/IP
Modbus TCP
Profinet
CANopen
Explanation - Ethernet/IP uses a master‑slave model over Ethernet.
Correct answer is: Ethernet/IP
Q.210 What does the 'RUNG' instruction represent in ladder logic?
A logical chain executed each scan
A memory block
An input device
An output device
Explanation - Rungs are executed during each scan cycle.
Correct answer is: A logical chain executed each scan
Q.211 Which of the following PLC manufacturers uses the 'S7-300' series?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - Simatic S7-300 is a Siemens PLC line.
Correct answer is: Siemens
Q.212 What is the purpose of a 'diagnostic port' on a PLC?
To allow troubleshooting and monitoring
To provide power
To connect I/O devices
To upgrade firmware
Explanation - Diagnostic ports provide status and error codes for debugging.
Correct answer is: To allow troubleshooting and monitoring
Q.213 Which PLC manufacturer uses the 'CompactLogix 9000' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - CompactLogix 9000 is a Rockwell Automation product.
Correct answer is: Rockwell Automation
Q.214 Which PLC communication protocol is commonly used in building automation for HVAC control?
BACnet
Modbus TCP
Ethernet/IP
CANopen
Explanation - BACnet is the standard for building automation networks.
Correct answer is: BACnet
Q.215 What does the 'TON' instruction in ladder logic do?
Start a timer when the input is true
Stop a timer when the input is false
Toggle an output
Reset a counter
Explanation - TON initiates timing when the condition is satisfied.
Correct answer is: Start a timer when the input is true
Q.216 Which PLC manufacturer uses the 'Simatic S7-200' line?
Siemens
Rockwell Automation
Mitsubishi
Omron
Explanation - Simatic S7-200 is a Siemens PLC family.
Correct answer is: Siemens
Q.217 In PLC ladder logic, what does the 'XIO' contact represent?
Examine if input is off
Examine if input is on
Set output to 1
Reset output to 0
Explanation - XIO is a normally closed contact that passes current when the input is false.
Correct answer is: Examine if input is off
Q.218 What is the main advantage of using a PLC in a manufacturing line?
Reduced wiring
Simplified troubleshooting
Improved reliability
All of the above
Explanation - PLCs reduce wiring, simplify troubleshooting, and improve reliability.
Correct answer is: All of the above
Q.219 Which PLC manufacturer uses the 'CompactLogix 4000' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - CompactLogix 4000 is a Rockwell PLC family.
Correct answer is: Rockwell Automation
Q.220 What is a typical use of PLCs in the chemical processing industry?
Control temperature and pressure
Design chemical molecules
Manage payroll
Produce marketing materials
Explanation - PLCs manage valves, pumps, and temperature/pressure control loops.
Correct answer is: Control temperature and pressure
Q.221 Which PLC manufacturer uses the 'MicroLogix 7000' line?
Rockwell Automation
Siemens
Mitsubishi
Omron
Explanation - MicroLogix 7000 is a Rockwell PLC family.
Correct answer is: Rockwell Automation