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Programmable Logic Controller (PLC) Technician Certification Practice Exam Questions And, Exams of Engineering

Chamberlain College of NursingEngineering

Programmable Logic Controller (PLC) Technician Certification Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

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2025/2026

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Programmable Logic Controller (PLC)
Technician Certification Practice Exam
Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary function of a PLC in an industrial system?
A. Human–machine communication
B. Control of machines and processes
C. Data storage only
D. Power distribution
PLCs are designed to monitor inputs and control outputs to
automate machines and processes.
2. Which PLC component executes the user program?
A. Power supply
B. Input module
C. CPU
D. Output module
The CPU scans inputs, executes logic, and updates outputs.
3. What type of input device provides an on/off signal?
A. Thermocouple
B. Analog pressure sensor
C. Limit switch
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Download Programmable Logic Controller (PLC) Technician Certification Practice Exam Questions And and more Exams Engineering in PDF only on Docsity!

Programmable Logic Controller (PLC)

Technician Certification Practice Exam

Questions And Correct Answers (Verified

Answers) Plus Rationales 2026 Q&A | Instant

Download Pdf

  1. What is the primary function of a PLC in an industrial system? A. Human–machine communication B. Control of machines and processes C. Data storage only D. Power distribution PLCs are designed to monitor inputs and control outputs to automate machines and processes.
  2. Which PLC component executes the user program? A. Power supply B. Input module C. CPU D. Output module The CPU scans inputs, executes logic, and updates outputs.
  3. What type of input device provides an on/off signal? A. Thermocouple B. Analog pressure sensor C. Limit switch

D. RTD

Limit switches provide discrete (digital) signals.

  1. Which voltage level is commonly used for PLC digital inputs? A. 5 VDC B. 24 VDC C. 120 VDC only D. 480 VAC 24 VDC is standard for industrial control inputs.
  2. What does an output module do? A. Reads sensor signals B. Stores programs C. Controls external devices D. Converts AC to DC Output modules energize actuators like relays, solenoids, or motors.
  3. Which programming language is most common for PLCs? A. Python B. C++ C. Ladder Logic D. Java Ladder Logic resembles relay control diagrams and is widely used.
  4. A normally open contact in Ladder Logic conducts when: A. The rung is false B. The associated bit is true C. Power is removed D. The PLC is in program mode Normally open contacts close when their bit is energized.
  1. What does an HMI provide? A. Motor control B. Power conditioning C. Operator interface D. Safety interlocking HMIs allow operators to monitor and control processes.
  2. Which PLC mode allows editing the program? A. Run B. Fault C. Program D. Test only Program mode permits changes to logic.
  3. What is the function of a relay output? A. Measure voltage B. Store logic C. Switch higher loads using isolation D. Convert signals Relay outputs isolate PLC electronics from load circuits.
  4. What symbol represents a coil in Ladder Logic? A. Parallel lines B. Parentheses C. Triangle D. Square Coils are shown as parentheses at the end of a rung.
  5. What does a timer do in a PLC? A. Counts parts B. Measures elapsed time

C. Scales analog signals D. Stores recipes Timers delay or measure time-based events.

  1. Which timer activates after a preset delay? A. Retentive timer B. On-delay timer C. Off-delay timer D. High-speed timer On-delay timers energize after the set time expires.
  2. What is a counter used for? A. Measuring temperature B. Timing events C. Counting occurrences D. Power conversion Counters increment or decrement based on events.
  3. What does a normally closed contact do when its bit is true? A. Conducts B. Opens C. Latches D. Resets Normally closed contacts open when energized.
  4. Which communication protocol is common for PLC networks? A. HDMI B. USB only C. Ethernet/IP
  1. Which document shows PLC wiring connections? A. Flowchart B. Electrical schematic C. Ladder diagram D. Block diagram Schematics detail wiring and terminal connections.
  2. What is the purpose of a seal-in circuit? A. Reset outputs B. Maintain an output after a momentary input C. Measure current D. Count cycles Seal-in circuits latch outputs.
  3. Which input device detects fluid level? A. Encoder B. Float switch C. Relay D. Contactor Float switches change state with liquid level.
  4. What does I/O stand for? A. Internal operation B. Input/Output C. Interface option D. Integrated operation I/O refers to field signals to and from the PLC.
  5. What is a PLC rack used for? A. Cooling B. Mounting modules and providing backplane communication

C. Programming D. Power generation Racks house modules and connect them electrically.

  1. Which fault is caused by shorted field wiring? A. Logic error B. Overcurrent fault C. Memory fault D. Scan fault Shorts draw excessive current.
  2. What is the function of a power supply module? A. Execute logic B. Convert AC to regulated DC C. Count pulses D. Communicate data Power supplies provide stable DC power.
  3. Which PLC addressing identifies an input? A. O:0/ B. I:0/ C. T4: D. C5: Input addresses begin with I.
  4. What does retentive memory do? A. Clears on power loss B. Retains values when power is removed C. Stores only logic D. Increases speed Retentive data is preserved.

C. Thermocouple D. Unshielded analog Discrete signals with shielding resist noise.

  1. What is the purpose of simulation mode? A. Run motors B. Test logic without field devices C. Increase speed D. Load firmware Simulation verifies programs safely.
  2. Which safety device stops motion immediately? A. Selector switch B. Emergency stop C. Pilot light D. Proximity sensor E-stops remove power quickly.
  3. What is a proximity sensor used for? A. Measure temperature B. Detect object presence without contact C. Count time D. Regulate voltage Proximity sensors detect nearby objects.
  4. Which PLC instruction stores a value? A. Compare B. Move (MOV) C. Jump D. Clear MOV transfers data between registers.
  1. What does a latch instruction do? A. Turns off outputs B. Holds a bit on until reset C. Counts pulses D. Times delays Latches maintain state.
  2. Which device isolates PLC from high voltage? A. Encoder B. Optocoupler C. Resistor D. Inductor Optocouplers provide electrical isolation.
  3. What is the role of a backplane? A. Cooling B. Communication between modules C. Power storage D. Programming interface The backplane links modules.
  4. Which fault is caused by incorrect logic? A. Hardware short B. Programming error C. Power surge D. Ground fault Logic errors stem from code issues.
  5. What does an off-delay timer do? A. Delays turning on B. Delays turning off
  1. Which sensor detects metal objects? A. Capacitive B. Inductive C. Optical D. Ultrasonic Inductive sensors respond to metal.
  2. What does a normally open pushbutton do when pressed? A. Opens circuit B. Closes circuit C. Latches output D. Resets timer Pressing closes the contact.
  3. Which PLC data type stores whole numbers? A. Float B. Integer C. Boolean only D. String Integers store whole-number values.
  4. What causes electrical noise in control panels? A. Low voltage B. Motors and switching devices C. Documentation D. Proper grounding Switching loads generate interference.
  5. What is the main benefit of modular PLCs? A. Fixed I/O B. Expandability

C. No wiring D. No programming Modules can be added as needed.

  1. Which instruction compares two values? A. MOV B. CMP C. TON D. RES Compare instructions evaluate conditions.
  2. What is a photoelectric sensor? A. Temperature sensor B. Light-based detection device C. Pressure switch D. Relay Photoelectric sensors use light beams.
  3. Which PLC output is best for high-speed switching? A. Relay B. Transistor C. Mechanical contactor D. Manual switch Transistor outputs switch quickly.
  4. What does redundancy improve? A. Cost B. Reliability C. Programming time D. Noise Redundancy ensures continued operation.

C. Sensor accuracy D. Motor speed Firmware manages internal operations.

  1. Which device converts AC motor speed? A. Relay B. VFD C. Contactor D. Transformer VFDs vary motor frequency.
  2. What is a setpoint? A. Input address B. Desired value for control C. Fault code D. Memory limit Setpoints define targets.
  3. Which PLC instruction resets a counter? A. CTU B. RES C. TON D. MOV RES clears accumulated values.
  4. What is an advantage of solid-state outputs? A. Mechanical wear B. Long life and fast response C. High noise D. Manual operation Solid-state devices lack moving parts.
  1. Which device measures temperature accurately in industry? A. Limit switch B. RTD C. Relay D. Encoder RTDs provide precise temperature readings.
  2. What is the purpose of labeling wires? A. Decoration B. Ease of troubleshooting C. Increase voltage D. Reduce current Labels identify circuits quickly.
  3. Which PLC function block controls continuous processes? A. Counter B. PID C. Latch D. Jump PID regulates variables smoothly.
  4. What does a grounding fault indicate? A. Open circuit B. Unintended connection to ground C. Logic error D. Program loss Ground faults pose safety risks.
  5. Which PLC mode allows monitoring without changes? A. Program B. Run

D. Sensor Transformers change voltage levels.

  1. What is a normally closed contact at rest? A. Open B. Closed C. Latched D. Timed NC contacts conduct until energized.
  2. Which PLC component dissipates heat? A. Input card B. Cooling fan or heat sink C. Programming cable D. Label Cooling prevents overheating.
  3. What does commissioning involve? A. Buying equipment B. Testing and verifying system operation C. Writing manuals D. Removing wiring Commissioning ensures proper function.
  4. Which signal is least affected by distance? A. Voltage analog B. Current analog (4–20 mA) C. Digital unshielded D. Thermocouple Current loops resist voltage drop.
  1. What is a PLC tag? A. Physical label B. Named variable in the program C. Output device D. Network cable Tags identify data points.
  2. Which fault requires immediate shutdown? A. Minor logic warning B. Safety circuit fault C. Documentation error D. Network delay Safety faults demand prompt action.
  3. What is the role of preventive maintenance? A. Increase downtime B. Reduce failures C. Eliminate training D. Increase noise Maintenance improves reliability.
  4. Which device converts mechanical motion to pulses? A. Solenoid B. Encoder C. Relay D. Switch Encoders provide motion feedback.
  5. What does a PLC input filter do? A. Amplify signal B. Reduce noise and bounce