Programmable Logic Controller (PLC) Technician Certification Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf
- Which component stores the user program in a PLC?
- Input module
- Output module
- Memory module
- Power supply
Answer: C
Memory modules contain program instructions and data used during PLC operation.
- What is the primary function of a PLC scan cycle?
- Convert analog to digital signals
- Read inputs, execute logic, update outputs 1 / 4
- Power the CPU
- Store backup data
Answer: B
The PLC scan cycle sequentially processes inputs, logic, and outputs each cycle.
- Which logic state does a normally open (NO) input represent when
- Logic 0
- Floating
- Logic 1
- Undefined
activated?
Answer: C
NO contacts close when energized, producing a logic high (1).
- Ladder logic was originally modeled after what system?
- Computer networks
- Relay control circuits
- Hydraulic diagrams
- HVAC schematics
Answer: B
Ladder diagrams replicate relay-based industrial control drawings.
- Which PLC component performs arithmetic operations? 2 / 4
- Power supply
- I/O chassis
- CPU/processor
- Terminal block
Answer: C
The CPU executes user logic and handles math, comparisons, and control functions.
- What type of instruction is used to hold an output energized after input
- Timer
- Counter
- Sequencer
- Latch
removal?
Answer: D
Latch instructions maintain output states without continuous input conditions.
- What is the purpose of a watchdog timer in a PLC?
- Save memory
- Monitor scan time to ensure proper CPU operation
- Control analog outputs
- Verify feedback loops
Answer: B
A watchdog timer resets or faults the PLC if scan time exceeds limits. 3 / 4
- An analog input module converts signals into what form?
A. PWM
- Relay signals
- Digital values
- AC voltages
Answer: C
Analog modules change continuous signals into digital data for CPU use.
- Which of the following is a discrete PLC input?
- 4–20 mA
B. 0–10 V
- 24 VDC on/off signal
D. 1–5 V
Answer: C
Discrete inputs detect only two states: ON or OFF.
10. A timer that accumulates only while its input stays true is called:
A. TOF
B. RTO
C. TON
D. PTO
Answer: C
The TON instruction counts upward while input conditions remain energized.
- / 4