Download C 207 Programmable Controller Systems 1 Practice Exam and more Exams Technology in PDF only on Docsity!
Exam
Question 1. What is the primary function of a Programmable Logic Controller (PLC) in industrial automation? A) Data storage B) Sequential control C) Network monitoring D) File management Answer: B Explanation: PLCs are designed mainly for sequential control of machines and processes in industrial automation. Question 2. Which device did PLCs primarily replace in industrial control systems? A) Microcontrollers B) Electromechanical relays C) Personal computers D) SCADA systems Answer: B Explanation: PLCs replaced electromechanical relays, offering greater flexibility and reliability. Question 3. What is a major advantage of PLCs over traditional relay control systems? A) Increased wiring complexity B) Reduced troubleshooting time C) Higher power consumption D) Slower response time
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Explanation: PLCs simplify troubleshooting due to their diagnostic features and organized logic. Question 4. Which component of a PLC is responsible for executing control logic? A) Power Supply B) Central Processing Unit (CPU) C) Input Module D) Output Module Answer: B Explanation: The CPU processes and executes the control program logic. Question 5. What does the memory system in a PLC store? A) Only input data B) Program logic and data values C) Only output data D) Network configurations Answer: B Explanation: PLC memory stores the user program, data, and sometimes the operating system. Question 6. Which of the following best describes the function of the PLC’s Input/Output section? A) Provides power to the CPU B) Interfaces with field devices C) Stores user program D) Monitors network traffic
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Explanation: It’s the interface for programming and monitoring PLC operations. Question 10. In PLC terminology, what is a “sinking” input module? A) Provides voltage to external devices B) Accepts current from external devices C) Requires AC input only D) Only works with analog signals Answer: B Explanation: Sinking modules accept current from field devices, completing the circuit to 0V. Question 11. Which output type offers the fastest switching speed in PLCs? A) Relay B) Transistor (solid-state) C) TRIAC D) Mechanical switch Answer: B Explanation: Transistor outputs are solid-state and switch rapidly compared to relays. Question 12. What is a TRIAC output module typically used for? A) Switching DC loads B) Controlling AC loads C) Providing analog outputs D) Data communication
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Explanation: TRIACs control AC loads due to their ability to switch AC power efficiently. Question 13. Analog input modules in PLCs can accept which type of signals? A) Digital only B) 4-20 mA or 0-10 V C) Only relay signals D) Ethernet signals Answer: B Explanation: Analog modules accept current (4-20 mA) or voltage (0-10 V) signals. Question 14. Which process converts analog signals to digital in a PLC? A) DAC B) ADC C) CPU D) I/O mapping Answer: B Explanation: Analog-to-Digital Conversion (ADC) translates analog signals to digital values. Question 15. What does the resolution of an analog module refer to? A) Number of output channels B) Level of detail in signal conversion C) Type of power supply D) Speed of scan cycle
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Explanation: PID modules manage closed-loop control for processes like temperature or flow. Question 19. What is I/O addressing in PLCs? A) Assigning memory locations to inputs/outputs B) Changing power supply voltage C) Programming the CPU D) Modifying scan time Answer: A Explanation: Inputs and outputs are referenced by specific addresses within the program. Question 20. What is the I/O image table in PLC operation? A) Table of all errors B) Memory area storing statuses of all I/O points C) Power supply map D) List of network devices Answer: B Explanation: The image table holds the real-time status of all inputs and outputs. Question 21. Which step occurs first in the typical PLC scan cycle? A) Update outputs B) Execute program logic C) Read inputs D) Housekeeping/communication Answer: C
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Explanation: The PLC first reads all input statuses before logic execution. Question 22. The scan time of a PLC refers to: A) Time to power up B) Time to complete one scan cycle C) Time to save the program D) Time to update passwords Answer: B Explanation: Scan time is the duration the PLC takes to finish one full scan cycle. Question 23. Volatile memory in PLCs: A) Retains data after power loss B) Loses data when power is removed C) Is used for permanent storage D) Is never used in PLCs Answer: B Explanation: Volatile memory (e.g., RAM) loses its contents when power is off. Question 24. Non-volatile memory in PLCs: A) Stores temporary data B) Retains data even after power loss C) Requires constant refreshing D) Is used only for I/O tables
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Explanation: NO contacts are open unless energized by their controlling device. Question 28. What does a coil symbol in ladder logic represent? A) An input device B) An output device C) A memory location D) A comment Answer: B Explanation: Coils control output devices such as relays or actuators. Question 29. What is the function of a latch coil in ladder logic? A) Maintains output ON until explicitly reset B) Turns output off immediately C) Stores analog value D) Measures input frequency Answer: A Explanation: Latch coils keep outputs ON even if the activating condition goes away. Question 30. The rung continuity principle in ladder logic means: A) Power must flow from left to right for outputs to activate B) Program executes right to left C) Comments are required on each rung D) Only analog signals are processed Answer: A
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Explanation: Power (logic) flows left to right; all elements must be true for output activation. Question 31. How is AND logic implemented in ladder logic? A) Parallel contacts B) Series contacts C) Coil outputs D) Timer instructions Answer: B Explanation: AND logic is achieved by placing contacts in series; all must be true. Question 32. OR logic in ladder diagrams is accomplished by: A) Series contacts B) Parallel contacts C) Timer rungs D) Output coils Answer: B Explanation: Parallel contacts represent OR logic; any one being true activates the output. Question 33. What is the main purpose of one-shot (differentiation) instructions in ladder logic? A) Generate a continuous pulse B) Execute an action for one scan only C) Store analog values D) Repeat output
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Explanation: The ON-delay timer activates its output after a preset delay when the input is ON. Question 37. What is the function of an OFF-delay timer in a PLC? A) Delays output ON after input turns ON B) Delays output OFF after input turns OFF C) Counts pulses D) Latches outputs Answer: B Explanation: The OFF-delay timer maintains output ON for a set time after input turns OFF. Question 38. Retentive timers differ from standard timers by: A) Accumulating elapsed time across power cycles B) Losing time when power is lost C) Only working with analog signals D) Not requiring a preset value Answer: A Explanation: Retentive timers retain their accumulated value through power cycles. Question 39. The Preset Value (PRE) of a timer is: A) The current elapsed time B) The total time the timer should run before activating C) The last scan time D) The I/O address
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Explanation: PRE sets the time duration before the timer output is activated. Question 40. What does the Done (DN) bit of a timer indicate? A) Timer is disabled B) Timer has reached its preset value C) Timer is running D) Timer is reset Answer: B Explanation: DN is set when the timer’s accumulated value equals or exceeds the preset. Question 41. Which type of counter increases its value with each event? A) Count Down (CTD) B) Count Up (CTU) C) Retentive Timer D) Analog Counter Answer: B Explanation: CTU increases the count every time its input condition is met. Question 42. What is the primary application of a Count Down (CTD) counter? A) Incrementing values B) Decrementing values C) Timing delays D) Scaling analog signals
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Explanation: DN is set when the accumulated value matches the preset. Question 46. The Overflow (OV) bit in counters serves to: A) Indicate the counter exceeded its maximum value B) Show the counter is reset C) Display timer completion D) Activate analog output Answer: A Explanation: OV alerts when the count surpasses its allowable range. Question 47. Which PLC instruction transfers data from one memory location to another? A) MOV (Move) B) ADD C) TON D) CTU Answer: A Explanation: MOV moves data between registers or tags. Question 48. Comparison instructions in PLCs are used to: A) Compare sensor readings or values for conditional logic B) Move data between locations C) Activate timers D) Store programs Answer: A
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Explanation: Comparison instructions trigger actions when specified conditions are met. Question 49. Which instruction checks if two values are equal? A) Greater Than (>) B) Equal To (=) C) Less Than (<) D) MOV Answer: B Explanation: The Equal To instruction compares two values for equality. Question 50. What does the Not Equal To (≠) instruction do in a PLC? A) Activates output if values are the same B) Activates output if values are different C) Moves data D) Resets timers Answer: B Explanation: Output is activated when the two compared values do not match. Question 51. Which comparison instruction is used to check if a value is greater than another? A) Equal To (=) B) Less Than (<) C) Greater Than (>) D) MOV Answer: C
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Explanation: SUB deducts one value from another. Question 55. When would a Division (÷) instruction be used in PLCs? A) To combine values B) To separate values C) To calculate ratios or scale values D) For input addressing Answer: C Explanation: Division is used for creating ratios or scaling analog data. Question 56. What is the main purpose of using tag descriptions in PLC programs? A) Increase program size B) Improve documentation and clarity C) Change scan cycle D) Store analog values Answer: B Explanation: Tag descriptions clarify each element’s function for easier understanding. Question 57. What is meant by the term “seal-in circuit” in motor control? A) Circuit that turns motor off quickly B) Circuit that maintains motor ON after start button is released C) Uses only analog inputs D) Circuit that resets after power loss
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Explanation: Seal-in holds motor ON using a holding contact after the start button is released. Question 58. Why are status bits important in PLC programming? A) Store analog values B) Indicate the current state of timers, counters, or instructions C) Increase program speed D) Reduce memory usage Answer: B Explanation: Status bits provide feedback on instruction states for logic decisions. Question 59. What is the role of the Enable (EN) bit in timer instructions? A) Shows timer is disabled B) Shows timer is enabled and running C) Indicates timer completion D) Resets timer Answer: B Explanation: EN bit signals that the timer is actively timing. Question 60. Which PLC instruction can be used to activate an alarm if a temperature exceeds a set point? A) MOV B) Equal To (=) C) Greater Than (>) D) SUB
