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PLC Timers and Counters: Questions and Answers, Exams of Social Sciences

United States International UniversitySocial Sciences

A series of questions and answers related to plc (programmable logic controller) timers and counters. It covers topics such as timer instructions, retentive and non-retentive timers, counter operations, and their applications in industrial automation. The questions address the functionality, parameters, and differences between various timer and counter types, offering a comprehensive review for students and professionals in the field of automation and control systems. It includes practical scenarios and multiple-choice questions to test understanding and application of plc concepts. This material is useful for exam preparation and reinforcing key concepts in plc programming.

Typology: Exams

2025/2026

Available from 12/13/2025

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ADV PLC CH 2 QUESTIONS & ANSWERS
PLC timers are input instructions that provide the same functions as mechanical timing
relays. - Answer -F
Timer instructions are no all PLCs manufactured today, manufactured today - Answer -
T
The retentive timer reset (RES) instruction is always given the same address as the
timer it resets - Answer -T
A lamp is to be switched on whenever a piping system has sustained a cumulative
overpressure of 60 s. The most directly applicable timer to use would be the on-delay
non retentive timer - Answer -F
A lamp is to be switched off 10s after a switch has been switched from it's on to off
position. The most directly applicable timer to use would be the off-delay non retentive
timer - Answer -T
When time delay period longer than the maximum preset time allowed for a single timer
is required, the problem can be solved by programming two or more timers together. -
Answer -T
Normally, the reset input to a timer will override the control input of the timer. - Answer -
T
A retentive timer must be completely timed out to be reset - Answer -F
Retentive timers lose the accumulated time every time the rung condition becomes
false. - Answer -F
The instantaneous contacts of a timer have no time-delay period associated with them. -
Answer -T
The accumulated time of a TOF timer is reset by causing the ring to go true momentarily
- Answer -F
A RES (reset) instruction must be used zero the accumulated value in an RTO timer. -
Answer -T
A timer delay time equals the value in the ACC multiplied by the time base. - Answer -F
Timers can be retentive or non-retentive. - Answer -T
An RTO timer retains the present accumulated value when the false - Answer -T
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Download PLC Timers and Counters: Questions and Answers and more Exams Social Sciences in PDF only on Docsity!

ADV PLC CH 2 QUESTIONS & ANSWERS

PLC timers are input instructions that provide the same functions as mechanical timing relays. - Answer - F Timer instructions are no all PLCs manufactured today, manufactured today - Answer - T The retentive timer reset (RES) instruction is always given the same address as the timer it resets - Answer - T A lamp is to be switched on whenever a piping system has sustained a cumulative overpressure of 60 s. The most directly applicable timer to use would be the on-delay non retentive timer - Answer - F A lamp is to be switched off 10s after a switch has been switched from it's on to off position. The most directly applicable timer to use would be the off-delay non retentive timer - Answer - T When time delay period longer than the maximum preset time allowed for a single timer is required, the problem can be solved by programming two or more timers together. - Answer - T Normally, the reset input to a timer will override the control input of the timer. - Answer - T A retentive timer must be completely timed out to be reset - Answer - F Retentive timers lose the accumulated time every time the rung condition becomes false. - Answer - F The instantaneous contacts of a timer have no time-delay period associated with them. - Answer - T The accumulated time of a TOF timer is reset by causing the ring to go true momentarily

  • Answer - F A RES (reset) instruction must be used zero the accumulated value in an RTO timer. - Answer - T A timer delay time equals the value in the ACC multiplied by the time base. - Answer - F Timers can be retentive or non-retentive. - Answer - T An RTO timer retains the present accumulated value when the false - Answer - T

A TOF timer starts accumulate time when the rung becomes true. - Answer - F A TOF timer starts to accumulate time when the rung makes a true to false transition transition - Answer - T Programmed counters can serve the function as mechanical counters - Answer - T Every PLC model offers some form of counter instruction. - Answer - T Counters are similar to timers, that except that they do not operate on an internal clock - Answer - T The output of the counter is energized whenever the accumulated count is less than or equal to the preset count - Answer - F PLC counters are normally non retentive - Answer - F Some PLC counters operate on the leading edge of the input signal, while others operate on the trailing edge - Answer - f All PLC manufacturers require the reset rung or line to be true to reset the counter - Answer - F A transitional off-to-on contact will allow logic continuity for one scan and then open, even though theTriggering signal may stay on - Answer - T A down counter output instruction wi decrement by 1 each time the counted event occurs - Answer - T In normal use, the down counter is used in conjunction with the up counter to form an up/down-counter - Answer - T All up-counters count only to their preset values, and additional counts are ignored. - Answer - F The counter reset (RES) instruction, it is always given the same address as the counter it is to reset. - Answer - T The counter enable bit is true whenever the instruction is false. - Answer - F The counter accumulated value is the current count based on the number of times the ring goes from false to true. - Answer - T The counter number C5:4 represents counter file 5, counter 4 in that file. - Answer - T Encoder pulses can be counted to measure distance. - Answer - T

a. ladder rung switches from false to true. b. ladder rung switches from true to false. c. accumulated value equals its preset value d. accumulation is greater than its present value - Answer - ladder rung switches from true to false. The main difference between a TON and TOF timer is that the: a. TON timer can maintain its accumulated time on loss of power or logic continuity. b. TOF timer can maintain its accumulated time on loss of power or logic continuity. c. TOF timer begins timing when logic continuity to the timing rung is lost. d. TON timer begins timing when logic continuity to the timing rung is lost. - Answer - TOF timer begins timing when logic continuity to the timing rung is lost The operation of a PLC retentive timer is similar to that of an: a. electromagnetic pneumatic timer c. off-delay timer. b. electromechanical motor-driven timer. d. on-delay timer - Answer - electromechanical motor-driven timer. The main difference between a PLC retentive and non retentive timer is that the: a. retentive timer can be programmed for much longer time delay periods. b non retentive timer can be programmed for much longer time delay periods. C. retentive timer maintains the current time should power be removed from the device or when the timer rung goes false. d. non retentive timer maintains the current time should power be removed from the device or when the timer rung goes false - Answer - retentive timer maintains the current time should power be removed from the device or when the timer rung goes false. Unlike the TON timer, the RTO timer requires (an) a. timer reset instruction c. internal relay instruction. b. input condition instruction. d. instantaneous contact instruction. - Answer - timer reset instruction When addressing an RES instruction, it must be addressed to: a. a TOF instruction. b. a TON instruction.any c. any address other than the of the RTO instruction. d. the same address as that of the RTO instruction. - Answer - the same address as that of the RTO instruction. To reset a retentive timer, the: a. AC time must be greater than the PR time. b. PR time must be greater than the AC time. c. AC time must equal the PR time.

d. none of these. - Answer - none of these. The interconnecting of timers is commonly called a. grouping B.sequencing b. programming d. cascading - Answer - cascading Which instruction can best be used to turn an output coil on or off after the ring has been false for a desired time? a. RTO C.ON OR ONOF b. TON d TOF - Answer - TOF The amount of time for which a timer is programmed is called the a. Preset c. Set Point b. Desired Time d .Elapsed Time - Answer - Preset When the timing of device is not reset on a loss of power, the timing is said to be: a. continuous C. retentive B holding d saved - Answer - retentive RES instructions are used with: a. TOF timers b. TON timers C. RTO timers d. all of these - Answer - RTO timers Programmed counters can A. Count up B. Countdown C. be combined to count up and down. d. all of these. - Answer - all of these. The counter instruction is found on: a. all PLCS b. small-size PLC C. Medium size plc d large-size PLC - Answer - small-size PLC The output of a PLC counter is energized when the:

B. Be false c. Be either true or false, depending on the manufacturer. d. Undergo a true-to-false transition - Answer - Be either true or false, depending on the manufacturer. Normally counters are retentive. This means that if your accumulated count is up to 300 and power to your system is lost, when power is restored the accumulated count will be: a: 000 B. c. 300 D. 999 - Answer - 300 A one-shot, or transitional, contact: a. operates the same as an NO contact instruction b. operates the same as an NC contact instruction c operates the same as a timed closed contact d closes for only one program scan when actuated - Answer - closes for only one program scan when actuated A PLC down-counter (CTD) counter counts a. scan transitions. b. true-to-false transitions. c. false-to-true transitions d. both b and c - Answer - false-to-true transitions The accumulated count of a CTD counter a. increments with each true-to-false transition b. decrements with each true-to-false transition C. decrements with each false-to-true transition d. increments with each false-to-true transition - Answer - decrements with each true-to- false transition The accumulated count of a CTU counter: a. increments with each true-to-false transition b. decrements with each true-to-false transition c. decrements with each false-to-true transition d. increments with each false-to-true transition. - Answer - increments with each true-to- false transition A counter is to be programmed to keep track of the number of parts coming off a production line. If you wanted to subtract the number of rejected parts so your counter would count only the good parts, you would program. a two up-counters b. two down-counters c. an up/down-counter d. a counter with a traditional contact input - Answer - an up/down-counter

The counter file for SLC 500 controllers

  • A. C
  • B. C
  • C. C
  • D. C5 - Answer - C