Deck 5: Programming Timers

Question 1

PLC timers are input instructions that provide the same functions as mechanical timing relays.

Answer 1

False

Question 2

A RES (reset) instruction must be used to zero the accumulated value in an RTO timer.

Answer 2

True

Question 3

For the timer relay contact shown, when the relay coil is de-energized, there is a time delay before the contact closes.

Answer 3

True

Question 4

A TOF timer starts to accumulate time when the rung becomes true.

Question 5

For the timer relay contact shown, when the relay coil is energized, there is a time delay before the contact opens.

Question 6

For the timer relay contact shown, when the relay coil is energized, there is a time delay before the contact closes.

Question 7

The accumulated time of a TOF timer is reset by causing the rung to go true momentarily.

Question 8

Timers can be retentive or nonretentive.

Question 9

The retentive timer reset (RES) instruction is always given the same address as the timer it resets.

Question 10

When a 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.

Question 11

Timer instructions are found on all PLCs manufactured today.

Question 12

An alarm is to be switched on whenever a piping system has sustained a cumulative overpressure of 60 seconds. The most directly applicable timer to use would be the on-delay nonretentive timer.

Question 13

Retentive timers lose the accumulated time every time the rung condition becomes false.

Question 14

Normally, the reset input to a timer will override the control input of the timer.

Question 15

An RTO timer retains the present accumulated value when the rung goes false.

Question 16

The instantaneous contacts of a timer have no time-delay period associated with them.

Question 17

A timer's delay time equals the value in the ACC multiplied by the time base.

Question 18

A retentive timer must be completely timed out to be reset.

Question 19

A lamp is to be switched off 10 seconds after a switch has been switched from its on to off position. The most directly applicable timer to use would be the off-delay nonretentive timer.

Question 20

For the timer relay contact shown, when the relay coil is de-energized, there is a time delay before the contact opens.

Question 21

In the hardwired circuit shown, the light will stay on:

A)as long as S1 is closed.
B)for 5 s after coil TD is energized.
C)for 5 s after coil TD is de-energized.
D)as long as S1 is closed and for 5 s after coil TD is de-energized.

Question 22

For the timer program shown, output C is switched ON when:

A)power is applied.
B)input A is closed.
C)the timer is accumulating time.
D)the accumulated value equals the preset value.

Question 23

Which one of the following timer parameters represents the value that increments as the timer is timing?

A)Accumulated time.
B)Preset time.
C)Timer address.
D)Time base.

Question 24

Which one of the following timer parameters determines the time duration for the timing circuit?

A)Accumulated time.
B)Preset time.
C)Timer address.
D)Time base.

Question 25

For the programmed timer circuit shown the ____ bit of the timer functions similar to an instantaneous contact.

A)DN
B)EN
C)PB1
D)PB2

Question 26

For the on-delay timer instruction shown the timer number is:

A)0
B)200
C)T4:3
D)0.1

Question 27

For the timer circuit shown, the timer accumulated value will reset to zero whenever:

A)input A switch is opened.
B)input A switch is closed.
C)the DN bit is set to 1.
D)the EN bit is set to 1.

Question 28

Which one of the following timer parameters determines the accuracy of the timer?

A)Accumulated time.
B)Preset time.
C)Timer address.
D)Time base.

Question 29

Certain contacts of a mechanical timing relay are designed to operate at a preset time interval:

A)after the coil is energized.
B)after the coil is de-energized.
C)after power is applied to the circuit.
D)after the coil is energized or de-energized.

Question 30

The on-delay timed period for the timer shown would be:

A)3 seconds
B)4 seconds
C)20 seconds
D)200 seconds

Question 31

A TOF timer starts to accumulate time when the rung makes a true to false transition.

Question 32

The on-delay timer (TON) starts timing when the timer's:

A)ladder rung switches from false to true.
B)ladder rung switches from true to false.
C)accumulated value equals its preset value.
D)accumulated value is greater than its preset value.

Question 33

The off-delay timer (TOF) starts timing when the timer's:

A)ladder rung switches from false to true.
B)ladder rung switches from true to false.
C)accumulated value equals its preset value.
D)accumulated value is greater than its preset value.

Question 34

The relay contact drawn is designed to operate so that:

A)when the relay coil is energized, there is a time delay in closing.
B)when the relay coil is energized, there is a time delay in opening.
C)when the relay coil is de-energized, there is a time delay before the contact opens.
D)when the relay coil is de-energized, there is a time delay before the contact closes.

Question 35

For the timer table shown, bit level addressing is used for:

A)EN, TT, PRE, and ACC
B)EN, TT, and DN
C)PRE, ACC, TT, and EN
D)PRE and ACC

Question 36

For the timer program shown, output D is switched ON when:

A)power is applied.
B)input A is closed.
C)the timer is accumulating time.
D)the accumulated value equals the preset value.

Question 37

The timer file for SLC 500 controllers is:

A)T1
B)T2
C)T3
D)T4

Question 38

For the timer program shown, output B is switched ON when:

A)power is applied.
B)input A is closed.
C)the timer is accumulating time.
D)the accumulated value equals the preset value.

Question 39

For the programmed timer circuit shown, the ____ bit of the timer functions similar to a timed contact.

A)DN
B)EN
C)PB1
D)PB2

Question 40

For the hardwired timer circuit shown, contact TD-1 is the ____ contact and TD-2 is the ____ contact.

A)ON, OFF
B)OFF, ON
C)instantaneous, timed
D)timed, instantaneous

Question 41

For the programmed timers shown, the output of timer T4:5:

A)turns on after a 10-s time delay and remains on.
B)turns off after a 2-s time delay and remains off.
C)turns on after a 3-s time delay and remains on.
D)is pulsed on and off at 1-s intervals.

Question 42

For the programmed timer circuit shown, the pilot light should come on:

A)as soon as the switch is closed.
B)before the switch is closed.
C)for 15 seconds after the switch is opened.
D)as soon as the switch is closed and for 15 seconds after the switch is opened.

Question 43

For the program shown, the timer accumulated time is set to zero anytime:

A)PB1 is closed.
B)PB2 is closed.
C)PB1 is open.
D)PB2 is open.

Question 44

One of the advantages of using a PLC for timing circuit applications is the entire timing function occurs inside the controller.

Question 45

The interconnecting of timers is commonly called:

A)grouping.
B)programming.
C)sequencing.
D)cascading.

Question 46

For the programmed timer circuit shown, when the switch is initially closed motor(s) _____ start(s) immediately.

A)M1
B)M2
C)M3
D)all of these

Question 47

The accuracy and repeatability of PLC timers are not as good as that of mechanical and electronic timing relays.

Question 48

For the program shown, the timer starts timing when:

A)PB1 is closed.
B)PB2 is closed.
C)both PB1 and PB2 are closed.
D)either PB1 or PB2 is closed.

Question 49

The type of timer program shown is a:

A)retentive on-delay.
B)retentive off-delay.
C)nonretentive off-delay
D)nonretentive on-delay.

Question 50

The main difference between a PLC retentive and nonretentive timer is that the:

A)retentive timer can be programmed for much longer time delay periods.
B)nonretentive 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)nonretentive timer maintains the current time should power be removed from the device or when the timer rung goes false.

Question 51

When the timing of a device is not reset on a loss of power, the timing is said to be:

A)continuous
B)holding
C)retentive
D)saved

Question 52

Which instruction can best be used to turn an output coil on or off after the rung has been false for a desired time?

A)RTO
B)TON
C)ON OFF
D)TOF

Question 53

When addressing an RES instruction, it must be addressed to:

A)a TOF instruction.
B)a TON instruction.
C)any address other than that of the RTO instruction.
D)the same address as that of the RTO instruction.

Question 54

The operation of a PLC retentive timer is similar to that of an:

A)electromagnetic pneumatic timer.
B)electromechanical motor-driven timer.
C)off-delay timer.
D)on-delay timer.

Question 55

For the programmed timer circuit shown, assume the switch is closed for 5 seconds and than opened. After 12 seconds have elapsed motor(s) ____ will still be operating.

A)M1, M2, M3
B)M2, M3
C)M3
D)none of these

Question 56

The amount of time for which a timer is programmed is called the

A)preset.
B)desired time.
C)set point.
D)lapsed time.

Question 57

Unlike the TON timer, the RTO timer requires a(n):

A)timer reset instruction.
B)input condition instruction.
C)internal relay instruction.
D)instantaneous contact instruction.

Question 58

RES instructions are used with:

A)TOF timers
B)TON timers
C)RTO timers
D)all of these

Question 59

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.

Question 60

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.

Question 61

The preset time of a TON timer instruction represents the amount of time that has elapsed from when the instruction became true.

Question 62

Reciprocating timers are used in situations where a constant cycling of an output is required.

Question 63

The only way to reset a TON instruction is to use a Reset (RES) instruction.

Question 64

The loss of logic continuity to either a TON or TOF timer causes the timer instruction to reset.

Question 65

The intervals that timers time out at are referred to as the time base.

Question 66

Cascading timers provide a method to extend the timing range.

Question 67

The Enable bit of a TON timer will be true (1) immediately upon the beginning of the timing cycle.

Question 68

For ControlLogix controllers the time base is fixed at 1 second.

Question 69

A retentive on-relay timer is capable retaining the accumulated value in the event of a power loss to the controller.

Question 70

A typical application for a PLC circuit combining both cascading and reciprocating functions would be the control of traffic signals.