Deck 7: Programming Timers

Question 1

A lamp is to be switched off 10 s 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 nonretentive timer.

Answer 1

True

Question 2

Timers can be retentive or non-retentive.

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 opens.

Answer 3

True

Question 4

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

Question 5

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

Question 6

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

Question 7

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 8

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

Question 9

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

Question 10

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

Question 11

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

Question 12

An alarm 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 nonretentive timer.

Question 13

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

Question 14

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

Question 15

Timer instructions are found on all PLCs manufactured today.

Question 16

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

Question 17

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

Question 18

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

Question 19

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

Question 20

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

Question 21

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 is greater than its preset value.

Question 22

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

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

Question 23

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 24

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

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

Question 25

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 26

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 27

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 28

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 29

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 30

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 31

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 32

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 33

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 34

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

Question 35

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 is greater than its preset value.

Question 36

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 37

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)both a and c.

Question 38

The timer file for SLC 500 controllers is:

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

Question 39

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)either a or b.

Question 40

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 41

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)both a and c.

Question 42

RES instructions are used with:

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

Question 43

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 44

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 45

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 46

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 47

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 48

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 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 time 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

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 52

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 53

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 54

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 55

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 56

The interconnecting of timers is commonly called:

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

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

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