EXAM 4 REVIEW QUESTIONS

Question 1

For the timer relay contact shown, when the relay coil is energized, there is a time delay before the contact closes. (Its a NO switch)

Answer 1

True

Question 2

For the timer relay contact shown, when the relay coil is energized, there is a time delay before the contact opens. (Its a NC switch)

Answer 2

True

Question 3

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 off-delay nonretentive timer.

Answer 3

False

Question 4

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.

Answer 4

True

Question 5

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

Answer 5

True

Question 6

A retentive timer must be completely timed out to reset.

Answer 6

False

Question 7

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

Answer 7

False

Question 8

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

Answer 8

True

Question 9

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

Answer 9

False

Question 10

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

Answer 10

False

Question 11

Which 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

Answer 11

A

Question 12

Which of the following timer parameters determines the accuracy of the timer?
A. Accumulated time
B.. Preset time
C. Timer address
D. Time base

Answer 12

D

Question 13

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 it’s preset value.

Answer 13

B

Question 14

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 continuitity.
B. TOF timer maintain its accumulated time on loss of power of logic continuity.
C. TOF timer begins timing when logic continuity tot he timing rung is lost.
D. TON timer begins timing when logic continuity to the timing rung is lost.

Answer 14

C

Question 15

Every PLC model offers some form of counter instruction.

Answer 15

True

Question 16

Counters are similar to timers, except that they do not operate on an internal clock.

Answer 16

True

Question 17

The output of the counter is energized whenever the accumulated count is less than or equal to the preset count.

Answer 17

False

Question 18

A down-counter output instruction will decrement by 1 each time the counted event occurs.

Answer 18

True

Question 19

In normaluse, the down counter is used in conjunction with the up-counter to form an up/down-counter.

Answer 19

True

Question 20

All up-counters count only to their prest values, and additional counts are ignored.

Answer 20

False

Question 21

The counter number C5:4 represents counter file 5, counter 4 in that file.

Answer 21

True

Question 22

A counter instruction is an input instruction.

Answer 22

False

Question 23

Counters can count past their preset values.

Answer 23

True

Question 24

Programmed counters can:
A. Count up 
B. Count down
C. Be combined to count up and down.
D. All of these

Answer 24

D

Question 25

The counter instruction is found on:
A. All PLC's
B. Small-size PLC's
C. Medium-size PLC's
D. Large-size PLC's

Answer 25

A

Question 26

Which of the following is not usually associated with a PLC counter instruction?
A. Address
B. Preset value
C. Time Base
D. Accumulated Value

Answer 26

CWeh

Question 27

When the up-counter reset is set to true, the following happens:
A. The preset value is set to 0.
B. The preset value increments.
C. The accumulated value is set to 0.
D. The accumulated value is set to the maximum.

Answer 27

C

Question 28

The accumulated count of a CTD counter:
A. Increments with each tue-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 28

C

Question 29

A RES (reset) instruction MUST be used to zero the accumulated value in a TON timer.

Answer 29

False

Question 30

The output of the counter is energized whenever the accumulated count is greater than or equal to the preset count.

Answer 30

True

Question 31

Some PLC counters operate on the leading edge of the input signal, while others operate on the trailing edge.

Answer 31

False

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 signals equals its preset value.
D. accumulated is greater than its preset value.

Answer 32

A

Question 33

The output of a PLC counter is energized when the:
A. accumulated count equals the preset count.
B. preset count is greater than the accumulated count.
C. counter input rung is true.
D. accumulated count is greater than or equal to the preset count.

Answer 33

D

Question 34

For the PLC counter to reset, the counter reset rung must:
A. be true
B. be false
C. lose continuity
D. undergo a true-to-false transition

Answer 34

A

Question 35

A PLC down-counter (CTD) counter counts:
A. scan transitions.
B. true-to-false transitions
C. false-to-true transitions
D. loss of rung continuity.

Answer 35

C