Deck 6: Developing Fundamental Plc Wiring Diagrams and Ladder Logic Programs

Question 1

A relay usually will have only one coil but a number of different contacts.

Answer 1

True

Question 2

Reed switches are activated by magnetism.

Answer 2

True

Question 3

Changes to dual-in-line package (DIP) switch settings are made mainly during installation.

Answer 3

True

Question 4

The programmed latching relay instruction is retentive; that is, if the relay is latched, it will unlatch if power is lost and then restored.

Question 5

In a magnetic motor starter, the control circuit is required to handle the full load current of the motor.

Question 6

A normally closed (NC) relay contact is closed when current flows through the coil.

Question 7

In general, control relay contacts are designed to handle higher currents than contactors.

Question 8

A small current flows through a solid-state proximity sensor even when the output is turned OFF.

Question 9

Weight strain gauges operate by detecting small changes in temperature.

Question 10

Proximity switches usually sense the presence or absence of a target by means of physical contact.

Question 11

An electromechanical relay uses electromagnetism to operate contacts.

Question 12

Fiber optic sensor systems are completely immune to all forms of electrical interference.

Question 13

Ultrasonic sensors operate using high-frequency light waves.

Question 14

Encoders are used in applications where positions have to be precisely determined.

Question 15

All servo motors operate in open loop.

Question 16

An inductive proximity sensor is actuated by conductive and nonconductive materials.

Question 17

A through-beam photoelectric sensor is used to detect the light beam reflected from a target.

Question 18

Latching relays are used when it is necessary for contacts to stay open and/or closed, even though the coil is momentarily energized.

Question 19

LED light sources used in photoelectric sensors normally emit a continuous beam of light.

Question 20

A selector switch is rotated to open and close contacts.

Question 21

The symbol shown is that for a:

A)pressure switch.
B)temperature switch.
C)proximity switch.
D)level switch.

Question 22

Strain gages are used for pressure/force sensing.

Question 23

Hysteresis for sensors means that there is an on point and a separate off point.

Question 24

A through-beam sensor has the shortest sensing range of the three types of photo sensors.

Question 25

The pushbutton symbol shown would be classified as a(n):

A)NO pushbutton.
B)NC pushbutton.
C)break-before-make pushbutton.
D)ON/OFF pushbutton.

Question 26

There is more than one correct way to implement the ladder logic for a given control process.

Question 27

The symbol shown is that for a:

A)pressure switch.
B)temperature switch.
C)limit switch.
D)level switch.

Question 28

In the hardwired relay control circuit shown, when the switch is closed, CR coil is:

A)energized, and the red and green lights are both on.
B)de-energized, the red light is off, and the green light is on.
C)energized, the red light is on, and the green light is off.
D)energized, the red light is off, and the green light is on.

Question 29

An electromagnet control relay is basically a(n):

A)electromagnet used to switch contacts.
B)electromagnet used to relay information.
C)manually operated control device.
D)pressure-operated control device.

Question 30

In the relay shown, the coil would be considered to be:

A)energized.
B)de-energized.
C)operated from an ac source.
D)both energized and operated from an ac source.

Question 31

In the motor starter circuit shown, the main contacts M are:

A)part of the power circuit.
B)part of the control circuit.
C)designed to handle the full load current of the motor.
D)both part of the power circuit and designed to handle the full load current of the motor.

Question 32

In the relay shown, the contact No. 1 is an:

A)NO fixed contact.
B)NC fixed contact.
C)NO movable contact.
D)NC movable contact.

Question 33

Digital sensors are sometimes called discrete sensors because there are two discrete states: on or off.

Question 34

A limit switch is usually actuated by:

A)hand.
B)pressure.
C)contact with an object.
D)an electromagnet.

Question 35

A proximity switch can be actuated:

A)without any physical contact.
B)by a change in light intensity.
C)by a change in capacitance.
D)by all of the these.

Question 36

The motor starter coil M is:

A)part of the power circuit.
B)energized to start the motor.
C)energized only as long as the start button is pressed.
D)All of these choices are correct

Question 37

The abbreviations NO (normally open) and NC (normally closed) represent the electrical state of switch contacts when:

A)power is applied.
B)power is not applied.
C)the switch is actuated.
D)the switch is not actuated.

Question 38

The device represented by the symbol is a:

A)drum switch.
B)selector switch.
C)sequence switch.
D)toggle switch.

Question 39

Any overload current is sensed by the:

A)starter coil.
B)control contact M.
C)OL coils.
D)OL contact.

Question 40

A contactor:

A)is another name for a relay.
B)is designed to handle heavy power loads.
C)always has an overload relay physically and electrically attached.
D)is a physically small relay.

Question 41

The symbol shown is that for a:

A)proximity switch.
B)temperature switch.
C)limit switch.
D)level switch.

Question 42

A(n) ___ operates by sending sound waves toward a target and measuring the time it takes for the pulses to bounce back.

A)pressure sensor
B)bar code scanner
C)ultrasonic sensor
D)flowmeter

Question 43

The symbol shown is that for a:

A)pressure switch.
B)temperature switch.
C)limit switch.
D)proximity switch.

Question 44

Capacitor proximity sensors:

A)are actuated by both conductive and nonconductive materials.
B)are actuated by conductive materials only.
C)produce an electromagnetic field.
D)have a long sensing range.

Question 45

An inductive proximity sensor is actuated by:

A)a metal object.
B)a light beam.
C)a nonconductive material.
D)any of these.

Question 46

The resistor shown in the circuit:

A)is called a bleeder resistor.
B)is used to power the sensor continuously.
C)allows enough current for the sensor to operate but not enough to turn on the input.
D)all of these

Question 47

The light source used in most industrial photoelectric sensors is a(n):

A)LED.
B)phototransistor.
C)photovoltaic cell.
D)miniature incandescent lamp.

Question 48

The force applied to a strain gauge causes it to bend and change its:

A)temperature.
B)resistance.
C)voltage.
D)current.

Question 49

The most common actuator for a reed switch is:

A)a permanent or electromagnet.
B)a light beam.
C)application of pressure.
D)a heat source.

Question 50

Fiber optic sensors:

A)are not affected by electrical interference.
B)carry light signals.
C)use a flexible cable containing tiny fibers.
D)all of these.

Question 51

The symbol shown is that for a:

A)heater.
B)horn.
C)solenoid.
D)motor.

Question 52

Most proximity switches come equipped with an LED status indicator to:

A)indicate that power is being applied to the switch.
B)indicate that the target is within sensing range.
C)indicate a blown fuse within the switch.
D)verify the output switching action.

Question 53

A(n) ____converts light energy directly into electric energy.

A)LED
B)phototransistor
C)solar cell
D)photoconductive cell

Question 54

The circuit shown is that of a:

A)one-wire proximity sensor
B)two-wire proximity sensor
C)three-wire proximity sensor
D)four-wire proximity sensor

Question 55

Bar code scanners are used primarily for:

A)data collection.
B)temperature measurement.
C)pressure measurement.
D)flow measurement.

Question 56

The symbol shown is that for a:

A)solenoid valve.
B)motor starter coil.
C)overload relay coil.
D)overload relay contact.

Question 57

The application shown is a typical application for a:

A)level switch.
B)temperature switch.
C)proximity sensor.
D)limit switch.

Question 58

For the photoelectric sensor part 1 is the ___ and part 2 is the___.

A)input, output
B)primary, secondary
C)transmitter, receiver
D)high side, low side

Question 59

The symbol shown is that for a:

A)light sensor.
B)heat sensor.
C)pressure sensor.
D)proximity sensor.

Question 60

The light sensor shown would be classified as a:

A)solar cell.
B)photoconductive cell.
C)photovoltaic cell.
D)all of these.

Question 61

What is the type of the instruction associated with the selector switch?

A)OTE
B)OTD
C)XIC
D)XIO

Question 62

Assume that an NC limit switch is substituted for the NO limit switch. For the circuit to operate in the same manner as before:

A)the wires to the limit switch would have to be reversed.
B)the address of the limit switch would have to be changed to I:1/4.
C)the instruction representing the limit switch would have to be changed to an XIO.
D)
The address of the limit switch would have to be changed to I:1/4 and the instruction representing the limit switch would have to be changed to an XIO.

Question 63

The instruction at address B3:1/3 is associated with:

A)an internal relay coil.
B)an external input device.
C)an external output device.
D)the solenoid.

Question 64

A thermocouple, when heated:

A)produces a small dc voltage.
B)produces a small ac voltage.
C)increases its resistance value.
D)decreases its resistance value.

Question 65

An encoder is used to:

A)encode signals from a scanner.
B)decode signals from a scanner.
C)change DC to AC.
D)convert motion into a digital signal.

Question 66

If the XIC instruction at address I:1/3 is True:

A)output B3:1/3 will also be True.
B)output O:2/0 will also be True.
C)input I:1/2 will also be True.
D)both output B3:1/3 will also be True and output O:2/0 will also be True.

Question 67

Rung 2 will be True whenever:

A)the pressure switch is closed.
B)the pushbutton is closed.
C)the selector switch is closed and rung 1 is True.
D)the pressure switch is closed or the selector switch is closed and rung 1 is True.

Question 68

The purpose of the M contact shown in the circuit is to:

A)open the circuit in the case of a motor overload.
B)start the motor from a remote location.
C)keep the starter coil energized when the start button is released.
D)keep the starter coil de-energized when the start button is released.

Question 69

Programmed latching circuits are retentive. This means that if power is interrupted the output will ____ when power is returned.

A)switch to the ON state
B)switch to the OFF state
C)remain in its original ON or OFF state
D)flash ON and OFF

Question 70

Rung 1 will be True whenever the:

A)pushbutton and limit switch are closed.
B)selector switch and pressure switch are closed.
C)selector switch and pushbutton are closed.
D)pressure switch and pushbutton are closed.

Question 71

For the program shown, what is the address of the instruction associated with the pressure switch?

A)I:1/0
B)I:1/1
C)I:1/2
D)I:1/3

Question 72

The sensor illustrated is a:

A)thermocouple.
B)turbine flow meter.
C)strain gauge load cell.
D)retroreflective sensor.

Question 73

The electromagnetic latching relay:

A)is used to lock in a condition.
B)uses a latch coil to set and hold the relay in the latched position.
C)uses an unlatch coil to disengage the mechanical latch.
D)all of these.

Question 74

A(n) ____ converts electrical pulses applied to it into discrete rotor movements.

A)tachometer
B)solenoid
C)stepper motor
D)electronic magnetic flowmeter

Question 75

An actuator is a device that:

A)changes AC to DC.
B)changes DC to AC.
C)converts an electrical signal into mechanical movement.
D)converts mechanical movement into an electrical signal.

Question 76

The Output Latch (OTL) instruction:

A)can turn an output on, but it cannot turn the output off.
B)is used only to turn a bit on and latch it on.
C)allows the output to remain on even if the rung changes to false.
D)all of these

Question 77

For the programmed latching operation shown, which two instructions must have the same address?

A)ON and OFF inputs.
B)Latch and unlatch outputs.
C)ON input and latch output.
D)OFF input and unlatch output.

Question 78

All servo motors:

A)operate in the closed-loop mode.
B)operate in the open-loop mode.
C)operate without feedback.
D)operate in the open-loop mode and without feedback.

Question 79

A tachometer normally refers to a(n) ____ used for speed measurement.

A)load cell
B)capacitive proximity sensor
C)ultrasonic sensor
D)small generator

Question 80

Solenoid valves are available to control:

A)oil flow.
B)air flow.
C)water flow.
D)all of these