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Fourth Year Electrician > Programmable Logic Controllers > Flashcards

Programmable Logic Controllers Flashcards

PLC stuff

1
Q

Sectors that PLCs are used include (5 items)

A

1: Chemical/petrochemical
2: Auto manufacturing
3: Metal smelting/mining
4: Lumber/pulp/paper
5: Food/beverage production

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2
Q

Smaller PLCs are hardly more than _____.

A

Smart relays.

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3
Q

Large PLCs may have over.120 000 IO points. T or F.

A

True.

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4
Q

Three items that control systems consist of are:

A

1: Input devices
2: Controller
3: Output devices

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5
Q

Three examples of input devices are:

A

Switches, limits, thermostats.

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6
Q

A controller can receive input info in what two ways?

A

Hard wired circuit or software program.

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7
Q

Three examples of output devices are:

A

1: Relays
2: Contactors
3: Solenoids

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8
Q

Output devices control devices such as: (5 items)

A

1: Motors
2: Pumps
3: Heaters
4: Fans
5: Valves

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9
Q

PLCs are able to perform their own _____

A

Internal diagnostics

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10
Q

Four advantages of PLCs over relay control are:

A

1: Lower cost
2: Programmability
3: Reliability
4: Expandability

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11
Q

Troubleshooting on a PLC system is _____ and reduces _____.

A

Easier

Down-time

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12
Q

PLCs are physically smaller than _____ with smaller _____ requirements.

A

Control panels with numerous relays

Energy

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13
Q

Does hard wiring need to be changed to re-program or update PLC software?

A

No

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14
Q

A program is usually _____.

A

Ladder logic

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15
Q

A program graphically displays _____ as well as _____.

A

Status of devices

Power flow in program

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16
Q

Ambient conditions that some PLCs are designed to withstand are:

A

Excessive heat, humidity, exposure to mechanical damage (vibration).

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17
Q

Static electronic switching means _____.

A

No moving parts.

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18
Q

Two ways to expand PLC systems are:

A

1: New modules plug into existing PLC
2: Add another PLC and link/group with communication data highway

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19
Q

Communication data highway is a means of _____.

A

Connecting multiple PLCs in a system.

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20
Q

Discreet input devices are _____ (3 items) that are either off or on.

A

1: Switches
2: Relay contacts
3: Sensors

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21
Q

Discreet output devices such as _____ (4 items) respond to either being energized or de-energized.

A

1: Pilot lights
2: Contactor coils
3: Relay coils
4: Solenoids

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22
Q

Discreet input and output devices require _____.

A

Power from a separate source.

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23
Q

Optoisolating is how _____ is achieved between the discreet IO circuits and the internal circuitry of the processor module.

A

Electrical Isolation.

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24
Q

Analogue devices are either on or off. T or F.

A

F. They operate over a range of voltage or current.

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25
Q

A solid state electronic switch for DC would be a _____.

A

Transistor

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26
Q

A solid state switch for AC is a _____.

A

Triac

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27
Q

An interposing relay does what function?

A

Relay coil that can handle higher current and is operated by the solid state switch.

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28
Q

Some examples.of measured values are:

A

Temperature, pressure, speed, position.

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29
Q

The most common analog current standard is _____.

A

4 mA - 20 mA

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30
Q

Minimum signal for 4-20 mA analog is 4 mA because _____.

A

Allows PLC to tell difference between 0% signal and broken wire connector.

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31
Q

Proportional control is gained using an analog output card for processes such as a _____.

A

VFD motor speed controller.

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32
Q

A shield in STP cable is also called a _____.

A

Drain

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33
Q

STP cable means _____.

A

Shielded twisted pair

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34
Q

The drain is usually grounded at only one end, usually _____.

A

In the PLC panel.

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35
Q

PLC programming evolved from _____.

A

Boolean algebra programs

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36
Q

Three graphic based languages used for PLC programming are:

A

1: Ladder diagrams
2: Function block diagrams
3: Sequential functions/flow chart

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37
Q

Two text based languages for PLC programming are:

A

1: Structured text
2: Instruction lists

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38
Q

The most common programming language is _____.

A

Ladder diagram

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39
Q

The numbers used above symbols in a ladder diagram represent _____.

A

Input/output terminal address

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40
Q

Each function block may have several inputs and _____.

A

Settable parameters

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41
Q

Function blocks can be thought of as _____.

A

Small programs within a main program.

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42
Q

Function block diagrams are commonly used in _____.

A

Europe

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43
Q

Sequential Function Charts are used for large process controls and can involve _____.

A

Logic or several LD or FBD.

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44
Q

Text based programs were once commonly used with _____.

A

Hand held programmers

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45
Q

Structured Text is similar to what computer programming language?

A

Basic

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46
Q

Instructiom Lists are similar to _____.

A

Assembler language programs

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47
Q

Instruction Lists are more like the machine code used to make a _____ function than a process to be controlled.

A

Microchip

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48
Q

Four major hardware components of a modular PLC are:

A

1: Power Supply
2: Backplane
3: Processor (CPU)
4: IO modules (input/output

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49
Q

The power supplied to a PLC is clean, filtered/regulated and provides _____.

A

Protection to system components

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50
Q

Does a PLC supply any of the field IO devices?

A

No

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51
Q

Field IO devices are _____ from the backplane, CPU and power supply.

A

Isolated electrically

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52
Q

The means for a PLC to communicate with other components and distribute power for internal operations is done through _____.

A

A backplane

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53
Q

A backplane is a _____

A

Power and communications bus

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54
Q

What is another name for a complete unit PLC?

A

Shoebox PLC

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55
Q

Shoebox unit PLCs often replace _____.

A

Small relay systems.

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56
Q

What does a processor do?

A

Executes user programs and communicates with other devices.

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57
Q

What does STP stand for?

A

Shielded twisted pair

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58
Q

What is the sequence of carrying out processor functions called?

A

Processor scan

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59
Q

What type of memory is used in PLCs?

A

RAM, ROM, EEPROM.

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60
Q

What happens if volatile memory loses its electrical power source?

A

Memory cleared of all data

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61
Q

What is required for volatile memory to keep stored data and programs when power is removed?

A

Battery backup

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62
Q

Non-volatile memory is considered _____.

A

Permanent.

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63
Q

Is RAM a volatile memory or non volatile?

A

Most is volatile. Non volatile has self contained battery within package of memory chip.

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64
Q

ROM is volatile or non volatile?

A

Non volatile

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65
Q

ROM info may be altered or written to by a user, true or false?

A

False

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66
Q

What does RAM mean?

A

Random Access Memory

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67
Q

What does ROM mean?

A

Read Only Memory

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68
Q

What does EEPROM mean?

A

Electrically erasable programmable memory

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69
Q

EEPROM is integrated circuit memory considered to be (volatile, non volatile?)

A

Non volatile

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70
Q

An example of EEPROM is _____.

A

Flash memory cards/USB drive

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71
Q

What are some switches that may be used as a sensing device?

A

Pressure, temperature, or mechanical limit switches with an on/off signal

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72
Q

Analogue sensing devices would have signals of changing levels of _____ or _____.

A

Voltage, current.

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73
Q

7 control functions that special IO modules are used for:

A

1: Position control
2: High speed counters
3. Temperature controls
4: Proportional integral derivative control (PID)
5: Fuzzy logic control
6: Identification sensors cam positoners
7: Analogue IO

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74
Q

How many cables would be between a remote IO and a PLC?

A

1

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75
Q

What is a data highway?

A

LAN cabling that connects a number of PLCs (and PCs) to exchange programs/data

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76
Q

What is the most common analogue voltage standard?

A

0 - 10 V DC

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77
Q

PLCs are actually an _____ _____ with specially designed hardware and software.

A

Industrial computer

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78
Q

“Hardware” in PLCs refers to _____. (3 items)

A

Mechanical, electrical, and electronic components.

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79
Q

What are the four basic components of an Automated Control System?

A

1: PLC
2: Input devices
3: Output devices
4: AC circuits

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80
Q

CPU power supply, input devices and output devices all need their own _____.

A

Separate AC supply.

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81
Q

Lights, coils, solenoids, magnetic starters and meters are examples of _____.

A

Output devices

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82
Q

Is the programming device required when the program is running?

A

No, except to monitor the program.

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83
Q

A desktop computer, laptop or hand held programmer are examples of _____

A

Programming device.

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84
Q

Desktop computers, laptops and handheld programmers are also called _____.

A

HMI, Human Machine Interface

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85
Q

The power supply of a CompactLogix controller is located where in the module?

A

Anywhere in the 2nd to Fourth position.

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86
Q

The power supply of a CompactLogix controller is located where in the module?

A

Anywhere in the 2nd to Fourth position.

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87
Q

What is the maximum position for the IO modules in a CompactLogix?

A

12

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88
Q

In a single bank CompactLogix system, you cannot place more than _____ between the power supply and end cap, making a maximum of _____ modules.

A

8 I/O modules, 11

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89
Q

Data is _____ (received) by a processor and _____ (sent) to other PLC components

A

Read, write

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90
Q

A processor module has _____ ports and _____ for a _____.

A

Two communication, one slot, memory card.

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91
Q

The power supply will be sized to accomodate the load of _____.

A

All of the cards in the assembly.

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92
Q

Input/Output modules provide an _____ between the processor and the _____.

A

Interface, discreet field device

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93
Q

Analogue modules provide an _____ between the processor and the _____.

A

Analogue IO field devices.

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94
Q

Endplates complete the assembly, with the leftmost housing _____ and the rightmost housing _____.

A

Battery for the EEprom

Terminal assembly to terminate backplane.

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95
Q

Can a programming device both read and write to a PLC processor?

A

Yes

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96
Q

What provides housing for the modules?

A

A chassis or separate enclosure.

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97
Q

What does a power supply do?

A

Converts AC or DC voltage to specified value with required VA capacity to operate electronic equipment

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98
Q

The power supply is considered the first line of _____.

A

System reliability and integrity.

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99
Q

PLC power supplies are designed to operate under constant frequency and voltage only. T or F.

A

False. Designed for wide range of fluctuations that may occur in a large system.

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100
Q

If the supply frequency fluctuates more than the specified values, what will the PLC do?

A

Shut down the processor.

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101
Q

What is EMI?

A

Electromagnetic interference

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102
Q

Where would a power supply need to be shielded?

A

Areas where EMI is generated

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103
Q

Power supplies are selected according to _____.

A

The current requirements of the modules

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104
Q

What are two ways to provide power to the field IO devices?

A

External source or auxillary control transformer

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105
Q

What does Line Signal Conditioning do?

A

Purifies AC sine wave to eliminate voltage surges, current spines, or other incoming electrical noise.

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106
Q

Five duties of the power supply module are:

A

1: Line Signal Conditioning
2: Step down voltage
3: Rectifier converts AC to DC
4: Filter smooths DC to fairly constant, negligible ripple
5: Voltage Regulator provides steady output to components

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107
Q

Where is the power supply of the CompactLogix mounted in this lab? What are its output current ratings?

A

Immediate right of the processor.

4A at 5V DC and 2A at 24V DC

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108
Q

What system activities do a processor govern?

A

Receiving, analyzing, processing and transmitting data.

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109
Q

What are two other terms for processor?

A

CPU, microprocessor

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110
Q

The CPU is the _____ of the system.

A

Intelligence

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111
Q

The CPU and memory _____ to execute the _____ (+4 items).

A

Work together

Operating system, interpret/execute user programs, communicate with devices, perform other housekeeping.

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112
Q

Primary function of PLC processor that is also called Processor Scan:

A

Read/store status of all input devices, execute user program by solving ladder logic, update status of outputs.

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113
Q

What are the five steps of a processor scan? Which step is the longest?

A

1: Input scan
2: Program scan
3: Output scan
4: Service communications
5: Housekeeping/overhead

Program scan is the longest time interval.

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114
Q

A Watch Dog timer is part of what area of the system? What does it do?

A

Internal diagnostic system.

Shuts down processor and creates fault code if time out error occurs.

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115
Q

Is it dangerous to edit online when a controller key switch is on the RUN position?

A

Yes

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116
Q

Will the controller execute tasks while keyswitch is in PROG position?

A

No

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117
Q

Can you edit online in run mode of the REM keyswitch position?

A

Yes

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118
Q

Does battery backup continue running the processor during a power outage?

A

No. Only keeps programming intact.

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119
Q

Primary function of a processor is:

A

Read inputs, solve ladder logic, and update outputs

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120
Q

Which modules are used to electrically isolate the processor from the field devices?

A

I/O modules

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121
Q

Status indication on IO modules helps with _____.

A

Faster system analysis

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122
Q

Input modules take signals from devices and converts to a _____ _____ usable by the processor.

A

Voltage level

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123
Q

Sensing devices can be things such as: (5 items)

A

1: Switches
2: Photo-eyes
3: Proximity switches
4: Limit switches
5: Pressure transducers

124
Q

What is Opto-isolator?

A

Small relays/filter circuitry.

125
Q

What does optoisolating protect the processor from?

A

Voltage transients and magnetic interference.

126
Q

Output modules send information to an output field device via _____ _____.

A

Electrical interface.

127
Q

Are output modules equipped with surge protection and/or fusing?

A

No.

128
Q

What kind of protection is usually used for inductive loads?

A

Surge suppresion

129
Q

A loading resistor connected in parallel with a load will have what effect?

A

Limit the effects of leakage current through solid state outputs.

130
Q

What size resistor would be used for a loading resistor at 120 VAC? And for 240 VAC?

A

120: 15 kiloohm, 2 watt
240: 15 kiloohm, 5 watt

131
Q

What will develop over an unloaded output?

A

Hazardous condition.

132
Q

Discreet IO modules are available in _, __, or __ points per module.

A

8, 16, 32

133
Q

What are the AC ratings of digital AC input modules?

A

24, 120, 240

134
Q

What are the DC ratings of digital AC input modules?

A

5(TTL), 24, 48

135
Q

What are the AC and DC ratings of digital AC output modules?

A

120/240, 24VDC, 5 VDC(TTL)

136
Q

What is the current rating of digital AC output modules?

A

0.5 A - 2 A per output point

137
Q

What can a relay output of a digital DC combination module control?

A

5-265 VAC, 5-125 VDC, loads up to 2.5 A per point to a max of 20 A per card.

138
Q

What would the voltage be at 75% of the signal?

A

7.5 VDC

139
Q

What would the current be at 25% of the signal?

A

8 mA

140
Q

What would the voltage be if the current were 12 mA?

A

5 VDC

141
Q

What percentage of signal is 16 mA? What would the voltage be?

A

75%

7.5 VDC

142
Q

What would the current be at 0% signal and 0 VDC?

A

4 mA

143
Q

Special purpose modules for specialized needs could include applications such as:

A

Motion Control

Video Recognition module

ASCII module

High speed counter modules

Servo positioning module

Compact IO to PowerFlex drives

Thermocouple (mV) signals

Resistance temperature detector (RTD) input module

144
Q

What causes voltage transients?

A

Contact bounce and electrical noise

145
Q

Only some input modules use input filtering. T or F.

A

False.

146
Q

Analogue signals are typically interpreted as _____ _____ by the PLC

A

Integer value

147
Q

What are four items represented by analog signals?

A

Pressure, temperature, flow, weight.

148
Q

PLCs typically use __-bit signed binary processors.

A

16

149
Q

Analog signals use voltage or current with a _____ _____ to the process signal.

A

Proportional magnitude

150
Q

When might you want to use additional surge suppresion? (4 items)

A

Inductive loads such as relays, magnetic starters, solenoids and low VA motors

151
Q

Electrical isolation between processor and IO module is achieved by optical isolation as well as _____.

A

Small relays in the IO modules

152
Q

What is peripheral equipment?

A

Accessory or auxiliary to a central system

153
Q

What are some methods to input a program to a PLC processor?

A

1: PC or laptop with software
2: Operator Interface Devices
3: Modems
4: Printers
5: Alphanumeric displays
6: Communication devices
7: Memory device

154
Q

What is memory in a PLC?

A

A two dimensional array of storage cell, each cell storing a single bit of information.

155
Q

What values represent a bit of information?

A

A 0 or a 1.

156
Q

Binary data is stored in memory by a process called _____.

A

Write

157
Q

Binary data is retrieved from the memory by a process called _____.

A

Read

158
Q

Data storage locations, each identified by an address, is called _____.

A

Memory

159
Q

What is BIT an acronym for?

A

BInary digiT

160
Q

What are the 1s and 0s of binary representative of?

A

Presence or absence of voltage at that particular location.

161
Q

If a bit’s status is 1, is it considered ON (set) or OFF (reset)?

A

ON

162
Q

If a bit’s status is 0, is it considered ON (set) or OFF (reset)?

A

OFF

163
Q

When might you group bits for transferring?

A

Transferring numbers from a thumbwheel to digital readout or PLC.

164
Q

What is a byte?

A

A group of bits (the smallest value that can be handled simultaneously by the processor).

165
Q

What is a typical byte size?

A

8 bits

166
Q

What is a “word”?

A

Grouping/number of bits in a sequence treated as a unit.

167
Q

What is the word length of the CompactLogix PLC?

A

32 bits

168
Q

What is a memory flash card?

A

RAM memory module that can insert directly innto PLC processor.

169
Q

All PLCs must have memory allocated for _____ (4 items).

A

1: Executive programs
2: Processor work area / Scratch pad
3: Data area
4: User program area

170
Q

Which two items are not accessible to users and are part of the System Memory?

A

Executive and Scratch Pad

171
Q

System Memory could be described as equivalent to _____.

A

BIOS of a pc

172
Q

Executive memory is considered to be _____.

A

Permanent

173
Q

Scratch pad memory is considered ______ storage.

A

Temporary

174
Q

Which two items are accessible to the user?

A

Data Area and User Program

175
Q

Data Area and User Program can be described as _____.

A

Application memory

176
Q

Max memory size specified by the manufacturer will usually only include the _____.

A

Application memory

177
Q

What are the two basic items that memory stores?

A

State of input/outputs (Data area)

Program that controls the outputs (User program)

178
Q

A “tag” can refer to a _____ location or a structure location that is _____ in size.

A

Single bit

Multiple words

179
Q

What are the three properties assigned to a tag?

A

Type, Scope and Data Type

180
Q

What are the four types of tags?

A

1: Base tags
2: Alias tags
3: Produced tags
4: Consumed tags

181
Q

All data stored in four byte groupings in 32 bits of consecutive data is called _____ tag.

A

Base

182
Q

Alias tags refer to memory that is defined by _____.

A

Another existing tag

183
Q

Four ways that Alias tags can be used are:

A

1: Programming ladder
2: Assigning descriptive name to IO device
3: More simple name to complex tags
4: Descriptive name for element of an array

184
Q

Produced tags and Consumed tags are used when _____ and are always ______.

A

Information needs to be shared between controllers

Controller scoped tags

185
Q

Program Scope tags can be accessed by all routines in the controller. T or F.

A

False

186
Q

Controller Scope tags are accessible only by the parent program. T or F.

A

False

187
Q

What type of languages are most commonly used with PLCs?

A

Graphic based

188
Q

How many words of Data Table memory do counters and timers require? What are they?

A

Three - Accumulated, Preset, Address

189
Q

What is the max time that can be programmed in a TON instruction?

A
  1. 523 hrs
  2. 394 min
  3. 647 s
190
Q

When an output bit is “1”, it’s corresponding output terminal is “off”. T or F

A

False

191
Q

What does the accumulated value in a CTD need to be to turn off the .DN bit?

A

Below the preset value

192
Q

Data types may be ______ or ______.

A

Atomic or structured

193
Q

Five atomic data types are:

A

1: Bool (single bit of a 32 bit word)
2: Sint (short integer, 8 bits [1 byte] of a 32 byte word)
3: Int (integer, 16 bit group of 32 bit word)
4: Dint (double integer, 32 bit word)
5: Real (32 bits, includes decimal, used for math/analog process conrol.)

194
Q

What are the three kinds of strutures?

A

1: Module Defined Structures
2: Predefined structures
3: User Defined Structures

195
Q

Data, status and fault information is contained in which structure?

A

Module Defined Structures.

196
Q

Control, counter, and timer structures are found in which structure?

A

Predefined Structures

197
Q

Name, data type, style and radix are required by which structure?

A

User Defined Structures

198
Q

An array lets you group data under a common name as long as what condition is met?

A

They are of the same type

199
Q

Which part of C5[0] is the subscript?

A

0

200
Q

How many dimensions can an array have? What is the benefit of this?

A

As many as three. Flexibility for 1-3 subscripts.

201
Q

Three dimensional arrays are generally only used with ______ ______ programs

A

Motion control

202
Q

What is a reason for using arrays?

A

When upgrading from a different model.

203
Q

The data area of the CompactLogix PLC data area contains what?

A

Tags

204
Q

A basic unit of logic is called a _____.

A

Routine

205
Q

What types of logic can be used in a routine?

A

Ladder, function block, sequential function chart, structured text.

206
Q

What language would you use for machine interlocking and operations that may need to have maintenance personnel troubleshoot?

A

Ladder logic

207
Q

What language would you use for continuous process, drive control, and loop control?

A

Function block diagram

208
Q

High level management of multiple operations would be coded using which language?

A

Sequential function chart

209
Q

Complex mathematical operations, ASCII string handling, and specialized arrays would be coded using which language?

A

Structured text.

210
Q

A program contains every _____.

A

Routine

211
Q

JSR instruction means:

A

Jump to Subroutine

212
Q

If you do not want a program to run, where in the controller organizer should it be stored?

A

Unscheduled programs folder.

213
Q

Does a task define when a program will execute?

A

Yes

214
Q

Up to __ tasks can be configured in the controller.

A

6

215
Q

A watchdog will trigger a _____ if the task runs too long.

A

Fault

216
Q

Can you use 5 continuous tasks in a project?

A

No. Can only use 1.

217
Q

What is the max periodic tasks that are able to be used in a project?

A

6

218
Q

The time period of a periodic task can be configured from 1 ms to ____ s.

A

2000

219
Q

The default time period in a periodic task is __ ms.

A

10

220
Q

What are the position numbers of a PLC assembly?

A

1-5

221
Q

What are the slot numbers of a PL assembly? Which module goes in slot 0?

A

0-7. CPU/Processor

222
Q

If the location of the IO module is on the main DIN rail, what is the location part of the address?

A

LOCAL

223
Q

Describe the address LOCAL:2:I.DATA.0

A

LOCAL: location is on main DIN rail. “Adapter type and name” would be used if IO module is remote.

2: Slot number of the module being referenced.

I: Module type. I=Input O=Output

DATA: Discreet IO. Use “Channel #” for analog

0: Bit number from 0-15

224
Q

What does XIC mean?

A

Examine if closed

225
Q

What does XIO mean?

A

Examine if opened

226
Q

When an instruction becomes true, that means that it has been _____.

A

Energized

227
Q

When an input terminal is energized, it’s corresponding bit is __.

A

1

228
Q

When an input terminal is de-energized, it’s corresponding bit is __.

A

0

229
Q

What does the input module do before storing the result in the input tag data area?

A

Filters, isolates the incoming signal and changes it to 5 VDC

230
Q

Is electrical isolation required between the internal 5 VDC of the output module to the actual operating voltage of the lamp?

A

Yes

231
Q

Each word in the IO tags corresponds to what?

A

A specific slot within a certain chassis.

232
Q

Are timers input or output instructions?

A

Output

233
Q

Is there additional hardware needed for timers?

A

No. It is in the software.

234
Q

The minimum timer setting of a PLC timer an be as low as __ ms.

A

1

235
Q

All timers require how many words of memory in the timer area of the data table?

A

Three

236
Q

What does Mnemonic refer to?

A

The ‘label’ given to a specific bit.

237
Q

The three different types of timers are:

A

1: Timer On Delay
2: Timer Off Delay
3: Retentive Timer On (RTO)

238
Q

An integral part of most control systems are _____.

A

Timers

239
Q

What are five uses of timers?

A

1: Delay starting cycles
2: Control intervals
3: Repeat cycles
4: Flashers
5: Provide automatic resets

240
Q

A TON instruction begins accumulating time when the run goes _____.

A

True

241
Q

A TON instruction will be true until what happens?

A

The rung goes false or,

The accumulated value = preset value or,

A reset (RES) instrution, if added, is energized

242
Q

DINT refers to “double integer”, meaning what?

A

An actual number

243
Q

TIMER is a _____ structure.

A

Predefined

244
Q

TIME BASE is __ seconds.

A

0.001

245
Q

PRESET is the value which the timer must reach for the processor to do what?

A

Set the done bit (.DN)

246
Q

The ACCUMULATED VALUE is the number of _____ the instruction has counted.

A

Time increments

247
Q

How many status bits do timers have?

A

3

248
Q

Status bits are entered in _____.

A

Mnemonics

249
Q

(BOOL), or ‘Boolean’ means only ‘high’ and ‘set’. T or F

A

False.

High or low, set or reset, etc.

250
Q

In a TON, the TT bit is set when the rung goes _____ and remains set until _____.

A

True

Until ACCUMULATED = PRESET

251
Q

In a TON, the DN bit is set until:

A

The rung goes false

A reset instruction resets the timer.

252
Q

If a power failure or other circumstance interrupts the TON before the PRESET value is reached, what happens?

A

Timer enable remains set, TT remains set, ACCU remains the same.

253
Q

The timer is in the __ area of the tag base?

A

T4

254
Q

How many timer structures can each timer tag base contain?

A

Limited only by memory

255
Q

The time PRESET has a range of 0 - _____.

A

2,147,483,647

256
Q

A TOF instruction begins accumulating time when the rung goes _____.

A

False

257
Q

A TOF instruction will continue timing until what occurs?

A

The ACCU=PRESET

The rung goes true

258
Q

Can you use a RES with a TOF?

A

No

259
Q

If the rung goes true before the timer of a TOF has not timed out, will the accumulated value reset?

A

Yes

260
Q

In a TOF, the EN bit is set when the rung goes _____.

A

True

261
Q

In a TOF, the TT bit is set when the rung goes _____ and the ACCU value is _____.

A

False

Less than the PRESET value

262
Q

The TT bit of a TOF is reset when:

A

The rung goes true

The DN bit is reset

ACCU=PRESET

263
Q

The DN bit of a TOF is set when the rung goes _____.

A

True

264
Q

The DN bit of a TOF is reset when the ACCU is ______ the PRESET.

A

Equal to

265
Q

What needs to happen for the ACCU value of an RTO to reset?

A

Rung goes false, program mode, or power loss to the processor.

266
Q

When the processor resumes operation or the rung goes true, what value will an RTO that was de-energized with an ACCU value of 10s resume timing from?

A

10s

267
Q

How do you reset an RTO accumulated value?

A

A RES with the same addres in another rung.

268
Q

An RTO’s .EN bit is set when _____.

A

The rung goes true

269
Q

An RTO timing bit will be set when _____.

A

The rung goes true

270
Q

The .DN bit of an RTO timer is set when _____.

A

The ACCU=PRESET

271
Q

Can you use a RES instruction with a TOF?

A

No

272
Q

Why must you not use a RES instruction with a TOF?

A

May cause unpredictable operation that may result in injuries of personel.

273
Q

RTOs are in the __ area of the tag base.

A

T4

274
Q

Is a counter an output or input instruction?

A

Output

275
Q

Counters in PLCs provide the same functions as mechanical counters. T or F

A

True

276
Q

Counters only activate a device after reaching the preset value. T or F

A

False. Activates or deactivates

277
Q

Counter instructions are _____ outputs.

A

Internal

278
Q

Is additional hardware needed for PLC counters?

A

No

279
Q

What three words do counters require?

A

Control word

Preset register word

Accumulator register

280
Q

What are the three types of counters and their mnemonics?

A

Count Up = CTU

Count down = CTD

High Speed Counter = HSC

281
Q

What are five industrial applications for counters?

A

1: Packaging
2: Product tracking
3: Measuring lengths/speed
4: Keeping track of inventory
5: Reporting

282
Q

What is the range of a counter in ms?

A

-2,147,483,648 to +2,147,483,647

283
Q

The ACCU value of a counter will reset if the instruction is de-energized and then re-energized. T or F

A

False. Must have a reset.

284
Q

The PRESET value of a counter is a ___-bit integer value

A

32

285
Q

The accumulated value of a counter stops incrementing once the .DN bit is set. T or F

A

False

286
Q

A counter with an OV bit wil do what once the limit has been reached?

A

Wrap around and begin counting from the lower limit.

287
Q

What is the upper programmable limit in ms?

A

2,147,483,647 ms

288
Q

What is the programmable limit in minutes?

A

35,791.394

289
Q

What is the programmable limit in hours?

A

596.523

290
Q

CTUs and CTDs are in the _____ area of the tag base

A

C5

291
Q

Overflow bits are set when ______.

A

ACCU exceeds PRESET

292
Q

Should you use a negative preset value in a counter if also using a RES instruction?

A

No

293
Q

If a negative preset is used and a RES instruction is executed, what will happen?

A

Resets the .DN bit, and prevents the counter instruction from operating.

294
Q

What are the most common ways of transmitting analog signals?

A

Proportional voltage or current signals

295
Q

What are 4 common DC voltages?

A

0-5 Vdc

0-10 Vdc

2-10 Vdc

±10 Vdc

296
Q

Transmittors and sensors are not analog devices. T or F

A

False.

297
Q

Temperature, speed, flow, weight and pressure are all analog devices. T or F

A

True

298
Q

How many input and output channels do the CompactLogix analog IO modules have?

A

4 input, 2 output.

299
Q

4-20 mA is an analog signal that can be converted by the CompactLogix analog input module. T or F.

A

True

300
Q

Two methods of wiring analog IO modules are _____ and _____.

A

Single ended

Differential

301
Q

Are all inputs tied to a common ground using the single ended wiring method?

A

Yes

302
Q

Which wiring method isolates the channels from one another?

A

Differential

303
Q

What 5 things may cause errors in a measurement process?

A

1: Electrostatic fields
2: Inductive pickup
3: Radio frequency interference
4: Power line noise
5: Ground loop current

304
Q

What causes ground loop current?

A

Poor ground connection

Differing common mode voltages in the system

305
Q

Smaller systems are more likely to have ground loop issues. T or F

A

False. Large systems would.

306
Q

What are two ways to prevent ground loop current?

A

Proper grounding

Equipment with floating measurement

Same ground reference

Fourth Year Electrician (7 decks)

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