PLC Flashcards

1
Q

What does PLC stand for

A

Programmable logic controller

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2
Q

What are the 3 basic categories of PLC inputs

A

Discrete inputs
Analogue inputs
Pulse generating

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3
Q

What is an example of a discrete inputs

A

Contacts or electronic switches

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4
Q

What is an example of an analogue input

A

Potentiometer

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5
Q

What is an example of a pulse generating input

A

Shaft encoder

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6
Q

What is an example of a discrete output

A

Contactor

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7
Q

Example of an analogue output

A

VFD

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8
Q

Example of a pulse generating output

A

Stepper motor

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9
Q

What does CPU stand for

A

Central processing unit

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10
Q

PLC Programming devices should be able to perform what four functions

A

Program entry
Documentation
Run mode
Monitoring

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11
Q

What are 6 major advantages of a PLC over hard wired systems

A
Reliability
Flexibility 
Expandability 
Accuracy 
Ease of install
Maintainability
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12
Q

What are the two main sections of a PLC memory ?

A

Executive memory
- factory set, never changes

User memory
-user program, changing, adjustable

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13
Q

On a 16 byte machine , a 2 byte word is called what

A

A word length or just a “word of memory”

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14
Q

What is a input/output module used for

A

Provides a physical link between the actual field equipment and the CPU (central processing unit)

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15
Q

What is the most common type of I/O interface

A

Discrete

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16
Q

Analogue cards are also called what

A

Smart cards

17
Q

Typical analogue device inputs include what

A
Temperature transducers
Pressure transducers
Load cell transducers
Humidity transducers 
Flow transducers 
Potentiometers
18
Q

Typical analogue device Outputs include

A
Analogue control valves 
Actuators
Chart recorders 
Electric motor drives 
Analogue meters
Pressure transducers
19
Q

Analogue I/O are available in what (polarities)

A

Unipolar (positive)
And
Bipolar (positive and negative )

20
Q

Every discrete input module has what four basic functions

A

Termination
Signal conditioning (rectifier)
Isolation (opto-isolator)
Indication

21
Q

Dc only modules are available in what types

A

Sinking or sourcing

22
Q

Every discrete output card has what 4 functions

A

Termination
Noise suppression (MOVs, metal oxide varistors)
Isolation
Indication

23
Q

What are some important considerations when using output modules with Triacs

A

Triacs will leak a small amount of current. This leakage current can cause an output to appear on after the output is turned off

24
Q

What environmental factors should be taken into account when installing PLCS

A
Permissible limits of temperatures 
Humidity
Dust
Location
Vibration and shock
25
Q

What range of temperatures can PLCs be expected to work properly in

A

5 degree to 40 degree

26
Q

What is the main function of a MCR master control relay

A

It is used to shut off power to inputs and outputs

27
Q

What type of protection does the MCR provide

A

Low voltage protection

28
Q

Where is the best place to mount a PLC

A

In a motor control center

29
Q

Communications must be kept how many mm from power cables

A

300 mm

30
Q

Grounding and shielding in what fashion and why

A

Radial, and to prevent ground loops

31
Q

If 2 systems are in the same cable under what circumstances would the CEC allow this?

A

Rule 12-3030 1, B

If they are both controlling the same circuit

32
Q

What is an I/o update

A

It reads the input information and writes outputs based on that information

33
Q

What is a program scan

A

Executing or running the logic program , or executing a series of instructions that control the output sequence

34
Q

Processor scan is a combination of what ?

A

The I/o update and the program scan

35
Q

What is scan time

A

Scan time is the time it takes to execute 1 cycle of the process scan

36
Q

If the state of the inputs change mid way through a program scan, when do these changes take effect.

A

During the next program scan

37
Q

What are 3 things that the scan time of the processor depend on

A

Number of inputs and outputs
Size of program
Processor scan speed

38
Q

During what portion of the cycle does a processor read the input status and write to the outputs

A

During the I/O scan