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Flashcards in PLC Deck (38)
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1

What does PLC stand for

Programmable logic controller

2

What are the 3 basic categories of PLC inputs

Discrete inputs
Analogue inputs
Pulse generating

3

What is an example of a discrete inputs

Contacts or electronic switches

4

What is an example of an analogue input

Potentiometer

5

What is an example of a pulse generating input

Shaft encoder

6

What is an example of a discrete output

Contactor

7

Example of an analogue output

VFD

8

Example of a pulse generating output

Stepper motor

9

What does CPU stand for

Central processing unit

10

PLC Programming devices should be able to perform what four functions

Program entry
Documentation
Run mode
Monitoring

11

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

Reliability
Flexibility
Expandability
Accuracy
Ease of install
Maintainability

12

What are the two main sections of a PLC memory ?

Executive memory
- factory set, never changes

User memory
-user program, changing, adjustable

13

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

A word length or just a “word of memory”

14

What is a input/output module used for

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

15

What is the most common type of I/O interface

Discrete

16

Analogue cards are also called what

Smart cards

17

Typical analogue device inputs include what

Temperature transducers
Pressure transducers
Load cell transducers
Humidity transducers
Flow transducers
Potentiometers

18

Typical analogue device Outputs include

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

19

Analogue I/O are available in what (polarities)

Unipolar (positive)
And
Bipolar (positive and negative )

20

Every discrete input module has what four basic functions

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

21

Dc only modules are available in what types

Sinking or sourcing

22

Every discrete output card has what 4 functions

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

23

What are some important considerations when using output modules with Triacs

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

What environmental factors should be taken into account when installing PLCS

Permissible limits of temperatures
Humidity
Dust
Location
Vibration and shock

25

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

5 degree to 40 degree

26

What is the main function of a MCR master control relay

It is used to shut off power to inputs and outputs

27

What type of protection does the MCR provide

Low voltage protection

28

Where is the best place to mount a PLC

In a motor control center

29

Communications must be kept how many mm from power cables

300 mm

30

Grounding and shielding in what fashion and why

Radial, and to prevent ground loops

31

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

Rule 12-3030 1, B
If they are both controlling the same circuit

32

What is an I/o update

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

33

What is a program scan

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

34

Processor scan is a combination of what ?

The I/o update and the program scan

35

What is scan time

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

36

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

During the next program scan

37

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

Number of inputs and outputs
Size of program
Processor scan speed

38

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

During the I/O scan