PLC

Question 1

What does PLC stand for

Answer 1

Programmable logic controller

Question 2

What are the 3 basic categories of PLC inputs

Answer 2

Discrete inputs
Analogue inputs
Pulse generating

Question 3

What is an example of a discrete inputs

Answer 3

Contacts or electronic switches

Question 4

What is an example of an analogue input

Answer 4

Potentiometer

Question 5

What is an example of a pulse generating input

Answer 5

Shaft encoder

Question 6

What is an example of a discrete output

Answer 6

Contactor

Question 7

Example of an analogue output

Answer 7

VFD

Question 8

Example of a pulse generating output

Answer 8

Stepper motor

Question 9

What does CPU stand for

Answer 9

Central processing unit

Question 10

PLC Programming devices should be able to perform what four functions

Answer 10

Program entry
Documentation
Run mode
Monitoring

Question 11

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

Answer 11

Reliability
Flexibility 
Expandability 
Accuracy 
Ease of install
Maintainability

Question 12

What are the two main sections of a PLC memory ?

Answer 12

Executive memory
- factory set, never changes

User memory
-user program, changing, adjustable

Question 13

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

Answer 13

A word length or just a “word of memory”

Question 14

What is a input/output module used for

Answer 14

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

Question 15

What is the most common type of I/O interface

Answer 15

Discrete

Question 16

Analogue cards are also called what

Answer 16

Smart cards

Question 17

Typical analogue device inputs include what

Answer 17

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

Question 18

Typical analogue device Outputs include

Answer 18

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

Question 19

Analogue I/O are available in what (polarities)

Answer 19

Unipolar (positive)
And
Bipolar (positive and negative )

Question 20

Every discrete input module has what four basic functions

Answer 20

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

Question 21

Dc only modules are available in what types

Answer 21

Sinking or sourcing

Question 22

Every discrete output card has what 4 functions

Answer 22

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

Question 23

What are some important considerations when using output modules with Triacs

Answer 23

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

Question 24

What environmental factors should be taken into account when installing PLCS

Answer 24

Permissible limits of temperatures 
Humidity
Dust
Location
Vibration and shock

Question 25

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

Answer 25

5 degree to 40 degree

Question 26

What is the main function of a MCR master control relay

Answer 26

It is used to shut off power to inputs and outputs

Question 27

What type of protection does the MCR provide

Answer 27

Low voltage protection

Question 28

Where is the best place to mount a PLC

Answer 28

In a motor control center

Question 29

Communications must be kept how many mm from power cables

Answer 29

300 mm

Question 30

Grounding and shielding in what fashion and why

Answer 30

Radial, and to prevent ground loops

Question 31

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

Answer 31

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

Question 32

What is an I/o update

Answer 32

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

Question 33

What is a program scan

Answer 33

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

Question 34

Processor scan is a combination of what ?

Answer 34

The I/o update and the program scan

Question 35

What is scan time

Answer 35

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

Question 36

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

Answer 36

During the next program scan

Question 37

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

Answer 37

Number of inputs and outputs Size of program Processor scan speed

Question 38

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

Answer 38

During the I/O scan