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
