PLC Flashcards
What does PLC stand for
Programmable logic controller
What are the 3 basic categories of PLC inputs
Discrete inputs
Analogue inputs
Pulse generating
What is an example of a discrete inputs
Contacts or electronic switches
What is an example of an analogue input
Potentiometer
What is an example of a pulse generating input
Shaft encoder
What is an example of a discrete output
Contactor
Example of an analogue output
VFD
Example of a pulse generating output
Stepper motor
What does CPU stand for
Central processing unit
PLC Programming devices should be able to perform what four functions
Program entry
Documentation
Run mode
Monitoring
What are 6 major advantages of a PLC over hard wired systems
Reliability Flexibility Expandability Accuracy Ease of install Maintainability
What are the two main sections of a PLC memory ?
Executive memory
- factory set, never changes
User memory
-user program, changing, adjustable
On a 16 byte machine , a 2 byte word is called what
A word length or just a “word of memory”
What is a input/output module used for
Provides a physical link between the actual field equipment and the CPU (central processing unit)
What is the most common type of I/O interface
Discrete
Analogue cards are also called what
Smart cards
Typical analogue device inputs include what
Temperature transducers Pressure transducers Load cell transducers Humidity transducers Flow transducers Potentiometers
Typical analogue device Outputs include
Analogue control valves Actuators Chart recorders Electric motor drives Analogue meters Pressure transducers
Analogue I/O are available in what (polarities)
Unipolar (positive)
And
Bipolar (positive and negative )
Every discrete input module has what four basic functions
Termination
Signal conditioning (rectifier)
Isolation (opto-isolator)
Indication
Dc only modules are available in what types
Sinking or sourcing
Every discrete output card has what 4 functions
Termination
Noise suppression (MOVs, metal oxide varistors)
Isolation
Indication
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
What environmental factors should be taken into account when installing PLCS
Permissible limits of temperatures Humidity Dust Location Vibration and shock
