Review Flashcards
Define a programmable logic controller.
A solid-state control device that can be programmed to control process or machine operations. It consists of 5 basic components: the processor, memory, input/output modules, the power supply, and the programming device.
(Write out Q)
In the early years of their existence, PLCs were primarily used for…
ON/OFF control
The ______ and the ______ are the two basic sections of a programmable controller.
central processing unit; I/O interface system
Fill-in Q
The ladder program in a PLC is ______ inside the PLCs CPU.
softwired
True or False:
The monitoring capability of a PLC system can easily detect and correct field device failures.
True
What is the base of these number systems:
Hexadecimal
Binary
Octal
Decimal
Hexadecimal = 16 Binary = 2 Octal = 8 Decimal = 10
(Matching Q)
Why is the binary number system used in digital devices such as programmable controllers and computers?
Easier to design in systems that can only distinguish between 2 states (such as ON/OFF)
In binary, what is one plus one?
One-zero (10)
What are the most common binary codes?
- ASCII
- BCD
- Gray
(Multiple choice Q)
What format does the thumb wheel switch provide to the PLC?
BCD
Multiple choice Q
What logic type is more conventional?
Positive logic
What are the logic functions used in PLCs?
AND, OR, NOT
Multiple choice Q
What does 1 and 0 indicate?
1 = ON, TRUE, or HIGH 0 = OFF, FALSE, or LOW
How many bits are in a 3 byte word?
24 bits (8 bits per byte)
Ladder diagrams are also called…
Contact symbology
Multiple choice Q
Each symbol in a ladder rung has a(n) ______ by which a connected device is referenced.
unique reference number, address, and I/O interface reference terminal connection
What are the three components that form the CPU?
The processor, the memory system, and the power supply
Multiple choice Q
What encompasses all the elements that form the intelligence of a PLC system?
The CPU
Multiple choice Q
Software instructions that allow the interruption of a scan to receive inputs or to update outputs are known as…
immediate instructions
Parity check is sometimes called…
VRC or vertical redundancy check
Fill-in Q
True or False:
PLCs cannot use input voltages from a DC power source.
False
Multiple choice Q
Name the two most common programming devices used with programmable controllers.
Miniprogrammers and personal computers.
Fill-in Q
The total memory system in a PLC is composed of the ______ and the ______ memories.
executive; application
Fill-in Q
______ is the most commonly used application memory.
RAM
Fill-in Q
How long are words?
One byte or more
The executive and scratch pad areas are part of the ______.
System memory
The user program memory is reserved for storage of the ______.
Control logic
How many times can an address be used in a control program?
Unlimited. It can be used as many times as needed.
Multiple choice Q
A master rack refers to an enclosure that contains ______.
The processor
Multiple choice Q
True or False:
The address of an I/O device, which depends on its terminal connection and interface placement in the rack, identifies the device in the control program.
True
Multiple choice Q
Name the two sections of an AC/DC input module’s input circuit.
The power section and the logic section
How do isolated input interfaces differ from standard AC/DC modules?
Isolated input interfaces have separate return, or common, lines
Give two examples of output devices that interface with register output modules.
- Seven segment display
- BCD alphanumeric displays
- Small DC loads
(Fill-in Q)
True or False:
When a bypass/control station’s selector switch is in the OFF position, the PLC can control the connected field devices.
False
What type of signals are analog interfaces used for?
For control of continuous signals
Multiple choice Q
Analog interfaces accept either ______ or ______ types of voltages.
Unipolar; bipolar
The most common formats used to represent analog values in a PLC are ______ and ______.
Binary; BCD
Multiple choice Q
Analog interfaces can have either ______ or ______ input/output capabilities.
Single-ended (all commons tied together)
Differential (all commons separate)
Numerical data received at the module from the processor is converted into an analog voltage or current using a(n) ______.
digital to analog converter (D/A converter)
Fill-in Q
True or False:
Some PLCs use arithmetic instructions to access or send data to analog interfaces.
True
True or False:
In a ladder rung, the left-most side (left power line) simulates the L1 line of a relay ladder diagram.
True
True or False:
Functional blocks are part of the basic ladder language.
False. They’re part of the enhanced ladder language.
The programming language that uses AND, OR, and NOT logic functions to implement the control program is called ______.
Boolean language
How is a latched coil condition reset?
With an unlatch coil instruction
An up counter increments it’s counted value each time it’s referenced event makes a(n) ______ transition.
OFF-to-ON
What are three advantages of a PLC?
- modular
- less expensive
- easily replaceable
- reusable
What forms the connection between the field device and the control?
The input/output system
True or False:
In general, programmable controllers use binary numbers in one form or another to represent various codes and quantities.
True
Be able to draw AND, NAND, OR, and NOR gates
P. 66 of book
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