MODULE 7 PLC Tech- UHD EXAM
Allen-Bradley timers and counters have addresses based on their location in the
Data table
The computer characteristics of the PLC were introduced to the control system through the devlopment of
Data transfer instructions
When a CPU is scanning the I/O rack, if it detects a device which is hardwired normally closed in the field, it will instruct the PLC to change the state of the contacts in the program. This operation is called
EXAMINE ON/ EXAMINE OFF
The PLC instruction which overrides a stop button wired to the PLC making it impossible to turn off an output, is called the ____ instruction
Force
An Allen-Bradley I/O address begins with the character ____ or ____
I and O
The method of determining where a specific input or output device is located in a PLCs memory is called
I/O addressing
A device that is incorporated into a PLC system which removes power from output modules or equipment independently of the PLC is the
MCR
A device that is incorporated into a PLC system, which removes power from the output modules or equipment, independently of the PLC, is the
MCR
The EXAMINE ON instruction tests for a(n) ____ condition at a particular reference
ON, address
The EXAMINE ON instruction tests for a(n) ____ condition at a particular reference ____
ON----- Address
An instruction that only changes state when the input goes from zero to one is called
OSR
How do you change the type of switch used in the PLCLogix 500 I/O simulator?
Right click the switch
What is the name of the default timer file in RSLogix
T4
When an output instruction is required in a program, but no physical connection to a field device is needed a(n) ____ is used
internal coil
When an output instruction is required in a program, but no physical connection to a field device is needed, a(n) ____ is used
internal coil
In order to create an internal coil it is necessary to use an address which
isn't being used by an output device
In order to create an internal coil, it is necessary to use an address which
isn't being used by an output device
____ is a term used to describe the format used for schematic diagrams to be entered in a PLC
ladder
An output instruction that maintains an energized or de-energized state after power to the output has been removed is called a(n) ____ relay
latch
The maximum number of rungs allowed in a ladder logic program is usually
limited only by the PLCs memory
A latching relay is an output that
maintains an energized or de-energized state after power is removed
What is the programming error in the ladder logic circuit of figure 7-28
nesting
In ladder logic diagrams devices are shown in their ____ condition
normal
In ladder logic diagrams, devices are shown in their ____ condition
normal
Internal outputs are
not accessible at the I/O rack
Vertical contacts are
not used for PLC programming
In a ladder logic diagram all devices that make or break electrical contacts are shown
on the left of the diagram
How many bits of information can be held by a flip-flop?
one
In a ladder logic diagram, a normally closed input device is usually entered as normally ____
open
In a ladder logic program overload contacts are entered as normally
open
A ladder network consists of a number of rungs with each rung controlling a(n) ____
output
In a ladder logic diagram usually all ____ are entered as they appear
outputs
In ladder logic diagrams devices that perform a start function are usually connected in ____
parallel
In ladder logic diagrams, devices that perform a start function are usually connected in ____
parallel
Unlike a relay logic diagram a ladder network does not represent
physical connections
What is the programing error in the ladder logic circuit of figure 7-20
reverse power flow
PLC programming restrictions often forbid
reverse power flow, nesting, vertical contacts
PLCs will never scan in a
right to left direction
The means employed by the CPU to read a ladder logic program is called the ____
scan
Allen-Bradley PLCs use the
scan by rung method
The basic scan patterns used by PLCs include
scan by rung, scan by column
The PLC determines the status of input and output devices in the program by
scanning
The PLCs CPU determines the status of input and output devices in the program by
scanning
In ladder logic diagrams, devices which perform a stop function are usually connected in ____
series
All contacts associated with a device will change ____ when the device is energized
state
The third section in an Allen-Bradley I/O address determines
the I/O position in the module
During a program execution, if the processor encounters an EXAMINE ON instruction, examines the reference address, and it is OFF
the processor will not change the state of the NO contacts
During program execution, if their processor encounters an EXAMINE OFF instruction, examines the reference address, and it is ON
the processor will open the NC contacts
The second section in an Allen-Bradley I/O address determines
the rack and slot number
The second section in an allen bradley I/O address determines
the rack and slot number
In ladder logic circuits, overloads are entered _____ a coil
to the left of
A one shot pulse is also known as a(n)
transitional contact
Contacts which stay open or closed in the program for one scan only each time they are energized are called
transitional contacts
Contacts which stay open or closed in the program for one scan only, each time they are energized are called
transitional contacts
If a PLC has a total scan time of 7 ms and is required to monitor a signal that changes state ____ the CPU will never notice that the signal has changed state
twice in 5 ms
Master Control Relay functions in relay logic schematics are often represented by ____ contacts
vertical
The first character in an Allen-Bradley I/O address determines
whether the device is an input or an output
The steps involved in writing a ladder logic program include
write the ladder logic diagram, draw a sketch of the process operation, list the sequence of operations to be performed, define the process to be controlled
In ladder logic, only ____ and ____ are used to represent input and output devices
contacts---- Coils
Nesting is defined as
creating a branch within a branch
What are the two types of ladder language elements?
data transfer and relay logic instructions
What are two types of ladder language elements?
data transfer and relay logic instructions
Most PLC addresses use the first digit or character in the address to indicate
data type
Most PLC addresses use the first digit, or character, in the address, to indicate
data type
In order to run a ladder logic program you must first ____ it to the PLC
download
In order to run a ladder logic program, you must first ____ it to the PLC
download
Internal outputs are also called
dummy relays, software coils
In a relay logic to ladder conversion, the easiest way to eliminate nesting is often
duplicate contacts
In a relay logic to ladder logic conversion, the easiest way to eliminate nesting is often
duplicate contacts
SUS instructions are used to
evaluate multiple bits of data
A ladder network forms an electrical schematic diagram for the control of ___ and ___ devices
input, output
In a ladder logic diagram, usually all ____ are entered as normally open
inputs
Which of the following statements is true about ladder logic programming
inputs are entered as normally open
An SUS instruction has an ID number that can range between
-32,767 and +32,767
How long does it take a typical PLC to scan 128 inputs and outputs?
1 ms
The maximum number of contacts on a single rung for most PLCs is
15
Allen-Bradley I/O modules generally contain ____ inputs or outputs on a single module
16
Timers and counters have mnemonic sub elements including
ACC, PRE
Timers and counters have mnemonic sub-elements, including
ACC, PRE
Due to programming restrictions, would 45 considered too many contacts for a rung of a ladder logic program?
Yes
The term EXAMINE ON refers to
a normally open (NO) instruction
The term Examine ON refers to
a normally open (NO) instruction
An overload relay is a(n) ____ device
input
The memory address I:10/7 represents a(n)
input
The edit panel of the PLC lab simulation software provides
access to logic instructions
If a relay logic diagram is drawn in ladder logic input and output devices are represented by letters and numbers
address
If a relay logic diagram is drawn in ladder logic, input and output devices are represented by letters and numbers called ____
address
Non-retentive outputs should be used for
all outputs that are entered as normally closed
Ladder logic programs ____ have an end statement
always
An input in a ladder logic circuit is controlled by
an input field device
Devices connected in parallel with other devices are typically called
branches
In ladder logic diagrams, devices connected in parallel with other devices are often called ____
branches
A retentive coil
can be reset with an Unlatch Coil instruction
When a semiconductor is destroyed it
can produce either an open circuit or short circuit
A field closure refers to a control device, such as a Stop button, which is hardwired normally ____
closed
The last element to be entered on a ladder logic rung is a(n)
coil
