PLC Final Exam Questions With All Correct &
Verified Answers
The Accumulated (ACC) value of an Up/Down counter is equal to the number of up counts _______
the number of down counts. Correct answer-MINUS
Tag property local refers to module defined because tags are first defined in the Correct answer-
I/O module
serial comm is best described by Correct answer-connecting RS-232 cable (null Modem) between
devices
baud rate is how quickly data is Correct answer-exchanged
input images are the type of memory file used to addressed hardwired Correct answer-inputs
basic rule for a plc program is that the program that is currently used is the only one in Correct
answer-plc memory
is memory that can be overwritten often, Correct answer-RAM
____ stores the entire program to memory and isn't overwitten often. Correct answer-ROM
main use of an I/O diagram is to document the physical connections of the PLC to the machine
electrical Correct answer-hardware.
circuits in I/O modules reduce the effect of line noise on the input state, electrically separate the
control circuit and field circuit voltages and prevent transient line voltage from damaging system
Correct answer-optical isolators
if the system has complete failure, check Correct answer-power supply first
_____modules, directly control AC devices Correct answer-TRIAC OUTPUT
____ discrete output modules use a transistor as a switching device Correct answer-DC
Triac is for Correct answer-AC
transistor is for Correct answer-DC
Logics are - Correct answer-AND, OR, NOT, NOR, NAND
counters Correct answer-count up, count down, latch, unlatch
routines Correct answer-applications intructions, inputs, outputs.
subroutines - allow for several programs on a single plc routine programs, Correct answer-tasks.
are an example of plc programming language projects.
Bits are Correct answer-integers double intergers (DINT) word boolean
,5 commonly used numbering systems are Correct answer-hexadecimal, decimal binary octal binary
coded decimal (BCD)
weighted value Correct answer-LSD (least, furthest to the right) MFD(most, furthest to the left)
a plc output is wired to a motor starter, N.O auxiallary contact from the motor starter is an input to
the plc. if the output of the plc is off then the input to the plc will be what? Correct answer-off
numbering systems used to display timing or counter numbers are in a Correct answer-decimal
base
NPN device is one that can switch the negative side of the circuit while a PNP device switches the
Correct answer-positive side.
NPN schematic symbol points down, while PNP Correct answer-UP and in
RTO Correct answer-Retentive Timer On
NON Retentive Correct answer-Timer ON (TON) Timer off (TOF)
Serial communication is best described by connecting Correct answer-RS232 cable between cables
(null modem)
input images are the type of memory file used to Correct answer-address hardwired inputs
______ for a PLC program is that the program that is currently used is the only one in PLC memory.
Correct answer-basic rule
Ram is memory that can be Correct answer-overwritten often, status of input & output devices are
an exampl
_____ stores the entire program to memory and isn't overwritten often ** Correct answer-ROM
Handshake is Correct answer-sending info (ask and receive)
battery backup for Correct answer-memory
most popular communication protocols are ethernet and Correct answer-universal serial bus (USB)
Main us of an I/O diagram is to document the physical connections of the PLC to the machine
Correct answer-electrical hardware.
Active low input module: Current sinking input module must be used with a Correct answer-
current sourcing sensor
5 features of output modules; ss dc output modules use transistors for Correct answer-switches
You want to look at voltage required of the load device, current draw of the load device and
Correct answer-number of inputs required.
, the purpose of a digital output module is to energize loads in response to plc Correct answer-
instruction
a diode cannot be used with an AC control Correct answer-voltage
the best place to start when trouble shooting an issue with a PLC system is to identify the symptoms
of a Correct answer-specific problem
7 types of PLC faults : the first you should verify when there is a processor fault is to check the
processor fault messages on Correct answer-Error codes
at the start of an individual start up when trouble shooting a suspected PLC power supply problem
and the input AC voltage to a PLC is good Correct answer-the power supply fuse and the input
voltage selection jumper should be checked.
To verify that an output is sending the correct signal to a relay from the PLC output module you
should Correct answer-use a voltmeter to verify the correct voltage to the relay
wiring a field device causes the majority of PLC system Correct answer-failures
indicator lights on a plc are used for Correct answer-diagnostics & maintenance
PLC input lights are off, but if they are on it could be a Correct answer-faulty wiring , a defective
sensor, or a faulty power supply
you will not find provisions for human intervention beyond e-stop in the code of Correct answer-
automatic program
a hardwired master control relay (MCR) is used as a safety device to remove power from all Correct
answer-PLC outputs to disable all actions
when a hardwired master control relay (MCR) is automatically de-energized some input status lights
are on, the cpu running light is on, and Correct answer-all action output status light are off
to test a discrete input module. establishing a force is Correct answer-not a good way
if a known good input causes the light to illuminate on the input modules but the PLC program fails
to respond to the input Correct answer-the key switch is in REM
if the force indicator is not illuminated, other devices connected to the same module and functioning
correctly and you have tested contactor individually and found functionally Correct answer-The
PLC is not in run mode
an advantage of adding comments to ladder rungs and individual program instructions is because .
Correct answer-they improve execution efficiency
you should document the program after altering it to do an additional task by date, Correct
answer-the intended effect, & which line of the program you changed
a major difference between manual mode and an automatic mode of a plc controlled machine is the
logic uses Correct answer-different inputs for the operator
Verified Answers
The Accumulated (ACC) value of an Up/Down counter is equal to the number of up counts _______
the number of down counts. Correct answer-MINUS
Tag property local refers to module defined because tags are first defined in the Correct answer-
I/O module
serial comm is best described by Correct answer-connecting RS-232 cable (null Modem) between
devices
baud rate is how quickly data is Correct answer-exchanged
input images are the type of memory file used to addressed hardwired Correct answer-inputs
basic rule for a plc program is that the program that is currently used is the only one in Correct
answer-plc memory
is memory that can be overwritten often, Correct answer-RAM
____ stores the entire program to memory and isn't overwitten often. Correct answer-ROM
main use of an I/O diagram is to document the physical connections of the PLC to the machine
electrical Correct answer-hardware.
circuits in I/O modules reduce the effect of line noise on the input state, electrically separate the
control circuit and field circuit voltages and prevent transient line voltage from damaging system
Correct answer-optical isolators
if the system has complete failure, check Correct answer-power supply first
_____modules, directly control AC devices Correct answer-TRIAC OUTPUT
____ discrete output modules use a transistor as a switching device Correct answer-DC
Triac is for Correct answer-AC
transistor is for Correct answer-DC
Logics are - Correct answer-AND, OR, NOT, NOR, NAND
counters Correct answer-count up, count down, latch, unlatch
routines Correct answer-applications intructions, inputs, outputs.
subroutines - allow for several programs on a single plc routine programs, Correct answer-tasks.
are an example of plc programming language projects.
Bits are Correct answer-integers double intergers (DINT) word boolean
,5 commonly used numbering systems are Correct answer-hexadecimal, decimal binary octal binary
coded decimal (BCD)
weighted value Correct answer-LSD (least, furthest to the right) MFD(most, furthest to the left)
a plc output is wired to a motor starter, N.O auxiallary contact from the motor starter is an input to
the plc. if the output of the plc is off then the input to the plc will be what? Correct answer-off
numbering systems used to display timing or counter numbers are in a Correct answer-decimal
base
NPN device is one that can switch the negative side of the circuit while a PNP device switches the
Correct answer-positive side.
NPN schematic symbol points down, while PNP Correct answer-UP and in
RTO Correct answer-Retentive Timer On
NON Retentive Correct answer-Timer ON (TON) Timer off (TOF)
Serial communication is best described by connecting Correct answer-RS232 cable between cables
(null modem)
input images are the type of memory file used to Correct answer-address hardwired inputs
______ for a PLC program is that the program that is currently used is the only one in PLC memory.
Correct answer-basic rule
Ram is memory that can be Correct answer-overwritten often, status of input & output devices are
an exampl
_____ stores the entire program to memory and isn't overwritten often ** Correct answer-ROM
Handshake is Correct answer-sending info (ask and receive)
battery backup for Correct answer-memory
most popular communication protocols are ethernet and Correct answer-universal serial bus (USB)
Main us of an I/O diagram is to document the physical connections of the PLC to the machine
Correct answer-electrical hardware.
Active low input module: Current sinking input module must be used with a Correct answer-
current sourcing sensor
5 features of output modules; ss dc output modules use transistors for Correct answer-switches
You want to look at voltage required of the load device, current draw of the load device and
Correct answer-number of inputs required.
, the purpose of a digital output module is to energize loads in response to plc Correct answer-
instruction
a diode cannot be used with an AC control Correct answer-voltage
the best place to start when trouble shooting an issue with a PLC system is to identify the symptoms
of a Correct answer-specific problem
7 types of PLC faults : the first you should verify when there is a processor fault is to check the
processor fault messages on Correct answer-Error codes
at the start of an individual start up when trouble shooting a suspected PLC power supply problem
and the input AC voltage to a PLC is good Correct answer-the power supply fuse and the input
voltage selection jumper should be checked.
To verify that an output is sending the correct signal to a relay from the PLC output module you
should Correct answer-use a voltmeter to verify the correct voltage to the relay
wiring a field device causes the majority of PLC system Correct answer-failures
indicator lights on a plc are used for Correct answer-diagnostics & maintenance
PLC input lights are off, but if they are on it could be a Correct answer-faulty wiring , a defective
sensor, or a faulty power supply
you will not find provisions for human intervention beyond e-stop in the code of Correct answer-
automatic program
a hardwired master control relay (MCR) is used as a safety device to remove power from all Correct
answer-PLC outputs to disable all actions
when a hardwired master control relay (MCR) is automatically de-energized some input status lights
are on, the cpu running light is on, and Correct answer-all action output status light are off
to test a discrete input module. establishing a force is Correct answer-not a good way
if a known good input causes the light to illuminate on the input modules but the PLC program fails
to respond to the input Correct answer-the key switch is in REM
if the force indicator is not illuminated, other devices connected to the same module and functioning
correctly and you have tested contactor individually and found functionally Correct answer-The
PLC is not in run mode
an advantage of adding comments to ladder rungs and individual program instructions is because .
Correct answer-they improve execution efficiency
you should document the program after altering it to do an additional task by date, Correct
answer-the intended effect, & which line of the program you changed
a major difference between manual mode and an automatic mode of a plc controlled machine is the
logic uses Correct answer-different inputs for the operator
