There are 3 types of indicators: Status, Output, and Input. Of these indicators, which
indicator indicates that the PLC/processor is successfully executing its program? -
ANSWER RUN
You are investigating an automated machine. It was working before you were called over to
investigate. On the processor, there are status indicators (FORCE, RUN, POWER, IO), and a
scrolling message describing the project. What errors does the processor NOT display? -
ANSWER Error: I/0 field device failure
In a previously working PLC system, which of these problems will NOT appear as a processor
fault or fault message? - ANSWER Switches, solenoids, indicators, and contacts failures
Forcing is a way to manually switch bits from state to state (0 to1, 1 to 0, whatever). Forcing
bits to turn on or off would not affect the: - ANSWER Processor Mode
Which of the following provides voltage to the discrete inputs and electronic sensors wired
to the PLC. - ANSWER External power supply
The first troubleshooting step is to check the main power disconnect and then the AC
supplied to the DC power supply. What would be the next point to check? Refer to your PLC
packet - ANSWER TP2
You are investigating an automated machine.It was working before you were called over to
investigate.This means that it has suddenly failed.All of the PLC indicators are off (status,
output, and input).There are machines nearby operating normally.Which of these should you
do before the other others? - ANSWER Check fuses for continuity or circuit breakers.
1
, You are pushing an input button (PB1).The input indicators are turning on and off when you
press PB1.The output (L1) should be turning on but it's not. The output indicators are turning
on and off when you press PB1.You measured the voltage at the output terminal, and it does
change/switch from low to high (OVDC - 24VDC) when PB1 is pressed. What is the most
likely issue? - ANSWER Output device or wiring is bad.
Clamp and drill doesnt start at step one.The clamp does not extend after the operator
momentarily presses PB1.Which device is likely causing the issue. - ANSWER PB1
If the clamp and drill machine shown has stopped unexpectedly after performing step 1 of
its sequence, what are the most likely I/0 device failures? - ANSWER LS3, SOL1A
Before forcing an output on a PLC to test an output device, which of the following are not
required? - ANSWER Logic Program
When are I/0 forces first applied in a PLC? - ANSWER User must confirm the forces before
they are applied
If a PLC's input indicators are correct but expected outputs areNOT produced, what is the
easiest step (and therefore the first step) to troubleshoot the problem? - ANSWER Verify
that the processor's force indicator is off
What is systems-level troubleshooting? - ANSWER Using a series of tests to isolate the
problem to a specific component is a process of systems-level troubleshooting
I want you to close your eyes and imagine the clamp and drill sequence. Imagine, still and
quietly with your eyes closed, this clamp and drill sequence as a continuously reciprocating
cycle. You've given the normally open start pushbutton a momentary press. The process
starts. The machine begins to clamp and drill. Over and over. The machine unexpectedly
stops mid-sequence. All of the indicators on the PLC are normal and correct (status, outputs,
and input indicators are accurate).Where in is this issue most likely located? - ANSWER
I/0 field devices
2
indicator indicates that the PLC/processor is successfully executing its program? -
ANSWER RUN
You are investigating an automated machine. It was working before you were called over to
investigate. On the processor, there are status indicators (FORCE, RUN, POWER, IO), and a
scrolling message describing the project. What errors does the processor NOT display? -
ANSWER Error: I/0 field device failure
In a previously working PLC system, which of these problems will NOT appear as a processor
fault or fault message? - ANSWER Switches, solenoids, indicators, and contacts failures
Forcing is a way to manually switch bits from state to state (0 to1, 1 to 0, whatever). Forcing
bits to turn on or off would not affect the: - ANSWER Processor Mode
Which of the following provides voltage to the discrete inputs and electronic sensors wired
to the PLC. - ANSWER External power supply
The first troubleshooting step is to check the main power disconnect and then the AC
supplied to the DC power supply. What would be the next point to check? Refer to your PLC
packet - ANSWER TP2
You are investigating an automated machine.It was working before you were called over to
investigate.This means that it has suddenly failed.All of the PLC indicators are off (status,
output, and input).There are machines nearby operating normally.Which of these should you
do before the other others? - ANSWER Check fuses for continuity or circuit breakers.
1
, You are pushing an input button (PB1).The input indicators are turning on and off when you
press PB1.The output (L1) should be turning on but it's not. The output indicators are turning
on and off when you press PB1.You measured the voltage at the output terminal, and it does
change/switch from low to high (OVDC - 24VDC) when PB1 is pressed. What is the most
likely issue? - ANSWER Output device or wiring is bad.
Clamp and drill doesnt start at step one.The clamp does not extend after the operator
momentarily presses PB1.Which device is likely causing the issue. - ANSWER PB1
If the clamp and drill machine shown has stopped unexpectedly after performing step 1 of
its sequence, what are the most likely I/0 device failures? - ANSWER LS3, SOL1A
Before forcing an output on a PLC to test an output device, which of the following are not
required? - ANSWER Logic Program
When are I/0 forces first applied in a PLC? - ANSWER User must confirm the forces before
they are applied
If a PLC's input indicators are correct but expected outputs areNOT produced, what is the
easiest step (and therefore the first step) to troubleshoot the problem? - ANSWER Verify
that the processor's force indicator is off
What is systems-level troubleshooting? - ANSWER Using a series of tests to isolate the
problem to a specific component is a process of systems-level troubleshooting
I want you to close your eyes and imagine the clamp and drill sequence. Imagine, still and
quietly with your eyes closed, this clamp and drill sequence as a continuously reciprocating
cycle. You've given the normally open start pushbutton a momentary press. The process
starts. The machine begins to clamp and drill. Over and over. The machine unexpectedly
stops mid-sequence. All of the indicators on the PLC are normal and correct (status, outputs,
and input indicators are accurate).Where in is this issue most likely located? - ANSWER
I/0 field devices
2
