COURSE:
SUBJECT:
Lecturer:
Mechanical Engineering
Production Systems and Automation – MME 510
Dr. Sotiris Omirou
REVIEW QUESTIONS – A-
1.Basically, the function of a PLC is to:
1. ANSWER:……d……..
a.amplify various weak signal sources.
b.control a high voltage output with a low voltage input.
c.control the speed of motors.
d.make logical decisions and provide outputs.
2.The scan time is the time required:
2. ANSWER:……c……..
a.to record the status of all input devices.
b.to record the status of all output devices.
c.to execute one cycle of the total program.
d.for the information to pass from one circuit to another within the PLC
3.Unlike general purpose computers, PLCs are:
3. ANSWER:……c……..
a.very expensive.
b.harder to program.
c.designed for the industrial environment.
d.all of the above.
4.A programmed normally closed PLC contact:
4. ANSWER:……d……..
a.with a bit status of 1 will not allow current to flow through the contact.
b.is examined for an OFF condition.
c.is examined for an ON condition.
d.both a and b.
5.Parallel connections of a ladder logic program are typically called:
5. ANSWER:……d……..
a.rungs.
b.networks.
c.coils.
d.branches.
6.The last element to be entered in a ladder logic rung is a(n):
6. ANSWER:………a…..
a.coil.
b.contact.
c.EXAMINE IF CLOSED.
d.EXAMINE IF OPEN.
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7. Which module of the PLC is responsible for performing
logical operations ?
7. ANSWER:……a……..
a.Processor
b.Input
c.Output
d.Power supply
8. The status bit of switches and pushbuttons connected
to a PLC is stored in the:
8. ANSWER:……a……..
a.input image table
b.output image table file
c.user program
d.all of the above
9. Memory organisation defines how certain areas of memory
are used and is commonly referred to as a:
9. ANSWER:……d……..
a.program
b.data sheet
c.processor
d.memory map
10. In ladder logic programs, all outputs are represented by:
10. ANSWER:……c…..
a.contact symbols
b.coil symbols
c.schematic load devices
d.branches
11. The addressing format used with PLCs:
11. ANSWER:……d..
a.is always a five digit code
b.is always represented using the octal number system
c.is standard for all manufacturers
d.none of these
12. A rung consists of:
12. ANSWER:……a..
a. one or more inputs and only one output
b. a series of inputs and a series of outputs
c. NC or NO contacts.
d. push-buttons or toggle switches
13. Each complete horizontal line of a ladder logic diagram is
generally referred to as:
13. ANSWER:……a…..
a.rung
b.branch
c.input
d.output
14. The abbreviations NO (normally open) and
NC (normally closed) represent the electrical
14. ANSWER:……d…..
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state of switch contacts when:
a.power is applied
b.power is not applied
c.the switch is actuated
d.the switch is not actuated
15. A limit switch is usually actuated by:
15. ANSWER:……c…..
a.hand
b.pressure
c.contact with an object
d.an electromagnet
16. Solenoid valves are available to control:
16. ANSWER:………d..
a.oil flow
b.air flow
c.water flow
d.all of these
17. Field or real world devices refer to
17. ANSWER:……d…..
a.input devices only
b.output devices only
c.load devices only
d.all devices that are physically wired to the PLC.
18. The three main components of PLCs are
the input module, CPU, and
18. ANSWER:……b…..
a. actuator module
b. output module
c. operator interface
d. input device
19. Prior to PLCs, many control tasks were solved with
19. ANSWER:……a…..
a. hard-wired controls
b. actuator-sensor controls
c. programmable-logic
d. computer-controllers
20. A signal which varies continuously is called
20. ANSWER:……b…..
a. digital
b. analog
c. continuous
d. variable
21. One K memory (1K) means that there are
21. ANSWER:……b…..
3
a. 1000 bytes
b. 1024 bytes
c. 1048 bytes
d. 1096 bytes
22. Which of the following types of memory is designed to permanently store a program that
cannot be altered under any circumstances?
a. RAM
b. ROM
c. EPROM
22. ANSWER:……b…..
23. The binary concept makes use of the fact that certain information
a.
b.
c.
d.
can exist in one of two possible states
can be broken down into smaller units for easier analysis
can be divided into two or more categories
can be divided into two, or multiple of two, categories
23. ANSWER:……a…..
24. In conventional logic circuits, binary 1 represents
a. the presence of a signal
b. a high voltage level
c. the occurrence of some event
d. all the above
24. ANSWER:………d..
25. A single rung of a ladder logic program is arranged witha. Input conditions connected from left to right, with the output at the far right.
b. Input conditions connected from right to left, with the output at the far left.
c. The output in the center and the input conditions to the left and right of it.
d. All input conditions in parallel and all output conditions in series.
25. ANSWER:…a…..
26. Which of the following is not a factor in determining the total scan time of PLC?
a. Memory protection.
b. Program content.
c. Program length.
d.Total number of inputs and outputs used.
27.Programmed counters can:
26. ANSWER:…a……..
27. ANSWER:……d…..
a.count up.
b.count down.
c.be combined to count up and down.
d.all of these.
28. The PLC counter instruction is similar to the:
28. ANSWER:……d…..
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a.internal relay instruction
b.transitional contact instruction
c.relay coil and contact instruction
d.timer instruction
29.Unlike the TON timer, the RTO timer requires a(n):
29. ANSWER:……a..
a.timer reset instruction.
b.input condition instruction.
c.internal relay instruction.
d.instantaneous contact instruction.
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