Programmable Logic Controller (PLC) Assessment 1
PLC Proficiency Quiz
Test your knowledge and understanding of Programmable Logic Controllers (PLCs) with our comprehensive quiz designed for students, professionals, and enthusiasts alike. Dive into topics ranging from binary representation to PLC fun
This quiz offers:
- 30 carefully crafted questions
- Immediate feedback on your answers
- An opportunity to reinforce your learning
What does the binary 10110 represent in decimal form?
101
17
22
3
How many bits in a byte?
1
4
8
16
How many bytes in a word?
1
2
4
16
PLCs were originally designed as replacements for?
Microcomputers
Relay control panels
Analog controllers
Digital controllers
Basically, the function of a PLC is to?
Amplify various weak signal sources
Control a high voltage output with a low voltage input
Control the speed of motors
Make logical decisions and control outputs based on them
Modifying relay-type process control circuits usually involves changing the?
Circuit wiring
Input circuit modules
Output circuit modules
Circuit operating voltage levels
Which of the following is not an advantage that PLCs offer over the conventional relay-type of control system?
Smaller size
Less expensive
Higher current capacity
More reliable
The main difference between a PLC and relay control system is that?
Different types of input devices are used
Different types of output devices are used
Different input and output voltage levels are used
One uses hardwired relay control logic and the other uses programmed
The central processing unit?
Looks at the inputs, makes the decisions based on the program, and sets the outputs
Looks at the outputs, makes the decisions based on the program, and sets the inputs
Serves only to store the program in memory
Serves only to supply power to the backplane
The output interface module connects to?
Sensing devices such as switches or pushbuttons
Load devices such as lamps or solenoids
A programming device such as a computer
All of the above
Field or real-world devices refer to?
Input devices only
Output devices only
Load devices only
All devices that are physically wired to the PLC
The power required to operate the logic circuits of the processor unit is typically?
Low voltage ac
High voltage ac
Low voltage dc
High voltage dc
The control plan stored in the PLC is called?
A program
A Boolean ladder
FORTRAN
A microprocessor
The programming device?
Is used to enter the program into the memory of the processor
Is commonly a personal computer
Can be a hand-held device
All of the above
The programming device must be connected to the controller?
At all times
When entering a program
When monitoring a program
Both b and c
When a field device contact connected to the input module closes?
A logic 1 is recorded in the memory location of the coil with the same address
A logic 1 is recorded in the memory location of the contact with the same address
A logic 0 is recorded in the memory location of the coil with the same address
A logic 1 is recorded in the memory location of the contact with the same address
The scan or cycle time is the time required?
To record the status of all input devices
To record the status of all output devices
To execute one cycle of the total program
For the information to pass from input to output
A human machine interface (HMI)?
Allows the user to monitor a process
Allows the user to control a process
Can provide a graphical representation of a process
All of the above
Programmable logic controllers are categorized according to the?
Number of I/O points
Current rating of I/O modules
Power rating of the I/O modules
Cost of the I/O modules
The PLC power supply module normally is rated to provide the power for?
All field devices
Input field devices only
Output field devices only
PLC backplane and I/O modules
One disadvantage of modular I/O is its lack of flexibility?
TRUE
FALSE
A PLC power supply module does not normally supply power to the field devices?
TRUE
FALSE
Removing the programming device from the PLC will not affect the operation of the user program?
TRUE
FALSE
A ____ is an example of a device that could be used to provide a discrete input to a PLC?
Pushbutton
Selector switch
Limit switch
All of the above
A ____ is an example of an actuator that could be controlled by a discrete output from a PLC?
Pushbutton
Motor starter
Limit switch
All of the above
A/An ____ input or output is a continuously variable signal within a designated range?
Discrete
Digital
BCD
Analog
A discrete output interface module is designed to provide?
Output voltages only in the 5 VDC range
Varying AC or DC voltages depending on the type of module selected
ON/OFF switching of the output field device
Binary-coded outputs
Which of the following input field devices would most likely be used with an analog interface input module?
Pushbutton
Limit switch
Selector switch
Thermocouple
Status indicators are provided on each output of an output module to indicate that the?
Load has been operated
Input associated with the output is active
Module fuse has blown
Output is active
The purpose of the optical isolator is to?
Aid in fault diagnosis
Set the minimum level of voltage that can be detected
Protect against electrical noise interference
Separate the higher line voltage from the logic circuits
Typical analog inputs and outputs can vary from?
0 to 20 mA
4 to 20 mA
0 to 10 volts
All of the above
A ______ module is used to establish connections for the exchange of data?
Thumbwheel
Communication
Servo
PID
The____of an analog I/O module specifies how accurately an analog value can be represented digitally?
Number of inputs and outputs per card
Input impedance and capacitance
Resolution
Common mode rejection ratio
Electronic components found in PLC modules?
Are not effected by electrostatic voltages
Can be damaged by electrostatic voltages
Can have their performance degraded by electrostatic voltages
Both b and c
The decimal system has as its base?
2
5
8
10
Which of the following number systems has a base of 16?
Hexadecimal
Octal
Binary-coded decimal
Gray code
The decimal number 15 would be written in binary as?
1111
1000
4C
11001
The binary number 101 has the decimal equivalent of?
3
101
41
5
The binary number 101101 would be written in decimal as?
21
36
45
62
The hexadecimal number C4 would be written in decimal as?
21
48
182
196
The acronym BCD stands for?
Binary-coded decimal
Base code decoder
Binary code decoder
Base-coded decimal
If a given memory unit consists of 1250 16-bit words, the memory capacity would be rated?
1250 bits
20,000 bits
3260 bits
156 bits
The binary concept makes use of the fact that certain informal?
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 multiples of two, categories
A gate is a device that?
Allows current flow in one direction only
Changes alternating current to direct current
Performs a logical decision based on its inputs
Performs a logical decision based on its outputs
The basic rule for an AND gate is?
If all inputs are 1, the output will be 1
If all inputs are 1, the output will be 0
If all inputs are 0, the output will be 1
If one or more inputs are 1, the output is 1
The basic rule for an OR gate is?
If all inputs are 1, the output will be 1
If all inputs are 1, the output will be 0
If all inputs are 0, the output will be 1
If one or more inputs are 1, the output is 1
The OR function, implemented using contacts, requires contacts connected in?
Series
Parallel
Series/parallel
Parallel/series
An AND gate operates on the same principle as?
A series circuit
A parallel circuit
A series-parallel circuit
None of these
A thermocouple, when heated?
Produces a small dc voltage
Produces a small ac voltage
Increases its resistance value
Decreases its resistance value
An encoder is used to?
Encode signals from a scanner
Decode signals from a scanner
Change DC to AC
Convert motion into a digital signal
An actuator is a device that?
Changes AC to DC
Changes DC to AC
Converts an electrical signal into mechanical movement
Converts mechanical movement into an electrical signal
Solenoid valves are available to control?
Oil flow
Air flow
Water flow
All of these
All servo motors?
Operate in the closed-loop mode
Operate in the open-loop mode
Operate without feedback
Both b and c
The main difference between a PLC retentive and Non-retentive timer is that the?
Retentive timer can be programmed for much longer time delay periods
Non-retentive time can be programmed for much longer time delay periods
Retentive timer maintains the current time should power be removed from the device or when the timer rung goes false
Non-retentive timer maintains the current time should power be removed from the device or when the timer rung goes false
A one-shot, or transitional, contact?
Operates the same as an NO contact instruction
Operates the same as an NC contact instruction
Operates the same as a timed closed contact
Closes for only one program scan when actuated
When routing power and I/O signal wiring to and within a PLC enclosure you should?
Use the shortest possible wire runs for I/O signals
Never run signal and power wiring in the same conduit
Run low level signal conductors as shielded twisted pair
All of these
Certain input field devices may have a small leakage?
In the on state
In the off state
Examined for an on condition
Examined for an off condition
A high voltage spike is generated whenever current to?
An inductive load is turned off
An inductive load is turned on
A resistive load is turned off
A resistive load is turned on
Which of the following would not normally be included as part of a routine preventive maintenance program?
Inspection of I/O field devices
Monitoring the program
Checking connections to I/O modules
Cleaning of the PLC enclosure
Most PLC system faults are caused by?
Faulty power supplies
Malfunctioning microprocessors
Software failure
Field wiring and devices
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