Electronics and Controls Flashcards by Eric Saechao

Individual outputs of a typical AC output interface module usually have a maximum current rating of about:
a) 1 A or 2 A
b) 25 A or 50 A
c) 50 mA or 100 mA
d) 250 μA or 500 μA

a) 1 A or 2 A

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Which of the following input field devices would most likely be used with an analog interface input module?
a) Pushbutton
b) Limit switch
c) Selector switch
d) Thermocouple

d) Thermocouple

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The “ON state input voltage range” specification refers to:
a) the type of voltage device that will be accepted by the input
b) range of leakage voltage present at the input in its ON state
c) minimum and maximum output operating voltages
d) voltage at which the input signal is recognized as being ON

d) voltage at which the input signal is recognized as being ON

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Volatile memory elements can be classified as those that:
a) Do not retain stored information when the power is removed
b) retain stored information when the power is removed
c) do not require a battery backup
d) both b and c

a) Do not retain stored information when the power is removed

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_______ memory is used by the PLC’s operating system.
a) RAM
b) EEPROM
c) Flash
d) ROM

d) ROM

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_____ is a type of memory commonly used for temporary storage of data that may need to be quickly changed.
a) RAM
b) ROM
c) EPROM
d) EEPROM

a) RAM

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The most common form of memory used to store, back up, or transfer PLC programs is:
a) RAM
b) Flash EEPROM
c) EEPROM
d) Both b and c

d) Both b and c

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In the event of a power interruption, a(n) _____ is used in some processors to provide power to the RAM.
a) Inductor
b) Capacitor
c) Transistor
d) Resistor

b) Capacitor

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Which of the following is not a function of a PLC programming device?
a) To enter the user program
b) To change the user program
c) To execute the user program
d) To monitor the user program

c) To execute the user program

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Status indicators are provided on each output of an output module to indicate that the:
a) Load has been operated
b) Input associated with the output is active
c) Module fuse has blown
d) Output is active

d) Output is active

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The I/O system provides an interface between:
a) Input modules and output modules
b) The CPU and field equipment
c) The CPU and I/O rack
d) The I/O rack and I/O modules

b) The CPU and field equipment

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PLCs were originally designed as replacements for:
a) microcomputers
b) relay control panels
c) analog controllers
d) digital controllers

b) relay control panels

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Basically, the function of a PLC is to:
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 control outputs based on them

d) make logical decisions and control outputs based on them

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Modifying relay-type process control circuits usually involves changing the:
a) circuit wiring
b) input circuit modules
c) output circuit modules
d) circuit operating voltage levels

a) circuit wiring

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Which of the following is not an advantage that PLCs offer over the conventional relay-type control system?
a) Smaller size
b) Less expensive
c) Higher current capacity
d) More reliable

c) Higher current capacity

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What is the main difference between a PLC and relay control system?
a) Different types of input devices are used
b) Different types of output devices are used
c) Different input and output voltage levels are used
d) One uses hardwired relay control logic and the other uses programmed instructions

d) One uses hardwired relay control logic and the other uses programmed instructions

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The central processing unit:
a) Looks at the inputs, makes the decisions based on the program, and sets the outputs
b) Looks at the outputs, makes the decisions based on the program, and sets the inputs
c) Serves only to store the program in memory
d) Serves only to supply power to the backplane

a) Looks at the inputs, makes the decisions based on the program, and sets the outputs

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PLC proprietary architecture:
a) Is the opposite to open architecture
b) Makes it more difficult to connect to devices made by other PLC manufacturers
c) Does not allow programs to be interchanged between different PLC manufacturers
d) All of the above

d) All of the above

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The output interface module connects to:
a) Sensing devices such as switches or pushbuttons
b) Load devices such as lamps or solenoids
c) A programming device such as a computer
d) All of the above

b) Load devices such as lamps or solenoids

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Field or real-world devices refer to:
a) Input devices only
b) Output devices only
c) Load devices only
d) All devices that are physically wired to the PLC

d) All devices that are physically wired to the PLC

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The power required to operate the logic circuits of the processor unit is typically:
a) Low-voltage AC
b) High-voltage AC
c) Low-voltage DC
d) High-voltage DC

c) Low-voltage DC

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The control plan stored in the PLC is called:
a) A program
b) A Boolean ladder
c) FORTRAN
d) A microprocessor

a) A program

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The programming device:
a) Is used to enter the program into the memory of the processor
b) Is commonly a personal computer
c) Can be a handheld device
d) All of the above

d) All of the above

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The programming device must be connected to the controller:
a) At all times
b) When entering a program
c) When monitoring a program
d) Both b and c

d) Both b and c

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The symbol in a ladder logic diagram: a) Can be thought of as a normally open contact b) Represents a capacitor c) Is always at logic 0 d) Is always at logic 1

a) Can be thought of as a normally open contact

The symbol in a ladder logic diagram represents a: a) Set of normally closed contacts b) Virtual relay coil c) Seal-in contact d) Field input sensing device

b) Virtual relay coil

When a field device contact connected to the input module closes: a) A logic 1 is recorded in the memory location of the coil with the same address b) A logic 1 is recorded in the memory location of the contact with the same address c) A logic 0 is recorded in the memory location of the coil with the same address d) A logic 0 is recorded in the memory location of the contact with the same address

b) A logic 1 is recorded in the memory location of the contact with the same address

At the start of the PLC scan, the: a) Status of all inputs is read b) Status of all outputs is updated c) Program is executed d) Diagnostics and communications tasks are executed

a) Status of all inputs is read

The scan time is the time required: 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 input to output

c) To execute one cycle of the total program

Unlike personal computers, PLCs are: a) Equipped with input and output modules b) Equipped with a control programming language c) Designed for the industrial environment d) All of the above

d) All of the above

A human machine interface (HMI): a) Allows the user to monitor a process b) Allows the user to control a process c) Can provide a graphical representation of a process d) All of the above

d) All of the above

Programmable logic controllers are categorized according to the: a) Number of I/O points b) Current rating of I/O modules c) Power rating of the I/O modules d) Cost of the I/O modules

a) Number of I/O points

A ____ is an example of a device that could be used to provide a discrete input to a PLC. a) Pushbutton b) Selector switch c) Limit switch d) All of the above

d) All of the above

A ____ is an example of an actuator that could be controlled by a discrete output from a PLC. a) Pushbutton b) Motor starter c) Limit switch d) All of the above

b) Motor starter

A(n) ____ input or output is a continuously variable signal within a designated range. a) Discrete b) Digital c) BCD d) Analog

d) Analog

One function of a PLC input interface module is to: a) Accept signals from field devices and convert them into signals that can be used by the processor b) Convert signals from the processing unit into values that can be used to control the machine or process c) Input signals from the programming device and convert them into signals that can be used by the CPU d) Interpret and execute the user program that controls the machine or process

a) Accept signals from field devices and convert them into signals that can be used by the processor

The location of a specific input or output field device is identified by the processor by means of its: a) Voltage rating b) Current rating c) Wattage rating d) Address

d) Address

A discrete output interface module is designed to provide: a) Output voltages only in the 5-VDC range b) Varying AC or DC voltages depending on the type of module selected c) ON/OFF switching of the output field device d) Binary-coded outputs

c) ON/OFF switching of the output field device

The following statement that does not apply to the optical isolator circuit used in I/O modules is that it: a) Separates high-voltage and low-voltage circuits b) Rectifies AC signals c) Prevents damage caused by line voltage transients d) Reduces the effect of electrical noise

b) Rectifies AC signals

The PLC power supply module normally is rated to provide the power for: a) All field devices b) Input field devices only c) Output field devices only d) PLC backplane and I/O modules

d) PLC backplane and I/O modules

Which module of the PLC is responsible for performing logical operations? a) Processor b) Input c) Output d) Power supply

a) Processor

Which module of the PLC connects directly to field devices such as pilot lights, motor starters, and solenoids? a) Input b) Output c) Power supply d) Memory

b) Output

______ I/Os are typical of small PLCs that come in one package with no separate removable units. a) Fixed b) Modular c) Digital d) Analog

a) Fixed

PLC software that runs on a personal computer can be used to: a) Write a PLC program b) Document a PLC program c) Monitor the control process d) All of the above

d) All of the above

A control management PLC application normally requires a: a) Micro-size PLC b) Small-size PLC c) Medium-size PLC d) Large-size PLC

d) Large-size PLC

Which of the following is not a factor affecting the memory size needed for a particular PLC installation? a) Voltage rating of field devices b) Number of I/O points c) Size of control program d) Supervisory functions required

a) Voltage rating of field devices

What does PLC flashing run light indicate? A. No exchanges in progress B. PLC not configured C. PLC in stop or faulty D. Processor is running and all is ready to operate

D. Processor is running and all is ready to operate

If PLC indicates a fault position, to clear you should first check: A. DC supplies B. Ground wiring C. Outputs and inputs for function D. Fuses

C. Outputs and inputs for function

Which of the following does not require analog input from PLC? A. Photo switch B. Potentiometer C. Thermocouple D. Load cell

A. Photo switch

Single phasing occurs when any of the below occur except: A. Connection terminals are adequately tightened B. Loss of one of the phases from the supply C. One of the cables that supply motor is damaged D. Starter contactor is damaged

A. Connection terminals are adequately tightened

Answer: D.) 11.52 Volts

Before measuring voltage with a DMM, what must you ensure? A) The circuit is powered off B) The DMM is set to resistance C) The red lead is connected to COM D) The DMM is set to the correct voltage range

D.) The DMM is set to the correct voltage range

What happens if you try to measure current with the DMM set to measure voltage? A) The reading will be accurate B) The fuse in the DMM may blow C) The display will show "OL" D) The DMM will switch ranges automatically

B.) The fuse in the DMM may blow

Which symbol on a DMM indicates AC voltage? A) V~ B) V⎓ C) A⎓ D) Ω

A.) V~

What does a reading of 'OL' (overload) typically indicate on a DMM when measuring resistance? A) Infinite resistance (open circuit) B) Short circuit C) Low battery D) The DMM is set to the wrong function

A.) Infinite resistance (open circuit)

When measuring DC voltage, which jack does the black lead connect to? A) mA B) COM C) VΩ D) 10A

B.) COM

What would be the expected reading when measuring the voltage across a closed switch in a powered DC circuit? A) 0 volts B) OL C) Full source voltage D) Fluctuating voltage

A.) 0 volts

When should the DMM be set to the highest range? A) When testing low-voltage sensors B) When unsure of the expected voltage C) When measuring microamps D) Always for resistance measurements

B.) When unsure of the expected voltage

What setting should be used to test continuity? A) AC voltage B) Resistance (Ω) C) Capacitance D) Continuity mode with audible tone

D.) Continuity mode with audible tone

Which safety practice is MOST important when using a DMM? A) Hold the test leads near the metal probes B) Change DMM settings while connected to a live circuit C) Always test on high-voltage lines first D) Check leads and settings before applying to circuit

D.) Check leads and settings before applying to circuit

To measure resistance accurately with a DMM, what must you do first? A) Disconnect power from the circuit B) Connect in series with the circuit C) Leave the circuit energized D) Use the 10A port for better accuracy

A.) Disconnect power from the circuit

What is the function of a capacitor in an electrical circuit? A) Increase resistance B) Store electrical energy C) Convert AC to DC D) Amplify voltage

B) Store electrical energy

What does a rectifier do in an electrical system? A) Increases voltage B) Converts AC to DC C) Converts DC to AC D) Stores electrical energy

B) Converts AC to DC

A resistor is used in a circuit to: A) Store charge B) Amplify current C) Oppose current flow D) Convert AC to DC

C) Oppose current flow

What tool is typically used to measure current in a circuit? A) Oscilloscope B) Thermocouple C) Multimeter D) Spectrum analyzer

C) Multimeter

What happens if a fuse in a circuit is blown? A) Voltage increases B) The circuit is protected and opened C) Current flows faster D) The circuit becomes grounded

B) The circuit is protected and opened

In a schematic diagram, the symbol for a diode indicates: A) A switch B) One-way current flow C) A power supply D) Resistance

B) One-way current flow

What does “OL” on a digital multimeter indicate when testing resistance? A) Overload – resistance too high to measure B) Open loop – meter is not working C) Low resistance D) Overload – voltage too high

A) Overload – resistance too high to measure

What unit is used to measure capacitance? A) Ohms B) Amps C) Farads D) Volts

C) Farads

What component stores energy in a magnetic field? A) Capacitor B) Transformer C) Resistor D) Inductor

D) Inductor

What does a ground symbol indicate in a circuit diagram? A) Negative voltage supply B) Physical connection to earth C) Short circuit D) High current path

B) Physical connection to earth

Which component is used to protect a circuit from excessive current? A) Transistor B) Diode C) Circuit breaker D) Inductor

C) Circuit breaker

What is the main purpose of a transformer? A) Store electrical energy B) Control current direction C) Convert AC to DC D) Change voltage levels

D) Change voltage levels

A relay is typically used to: A) Measure voltage B) Amplify current C) Open or close a circuit based on a signal D) Convert AC to DC

C) Open or close a circuit based on a signal

What does a Zener diode do? A) Converts AC to DC B) Allows current to flow in both directions C) Maintains a constant voltage in reverse bias D) Stores magnetic energy

C) Maintains a constant voltage in reverse bias

What happens to a capacitor in a DC circuit after a long time? A) It continues charging B) It acts as a short circuit C) It acts as an open circuit D) It starts discharging

C) It acts as an open circuit

Which component amplifies electrical signals? A) Capacitor B) Diode C) Transistor D) Thermistor

C) Transistor

What is the function of a fuse in an electrical circuit? A) Increase voltage B) Protect from overcurrent C) Measure current D) Regulate resistance

B) Protect from overcurrent

What device would you use to view waveforms of electrical signals? A) Clamp meter B) Voltmeter C) Oscilloscope D) Multimeter

C) Oscilloscope

In a DC circuit, current flows from: A) Negative to positive B) Positive to negative C) Ground to hot D) Neutral to ground

B) Positive to negative

Electronics and Controls Flashcards

(81 cards)