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POWER ENGINEERING 4A - UNIT 9 - PLANT INSTRUMENTATION POWER ENGINEERING COURSE REVIEW 2025/2026 // QUESTION BANK // VERIFIED QUESTIONS AND ANSWERS GRADED A+ // INDUSTRIAL INSTRUMENTATION & CONTROL SYSTEMS STUDY GUIDE // GUARANTEED SUCCESS Valve actuators, damper drive motors, stepper motors and motor starters are all examples of electrically operated A) operating control elements B) final control elements
C) primary (sensing) control elements - CORRECT ANSWER - B
Final control elements are A) transmitters B) input devices C) output devices D) recording devices
E) monitoring devices - CORRECT ANSWER - C
Small PLCs tend to be A) monolithic (self-contained) B) modular
C) modular or monolithic (self-contained) - CORRECT ANSWER - A
Glass stem thermometers operate on the principle of A) two metals expanding at different rates. B) expansion due to temperature decrease. C) contraction due to temperature increase. D) expansion due to temperature increase.
E) capillary action. - CORRECT ANSWER - B
Stepper motors have multiple _______________ arranged around an iron stator. A) electro-mechanical limit switches B) brushes C) salient electromagnetic pole pieces
D) electronic sensors - CORRECT ANSWER - C
The NDIR (Non-Dispersive Infrared Radiation) detector consists of an infrared (IR) light source, ______________ , and a sample tube for the gas to pass through. A) IR recorder B) IR detector C) controller
D) secondary transmitter - CORRECT ANSWER - B
One pound per square inch (psi) pressure is equal to A) 1 kilopascal. B) 6.89 kPa. C) 100 kPa. D) 1 newton per meter squared.
E) 1 kilogram per meter squared. - CORRECT ANSWER - B
A control loop controller: Select one: a. Constantly compares a process variable to the set point b. Eliminates all setpoint deviation
Select one: a. Must modulate from fully open to fully shut b. Provide tight flow shut-off c. Provide variable resistance in a piping system
d. Must fail closed - CORRECT ANSWER - C
A thermocouple measures: Select one: a. Light b. Velocity c. Temperature
d. Pressure - CORRECT ANSWER - C
Pressure controllers can be divided into two classes: Select one: a. High and low voltage b. High and low flow c. High and low pressure
d. High and low temperature - CORRECT ANSWER - C
The variable area meter consists of: Select one: a. An opening that can be varied as required b. A tapered tube in which the fluid being measured flows through the tube from the bottom to the top c. A float across which the differential pressure varies d. A fluid being measured, flowing through the tube from the top to the
bottom - CORRECT ANSWER - B
A PLC needs to be able to check itself for safe operation. This is called: Select one: a. Start up Check b. maintenance scan c. housekeeping scan
d. Self check - CORRECT ANSWER - C
A discrete input is not: Select one: a. limit switch b. temperature sensor c. push button
d. proximity switch - CORRECT ANSWER - B
Automatic systems which can make decisions are termed A) annunciation systems. B) logic systems. C) indicating systems. D) open loop systems.
E) cascading systems. - CORRECT ANSWER - B
In an automatic control system, the controller output signal manipulates the A) transmitter. B) sensing element. C) recorder.
______________ are designed for technical applications. A) Workstations B) Personal computers C) Controllers D) Servers
E) Technical laptops - CORRECT ANSWER - A
The type of air damper to provide with a much more precise air flow control, especially at small openings, is A) parallel blade damper B) opposed blade damper C) variable outlet vane damper
D) variable inlet vane damper - CORRECT ANSWER - B
The Chromel-Alumel (Type K) thermocouple can be used in the temperature range of A) - 184 oC to 371oC B) - 18oC to 760oC C) - 185oC to 1260oC D) 538oC to 1482oC
E) 200oC to 3000oC - CORRECT ANSWER - C
One common mass flow meter is called A) Weir meter B) Coriolis meter C) Variable area meter
D) Doppler meter - CORRECT ANSWER - B
With reference to the controller design, CPU stands for A) central processing unit B) controlled programmable utility C) combined power utility
D) controlled personal unit - CORRECT ANSWER - A
A Bourdon tube is often in the shape of a spiral so that A) its final output has less travel. B) gears can be used for final output. C) higher pressures can be sensed. D) more power and travel of the free end occurs.
E) its sensitivity will be decreased. - CORRECT ANSWER - D
Smart transmitters cannot: A) Receive multiple inputs and outputs B) Communicate and change configuration details C) Change the power source(s)
D) Signal alarms and error conditions - CORRECT ANSWER - C
In a power plant, networking of computers is advantageous because A) operators can use any computer to regulate the process. B) shift operators can communicate with each other by e-mail. C) computing power is distributed and the loss of one computer is less serious. D) complete control will be maintained during a power failure.
E) viruses may be easily eradicated throughout the system. -
CORRECT ANSWER - C
Immersion thermostat (Aquastat) is used to sense and control the temperature of A) solids B) non-homogeneous substances C) vapors D) gases
E) liquids - CORRECT ANSWER - E
In computer terminology, HDD means A) hard documented drive B) home directed device C) home disk drive D) hard disk drive
E) homogeneous digital drive - CORRECT ANSWER - D
The DCS controller receives information from input modules and sends information to A) field transmitters B) transducers C) output modules D) workstations
E) HMIs - CORRECT ANSWER - C
A multiplexer is used to regulate tasks in sequence as often as A) once per hour. B) twice per minute. C) four times per minute.
D) once every few seconds.
E) billions of operations per second. - CORRECT ANSWER - E
A momentary contact switch can be used to A) turn the boiler on or off B) limit the boiler firing rate C) silence the alarm horn
D) place the boiler in automatic or manual control - CORRECT
ANSWER - C
Liquids must be vaporized A) in order to measure density. B) if purity is to be measured. C) when analyzed using a chromatograph. D) when conductivity is measured.
E) when resistance or reluctance is being measured. - CORRECT
ANSWER - C
When the controller is notified ahead of time about an upcoming process (controlled variable) change, so that it can respond before the change takes place. This is referred to as A) cascade control B) split range control C) feedback control
D) feedforward control - CORRECT ANSWER - D
A valve which has two seats, gives good throttling action, but does not close tightly is the
The most common medium for powering control valves and dampers is A) pneumatic signal (compressed air) B) hydraulic signal (hydraulic fluid) C) electronic signal
D) electrical signal - CORRECT ANSWER - A
The apparatus which converts current signals to pneumatic and pneumatic to current signals is called a: Select one: a. Transformer b. Inverter c. Transducer
d. Converter - CORRECT ANSWER - C
In a basic electrical control system the device that senses a drop in air temperature is called the: Select one: a. Thermostat b. Humidistat c. Pneumatic temperature sensor
d. Final controlled device - CORRECT ANSWER - A
A basic electric control circuit has 2 major pieces: Select one: a. solenoid valve and final control element b. sensor and thermostat c. sensor switch and final control element
d. controller and sensor - CORRECT ANSWER - C
Modular PLC's can be expanded by adding___________. Select one: a. cards b. memory c. inputs
d. outputs - CORRECT ANSWER - A
Some of the components of an automatic control loop are a sensing element, a transmitter, a _____ and a control valve. Select one: a. Converter b. Transformer c. Transducer
d. Controller - CORRECT ANSWER - D
The constant head connection in a remote water level indicator is made to the: Select one: a. Steam space b. Atmosphere c. Feed water pump discharge
d. Water space - CORRECT ANSWER - A
An electrical actuator used to position dampers and control valves is called: Select one: a. A transformer
A valve which gives good throttling action, takes less actuator force, but does not seal well is a: Select one: a. Direct acting valve b. Reverse acting valve c. Single seated valve
d. Double seated valve - CORRECT ANSWER - D
A computer displays information to the operator via Select one: a. a CPU b. a CAD c. a monitor
d. an icon - CORRECT ANSWER - C
The Bourdon tube is often shaped in the form of a "C", having an arc span of about: Select one: a. 270 degrees b. 90 degrees c. 180 degrees
d. 200 degrees - CORRECT ANSWER - A
Computers are used in plants for managing maintenance, one function that cannot be done by computer alone is: Select one: a. prepare scheduled maintenance work orders
b. maintenance cost reports c. inventory maintenance
d. equipment operating times - CORRECT ANSWER - B
PLC's for Burner Management Systems can: Select one: a. Be used without any field testing b. Have limited field configurations c. Be set up by technicians at burner repair companies
d. Be programmed by operators - CORRECT ANSWER - B
A valve actuator: Select one: a. Position is a function of controller output b. Is a two-position device c. Will always have one side of the diaphragm open to atmosphere
d. Cannot be reverse acting - CORRECT ANSWER - A
In an electric control circuit, the sensing unit may also be the__________ Select one: a. controller b. final control element c. thermostat
d. humidistat - CORRECT ANSWER - A
c. They can fit in narrower enclosures
d. Its final output has less travel - CORRECT ANSWER - A
Run time totals, recorded by a computer, are commonly used: Select one: a. For maintenance management b. For logic supervisory systems c. For inventory control
d. In graphic displays - CORRECT ANSWER - A
A device which will cause a visible light signal to become an instrument analog signal is the: Select one: a. Current-to-pneumatic transducer b. Controller c. PE switch
d. Photoelectric transducer - CORRECT ANSWER - D
A proportional controller: Select one: a. Allows the process variable to always be maintained at the set-point b. Provides on-off control c. Provides a proportional output based on the error between process variable and set-point
d. Is also called a multi-position controller - CORRECT ANSWER - C
Digital output signals are processed by _____ before an analog controls can react to them.
Select one: a. Analog converters b. the CPU c. Logic controllers
d. Digital receivers - CORRECT ANSWER - A
Why were PLC's developed? Select one: a. No maintenance or programming is required b. Remove the requirement of sensors for feedback c. Ability or run without human intervention
d. To allow use of multiple inputs and outputs - CORRECT ANSWER
- D
Sharing and transferring information between computers is termed: Select one: a. Networking b. Number crunching c. Plotting
d. Central processing - CORRECT ANSWER - A
Cascade control utilizes: Select one: a. Two controllers, two transmitters and one valve. b. Two controllers, two transmitters and two valves. c. Two controllers, one transmitter and two valves.
