Pangasinan State University

Lingayen Campus
Lingayen, Pangasinan
COLLEGE OF TECHNOLOGY

ET 120 INDUSTRIAL PROCESS CONTROL

MIDTERM EXAMINATION

Name: _________________________________________________Date:_______________
Section: ________________________________________________Score:______________

Direction: Choose the best answer and write it on the space provided.

______1. What is the main objective of process control?

A. to control physical parameters
B. to control mechanical parameters
C. to control optical parameters
D. to control electrical parameters

______2. In open loop control system:

A. Output is independent of control input
B. Output is dependent of control input
C. Only system parameters have effect on the control output
D. None of the above

______3. What is a process control system?

A. system to keep the parameters at zero value
B. system to maintain the parameters constant
C. system to keep the parameters at highest value
D. system to check the voltage

______4. The _________ of metals is a function of temperature and increases with increasing
temperature.
A. Coefficient of material
B. Resistance
C. Conductivity
D. Kappa

______5. Physical parameters change due to ________.

A. voltage
B. current
C. internal and external disturbances
D. power

______6. Which of the following is correct for tactile sensors?

A. Touch sensitive
B. Pressure sensitive
C. Input voltage sensitive
D. Humidity sensitive
______7. A process control system consists of ________.
A. 10 elements
B. 6 elements
C. 2 elements
D. 4 elements

______8. Change in output of sensor with change in input is ____________

A. Threshold
B. Slew rate
C. Sensitivity
D. none of the mentioned

______9. A transducer converts ________.

A. mechanical quantity to electrical form
B. electrical quantity to physical form
C. physical quantity to electrical form
D. chemical quantity to physical form

_______10. The reason process control is so popular is the increased of __________.

A. Safety
B. Operationability
C. Profitability
D. All of the above

_______11. For open loop control system which of the following statements is incorrect?
A. Less expensive
B. Recalibration is not required for maintaining the required quality of the output
C. Construction is simple and maintenance easy
D. Errors are caused by disturbances

_______12. Any radiation of appropriate wavelength fall on the depletion layer of p-n
junction develops a potential difference between the junctions’ is working principle of
A Hall Effect sensor
B Proximity sensor
C Light sensor
D All of the above
_______13. Block diagram of a simple standard control system is shown below in the figure.
Which of the following statement about the above control system is wrong?

A. The transfer functions of the measuring element and the process is represent
by H and G2 respectively
.B The overall transfer function for the change in load (X = 0) is given by Y/X1 =
(Gc . G1 . G2)/(1 +  Gc . G1 . G2 . H)
C. The overall transfer function for the change in set point (X1 = 0) is given by Y/X =
(Gc . G1 . G2)/(1 +  Gc . G1 . G2 . H)
D. Manipulated variable is represented by C

_______14. What is the number of root locus segments which do not terminate on zeros?
A. The number of poles
B. The number of zeros
C. The difference between the number of holes and the number of zeros
D. The sum of the number of poles and the number of zeros

_______15. Pick out the symbol for "locally mounted instrument" in instrumentation
diagram.

_______16. Type of sensor used to detect both metallic and non-metallic objects
A. Capacitive sensor
B. Inductive sensor
C. Thermocouple sensor
D. pH Sensor

________17. Thermocouples consist of a pair of wires made of dissimilar metals joined

together at one or more junctions that generate a voltage when subjected to a temperature
gradient. This phenomenon is known as the _________
A. Seebeck effect
B. Piezolelectric effect
C. Photovoltaic
D. Photoconductor

________18. _________ have been utilized in thermostats for years. They are mechanically
connected to a switch, such as a mercury switch, to control heaters.
A. Unimetal
B. Bimetallic
C. Trimetallic
D. Quadrametallic

________19. The objective of process control is to keep key process operating parameters
within narrow bounds of the ____________
A. Reference value
B. Spot
C. Pith
D. Inception point
_______20. In a closed loop system, the process to be controlled is an integrating process
with transfer function 1/2s. The controller proposed to be used in an integral controller with
transfer function 1/T1s. When a step change in set point is applied to such a closed loop
system, the controlled variable will exhibit
A. Overdamped response
B. Underdamped response
C. Undamped response
D. Unstable response

_______21. It is speed control system output rate feedback is used to

A. Limit the speed of motor
B. Limit the acceleration of the motor thing
C. Reduce the damping of the system
D. Increase the gain margin

______22.
It is a sensor is a device that converts:
A. Physical quantity into measurable signals
B. Physical quantity into mechanical signal
C. Electrical signal into physical quantity
D. Physical quantity into electric signal only

_______23. What is the characteristic of a good control system?

A. Sensitive to parameter variation
B. Insensitive to input commands
C. Neither sensitive to parameter variation nor sensitive to input commands
D. Insensitive to parameter variation nor sensitive to input commands
______24. What does CPR stand for?
A. Cycles per revolution
B. Counts per revolution
C. Both A and B
D. None of the above.

______25.In closed loop control system, with positive value of feedback gain the overall gain
of the system will_______.
A. Decrease
B. Increase
C. Be unaffected
D. Any of the above
______26. The negative lead of a thermocouple is always colored:
A. Blue
B. Yellow
C. Red
D. White

______27. The most rugged temperature sensing element listed here is a/an:
A. Thermocouple
B. Orifice plate
C.RTD
D. Filled bulb

______28.
Change in output of sensor with change in input is ____________
A. Threashold
B. Slew rate
C. Sensitivity
D. None of the mentioned

_______29. When the reference junction is the same temperature as the measurement
junction in a thermocouple circuit, the output voltage (measured by the sensing instrument)
is:
A. Zero
B. Reverse polarity
C. Noisy
D. AC instead of DC
______30. A closed loop system is distinguished from open loop system by which of the
following?
A. Servomechanism
B. Feedback
C. Output pattern
D. Input pattern

______31. On which of the following factors does the sensitivity of a close loop system to
gain changes and load disturbances depend ?
A. Frequency
B. Loop gain
C. Forward gain
D. All of the above

______32. Sensitivity of a sensor can be depicted by _______________

A. Niquist plot
B. Pole- zero plot
C. Bode plot
D. None of the mentioned

______33. Reference junction compensation is necessary in thermocouple-based temperature

instruments because:
A. Copper extension wire has a tendency to corrode
B. Thermocouples are inherently nonlinear
C. The reference junction generates a temperature-dependent voltage
D. The junction’s electrical resistance varies with temperature

______34. A control system in which the control action is somehow dependent on the output
is known as_______.
A. Closed loop system
B. Semi closed loop system
C. Open system
D. Open Loop system

_______35. Identify the thermocouple type with the highest temperature limit from those
listed here:
A. Type J
B. Type K
C. Type S
D. Type T

_______36. Latent heat is:

A. The heat required to raise the temperature of a substance
B. The amount of heat energy present in ambient conditions
C. The potential energy residing in a sample of unburnt fuel
D. The heat required to make a substance change phase

_______37. Thermocouple extension wire may be readily distinguished from regular

thermocouple-grade wire by:
A. Different metal types
B. Outer sheath color
C. Special markings on the wire’s insulation
D. Thickness

______38. The frequency and time domain are related through which of the following?
A. Laplace Transform and Fourier Integral
B. Laplace Transform
C. Fourier Integral
D. Either B and C

______39. A type J thermocouple is made of the following metals:

A. Aluminum and Tungsten
B. Iron and Constantan
C. Platinum and Platinum/Rhodium alloy
D. Copper and Constantan

______40. Which sensor can detect nearby objects?

A. Proximity sensor
B. Humidity sensor
C. Touch sensor
D. Pressure sensor

______41. Traffic light system is the example of:

A. Open-loop system
B. Closed-loop system
C. Both (a) and (b)
D. None of these
_______42. Thermocouple is a ______________
A. Primary device
B. Secondary transducer
C. Tertiary transducer
D. None of the mentioned

______43. Which of the following element is used as a thermocouple in nuclear reactor?

A. Boron
B. Platinum
C. Copper
D. Iron

______44. Thermocouple cannot be used to measure ____________

A. Temperature of gas
B. Temperature of liquid
C. IR radiation
D. None of the mentioned

______45. The negative feedback closed-loop system was subjected to 15V. The system has
a forward gain of 2 and a feedback gain of 0.5. Determine the output voltage and the error
voltage.
A. 15V, 10V
B. 6V, 5V
C. 15V, 7.5V
D. 5V, 10V

_____46. Transient response in the system is basically due to ______.

A. Forces
B. Friction
C. Stored energy
D. Coupling
_____47. Effect of feedback on the plant is to
A. Control system transient response
B. Reduce the sensitivity to plant parameter variations
C. Both (a) and (b)
D. None of these

_____48. In an open loop system:

A. Output control the input signal
B. Output has no control over input signal
C. Some other variable control the input signal
D. Neither output nor any other variable has any effect on input

______49. Transfer function of a system can used to study its _____.

A. Steady state behavior
B. Transient behavior
C. Both (a) and (b)
D. None of these

______50. _________________ can be used as a replacement for thermocouple lead.

A. Replacement lead
B. Replica lead
C. Compensating lead
D. None of the mentioned