Elstan’s Marine Electrical Technology Guide

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Chapter 2 – Process Control Theory

a)    A control system is an interconnection of ____.

b)    A thermostat is used to monitor ____.

c)     Closed-loop control is a process where ____.

d)    The set point is also known as ____.

e)     An automatic control system has two process variables associated with it - namely a ____ and a ____.

f)      There are two types of feedback control namely____ and ____.

g)     ____feedback is the most useful control type since it typically helps a system converge toward a state of equilibrium.

h)    ____feedback can lead a system away from an equilibrium state thus rendering it unstable

i)      Unless stated explicitly, the term feedback control most often refers to ____ feedback.

j)      A controller is a device where the process control system operation generates the ____ signal based on the ____ signal it receives.

k)     The signal that represents the desired value of a controlled variable and is also called the ____.

l)      The feedback signal is a function of the ____ signal.

m)   The algebraic sum of the reference input signal and feedback signal is called the ____ signal.

n)    The manipulated variable is ____.

o)    The feedback elements are components needed to ____.

p)    Deviation is the difference between the ____ of a process variable and its ____.

q)    The dynamic / time response of a system is ____.

1.       What do you understand by a process control system?

2.       What is the sequence of actions that take place within a controlled system? How are the input and output variables related?

3.       How does an open loop system work? What are its drawbacks?

4.       With a suitable example, explain the principle of operation of a closed loop system.

5.       What is an automatic control system? What are its functional elements?

6.       What are the functions of automatic control?

7.       What is the significance of feedback in a control system?

8.       What is the effect of negative feedback?

9.    What are the various process time lags?

10.  How is stability achieved in an automatic control system?

11.    Briefly explain dynamic response of a system

12.    What do you understand by step response?

13.    How does a system behave in equilibrium?

14.    Write short notes on the following:

a)       Feedforward Control

b)       Feedforward plus Feedback Control

c)       Cascade Control

15.    Write short notes on the following:

a)       Ratio Control

b)       Digital Control

c)       Fuzzy Control

d)       Selective Control

Chapter 3 – Sensing Elements and Transducers

Fill in the blanks / complete the sentence for the following:

a)       The ____ is the primary sensing element and exists in close proximity to the process, representing the value of the process variable.

b)       In order to control a dynamic variable in a process, there must be information about ____.

c)       The ____ measures the controlled variable in the process and sends a non-standardized signal to the ____.

d)       A Transducer is a device that converts pressure, temperature, flow, viscosity, motion, etc., into ____ for the purpose of measurement and control.

e)       The transmitter is a device that responds to ____and delivers an input to the ____.

f)        The ____ current loop is a most popular and ideal sensor signalling standard for data transmission.

g)       Steady-state Gain (K) = ____.

h)       A material’s degree of resistance to electricity is defined by a property called ____.

i)        A  Pt100 sensor is a device with a typical resistance of ____ Ω at ____°C.

1.         List the most widely used sensors.

2.         With a suitable diagram, explain the role of sensor and transmitter.

3.      What are the differences between a transducer and a transmitter?

4.      What is the significance of the 4-20 mA current loop in a control system? 

5.         How does a voltage-to-current converter work?

6.         How is noise How is noise reduced in sensor line cables?

7.         What do you understand by transmission system dynamics?

8.      Write short notes on:

a.     Transducer

b.     Precision

c.      Linearity

d.     Accuracy

e.      Offset

9.      Write short notes on:

a.     Drift

b.    Span

c.     Range

10.   Write short notes on:

a.     Sensitivity

b.     Dead Band

c.     Response Time

d.     Hysteresis

11.   Write short notes on:

a.     Reproducibility

b.     Repeatability

c.     Resolution

12.      With suitable examples and diagrams, highlight the differences between switches and transducers.

13.      How does a pressure switch work? Explain with a suitable diagram.

14.      With a suitable diagram, explain the temperature range of various electrical sensors.

15.      What are non-contact temperature sensors?

16.      List the four basic types of temperature measuring devices and explain their working principles.

17.      How does a bimetallic strip thermometer work?

18.      What is an RTD? Where is it normally used?

 

 

19.   With a suitable circuit diagram, explain temperature detection using a Pt100 sensor.

20.      How does the three-wire measurement method work for a Pt100 sensor?

21.   What is a thermistor? How does it work and where is it used?

22.      What are the applications of thermistors?

23.      Write short notes on the three types of thermocouple junctions.

24.      With suitable sketches, explain the working principle of thermocouples.

25.       What do you understand by cold junction compensation?

26.     Briefly explain the working principle of a thermopile.

27.      How can semiconductor devices also be used to measure temperature?

28.        With suitable diagrams / graphs, differentiate the various characteristics of sensors.

29.      How do infrared temperature sensors work?

30.      With suitable sketches, briefly explain how mechanical input can be converted to electrical output.

31.      Why are diaphragms and bourdon tubes popular with pressure measuring devices? Justify your answer with suitable diagrams.

32.   What is a strain gauge? Where can it be used?

33.      Why is a piezoelectric transducer gaining popularity as an active transducer? Explain its working principle with suitable examples and diagrams.

34.      With suitable sketches, highlight the differences between inductive and reluctive pressure sensors.

35.      How do linear variable differential transformers work?

36.      What are the applications of capacitive pressure sensors?

37.      With a suitable diagram, explain the working principle of a variable capacitance transducer.

38.      With a suitable diagram, explain the working principle of an optical pressure transducer.

39.      What are the two basic methods to measure liquid level?

40.      List the 4 hydrostatic pressure methods used to measure liquid level. Explain each method with suitable diagrams.

41.      Write short notes on:

a.         Bubbler gauge for level measurement

b.         Resistance tape level measurement

c.          Conductivity probe method

d.         Hydrostatic head level sensors

e.          Capacitance level sensor 

42.      What is the significance of a gauge glass? How is it used in a boiler?

43.      With suitable examples and diagrams, explain the operating principle of differential pressure level transmitters.

44.      What is the importance of a three valve manifold in a DPT?

45.      How can the level measurement of electrically conductive materials be carried out?

46.      How can the level measurement of electrically non-conductive materials be carried out?

47.      How is a level sensor calibrated?

48.      With simple diagrams, explain the operation of an ultrasonic liquid level sensor.

49.      With a simple diagram, explain the working principle of a Tank Radar.

50.      How does a Rotameter work?

51.      What is an orifice flow meter? Draw simple diagrams to depict the three basic types of orifice plates used.

52.      How is a venturi flow meter better than an orifice flow meter? Explain with a suitable diagram.

53.      With a suitable diagram explain the operation of the flow nozzle.

54.      Where is the Pitot tube used? How does it work?

55.      With suitable diagrams explain the theory of the Doppler Effect ultrasonic flow meter.

56.      With suitable diagrams explain the theory of time of flight ultrasonic flow meter.

57.      With a suitable block diagram explain the operation of a smart transmitter.

58.      Write short notes on:

a.         Mechanical type flow meters

b.         Inferential type flow meters

c.          Electrical type flow meters

59.   Write short notes on:

a.    Turbine Flow Meter (Mechanical)

b.       Turbine Flow Meter (Electrical)

c.    Electromagnetic Flow meter

d.       Transit-Time Flow meters

e.     Ultrasonic Flow meter

60.      Write short notes on:

a.         An Intelligent Temperature Transmitter.

b.         An Intelligent Transmitter’s communication.

Chapter 4 – Miscellaneous Monitors

Fill in the blanks / complete the sentence for the following:

a)       Viscosity is the property of a fluid whereby ____.

b)       For two parallel layers in the direction of flow, a short distance apart, the viscous force is ____ (equal to / inversely proportional / proportional) to the velocity gradient between the layers.

c)       The constant of proportionality is also called the ____ of the fluid.

d)       Kinematic viscosity is the ratio of ____.

e)       Torque is defined as ____ where T = ____.

f)        The Combustible Gas Indicator (CGI) or Explosimeter is used to ____.

g)       A Tankscope measures the ____ in a sample of atmosphere.

h)       Synchros may also appear under names such as ____ and ____.

i)        In capacitive proximity sensors, the sensed object changes the ____between two plates.

1.       Write short notes on:

a)       Kinematic Viscosity

b)       Newtonian Fluid

2.       What is the basic working principle of a viscosity sensor (Viscometer)?

3.       With a suitable block diagram, explain the operation of a viscosity control system.

4.       How does the Electromagnetic Viscometer work?

5.       What is the principle of operation of a Fork-type Viscometer?

6.       How is torque measured?

7.       Explain power calculation with the help of a proximity torque system.

8.       With a suitable diagram, explain the principle of operation of the Torductor. 

 

9.       How does the Explosimeter work?

10.    With a suitable circuit diagram, explain the operation of a Combustible Gas Indicator.

11.    How does a Tankscope measure C/H gas?

12.    With suitable and simple sketches, explain the principle of operation of a fixed oxygen analyser.

13.    What is the significance of a fire alarm and detection system?

14.    Write short notes on:

a)       Heat detectors.  

b)       Smoke detectors.

c)       Detectors reacting to radiation emanating from flames.

15.    With suitable diagrams explain the construction and operating principle of a basic crankcase oil mist detector.

16.    With suitable diagrams explain the construction and operating principle of a comparison-type crankcase oil mist detector.

17.    Why is vibration monitoring so important? Briefly explain the basic operating principle of any vibration monitoring system.

18.    How do proximity sensors work? Explain these with suitable diagrams.

19.    With a suitable circuit diagram explain the working principle of a Synchro chain.

20.    Write short notes on:

a)       Magnetic Velocity Vibration Transducer.

b)       Laser Displacement Vibration Sensor.

c)       Laser Doppler Vibrometers - Velocity Sensors.

d)       Reference-beam Vibrometers.

Chapter 5 – Automatic Control System Fundamentals

Fill in the blanks / complete the sentence for the following:

a)       The actions of controllers can be divided into groups based upon the functions of their control mechanism namely ____ and ____.

b)       Discrete controllers are also called ____.

c)       Continuous control is often called ____.

d)       PID stands for ____.

e)       Proportional action controls the ____of the controller.

f)        Stability can often be ensured using only the ____ term.

g)       Pure proportional action will result in ____.

h)       ____action eliminates offset.

i)        ____action is used to provide damping or shaping of the response.

j)        When there is an error (SP-PV), the controller makes a change in its output and it determines:

How fast? And then it adopts the ____mode of control.

How much? And then it adopts the ____mode of control.

How long? And then it adopts the ____mode of control.

k)       Rise Time is the time until the process variable (PV) first crosses the ____.

l)        Overshoot is defined as ____.

m)     Settling time is defined as ____.

n)       Steady-state error is the difference between the ____ and ____ position after the controller has finished applying corrections.

o)       Time Constant is defined as ____.

p)       In reality, the time constant is really the time taken for a signal or output to achieve its ____value from its ____value.

q)       Stability is the ability of a measured variable to ____.

1.       What are the two modes of control? Explain each mode with suitable diagrams.

2.       With suitable diagrams explain what you understand about a discrete controller.

3.       With suitable diagrams explain what you understand about a continuous controller.

4.       What are the applications of on-off control?

5.       Differentiate between direct and reverse-acting elements.

 

6.       List the advantages and disadvantages of on-off control.

7.       Write short notes on:

a)       Rise Time

b)    Peak Time

c)    Settling Time

8.       Write short notes on:

a)       Steady-state error

b)       Peak related criteria

c)       Time constant

d)       Dead band

9.       Write short notes on:

a)       Transfer lag

b)       Measurement lag

c)       Distance velocity lag

10.    Write short notes on:

d)       Hysteresis

e)       Stability

f)        Hunting

g)       Offset

h)       Proportional Band

11.    What are the sources of load changes?

12.    With suitable diagrams explain the function of Proportional Control.

13.    What are the limits of Proportional Action?

14.    Briefly explain the relationship between P-band and Offset.

15.    Briefly explain the relationship between Output and P Band.

16.    Define Controller Sensitivity or ‘Gain’.

17.    How does Integral control play a role in eliminating offset?

18.    Define Integral Action Time (IAT).

19.    With suitable diagrams, explain system behaviour with different Integral settings.

20.    What is the role of Rate or Derivative Control?

21.    With suitable examples and sketches, explain P + I + D Control.

 

 

22.    What do you understand by PID Control Strategy?

Chapter 6 – Pneumatic Controllers

Fill in the blanks / complete the sentence for the following:

a)       The output pressure of a nozzle-flapper is dependent on ____.

b)       Any variation of the supply pressure will affect a nozzle-flapper’s ____.

c)       Use of negative feedback in a nozzle-flapper is effective for reducing the ____.

d)       In a nozzle-flapper arrangement, the ____ is used to move the flapper back into position.

e)       A motion balance comparison mechanism in a controller linkage has two inputs - one is the ____and other is ____; the output is taken from a ____.

f)        The major limitation of a nozzle-flapper amplifier is ____.

g)       An air relay serves the similar purpose as ____.

1.         With suitable diagrams, explain a nozzle-flapper’s characteristics.

2.         Explain the working principle of the nozzle-flapper and its significance in a controller.

3.         State the working principle of a pneumatic relay.

4.         State the working principle of a pneumatic transmitter.

5.         State the working principle of an electro-pneumatic converter.

6.         State the working principle of a pneumatic PID controller.

7.         Explain the basic method of tuning a PID controller for optimum performance.

8.         State the advantages of pneumatic systems over electronic systems.        

9.         Write short notes on:

a)       Moment-balance Mechanism.

b)       Motion-balance Mechanism.

c)       Angular Motion-balance Mechanism.

 

10.      What are the main components of a true force-balance (stack) mechanism? How does it work?

11.      What are the limitations of a nozzle-flapper assembly?

12.      What is the purpose of an air relay? How does it work?

13.      What is a continuous bleed-type relay and how does it work?

14.      What is a non-bleed-type pneumatic relay? How does it work?

15.      With a suitable diagram explain the working principle of a second stage amplifier or “booster relay”.

16.      How does a direct-acting pneumatic booster relay work? How is it different from a reverse-acting booster relay?

17.      With a suitable diagram explain the principle of operation a pneumatic pressure transmitter.

18.      How does a pneumatic differential pressure transmitter work?

19.      What is the function of a square root extractor?

20.      With a suitable diagram explain the operation of an electro-pneumatic (I/P) transducer.

21.      How does the force-balance-type of an I/P converter work?

22.      What is a stack-type I/P converter? With a suitable diagram explain its operation.

23.      Define a pneumatic controller. Where is it used onboard a ship?

24.      With a suitable example, explain pneumatic proportional and integral control.

25.      How does a pneumatic liquid level P and I controller work?

26.      How is the proportional band varied in a pneumatic controller?

27.      What is a stacked-type controller?

28.      What are the steps to tune a PID controller?

29.      How is basic fault finding carried out in control systems?

30.      With a suitable sketch, explain the operation of a typical level control system.

31.      How is a feedforward control system different from a feedback control system?

32.      What do you understand by feedforward-feedback control?

33.      With a suitable diagram, explain what you understand about split range control.

34.      How is cascade control special? What are its advantages?

35.      How is an engine’s jacket cooling water temperature generally controlled?

36.      How is an engine’s piston cooling water temperature generally controlled?

37.      With a simple diagram, explain an engine’s lubricating oil temperature control system.

38.      How is three-term control of a boiler’s water level control system different from a two-term controller? Justify your answer with a suitable diagram.

39.      How is steam temperature controlled?

40.      What do you know about a deaerator level controller? Explain its operation with a suitable diagram.

41.      What is wrong when?

a)       The controlled condition goes to one or other extremes of its range.

b)       The controlled condition stays at a zero.

c)       The controlled condition oscillates.

Chapter 7 – Electronic Analog and Digital Controllers

1.          What is an operational amplifier and what are its characteristics?

2.          With a suitable block diagram, explain the functions of feedback and gain.

3.          Voltage gain of the overall circuit depends entirely on the ratio of ______

4.          Why does an op amp work better with negative feedback?

5.          In an op amp, the error e = _________

6.          With a simple block diagram explain the features of an electronic PID controller.

7.          How is the PID controller effectively used in a steering control system?

8.          With suitable graphs, explain the operation of a PID control system.

9.          What do you understand by digital control?

10.      How does a digital controller work in a continuous feedback system?

11.      What are the main features of an electronic governor?

12.      How does a magnetic a speed pick-up work in an electronic fuel control system?

13.      What do you understand by a distributed control system? Explain its architecture with a suitable diagram.

14.      What is a HART transducer and how does FSK work in a HART protocol?

15.      Where is the HART protocol applied?

16.      What do you understand by the HART Multidrop mode?

17.   What are the three main elements in a WirelessHART network?

18.   With a suitable diagram explain the fieldbus networking system.

19.   How is a fieldbus network applicable for a process control system?

20.   What is the difference between analog and fieldbus communication systems?

21.      How is process control and automation achieved using a Modbus Protocol?

22.      With a suitable block diagram, explain the computational structure of a Fuzzy controller.

23.      How is a Fuzzy Logic system unique as compared to other systems?

24.      With a suitable example explain the use of Defuzzification

25.      How is a Supervisory Control and Data Acquisition (SCADA) System effective in the control of large processes spread over wide networks?

26.      What is an RTU?

27.      With a suitable block diagram, explain a simple SCADA application.

28.      With suitable sketches, explain what you understand about the architecture of a SCADA system. How is it used in a WAN?

Chapter 8 – Programmable Logic Controllers

Fill in the blanks / complete the sentence for the following:

a)       In a PLC, a contact is a computer code that monitors the status of the____.

b)     In a PLC, a computer code that monitors the status of the_____.

c)      The left vertical line in a ladder diagram is called a ____ or ____.

d)       The horizontal lines between two vertical rails that branch off to the right in a ladder logic program are called ____.

1.       Write short notes on the following basic instructions:

a)    Load

b)    LoaDBar

c)     Out

d)    Outbar

2.        Write short notes on the functions of the following components:

a)  Input Relays (contacts)

b)  Internal Utility Relays (contacts)

c)   Counters

d)  Timers

e)   Output Relays (Coils)

f)    Data Storage

3.      Write short notes on:

a)   Counters

b)   On-delay Timer

c)    Off-delay timer

d)   Retentive or Accumulating timer

4.       What is a PLC? What are its main building blocks?

5.       List the advantages of a PLC

6.       How can you compare a conventional control system to a PLC?

7.       What are the various inputs to a PLC?

8.       How does an optocoupler play a role in connecting the inputs and outputs to a PLC’s CPU?

9.       With suitable examples, briefly explain what you understand about PLC registers.

10.    What are Latch Instructions?

11.    How are timers used in a PLC?

12.    With suitable sketches, explain control relay logic in a PLC

13.    How are logical functions incorporated in a PLC?

Chapter 9 – Final Control Elements

1.       What is a control valve and what is its role in a process control system?

2.       Write short notes on:

a)       Capacity

b)       Range

c)       Shutoff

d)       Pressure Loss

3.       Write short notes on:

a)       Dead Band

b)       Dynamic Response

c)       Plugging

d)       Balance

e)       Accuracy

4.       Write short notes on:

a)       Flashing

b)       Cavitation

c)       Drift

5.       Write short notes on:

a)       Hysteresis

b)       Linearity

c)       Repeatability

6.       Write short notes on:

a)       Reproducibility

b)       Response Time

c)       Span

7.       Write short notes on:

a)       Globe Valve

b)       Ball Valve

c)       Butterfly Valve

d)       Diaphragm Valve

e)       Gate Valve

8.       With a simple sketch, explain the functions of the main parts of a final control element.

9.       With a suitable diagram, explain the operation of an actuator?

10.    What are the limiting forces that can inhibit an actuator’s operation?

11.    How does a diaphragm actuator work?

12.    With a suitable sketch, explain the various combinations of actuators and valves.

13.    With suitable sketches, explain the differences between direct-acting and reverse-acting valves.

14.    What can happen to the pressure of the liquid when it passes through a valve?

15.    What is the significance of a double seat valve?

16.    How is a three-port valve special? Where is it used?

17.    With suitable diagrams explain the 3 types of valve plugs.

18.    With a suitable diagram, explain the characteristics of a valve.

19.    What are positioners? Where are they used?

20.    With a suitable block diagram, explain the operation of a control valve positioner.

21.    Briefly explain the three types of valve positioners.

22.    What are the main advantages of positioners?

23.    What do you understand by hysteresis in a control valve?

24.    Write short notes on the following:

a)       Force-balance positioner

b)       Cylindrical valve positioner

25.    How is zero and span adjustment carried out for a spool valve?

26.    What is the general relationship between cylinder bore and response time of a cylindrical valve positioner.

27.    With a suitable diagram explain the operation of an electro-pneumatic force balance positioner.

28.    How does a digital valve positioner work? What are its advantages?

29.    How is a digital valve positioner calibrated?

30.    What is a Piezo valve and how does it work? Draw a suitable diagram to depict its parts.

Chapter 10 – Calibration of Process Components

  1. What is calibration? How important is it to periodically calibrate a process instrument?
  1. Write short notes on the following:
    1. Accuracy
    1. Precision
    1. Resolution
  1. Write short notes on the following:
    1. Dead Zone
    1. Re-Ranging
    1. Bias / Offset Error
  1. With a simple block diagram, explain the process of calibration under controlled conditions.
  1. With simple sketches and graphs, explain zero and span error.
  1. What do you understand by hysteresis calibration error?
  1. How can zero and span errors be adjusted?
  1. With a simple block diagram, explain the calibration procedure for an analog linear instrument.
  1. How is a pressure transmitter calibrated?
  1. How is a decade resistance box used to calibrate a PT100 sensor?
  1. How is a Thermocouple calibrated?
  1. With a suitable sketch, explain the calibration procedure for a DPT.
  1. How is a current-to-pressure (I/P) converter calibrated?
  1. How will you calibrate a smart transmitter using a HART device?