Pole- Zero effect on process response Objective Questions and Answers 1. Pressure error can be measured by which of the following? a) Differential bellows and strain gauge b) Selsyn c) Strain gauge d) Strain gauge and potentiometer Answer: Differential bellows and strain gauge 2. Zeroes are defined as _______ a) Roots of the denominator of the closed loop transfer function b) Roots of the numerator of the closed loop transfer function c) Parts of the numerator d) Parts of the denominator Answer: Roots of the numerator of the closed loop transfer function 3. Addition of __________  increases the stability. a) zero b) one  c) number d) none of the mentioned Answer: zero 4. _____________ is not a final control element. a) Control valve b) Potentiometer c) Electro-pneumatic converter d) Servomotor Answer: Potentiometer 5. A control system is generally met with the time response specifications  _____________ a) Steady state accuracy b) Damping factor c) Setting time d) All of the mentione

  Approximation of higher order models  Objective Questions and Answers 1. The second derivative input signals modify which of the following? a) The time constant of the system b) Damping of the system c) The gain of the system d) The time constant and suppress the oscillations Answer: The time constant and suppress the oscillations 2. Which of the following statements is correct for a system with gain margin close to unity or a phase margin close to zero? a) The system is relatively stable b) The system is highly stable c) The system is highly oscillatory d) The system is stable Answer: The system is highly oscillatory 3. Zero initial condition for a system means? a) Input reference signal is zero b) Zero stored energy c) Initial movement of moving parts d) System is at rest and no energy is stored in any of its components Answer: System is at rest and no energy is stored in any of its components 4. On which of the following factors does the sensitivity of a closed loop system to gain

  Dead time Multiple Choice Questions 1. Dead time of the instrument is a) The time required by an instrument for initial warming up b) The time required by an instrument to begin to respond to a change in the measured value c) The largest change of input quantity for which there is no output of the instrument d) None of the above Answer: The time required by an instrument to begin to respond to a change in the measured value 2. The dead time of an instrument refers to _____ a) Large change of input quantity for which there is no output. b) The time encountered when the instrument has to wait for some reactions to take place. c) The time before the instrument begins to response after the quantity has altered. d) Retardation or delay in the response of an instrument to a change in the input signal. Answer: The time before the instrument begins to response after the quantity has altered.

  Process Control Multiple Choice Questions 1. When we adjust integral time in a controller a) We determine an RC time constant in the controller’s internal feedback path b) We adjust the time it will take for integral to equal derivative c) We set the process time constant so that it will always equal 1 d) What happens specifically depends on the type of controller, pneumatic Answer: We determine an RC time constant in the controller’s internal feedback path 2. For proper feedback in a process control element, it is required to ________ a) measure P b) measure set point c) measure error d) measure comparator Answer: measure P 3. If in a proportional-plus-integral controller measurements away from the set point for a long period, the controller’s output will be a) 0 b) Unknown c) 0 d) 100 percent Answer: 0 4. In the modem controller, derivative action is applied only to the a) Error b) Measurement c) Setpoint d) Integral circuit Answer: Measurement 5. What is the main objective of proc

  Control Of Air To Fuel Ratio The fuel/air ratio is the lowest if excess air level (measure in percent of oxygen 02) is present in the flue gas at a set firing rate without the carbon monoxide (CO) being produced. At low firing rates; the burner design requires more excess air to ensure the mixing of air with the fuel in proper ratio. At higher firing rates there is enough differential pressure drop (burner wind box to combustion chamber area) for the air to mix with the fuel. All boilers have a fuel/air ratio curve and it is extremely important that the plant has this documented information. In other words ratio control is adopted to maintain the air fuel ratio. The air to fuel ratio is the proportion of air to fuel supplied during combustion process. The optimal ratio (the stoichiometric ratio) occurs when all the fuel and oxygen in the reaction chamber balance each other perfectly. Rich burning occurs when there is more fuel than air in the combustion chamber while lean burning occ