AVR Microcontroller Architecture 1. Is the following instruction correct LDI R3,50? a) Yes b) No c) Cant be said d) None of the mentioned Answer: No 2. Registers R0-R31 are used for what type of works? a) they are used for arithmetic and logic instructions b) they are used for data copy c) they are used for calculations d) none of the mentioned Answer: they are used for arithmetic and logic instructions 3. The largest value that can be loaded in an 8 bit register is? a) 11111111H b) FH c) FFH d) 00H Answer: FFH 4. The total space for the data memory available in the AVR based microcontroller is? a) FFH b) FFFH c) FFFFH d) FFFFFH Answer: FFFFH 5. Which of the following instructions affect the flags of the status register? a) AND b) INC c) OR d) All of the mentioned Answer: All of the mentioned 6. What is the difference between the two given instructions? LDI R16,0x34 and LDI R16,$34 a) One copies the hexadecimal value to R16 and the other copies the decimal value to the R16 register b

  Orifice Plate   The orifice plate is the most common form of restriction that is used in flow measurement. An orifice plate is basically a thin metal plate with a hole bored in the center. It has a tab on one side where the specification of the plate is stamped. The upstream side of the orifice plate usually has a sharp, edge. below Figure shows a representative orifice plate. When an orifice plate is installed in a flow line (usually clamped between a pair of flanges), increase of fluid flow velocity through the reduced area at the orifice develops a differential pressure across the orifice. This pressure is a function of flow rate.  With an orifice plate in the pipe work, static pressure increases slightly upstream of the orifice (due to back pressure effect) and then decreases sharply as the flow passes through the orifice, reaching a minimum at a point called the vena contracta where the velocity of the flow is at a maximum. Beyond this point, static pressure starts to recover as

  Flange Taps   Flange taps are the most widely used pressure tapping location for orifices. They are holes bored through the flanges, located one inch upstream and one inch downstream from the respective faces of the orifice plate. A typical flange tap installation is shown in below Figure. The upstream and downstream sides of the orifice plate are connected to the high pressure and low-pressure sides of a DP transmitter. A pressure transmitter, when installed to measure flow, can be called a flow transmitter. As in the case of level measurement, the static pressure in the pipe-work could be many times higher than the differential pressure created by the orifice plate. In order to use a capsule that is sensitive to low differential pressure, a three valve manifoldhas to be used to protect the DP capsule from being over ranged. The three valve manifold is discussed in more detail in the  level measurement.

  Three Valve Manifold  A three-valve manifold is a device that is used to ensure that the capsule will not be over-ranged. It also allows isolation of the transmitter from the process loop. It consists of two block valves - high pressure and low- pressure block valve and an equalizing valve. Below Figure shows a three valve manifold arrangement. During normal operation, the equalizing valve is closed and the two block valves are open. When the transmitter is put into or removed from service, the valves must be operated in such a manner that very high pressure is never applied to only one side of the DP capsule. Operational Sequences of Three-Valve Manifold Valving Transmitter into Service  To valve a DP transmitter into service an operator would perform the following steps: Check all valves closed.  Open the equalizing valve ñ this ensures that the same pressure will be applied to both sides of the transmitter, i.e., zero differential pressure.  Open the High Pressure block valve slow

Level Measurement Basics  Very simple systems employ external sight glasses or tubes to view the height and hence the volume of the fluid. Others utilize floats connected to variable potentiometers or rheostats that will change the resistance according to the amount of motion of the float. This signal is then inputted to transmitters that send a signal to an instrument calibrated to read out the height or volume.  In this module, we will examine the more challenging situations that require inferential level measurement. This technique obtains a level indication indirectly by monitoring the pressure exerted by the height of the liquid in the vessel.  The pressure at the base of a vessel containing liquid is directly proportional to the height of the liquid in the vessel. This is termed hydrostatic pressure. As the level in the vessel rises, the pressure exerted by the liquid at the base of the vessel will increase linearly. Mathematically, we have:  P = S.H where  P = Pressure (Pa)  S =

  Orifice Plate   The orifice plate is the most common form of restriction that is used in flow measurement. An orifice plate is basically a thin metal plate with a hole bored in the center. It has a tab on one side where the specification of the plate is stamped. The upstream side of the orifice plate usually has a sharp, edge. below Figure shows a representative orifice plate. When an orifice plate is installed in a flow line (usually clamped between a pair of flanges), increase of fluid flow velocity through the reduced area at the orifice develops a differential pressure across the orifice. This pressure is a function of flow rate.  With an orifice plate in the pipe work, static pressure increases slightly upstream of the orifice (due to back pressure effect) and then decreases sharply as the flow passes through the orifice, reaching a minimum at a point called the vena contracta where the velocity of the flow is at a maximum. Beyond this point, static pressure starts to recover as

  Flow Detectors  To measure the rate of flow by the differential pressure method, some form of restriction is placed in the pipeline to create a pressure drop. Since flow in the pipe must pass through a reduced area, the pressure before the restriction is higher than after or downstream. Such a reduction in pressure will cause an increase in the fluid velocity because the same amount of flow must take place before the restriction as after it. Velocity will vary directly with the flow and as the flow increases a greater pressure differential will occur across the restriction. So by measuring the differential pressure across a restriction, one can measure the rate of flow.

   Atomic absorption spectrophotometer 1. Which of the following is the principle of Atomic Absorption Spectroscopy? a) Radiation is absorbed by non-excited atoms in vapour state and are excited to higher states b) Medium absorbs radiation and transmitted radiation is measured c) Colour is measured d) Colour is simply observed Answer: Radiation is absorbed by non-excited atoms in vapour state and are excited to higher states 2. In Atomic Absorption Spectroscopy, which of the following is the generally used radiation source? a) Tungsten lamp b) Xenon mercury arc lamp c) Hydrogen or deuterium discharge lamp d) Hollow cathode lamp Answer: Hollow cathode lamp 3. In Atomic Absorption Spectroscopy, with what material is the cathode in Hollow cathode lamp constructed ? a) Tungsten b) Quartz c) Element to be investigated d) Aluminium Answer: Element to be investigated 4. How can the intensity of radiation be increased in Hollow cathode lamp? a) Addition of non-conductive protective shield of m

  Working Principle of Vortex Flow Meter Vortex flow meters utilize a bluff body or cylinder mounted in a pipe spool that creates alternating vortices behind the cylinder. The frequency of the alternating vortex is proportional to the fluid velocity. Vortex flow meters have no moving parts to maintain or repair, and the signal is read electronically and simply converted to a flow rate. Vortex meters work well with most clean fluids and have similar application ranges to DP  flow  meters. Vortex flow meters are also referred to as vortex shedding flow meters or oscillatory flow meters. These types of flow meters are used to measure the vibrations of the downstream vortexes caused by an obstruction in the flowing stream. Each obstruction has a vital liquid flow speed at which vortex shedding takes place. This vortex shedding occurs at the instant when alternating low pressure zones gets created in the downstream. These sporadic pressure zones enable the barrier to move towards the low pr

  Control System Components Industrial Control Devices: Switches 1.The contact resistance of a manually operated switch is    A. Zero    B. Very high    C. Very low    D. None of the above Answer: Very low   2. Which one of these is not a manually operated switch?    A. Thumbwheel switch    B. Rotary selector switch    C. Crossbar switch    D. Toggle switch Answer: Crossbar switch   3. A switch should have    A. High insulation resistance    B. Low insulation resistance    C. Insulation resistance equal to contact resistance    D. None of the above Answer: High insulation resistance 4. A Thumbwheel switch    A. Has an operating wheel which has numbers on it    B. Is an alternative form of rotary switch    C. Requires half the operating torque required in a rotary switch    D. Supports the features A, B and C Answer: Supports the features A, B and C 5.  When a membrane key switch is pressed    A. The row conductor sheet gets separated from the column contact conductor sheet    B. The ro

  Bode Plots 1. Assertion (A): Relative stability of the system reduces due to the presence of transportation lag. Reason (R): Transportation lag can be conveniently handled by Bode plot. a) Both A and R are true but R is correct explanation of A b) Both A and R are true but R is correct explanation of A c) A is true but R is false d) A is false but R is true Answer: Both A and R are true but R is correct explanation of A 2. Assertion (A): The phase angle plot in Bode diagram is not affected by the variation in the gain of the system. Reason(R): The variation in the gain of the system has no effect on the phase margin of the system. a) Both A and R are true but R is correct explanation of A b) Both A and R are true but R is correct explanation of A c) A is true but R is false d) A is false but R is true Answer: A is true but R is false 3. A system has poles at 0.01 Hz, 1 Hz and 80Hz, zeroes at 5Hz, 100Hz and 200Hz. The approximate phase of the system response at 20 Hz is : a) -90° b) 0

  Correlation between Time and Frequency Response 1. The forward path transfer function of a unity feedback system is given by G(s) = 100/(s2+10s+100). The frequency response of this system will exhibit the resonance peak at: a) 10 rad/sec b) 8.66 rad/sec c) 7.07 rad/sec d) 5rad/sec Answer: 7.07 rad/sec 2. Assertion (A): All the systems which exhibit overshoot in transient response will also exhibit resonance peak in frequency response. Reason (R): Large resonance peak in frequency response corresponds to a large overshoot in transient response. a) Both A and R are true and R is the correct explanation of A b) Both A and R are true and R is not the correct explanation of A c) A is true but R is false d) A is false but R is true Answer: Both A and R are true and R is the correct explanation of A 3. The transfer function of a system is given by Y(s)/X(s) = e−0.1s/1+s. If x(t) is 0.5sint, then the phase angle between the output and the input will be: a) -39.27° b) -45° c) -50.73° d) -90°

  Frequency Response 1. Scientist Bode have contribution in : a) Asymptotic plots b) Polar plots c) Root locus technique d) Constant M and n circle Answer: Asymptotic plots 2. Scientist Evans have contribution in : a) Asymptotic plots b) Polar plots c) Root locus technique d) Constant M and n circle Answer: Root locus technique 3. Scientist Nyquist have contribution in: a) Asymptotic plots b) Polar plots c) Root locus technique d) Constant M and n circle Answer: Polar plots 4. For a stable closed loop system, the gain at phase crossover frequency should always be: a) < 20 dB b) < 6 dB c) > 6 dB d) > 0 dB Answer: > 0 dB 5. Which one of the following methods can determine the closed loop system resonance frequency operation? a) Root locus method b) Nyquist method c) Bode plot d) M and N circle Answer: M and N circle 6. If the gain of the open loop system is doubled, the gain of the system is : a) Not affected b) Doubled c) Halved d) One fourth of the original value Answer:

  Compensators 1. Which of the following is not the correct reason to select feedback compensation over cascaded one? a) No amplification is required as the energy transfer is from higher to lower level. b) Suitable devices are not available for compensation(series) c) It is economical d) Provides greater stiffness against load disturbances Answer: It is economical 2. Operations performed by pneumatic controllers: a) Flexible operations b) High torque high speed operations c) Fire and explosion proof operation d) All of the mentioned Answer: Fire and explosion proof operation 3. Operations performed by hydraulic controllers: a) Flexible operations b) High torque high speed operations c) Fire and explosion proof operation d) All of the mentioned Answer: High torque high speed operations 4. Operations performed by electronic controllers: a) Flexible operations b) High torque high speed operations c) Fire and explosion proof operation d) All of the mentioned Answer: Flexible operations 5.

  Root Locus 1. Which one of the following statements is not correct? a) Root loci can be used for analyzing stability and transient performance b) Root loci provide insight into system stability and performance c) Shape of the root locus gives idea of type of controller needed to meet design specification d) Root locus can be used to handle more than one variable at a time Answer: Root locus can be used to handle more than one variable at a time 2. Root locus of s(s+2)+K(s+4) =0 is a circle. What are the coordinates of the center of this circle? a) -2,0 b) -3,0 c) -4,0 d) -5,0 Answer: -4,0 3. The main objective of drawing root locus plot is : a) To obtain a clear picture about the open loop poles and zeroes of the system b) To obtain a clear picture about the transient response of feedback system for various values of open loop gain K c) To determine sufficient condition for the value of ‘K’ that will make the feedback system unstable d) Both b and c Answer: Both b and c 4. While incr