Mangalore Refinery and Petrochemicals Ltd(MRPL) Placement Paper Contributed by Aruna updated on Jul 2019

                                                 MRPL Solved Model Question Paper

Instrumentiaon Engineering Questions with Answers

1. A surface height profile is given by, y = a + b sin 2 p x l (0 x l) where a, b, l are constants and x is the horizontal coordinate. The roughness of the surface, based on absolute deviation, is
A) 2b p
B) 4b p
C) 6b p
D) 8b p Y
Answer : A

2. For N-bit Successive Approximation ADCs, other parameters such as clock frequency remaining constant, the conversion time is proportional to
A) N 2
B) Ö N
C) log N
D) N
Answer B

3. The radius of a sphere is given as (40.0 ± 0.5)mm. The estimated error in its mass is:
A) ± 3.75%
B) ± 1.25%
C) ± 12.5%
D) ± 0/125%
Answer B

4. A zero error in a vernier caliper is termed as
A) accidental error
B) interference error
C) systematic error
D) random error
Answer B

5. Given the discrete-time sequence x[n] = [2, 0, -1,-3, 4, 1, -l, X(e j p ) is
A) 8
B) 6 p
C) 8 p
D) 6 
Answer C

6. Linear variable differential transformer has
A) two primary coils connected in phase and a secondary coil
B) two primary coils connected in opposition and a secondary coil
C) one primary coil and two secondary coils connected in phase
D) one primary coil and two secondary coils connected in opposition
Answer D

7. Position sensor units having a constant sensitivity of lV/mm are used for feedback in number of position controlled system units, each having an overall forward path dc gain of 50. If the random dc bias errors in the outputs of various sensor units are characterized as normal with mean 0 and standard deviation ( s ) 0.01V, for a constant set point of 5V, the true position outputs of the various controlled system units can be characterized as normal with
A) mean of 5.0, s of 0.01
B) mean of 0.0, s of 0.01
C) mean of 5.0, s of 0.0098
D) mean of 4.902, s of 0.0098
Answer C

8. The refractive index of the core of an optical fiber is n 1 and that of the cladding is nf If (n 1 – n 2 ) = D n,then the fiber can be made single mode with numerical aperture unchanged by
A) reducing core diameter and increasing D n
B) reducing both core diameter and D n
C) reducing core diameter alone
D) reducing D n alone
Answer D

9. For a suppressed carrier amplitude modulator (AM-SC) system, the carrier and the modulating inputs are x c (t) = cos w c t and x m (t) = 0.5 sin w m t, respectively. The output of the system is proportional to
A) sin ( w c + w m ) t – sin ( w c - w m ) t
B) sin ( w c + w m ) t + cos ( w c - w m ) t
C) (1 + 0.5 sin w m t) cos w c t
D) (1- 0.5 sin w m t) cos w c t
Answer B

10. The 3-dB cut-off frequency of a first analog high pas filter is w c the output will have a phase shift of
A) - p 2
) - p 4
C) p 2
D) p 2
Answer B

11. In an INTEL 8085 microprocessor the ADDRESS-DATA bus and the DATA bus are
A) Non multiplexed
B) Multiplexed
C) Duplicated
D) Same as CONTROL
Answer B

12. A 3 ½ digit nultimeter has an accuracy specification of (± 0.5% of reading ± 5 counts). If the meter reads
2.00 mA on a full scale of 20mA, the worst-case error in the reading is
A) 0.5%
B) 2.5%
C) 3.0%
D) 5.5%
Answer C

13. The measurements of a source voltage are 5.9V, 5.7V and 6.1V. The sample standard deviation of the readings is
A) 0.013
B) 0.04
C) 0.115
D) 0.2
Answer D

14. Consider the following systems: System 2: G(s) = 1 2(2s+1) System 1: G(s) = 1 2(5s+1) The true statement regarding the system is
A) Bandwidth of system 1 is greater than the bandwidth of system 2
B) Bandwidth of system 1 is lower than the bandwidth of system 2
C) Bandwidth of both the systems are the same
D) Bandwidth of both the systems are infinite
Answer A

15. The transfer function of a system is A s 2 + w 2 The steady-state gain of the system to a unit-step input is
A) A w 2
B) 0
C) ¥
D) not possible to be determined
Answer C

16. In 8085 microprocessor, CY flag may be set by the instruction
A) SUB
B) INX
C) CMA
D) ANA
Answer A

17. V 1 and V 2 are the input voltages of an instrumentation amplifier. The output of the instrumentation amplifier is found to be 100(V 1 – V 2 ) + 10 -4 (V 1 + V 2 ). The gain and the common mode rejection ratio (CMRR) of the instrumentation amplifier respectively are
A) (50, 60 d
B) B) (50, 120 dB)
C) (100, 60dB)
D) (100, 120 dB)
Answer C

18. The sequence x[n] whose z-transform is X[z] = e (1/Z) is
A) 1 n! u[n]
B) 1 -n! u[-n]
C) (-1) n 1 n! u[n]
D) 1 -(n+1)! u[-n-1]

19. The time taken by an ionized atom, of mass m kg and charge e Coulombs, pulsed into a field-free region with V volts, to reach a detector L meters away is
A) 1 L Ö m 2eV
B) L Ö m 2eV
C) m Ö L 2eV
D) 2 L Ö m 2eV
Answer B

20. The clock frequency of a timer-counter is 10MHz. The timer-counter is used in the period mode and the input to the timer-counter is a square wave of frequency 2 kHz. The display of the timer-counter will show a value 
A) 200
B) 2000
C) 5000
D) 50000
Answer C

21. In an 8085 microprocessor, which one of the following is the correct sequence of the machine cycles for the execution of the DCR M instruction?
A) op-code fetch
B) op-code fetch, memory read, memory write
C) op-code fetch memory read
D) op-code fetch memory write, memory write
Answer B

22. lim x ® p /4 sin 2 [ x - p 4 ] x - p 4 equals
A) 0
B) 1 2
C) 1
D) 2
Answer D

23. Three DC currents I 1 , I 2 and I 3 meet at a node with I 1 entering and I 2 and I 3 leaving the node. I 1 and I 2 are measured as 100mA and 99 mA with a ± 1% accuracy. Then the value of I 3 and the accuracy of I 3 are 
A) 1 mA ± 2%
B) 199 mA ± 2%
C) 1 mA ± 2%
D) 1 mA ± 199%
Answer C

24. The input-output characteristic of a Schmidt trigger has a hysteresis band of ± 0.1 V. If the input voltage is 5 sin (1000 p t), the delay between the corresponding zero cross-over points of the output and input signals is 
A) 6.37 m s
B) 0.02 m s
C) 63.7 m s
D) 2.0 m s
Answer A

25. In a spirit level, 2.5mm of movement of the bubble corresponds to a tilt angle of 25 seconds. The radius of curvature of the tube of the spirit level is
A) 52.1 m
B) 34.4 m
C) 26.3 m
D) 15.6 m
Answer B

26. The loop transfer function of a system is given by G(S)h(s) = 10 e -Ls s . The phase cross-over frequency is 5 rad/s. The value of the dead time L is
A) p /20
B) p /10
C) - p /20
D) zero
Answer B

27. An 8-bit microcontroller has an external RAM is the memory map from 8000H to 9FFFH. The number of bytes this RAM can store is
A) 8193
B) 8191
C) 8192
D) 8000
Answer C

28. Two copper-constantan thermocouples are connected such that the two constantan wires are joined together. The two copper wires are connected to the input of a low noise chopper stabilized differential amplifier having a gain of 1000. One of the thermocouple junctions is immersed in a flask containing ice and water in equal proportion. The other thermocouple is at a temperature T. If the output of the amplifier is 2.050V, the temperature T is 
A) 205°C
B) 102.5°C
C) 51.25°C
D) 50°C
Answer D

29. For a first order instrument a 5% settling time is equal to
A) three times the time constant
B) two times the time constant
C) the time constant
D) time required for the output signal to reaches 5% of the final value
Answer A

30. The measurements of a source voltage are 5.9V, 5.7V and 6.1V. The sample standard deviation of the readings is
A) 0.013
B) 0.04
C) 0.115
D) 0.2
Answer D

31. In an INTEL 8085 microprocessor the ADDRESS-DATA bus and the DATA bus are
A) Non multiplexed
B) Multiplexed
C) Duplicated
D) Same as CONTROL bus
Answer B

32. The number of comparators required in an 8-bit flash-type AID converter is
A) 256
B) 255
C) (8 + 2)
D) 8
Answer B

33. An ultrasonic beam of frequency 1 MHz and intensity 0.5 W/cm 2 passes through a layer of soft tissue of thickness t with an attenuation coefficient of 1.18cm -1 . The ratio of output to input power is 1/e 2 . The thickness of the tissue is
A) 1 cm
B) 1.695 cm
C) 2.408 cm
D) 3.712 cm
Answer B

34. A twisted pair of wires is used for connecting the signal source with the instrumentation amplifier, as it helps reducing
A) the effect of external interference
B) the error due to bias currents in the amplifier
C) the loading of the source by the amplifier
D) the common mode voltage
Answer C

35.The output from a 633 nm He-Ne laser comes out from the mirror with a beam diameter of lmm and diverges to the far field. It is brought to a focus by a convex lens of focal length of 17 mm. The spot size diameter of the beam at the focal point is
A) 20 m m
B) 26 m m
C) 52 m m
D) 13 m m
Answer C

36. International temperature scale in the range 0-630oC is defined by means of a
A) mercury pressure spring thermometer
B) platinum-platinum. 10% rhodium thermocouple
C) platinum resistance thermometer
D) total radiation pyrometer.
Answer D

37. A microprocessor has an instruction XOR (r 1 , r 2 ) which performs an Exclusive OR operation of registers r 1 ,r 2 and stores the result in r 1 . After the following instructions are executed XOR (r 2 , r 1 ) XOR (r 1 ,r 2 ) XOR (r 2 ,r 1 ) Which one of the following is true?
A) Content of register r 1 is half sum of r 1 and r 2
B) Content of register r 2 is half sum of r 1 and r 2
C) Contents of registers r 1 and r 2 remain unaltered
D) Contents of registers r 1 and r 2 are swapped 
Answer D

38. A second order feedback system is found to be oscillating with a high frequency. The oscillations
A) can be reduced by increasing the proportional action
B) can be reduced by increasing the integral action
C) can be reduced by increasing the derivative action
D) cannot be reduced
Answer B

39. For a suppressed carrier amplitude modulator (AM-SC) system, the carrier and the modulating inputs are x c (t) = cos w c t and x m (t) = 0.5 sin w m t, respectively. The output of the system is proportional to
A) sin ( w c + w m ) t – sin ( w c - w m ) t
B) sin ( w c + w m ) t + cos ( w c - w m ) t
C) (1 + 0.5 sin w m t) cos w c t
D) (1- 0.5 sin w m t) cos w c t
Answer B

40. The vectored address corresponding to the software interrupt command RST7 in 8085 microprocessor is
A) 0017H
B) 0027H
C) 0038H
D) 0700H
Answer C

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