# Electronic Instrumentation - Electronics Engineering test questions

## Electronic Instrumentation - Electronics Engineering test questions

For questions 1 to 3 refer to the data given below:

Consider a Wheatstone bridge having the known resistances R1 = 500Ω +1%, R2 = 615Ω ± 1% and R3 = 100Ω ± 0.5%

(1) The nominal value of the unknown resistor is

(A) 3075 Ω
(B) 3000 Ω
(C) 3175 Ω
(D) 3125 Ω

(2) The limiting error of the unknown resistor is

(A) ±76.88Ω
(B) ±75.88Ω
(C) ±74.88Ω
(D) ±73.88Ω

(3) The percentage limiting error is

(A) ±4%
(B) ±2.5%
(C) ±3%
(D) ±6.25%

(4) A flowmeter is calibrated from 0 to 100 m² /sec. The accuracy = ±0.75% above 20% of scale reading. If the instrument indicates 80 m² /sec, the static error will be

(A) ±1.6 m³ /sec
(B) ±1.2 m³ /sec
(C) ±0.06 m³ /sec
(D) ±0.6 m³ /sec

For questions 5 to 8 refer to the data given below:

A set of ten independent measurements is given as:

1.570, 1.597, 1.591, 1.562, 1.577, 1.580, 1.564, 1.586, 1.550, 1.575

(5) The arithmetic mean is

(A) 1.515
(B) 1.5
(C) 1.5752
(D) 1.5702

(6) The average deviation is

(A) 0.10068
(B) 0.01068
(C) 0.10608
(D) 0.10806

(7) The standard deviation is

(A) 0.01426
(B) 0.0014
(C) 0.012
(D) None of the above

(8) The probable error of one reading will be

(A) 0.01068
(B) 0.0001
(C) 0.420
(D) 0.0024

(9) On CRO, a Lissajous pattern is obtained that is used to determine

(A) Phase shift and frequency
(B) Distortion in a system
(C) Current in a circuit
(D) Amplitude of applied signal

(10) The magnetic material that has least value of (B.H.)max is

(A) Cobalt steel
(B) Carbon steel
(C) Alnico
(D) Alcomax

(11) ___________ has least value of remenance (in Wb/m² )

(A) Tungsten steel
(B) Alini
(C) Alcomax
(D) Cobalt steel

(12) Ryall crest voltmeter is used to measure

(A) RMS voltage
(B) DC voltage
(C) Peak voltage
(D) All of the above

(13) Consider a helipot in which 40 turns per cm is provided. The arrangement of gear is such that one revolution of the main shaft causes five revolutions of the potentiometer shaft. The resolution of the potentiometer is

(A) 1 μm
(B) 2 μm
(C) 3 μm
(D) 5 μm

(14) The gauge factor for doped crystals is in the range of

(A) 100 to 5000
(B) 1 to 2
(C) 10 to 500
(D) 0.5 to 1

(15) Nixie tube display is based on the principle of

(A) Dot matrix
(B) Gaseous glow
(C) Display segment
(D) None of the above

(16) For yellow LED, the semiconductor material used is

(A) Ga As
(B) Ga AsP
(C) As P2
(D) Ga P2

(17) In a pyrometer, the dead zone is 0.125 % of span. The calibration is 400°C to 1000°C.What temperature change might occur before it is detected

(A) 1.5°C
(B) 2.6°C
(C) 3°C
(D) 0.75°C

(18) To measure the frequency in waveguides, the instruments used is

(A) Bolometer
(B) Galiometer
(C) Klystron
(D) Cavity resonator

(19) Under measurement a VTVM has negligible loading effect on the circuit because

(A) It has high input impedance
(B) It has high resistance range
(C) It offers low input resistance
(D) It has low current range

ANSWER: It has high input impedance

(20) Strain gauge in a load cell acts as a

(A) Comparator
(B) Protective device
(C) Secondary transducer
(D) Primary transducer

(21) Warm up time of a transistor voltmeter is

(A) Low
(B) Very high
(C) High
(D) Nil

(22) The purpose of using marker generator with a sweep generator is to

(A) Mark the frequency at any point on the response curve
(B) Extend the range of sweep generator
(C) Control the sweep frequency of the sweep generator
(D) All of the above

ANSWER: Mark the frequency at any point on the response curve

(23) Time constant of a thermometer is 3.5 s. It is quickly taken from 0°C to water bath at 100°C. What temperature will be indicated after 1.5 s?

(A) 35°C
(B) 50°C
(C) 100°C
(D) 0°C

(24) A vector diagram is most useful to check

(A) Linearity
(B) Colour purity
(C) Convergence
(D) None of the above

(25) To convert the input physical phenomenon into an output which is a function of time, the transducer used is

(A) Active transducer
(B) Passive transducer
(C) Analogue transducer
(D) Primary transducer

(26) The principle on which Q-meter works is

(A) Parallel resonant circuit
(B) Series resonant circuit
(C) Wave generator
(D) Sweep generator

(27) As a microwave detector one should use

(A) Junction transistor
(B) FET
(C) Junction diode
(D) Point contact diode

(28) The gauge that is used to measure low pressures of the order of 0.01mm Hg is

(A) Pirani gauge
(B) Strain gauge
(C) Monometer
(D) Compound pressure gauge

(29) A LVDT has

(A) One primary coil and two secondary coil
(B) One primary coil and one secondary coil
(C) Two primary coil and one secondary coil
(D) Two primary coil and two secondary coil

ANSWER: One primary coil and one secondary coil

(30) For delineating a sinusoidal waveform on the screen of a CRO, the required time base voltage waveform must be

(A) Exponential
(B) Linear
(C) Sinusoidal
(D) Saw tooth

(31) The circuit shown will be nearly non-reactive when (A) C = L / R²
(B) C = LR
(C) C = LR²
(D) C = L / R

ANSWER: C = L / R²

(32) On an oscilloscope screen the pattern shown in the figure is generated when frequency ratio and phase shift is (A) 1/3, 45°
(B) 1/3, 90°
(C) 1/2, 180°
(D) 1/2, 0°

(33) As compared to an absorption type of frequency meter, a heterodyne type of frequency meter can measure

(A) Medium frequency range
(B) Higher frequency range
(C) Lower frequency range
(D) None of the above

For questions 34 and 35 refer to the data given below:

To the vertical inputs of a free-running oscilloscope, a sinusoidal waveform at 5 KHz is applied

(34) The horizontal sweep speed is set so that a full cycle takes 0.4 m/sec. The resulting display for one sweep of beam will be

(A) 1/4th cycle of the input signal
(B) 1/2 cycle of the input signal
(C) 1 cycle of the input signal
(D) 2 cycles of the input signal

ANSWER: 2 cycles of the input signal

(35) For a sweep frequency of 10KHz the display will be

(A) Four cycles
(B) Two cycles
(C) One complete cycle
(D) One half cycle

For questions 36 and 37 refer to the data given below

Two pulse signals are observed on a dual trace oscilloscope. Sweep scale setting = 5 ms/cm. Pulse widths are 3.6 cm and 4.4 cm respectively. Distance between the start of each pulse is 2.5 cm.

(36) The time measurements for the pulse widths are

(A) 21 ms and 24 ms
(B) 20 ms and 25 ms
(C) 18 ms and 22 ms
(D) 20 ms and 20 ms

ANSWER: 18 ms and 22 ms

(37) The delay between the pulses is

(A) 11 ms
(B) 12.5 ms
(C) 10 ms
(D) 20 ms

For questions 38 and 39 refer to the data given below:

Two sinusoidal signals are observed on a dual trace oscilloscope. In measuring phase shift between them, the scale setting is adjusted so that one full cycle is 10 boxes

(38) The scale factor (degree 1 box) for this adjustment is

(A) 360°/box
(B) 120°/box
(C) 420°/box
(D) None of the above

(39) The amount of phase shift for a reading of 0.8 boxes will be

(A) 40.4°
(B) 28.8°
(C) 10°
(D) 20.1°

(40) A Vector meter measures

(A) Current
(B) Power factor
(C) KW and KV Ar
(D) All of the above