advanced sensor 2011

8/10/2019 Advanced Sensor 2011

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Name: .

Roll No.: .....

Invigilators Signature :..

CS/B.TECH(ICE)/SEM-7/EI-703B/2011-12

2011

ADVANCED SENSORS

Time Allotted: 3 Hours Full Marks: 70

The figures in the margin indicate full marks.

Candidates are required to give their answers in their own words

as far as practicable.

GROUP A

( Multiple Choice Type Questions )

1. Choose the correct alternatives for the following : 10 1 = 10

i) The CO2laser is

a) an atomic laser b) an excimer laser

c) a molecular laser d) an ion laser.

ii) The deflection of thin diaphragm in micropressure

sensors is measured by

a) mechanical means b) ultrasonic means

c) electrical means d) optical means.

iii) Micro-accelerometers are used to measure

a) velocity

b) displacement

c) dynamic forces associated with a rigid body moving

at variable speed

d) both (a) and (b).


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iv) Critical angle is given bya)

211 /sin nn b)

121 /sin nn

c)21

1 /cos nn d)12

1 /cos nn .

v) Doping is a process of

a) purifying the material

b) adding controlled impurities in the material

c) making the material crystalline

d) making the material amorphous.

vi) An active transducer is

a) strain gauge b) selsyn

c) photovoltaic cell d) photoemissive cell.

vii) Momentum of a photon of wavelength is

a) /h b) zero

c) 2/ ch d) ch / .

viii) In a photo-multiplier

a) gain is independent of stray magnetic fields

b) high frequency response is improved by improving

the number of dynodesc) secondary emission is used for amplification of low

photo-current

d) the electrons are directed to the anode by applying

a strong magnetic field.

ix) A fibre optics having core index of refraction of 147 and

a cladding index of refraction of 145, what will be the

critical angle of the fibre ?

a) 946 b) 1946

c) 15 d) None of these.


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x) In an optical fibre with the core and cladding havingrefractive indices

1n and

2n respectively, (

21nn > ), the

numerical aperture is ................ when the light enters

the fibre in air.

a) SQRT ( )21

22

nn b) SQRT ( )22

21

nn

c) SQRT ( )22

21

nn + d) none of these.

GROUP B

( Short Answer Type Questions )

Answer any threeof the following. 3 5 = 15

2. What different types of sensor-electrodes are known to be

used commercially ? How are they different construction-wise

and operation-wise ?

3. Describe an optical fibre sensor for temperature

measurement. Comment on its range, accuracy and

resolution.

4. Describe the basic principle of a Hall device and show how it

can be used as a magnetic field Sensor.

5. Draw the flow charts and discuss the steps in reactive

plasma etching. How does it differ from conventional dry

chemical etching ?

6. Explain the terms 'Diffusion' and 'Ion Implantation' with

figure.

GROUP C

( Long Answer Type Questions )

Answer any threeof the following. 3 15 = 45

7. a) What are the essential elements in smart sensor ?

Explain the operation of each element using the

diagram.


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b) What are the different deviations to be compensated insensor system ?

c) How is a non-linearity taken care of in modern smart

sensor ? 6 + 4 + 5

8. Explain with a neat diagram, the operation of a optical fibre

based liquid level sensor. What materials are used for solid

state radiation detectors and why ? 10 + 5

9. a) What is the difference between thick film and thin film

sensors ?

b) What is a chemical sensor ?

c) Explain on what factors do the selection of chemical

sensors depend.

d) Draw a schematic arrangement of typical chemical

sensor. 3 + 2 + 4 + 6

10. Write short notes on any threeof the following : 3 5

a) Photovoltaic cell

b) Reference electrode

c) MEMS

d) Semi-conductor IC Technology.

11. a) Describe the four micromachining techniques and

compare their advantages and uses.

b) What are the limitations of the height (depth) of

microstructures that can be produced by bulk

manufacturing technique ? ( 7 + 4 ) + 4

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advanced sensor 2011

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