instrumentation engineering : analytical, optical & biomedical instrumentation, the gate...

Analytical, Optical and

Biomedical Instrumentation

for

Instrumentation Engineering

By

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Syllabus A.O.B

THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th Cross, 10th Main, Jayanagar 4th Block, Bangalore-11 : 080-65700750, [email protected] © Copyright reserved. Web: www.thegateacademy.com

Syllabus for Analytical, Optical and Biomedical Instrumentation

Mass spectrometry. UV, visible and IR spectrometry. X-ray and nuclear radiation measurements.

Optical sources and detectors, LED, laser, Photo-diode, photo-resistor and their characteristics.

Interferometers, applications in metrology. Basics of fiber optics. Biomedical instruments, EEG,

ECG and EMG. Clinical measurements. Ultrasonic transducers and Ultrasonography. Principles of

Computer Assisted Tomography.

Analysis of GATE Papers

(Analytical, Optical and Biomedical Instrumentation)

Year Percentage of marks Overall Percentage

2013 3.0

12.12%

2012 6.0

2011 2.0

2010 9.0

2009 11.0

2008 16.0

2007 16.0

2006 14.66

2005 12.66

2004 25.0

2003 18.0

Contents A.O.B


C O N T E N T S

Chapter Page No. #1. U.V, Visible and IR spectrometry 1 - 15

Analytical Instrumentation 1 - 3 Beer – Lamberts law 3 - 7 Infrared Spectroscopy Instrumentation 7 - 9 Assigment 1 10 - 11 Assigment 2 11 - 12 Answer Keys 13 Explanations 13 - 15

#2. Mass Spectrometer 16 - 22 Introduction 16 - 17 Time of Flight Mass Spectrometer 17 - 18 Assignment 19 - 20 Answer Keys 21 Explanations 21 - 22

#3. X ray and Nuclear Radiation Measurements 23 - 34 Origin of X rays 23 - 24 X-ray Diffraction – Bragg’s Law 24 - 26 Nuclear Detectors 26 - 28 Assignment 1 29 - 30 Assignment 2 30 - 31 Answer Keys 32 Explanations 32 - 34

#4. Optical Sources and Detectors 35 - 55 Optical Sources 35 - 37 LASER 37 - 41 Photo Detectors 41 - 49 Assignment 1 50 - 51 Assignment 2 51 - 52 Answer Keys 53 Explanations 53 - 55

#5. Interferometer, Applications in Metrology 56 – 63 Introduction 56 Michelson’s Interferometer Working 56 - 57 Application in Metrology 57 - 58 Assignment 59 - 60

Contents A.O.B


Answer Keys 61 Explanations 61 - 63

#6. Basics of Fiber Optics 64 – 76 Introduction 64 Construction 64 - 66 Fibre Characteristics and Classification 66 - 69 Assignment 1 70 - 71 Assignment 2 71 - 72 Answer Keys 73 Explanations 73 - 76

#7. Ultrasonic Transducers and Ultrasonography 77 - 83 Introduction 77 Acoustic Impedence(z) 77 Ultrasonic Transducers 78 - 79 Doppler Shift Ultrasound Transducer 79 Assignment 80 - 81 Answer Keys 82 Explanations 82 - 83

#8. ECG EEG EMG 84 - 102 Sources of Bioelectric Potentials 84 - 87 ECG (Electro Cardio Gram) 87 - 89 EEG (Electro Encephalogram) 89 - 91 EMG (Electromyogram) 91 - 94 Assignment 1 95 - 96 Assignment 2 97 - 98 Answer Keys. 99 Explanations. 99 - 102

#9. Clinical Measurement and Computer Assisted Tomography 103 - 114 Introduction 103 Measurement of Blood Pressure 103 - 104 Measurement of Blood Volume 104 Measurement of Heart Sounds 105 Test on Blood Cells 105 - 109 Principle of Computer Assisted Tomography 109 - 110 Assignment 111 - 112 Answer Keys 113 Explanations 113 - 114

Contents A.O.B


Module Test 115 - 126 Test Questions 115 - 119 Answer Keys 120

Explanations 120 - 126 Reference Books 127

Chapter 1 A.O.B

THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th Cross, 10th Main, Jayanagar 4th Block, Bangalore-11 : 080-65700750, [email protected] © Copyright reserved. Web: www.thegateacademy.com Page 1

CHAPTER 1

U.V, Visible and IR spectrometry

Analytical Instrumentation

Analytical instruments are primarily used to obtained qualitative and quantitative information regarding the composition of a given unknown sample.

The basic building blocks are:

Chemical information source generates signal containing information of the unknown

sample.

Analytical instruments then generate signal based on the composition of the sample. This

stage forms an important building block in analytical instruments where the separation,

detection and of the composition is done by employing either emission or absorption or

scattering of electromagnetic radiation as the key principle of detection.

Electromagnetic Radiation

Electromagnetic radiation is a type of energy that is transmitted through space at a speed of

3 × m/sec.

These radiations do not require a medium of propagation and can also travel through

vacuum.

Relation between the energy of electromagnetic radiation (normally called as photons) and

frequency of its propagation is given by

where E: energy

h: Planck’s constant ergs-s (or) Joules-s

ν: frequency

If λ is the wavelength interval between successive maxima and minima of the wave), then C = νλ Where C: velocity of propagation of radiant energy in vacuum.

Interaction of radiation with matter S. No Radiation absorbed Energy changes involved 1. Visible, ultraviolet, x –

ray Electronic transitions, vibrational or rotational changes

Chemical

information

source

Analytical

instrument

Signal

conditioner Display

system

Chapter 1 A.O.B


2. Infrared Molecular vibrational changes with superimpose rotational changes

3. Microwave Rotational changes 4. Radio – frequency They are absorbed by an intense magnetic

field.

Spectroscopic methods and corresponding energy states of matter or basis of phenomenon S. No Method Phenomena employed

1. Nuclear magnetic resonance

Nuclear spin coupling with an applied magnetic field

2. Microwave spectroscopy Rotation of molecules 3. Infrared and Raman

spectroscopy Rotation or vibration of molecules, electronic transitions

4. UV – visible spectroscopy Electronic energy changes, 5. X-ray spectroscopy Diffraction and reflection of X-ray

radiation from atomic layers.

Electromagnetic Spectrum

Fig (1.1) shows the various regions of electromagnetic spectrum which are normally used in spectroscopic works.

Fig.1.1 Electromagnetic spectrum from DC to X-ray

In the following sections, we discuss the various methods employed (by the analytical instruments) for detection of the composition of the analyte sample in the different regions of the electromagnetic spectrum.

λ 3× m 3× m

10 kHz 100 kHz 1 MHz 30 MHz 450 MHz 1 GHz 10 GHz 300 GHz 4.3× z z z z

MICROWAVES

VERY LOW

FREQUENCY LOW

FREQUENCY

MEDIUM

FREQUENCY

HIGH

FREQUENCY

VERY HIGH

FREQUENCY

ULTRA HIGH

FREQUENCY

SUPER HIGH

FREQUENCY

EXTRA HIGH

FREQUENCY INFRARED VISIBLE ULTRAVIOLET X-RAY

FREQUENCY RANGE

OF HUMAN EYE

7000 – 4000 Å

300 m 10 m 0.67 m 30 m 3 cm m 7000 Å 3000 Å 30 Å 3×

MICROWAVE SPECTROSCOPY

2000 MHz – 300 GHz

20 – 100 MHz (~ 300 MHz IN

SUPERCONDUCTING INSTRUMENTS)

NUCLEAR MAGNETIC RESONANCE UV – VISIBLE SPECTROSCOPY

2.5𝛍 M – 2400 Å

0 – 15 kHz; FREQUENCY RANGE

OF AVERAGE HUMAN EAR NUCLEAR QUADRUPOLE

RESONANCE 2 – 1000 MHz ELECTRON SPIN

RESONANCE; X-BAND

9.46 GHz

INFRARED

SPECTROSCOPY 1 MM-

2.5 𝛍 M 10 – 4000 cm

RAMAN SPECTROSCOPY

Chapter 1 A.O.B


Visible and Ultraviolet: Calorimeter and Spectrophotometer

In the visible and ultraviolet region of spectrum, the method of analysis employed by the analytical instruments are based on the absorption of electromagnetic radiation.

Calorimeters and spectrophotometers are the analytical instruments used in this region.

Principle

Whenever a beam of radiant energy strikes the surface of a substance (analyte or sample), the radiation interacts with the atoms or molecules of the substance resulting in absorption (or) transmittance or scattering (reflection) depending on the properties of the sample.

Absorption spectroscopy is based on the principle that the amount of absorption that occurs

is dependent on the number of molecules present in the sample.

Here the analysis is done by studying the intensity of the radiant power leaving the

substance, i.e., the transmitted radiation which is an indication of concentration of the

sample.

The absorbance is calculated as;

Transmittance (T)

where:

p: energy transmitted

P : Incident energy

Absorbance log (

⁄ )

log (

)

Optical density log (

⁄ )

Beer – Lamberts Law

This law gives a relation between energy absorbed by the sample and the energy transmitted. Absorbance (A) = abc where: a is the absorptivity of the sample (constant)

Incident

Radiation

Absorbed

Radiation

Transmitted Radiation

Sample

Chapter 1 A.O.B


b is the thickness of the absorbing material c is the concentration of the sample

As we known, A log (

⁄ ) and T p

P ⁄

∴ log (

⁄ ) abc log (

) and T =

Assumptions

1. Here the radiation used is monochromatic (single wave length) in nature. 2. Sample is of low concentration. 3. The others factors that influence the absorption are not considered.

The instrument module for UV and visible spectrometry can be pictorized as below

Example: The transmittance of a coloured solution is 0.5, the absorption of the solution is?

A = log

= log ) = 0.3

Example: In a particular sample the absorption is 0.6 for a molar concentration of the solute of 1.0 moles and 2cm path length the molar absorptivity is?

A = abc a =

Substitute a = 3000

Radiation sources used are

1. Hydrogen or deuterium discharge lamp(U.V) 2. Incandescent filament lamps 350nm – 2.5µm 3. Tungsten halogen lamps (visible)

Wavelength selection is done with the various dispersive techniques given.

Optical Filters

Absorption Filter

These optical filters usually absorb the radiation and transmit light of single wavelength. There efficiency is poor, when compared to other filters.

Interference Filters

These filters use interference phenomena.

Radiant

Source

Wavelength

Selector

Solvent Photo

detector

Read out

device

Sample

Chapter 1 A.O.B


Thus, these filters normally have semi-transparent layers. Light, which is incident on it undergoes multiple reflections between the pair of semi

transparent layers and the wavelength that is transmitted through them is determined by the thickness of the dielectric layer.

The wavelength selection is done by the relation: m λ d n) sin θ where θ : angle of incidence d : thickness of dielectric spaces, n : refractive index of dielectric spacer. m : order of interference λ : wavelength

Monochromators

They are the another class of filters, which provide better isolation than optical filters. They are capable or isolating a narrow band of wavelengths effectively. Principle employed for separation of wavelength is done by using a dispersing medium,

where the radiant energy gets isolated. Dispersion of radiant energy into different wavelength’s is usually done by prism

monochromators or by diffraction grating.

Prism Monochromators

Here in prism monochromators, the isolation of different wavelengths is done by using the refractive index of wavelengths, which is different for different wavelengths.

Thus, radiation of different wavelengths gets disperssed at different angles by prism. Prisms are normally made of glass or quartz. Glass is used in visible region and quartz for

ultraviolet region.

Resolving Power (R)

The term resolving power is applied to spectrum producing devices and means as the ability of the instrument to form separate images of two closely adjacent spectral lines.

It is defined generally by the equation

where R: resolving power λ : wavelength dλ : smallest wavelength separation, which is separable with the instrument.

dλ λ λ and

.

For prism, the resolving power is given by the expression:

t

where dμ is the difference or refractive index t : base of the prism.

Example: A prism spectrometer uses flint glam prism with glam dispersion

952cm-1 and dλ =

6 0A at λ = 5893 0A find base t of prism?

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