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DEVELOPMENT OF ELECTRONIC TECHNIQUES FOR STUDYING THE PROFILE OF NATURAL FLUIDS FOR

INSTRUMENTATION APPLICATION

ABSTRACT OF THE '

THESIS SUBMITTED FOR THE AWARD OF THE DEGREE OF

©octor of ^f)ilos^opf)p \ r • IN '""

ELECTRONICS ENGINEERING

BY

ANWAR SADAT

DEPARTMENT OF ELECTRONICS ENGINEERING Z. H. COLLEGE OF ENGINEERING & TECHNOLOGY

ALIGARH MUSLIM UNJVERSITY ALIGARH (INDIA)

2008

ABSTRACT

Adulteration and impurities in the natural fluids affect the health of

human beings, performance of vehicles and machines in industries etc.

Various methods for determining the adulteration of the fluids have been

used in the past. Most of these methods are costly and time consuming as

they require a number of reagents, moderate laboratory facilities and

trained analysts to carry out the analysis. Thus, the need of the hour is to

carry out research for simple and accurate methods for the measurement

of such impurities and adulteration.

In the following paragraphs the development of new electronic

techniques for analyzing the properties and characteristics of some of the

natural fluids is summarized.

A novel technique for the measurement of liquid viscosity has been

proposed. The principle involves that the torque required to rotate a disk

by a motor, at constant speed, inside a liquid bath is directly proportional

to its viscosity. The current in a dc shunt motor being proportional to its

torque and hence, the current measures the viscosity of the liquid under

test. The change in motor current is further converted into a proportionate

voltage which is amplified by an instrumentation amplifier. Thus, the

viscosity of the liquid can directly be expressed in terms of the output

voltage of the instrumentation amplifier. The resulting linear variation,

between the voltage and the viscosity of oils is a desirable feature.

Therefore, one can easily and quickly measure the viscosity of the

required liquid, by simply observing the output voltage of the circuit,

without bothering for the difficulties involved with the different types of

viscometers being in use.

The second proposed electronic technique is useful for the determination

of the adulteration of natural milk with synthetic milk. Synthetic milk is

prepared by emulsifying vegetable oils with appropriate amount of

detergent and urea. A number of samples of the natural milk mixed with

synthetic milk are analyzed by the method of Electrical Admittance

Spectroscopy. The conductance of milk samples is measured by this

method which considerably varies with the variation of frequency

uptolOO kHz but, remains almost constant above this frequency. It is also

noted that the value of the conductance decreases with increase in the

concentration of the synthetic milk at a given frequency. The conductance

of the milk sample is measured by the operational-amplifier circuit. The

output voltage of this circuit is found inversely proportional to the

conductance of milk sample and hence, its adulteration.

The next developed electronic technique is suitable for the determination

of the adulteration in pure honey with different quantities of impurity.

This technique involves the measurement of the capacitances of the

mixture (adulterated honey) resulting from the variation of its dielectric

constant, with variable percentage of adulteration. It is observed that the

capacitance of the honey sample increases with the increase in its

adulteration. This variable capacitor is also connected in the circuit of a

relaxation oscillator and the change in capacitance varies the output

frequency of the oscillator. The frequency of the output signal is

measured using the digital counter which decreases with the percentage

increase of the syrup in honey.

An electronic technique is proposed to determine the adulteration of

petrol and diesel with kerosene. The principle involves the use of a light

emitting diode at one end of the fiber which provides sufficient radiant

energy over the wavelength region, where its absorption can be measured.

In the present technique, the light is guided inside an optical fiber through

the principle of total internal reflection. The cladding of an optical fiber is

removed over a small length of the fiber, the evanescent wave, and thus,

the guided light interacts with the measurand. The light received at the

other end of the fiber is converted into a proportional current using a

photodiode. This current is further converted into a proportionate output

111

voltage using a current to voltage converter. It is observed that the output

voltage decreases almost linearly with increase of kerosene adulteration

in petrol and diesel.

The last discussed electronic technique is meant for the discrimination of

vegetable oils viz; castor, olive, sunflower, mustard, and groundnut oils.

Monochromatic light at wavelengths of 635nm, 565nm, 470nm and

430nm, emitted from LED is passed through the oil sample, contained in

the polystyrene cuvette. A fraction of the incoming light is absorbed by

the oil sample resulting in its emergence with lower intensity. It is

detected by the photoconductor, which changes its electrical resistance.

This change in the electrical resistance of the photoconductor connected

with voltage controlled oscillator circuit changes its frequency. The

frequency of the output signal is measured with the help of a digital

frequency counter. The observations at 635nm, 565nm and 470nm

wavelengths do not discriminate the vegetable oils. However, at 430nm

the separation of all oil classes is successfiilly obtained.

The techniques thus, described will find applications in the design of low

cost instruments for studying the profiles of various natural fluids.

IV

RESEARCH PAPERS FROM THE THESIS

1. Determining the adulteration of natural milk using ac conductance

measurement, Journal of Food Engineering, Vol. 77, Issue 3, pp.

472-477, December 2006. (ELSEVIER Ltd.)

2. A Novel technique for the measurement of liquid viscosity. Journal

of Food Engineering, Vol. 80, Issue 4, pp. 1194-1198, June 2007.

(ELSEVIER Ltd.)

3. Discrimination of vegetable oils using monochromatic light,

Proceedings of the EFFoST / EHEDG Joint conference 2007,

Lisbon, Portugal, November 2007.

DEVELOPMENT OF ELECTRONIC TECHNIQUES FOR STUDYING THE PROFILE OF NATURAL FLUIDS FOR

INSTRUMENTATION APPLICATION

\ ^ THESIS

SUBMITTED FOR THE AWARD OF THE DEGREE OF

Bottor of pjilosioplip IN

II ELECTRONICS ENGINEERING

BY • ' ^ . . ; \ Ty^

ANWAR SADAT


ALIGARH MUSLIM UNIS/ERSITY ALIGARH (INDIA)

2008

:«t Ara^ if.;>^

T6922

Dedicated to the

Respected Teachers

A C K N O W L E D G E I M E N T

I am grateful to Prof. Zia A. Abbasi, Chairman, Department of Electronics

Engineering, Aligarh Muslim University, Aligarh for providing deep affection,

valuable suggestions as well as necessary facilities to carry out the research work.

I would like to record my sincere thanks to Prof. M. J. R. Khan for his keen

interest, supervision, encouragement and inspiring guidance throughout the work

reported in the thesis.

I wish to express my most sincere and deep sense of gratitude to Prof.

Mabfoozur Rehman, Ex-Chairman, for his encouragement and moral support during

the entire period for carrying out this work. I am also thankful to Prof. Parvez

Mustajab for his constant help and encouragement.

1 would like to record my sincere thanks to Prof. Muslim Taj, Principal, Z. H.

College of Engg. & Technology, for his blessing bestowed upon me to complete this

work.

It gives me a great pleasure to express my deep sense of gratitude to Prof.

Iqbal A. Khan, who was always at hand for his valuable suggestions, stimulating

discussions and critical evaluation of the thesis.

I am also thankful to Prof. Wasim Ahmed, Prof. Muzaffar A. Siddiqui,

Prof. Salim Beg and all my colleagues for their academic and moral support during

the research.

It is with immense pleasure that I record my indebtedness and heartfelt

gratitude to my mother Mrs. Noor Jahan, father Mr. Mohammed Ali Khan, brother

Dr. Mahmood Ali and all family members for their constant encouragement

throughout my career.

Finally, I am extremely grateful to my wife Dr. (Mrs.) Nazish, for her

patience, encouragement and help for correcting and comparing the typed script and

daughter Sarah, for love and patience.

(ANWAR SADAT)

Phones Office

CHAIRMAN Inter Texlex Fax

2721148 3125,3126 564-230 AMU IN 91-0571-2721148


ALIGARH MUSLIM UNIVERSITY, ALIGARH-202002, INDIA

Ref.No Dated,..2-.®,i.(.''.l.».,5?r, / ' " / •

CERTIFICATE

It is certified that the Thesis entitled ^^Development of Electronic

Techniques for Studying the Profile of Natural Fluids for

Instrumentation Application"^ submitted by Mr. Anwar Sadat for the

award of the degree oi Doctor of Philosophy in Electronics Engineering

is a record of candidate's own work, carried out by him, under my

supervision. To the best of my knowledge, the contents in the Thesis have

not been used for the award of any other degree.

Chairman

ABSTRACT

Adulteration and impurities in the natural fluids affect the health of

human beings, performance of vehicles and machines in industries etc.

Various methods for determining the adulteration of the fluids have been

used in the past. Most of these methods are costly and time consuming as

they require a number of reagents, moderate laboratory facilities and

trained analysts to carry out the analysis. Thus, the need of the hour is to

carry out research for simple and accurate methods for the measurement

of such impurities and adulteration.

In the following paragraphs the development of new electronic

techniques for analyzing the properties and characteristics of some of the

natural fluids is summarized.

A novel technique for the measurement of liquid viscosity has been

proposed. The principle involves that the torque required to rotate a disk

by a motor, at constant speed, inside a liquid bath is directly proportional

to its viscosity. The current in a dc shunt motor being proportional to its

torque and hence, the current measures the viscosity of the liquid under

test. The change in motor current is further converted into a proportionate

voltage which is amplified by an instrumentation amplifier. Thus, the

111

viscosity of the liquid can directly be expressed in terms of the output

voltage of the instrumentation amplifier. The resulting linear variation,

between the voltage and the viscosity of oils is a desirable feature.

Therefore, one can easily and quickly measure the viscosity of the

required liquid, by simply observing the output voltage of the circuit,

without bothering for the difficulties involved with the different types of

viscometers being in use.

The second proposed electronic technique is useful for the determination

of the adulteration of natural milk with synthetic milk. Synthetic milk is

prepared by emulsifying vegetable oils with appropriate amount of


synthetic milk are analyzed by the method of Electrical Admittance

Spectroscopy. The conductance of milk samples is measured by this

method which considerably varies with the variation of frequency

uptolOO kHz but, remains almost constant above this frequency. It is also

noted that the value of the conductance decreases with increase in the

concentration of the synthetic milk at a given frequency. The conductance

of the milk sample is measured by the operational-amplifier circuit. The

output voltage of this circuit is found inversely proportional to the

conductance of milk sample and hence, its adulteration.

IV

The next developed electronic technique is suitable for the determination

of the adulteration in pure honey with different quantities of impurity.

This technique involves the measurement of the capacitances of the

mixture (adulterated honey) resulting from the variation of its dielectric

constant, with variable percentage of adulteration. It is observed that the

capacitance of the honey sample increases with the increase in its

adulteration. This variable capacitor is also connected in the circuit of a

relaxation oscillator and the change in capacitance varies the output

fi-equency of the oscillator. The frequency of the output signal is

measured using the digital counter which decreases with the percentage

increase of the syrup in honey.

An electronic technique is proposed to determine the adulteration of

petrol and diesel with kerosene. The principle involves the use of a light

emitting diode at one end of the fiber which provides sufficient radiant

energy over the wavelength region, where its absorption can be measured.

In the present technique, the light is guided inside an optical fiber through

the principle of total internal reflection. The cladding of an optical fiber is

removed over a small length of the fiber, the evanescent wave, and thus,

the guided light interacts with the measurand. The light received at the

other end of the fiber is converted into a proportional current using a

photodiode. This current is further converted into a proportionate output

voltage using a current to voltage converter. It is observed that the output

voltage decreases almost linearly with increase of kerosene adulteration

in petrol and diesel.

The last discussed electronic technique is meant for the discrimination of

vegetable oils viz; castor, olive, sunflower, mustard, and groundnut oils.

Monochromatic light at wavelengths of 635nm, 565nm, 470nm and

430nm, emitted from LED is passed through the oil sample, contained in

the polystyrene cuvette. A fraction of the incoming light is absorbed by

the oil sample resulting in its emergence with lower intensity. It is

detected by the photoconductor, which changes its electrical resistance.

This change in the electrical resistance of the photoconductor connected

with voltage controlled oscillator circuit changes its frequency. The

frequency of the output signal is measured with the help of a digital

frequency counter. The observations at 635nm, 565nm and 470nm

wavelengths do not discriminate the vegetable oils. However, at 430nm

the separation of all oil classes is successfrilly obtained.

The techniques thus, described will find applications in the design of low

cost instruments for studying the profiles of various natural fluids.

VI

CONTENTS

Acknowledgement i

Certificate ii

Abstract iii

Contents vii

Frequently used Abbreviations x

Research Papers from the Thesis xiii

CHAPTER I

INTRODUCTION

1.1 Preamble 1

1.2 Review of available techniques 3

1.3 Organization of the Thesis 6

CHAPTER II

MEASUREMENT OF LIQUID VISCOSITY

2.1 Introduction 9

2.2 The Proposed Electronic Technique 11

2.3 Experimental Setup 17

2.4 Experimental Results 18

Vll

CHAPTER III

DETERMINATION OF THE ADULTERATION IN

NATURAL MILK

3.1 Introduction 23

3.2 The Conductance Measurement Method 26



CHAPTER IV


HONEY

4.1 Introduction 36

4.2 The Capacitance Based Technique 38

4.3 Experimental Method 41

4.4 Measurement Results 42

CHAPTER V

ESTIMATION OF THE ADULTERATION IN

PETROL AND DIESEL

5.1 Introduction 44

5.2 The Fiber Optic Method 47



VIU

CHAPTER VI

DISCRIMINATION OF VEGETABLE OILS

6.1 Introduction 52

6.2 The Optical Technique 54



CHAPTER VII

CONCLUSIONS

7.1 Introduction 60

7.2 Investigations of the Thesis 61 7.3 Future Scope 63

REFERENCES 65

IX

FREQUENTLY USED ABBREVIATIONS

Chapter II

>"

T

dc

°C

R

(0

ti{y,r)

h

y

Viscosity of liquid

absolute temperature

Direct current

Degree centigrade

radius of circular disk

angular velocity of disk

velocity distribution

clearance of the disk

vertical distance from th

r horizontal distance from the axis of rotation

r tangential stress on the disk surface

dr infinitesimal thickness

df differential tangential force

dTj differential torque

Tj torque on the disk

T, total torque on the disk

k device constant

T„ torque of the motor

T^ usable torque

Tf frictional torque

E supply voltage

/ motor current

V^ voltage proportional to current

/?^ current to voltage converter resistor

F„ output voltage

TEM thermoelectric module

rpm Revolution per minute

AD590 integrated circuit temperature sensor

Chapter III

Cj double layer capacitance of the electrolyte

Gj bulk electrolyte conductance

Q geometrical capacitance

Zj impedance of fixed value

Z, impedance of the electrolyte

F; input voltage

XI

Chapter IV

a plate area of capacitor

d plate separation

C capacitance

f, dielectric constant

£•0 permittivity of the free space

Vji^ and Vj.ff threshold voltages of the Schmitt-trigger

V ' DD

f

Chapter V

LED

PMMA

Chapter VI

566 IC

R^

fixed dc voltage

frequency of the output sign

Light emitting diode

polymethylmetacrilate

voltage controlled oscillator

external resistor

CI capacitor

Vc applied dc voltage

/„ center operating frequency

V^ control voltage

Xl l

RESEARCH PAPERS FROM THE THESIS

1. Determining the adulteration of natural milk using ac conductance

measurement. Journal of Food Engineering, Vol. 77, Issue 3, pp.

472-477, December 2006. (ELSEVIER Ltd.)

2. A Novel technique for the measurement of liquid viscosity, Journal

of Food Engineering, Vol. 80, Issue 4, pp. 1194-1198, June 2007.

(ELSEVIER Ltd.)

3. Discrimination of vegetable oils using monochromatic light,

Proceedings of the EFFoST / EHEDG Joint conference 2007,

Lisbon, Portugal, November 2007.

Xlll

CHAPTER I

INTRODUCTION

1.1 PREAMBLE

The principal aspects of the scientific methods are, accurate

measurement, selective analysis, and mathematical formulation.

Measurement is the process by which one can convert physical

parameters to meaningful numbers. The importance of measurement is

simply and eloquently expressed in the following statement by the

famous Physicist, Lord Kelvin: "I often say that when you can measure

what you are speaking about and can express it in numbers, you know

something about it; when you cannot express it in numbers, your

knowledge is of a meager and unsatisfactory kind". Instrumentation

methods are applied to physical, chemical, biological, medical and to

countless problems in the engineering sciences. They are also applicable

to social sciences, archaeology, geology, astronomy, and many others.

Adulteration is a severe problem in developing countries like India. The

major reasons for the practice is extra profits, shortages and increasing

prices, consumer demand for variety, a lack of awareness, negligence and

inadequate enforcement of laws and safety measures.

Adulteration in the natural fluids affects the characteristics of the fluid.

Fluids used by humans and machines are adulterated by the addition of

substances or by the removal of some of their ingredients making harmful

to them.

Adulterated food fluids are injurious to health or may be less nutritious.

They are also dangerous because they may be toxic and cause paralysis,

deprive of nutrients, essential for proper growth and development, may

cause blindness, rickets, etc. If they are infected, may give rise to diseases

like cholera and typhoid.

Adulterated petrol and diesel with kerosene results in severely damaging

of automotive engines and increased motor vehicle emissions, a major

concern to environmental pollution.

In order to evaluate the quality of or determining the adulteration in fluids

a number of techniques are already available. However, most of these

techniques are usually time consuming and costly for routine use in

industries. Hence, there is a large demand for rapid, cheap and effective

techniques for measurement and quality control.

The present work is concerned with the development of new electronic

techniques for studying the profiles of some of the natural fluids. The

electronic techniques thus developed may be used in the design of some

simple and low cost portable instruments for studying the characteristics

of various natural fluids. Moreover, the proposed electronic techniques in

the thesis are instantaneous or require a few minutes time as compared to

the available techniques which require hours of sample preparation and

their testing.

1.2 REVIEW OF AVAILABLE TECHNIQUES

A lot of work is reported in the literature for testing and measurement of

fluid properties and characteristics, based on their adulteration. A brief

review follows.

Liquid viscosity, a basic physical property, directly influences unit

operations such as pumping, filtratron, filling, distillation, extraction, and

evaporation, as well as heat and mass transfer. There are many

techniques, developed in the past to measure viscosity viz; capillary

tubes, falling ball viscometer, efflux type viscometers. Quartz crystal

resonator [1] and the ultrasonic plate wave [2]. With the above mentioned

measurement techniques the consideration of the effect of temperature is

quite time consuming and moreover requires considerable heating power

in them [3].

Natural milk is commonly adulterated by synthetic milk. Synthetic milk

is prepared by emulsifying vegetable oils with appropriate amount of

detergent and urea. A large number of methods are available for the

measurement of milk adulteration. These methods include determination

of fat and total solids by chemical or physical analysis, estimation of

sediment by forcing milk through filter pads and noting the residue left,

determination of bacterial count etc. [4-5]. Most of these measurement

methods are expensive and time consuming. Another commonly used

method is admittance or impedance spectroscopy [6-7]. In this method an

ac voltage is applied to the sample and both the in-phase current (related

to the conductance) and out of phase current (related to the capacitance)

are monitored over a range of frequencies using an impedance analyzer.

The equipment involved in this method is also very expensive.

Honey adulteration is a reprehensible practice which consists of

incorporating sugar syrups into the genuine product. A number of

methods exist to check the amount of adulteration, one of which

commonly used is the pollen analysis [8]. The ultrafilteration of the

honey, limits the applicability of this method. The other method available

in the literature is based on the stable carbon isotope ratio analysis

(SCIRA) [9]. But, this method is useful for higher percentage of

adulteration, approximately 20% or higher. Chromatographic methods

have also been reported [10-11]. However, these methods have the

drawbacks of slow testing and expensive experimental setups.

Commercial automotive fuels available on the Indian subcontinent like

petrol and diesel are heavily adulterated with kerosene. Kerosene is used

as a cooking fuel among the vast rural and urban populations in India. It

is heavily subsidized and hence, it becomes a cheap and commonly

available adulterant. There have been a number of methods proposed for

checking adulteration of petrol and diesel with kerosene. These methods

include, the filter test, testing through specific gravity, viscosity and an

odor based [12] methods. The later developments gave rise to ultrasonic

technique [13], titration technique [14-16] etc. The specific gravity

measurement suffers significant inaccuracy in the measurement, whereas

the viscosity measurement method has the drawback of generating the

same viscosity of the adulterated sample by adding a small amount of

high viscosity lubricating oils. Thus, due to these problems intelligent

mixing of kerosene with diesel and petrol do not show up in routine

analytical tests.

Fats and oils constitute one of the major categories of food products, as

they contain many nutrients. Several techniques are available in the

literature for the discrimination of vegetable oils. These include,

colorimetric reactions, determination of iodine value, saponification

value, density, viscosity, refractive index and ultraviolet absorbance [17].

However, they are time-consuming and require sample manipulation. Gas

and liquid chromatography techniques are being used at present for oil

analysis. This technique involves extraction and pre-concentration, which

makes the overall analysis also time-consuming. Therefore,

chromatographic methods cannot be used for real time in situ analysis.

Moreover, chromatographic methods are expensive, as they require

solvents of high purity for analytic separation and sample extraction.

Thus, Spectroscopic methods [18] present an alternative to

chromatography. However, they suffer the disadvantage of lack of

selectivity.

1.3 ORGANIZATION OF THE THESIS

The Thesis has been organized in seven chapters including the present

Chapter-I of Introduction which includes the relevant background

material.

Chapter-II describes a new technique for the measurement of liquid

viscosity. The principle of viscosity measurement used is that the torque

required to rotate a disk, at constant speed by a dc shunt motor, inside a

liquid bath is directly proportional to its viscosity. The current in a dc

shunt motor being proportional to its torque, is converted into a

proportionate voltage using a current to voltage converting Resistor. This

voltage is further amplified by an instrumentation amplifier. Thus, the

viscosity of the liquid can be expressed in terms of the output voltage of

the instrumentation amplifier. Chapter-Ill proposes an electronic method

for the determination of the adulteration of natural milk with synthetic

milk. For the sake of experimentation, the synthetic milk is prepared in

the laboratory, by emulsifying vegetable oils with appropriate amount of


synthetic milk are analyzed by the method of electrical admittance

spectroscopy and compared with the proposed electronic circuit, having

several advantages over it.

Chapter-IV is devoted for the measurement of adulteration in honey. The

technique involves the formation of the variable capacitance of the

mixture (adulterated honey) with the variation of its dielectric constant,

depending on the percentage of adulteration. The variable capacitor is

expressed in terms of the frequency of a relaxation oscillator. The

frequency of the output signal is measured using a digital counter which

is a measure of the adulteration of the honey.

Chapter-V deals with an electronic technique to determine the

adulteration of petrol and diesel with kerosene. The technique requires a

light emitting diode placed at one end of the fiber which provides

sufficient radiant energy over the wavelength region where absorption is

to be measured. The light is guided inside an optical fiber through the

principle of total internal reflection. The cladding of an optical fiber is

removed over a small length of the fiber the evanescent wave, and thus

the guided light, is able to interact with the measurand, and providing the

basis for sensing the adulteration.

Chapter-VI concerns with the development of an electronic technique for

the discrimination of different types of vegetable oils. Vegetable oils viz;

castor, olive, sunflower, mustard, and groundnut oils are analyzed by

emission of monochromatic light at different wavelengths of 635nm,

565nm, 470nm and 430mn. A fi-action of the incoming light is absorbed

by the oil sample, as a result, light of lower intensity emerges out of the

oil, which is measured using an electronic circuit forming a basis for its

discrimination.

The last Chapter-VII of the thesis concludes the findings of the

theoretical as well as the experimental results. A number of suggestions

for future work are also given to continue research in this area.

The references used for the preparation of this thesis are given at the end.

CHAPTER II

MEASUREMENT OF LIQUID VISCOSITY

2.1 INTRODUCTION

The measurement of liquid viscosity is quite important in a number of

industrial applications. In certain industrial machines and processes,

viscosity of the liquid used, plays an important role in their tribological

aspects such as their lubrication, wear and tear characteristics.

If a shear stress is applied to any portion of the confined fluid, the fluid

will move and a velocity gradient will be set within it. If the shear stress

per unit area at any point is divided by the velocity gradient, the ratio

obtained is defined as the viscosity of the fluid medium. Therefore, the

viscosity is a measure of the internal fluid fi"iction, which tends to oppose

any dynamic change in the fluid motion [19].

The liquid molecules are closely spaced, with strong cohesive forces

between molecules, and the resistance to relative motion between

adjacent layers of the fluid is related to these intermolecular forces. As

the temperature increases, these cohesive forces are reduced with a

corresponding reduction in resistance to motion. Since viscosity is an

index of this resistance, it follows that the viscosity is reduced by an

increase in temperature. The effect of temperature on viscosity, fi , can

be closely approximated using empirical formula. For liquids an

empirical equation that has been used [20] is:

B

H = De ' (2.1)

Where D and B are constants and T is the absolute temperature. This

equation is often referred to as Ardrade's equation.

There are many techniques, developed in the past to measure viscosity.

French physician, Jean Louis Poiseuille (1799 - 1869) used capillary

tubes to measure the viscosity. The other method developed is the falling

ball viscometer in which the resulting travel time or distance covered

determines the viscosity. In efflux type viscometers, the time of efflux for

a fixed quantity of liquid through a standardized short capillary is

determined. The measured time is a direct measurement of the viscosity.

The Quartz crystal resonator [1] and the ultrasonic plate wave [2] are also

used to measure the fluid viscosity.

The above mentioned measurement techniques offer satisfactory

performance, but the consideration of the effect of temperature is quite

time consuming and moreover requires considerable heating power in

them [3]. The effects of temperature on viscosity of liquids is studied by

several researchers [21-26].

10

This chapter presents a new technique for the measurement of liquid

viscosity. In this technique a disk is driven by a constant speed dc shunt

motor in the test liquid. The principle of viscosity measurement used is

that the torque required to rotate a disk, at constant speed, inside a liquid

bath is directly proportional to its viscosity. The current in a dc shunt

motor being proportional to its torque and hence, the current measures the

viscosity of the liquid. The change in motor current is converted into a

proportionate voltage which is further amplified by an instrumentation

amplifier. Thus, the viscosity of the liquid can be expressed in terms of

the output voltage of the instrumentation amplifier. The temperature of

the oil is controlled using a Peltier cooler/heater which is measured using

an AD590 two-terminal integrated circuit temperature sensor. The

viscosity of vegetable oils viz; groundnut, palm, sunflower and coconut

oils is measured at different temperature ranging from 20 °C to 60 °C and

the results are presented in the form of graphs.

2.2 THE PROPOSED ELECTRONIC TECHNIQUE

The proposed novel electronic viscometer is shown in Fig. 2.1. It consists

of a cylindrical liquid container made up of stainless steel. A circular disk

of radius R is made to rotate inside the liquid of viscosity, // at an

11

Figure 2.1 Schematic diagram of the experimental setup.

Figure 2.2 A ring on the disk surface with infinitesimal thickness dr.

12

angular velocity, a. The velocity distribution, u{y,r) between the disk

and top or bottom surfaces of the cylinder can easily be expressed as:

u{y,r) = r(o[\-^ (2.2)

where,

h is the fixed and equal clearance of top and bottom surfaces of the

cylinder from the disk,

y is the vertical distance from the disk surface and

r is the horizontal distance from the axis of rotation.

The tangential stress, r on the surface of the disk is readily given as:

T = M (2.3)

Employing Eq. (2.2) and (2.3), we get

T = M— (2.4) h

Considering, the ring of radius r having infinitesimal thickness, dr of the

disk as shown in Fig. 2.2, the differential tangential force, df is given by:

df = /jx — XITO-AT (2.5) h

Therefore, the differential torque, dT^ generated on the ring may be

expressed as:

dT,=dfxr (2.6)

13

Substituting the values of df from Eq. (2.5), results in

or, = ^^^Pdr (2.7) h

Integration of Eq. (2.7) within the limits from 0 to i?, gives the torque, T^

on one side of the disk as:

r, = 5 i ^ (2.8)

Neglecting shear on the outer disk edge, the total torque, T, on both sides

of the disk becomes twice of the torque, Tj referred to above and is

expressed as;

7 ; = ^ ^ (2.9)

h

Keeping co, h and R as constants in the above Eq. (2.9), the total torque

is directly proportional to the viscosity of the liquid. Thus,

T,=kM (2.10)

where k = , is the device constant. h

The torque generated by the dc shunt motor, T„ is given by:

T„=T,+T^ (2.11)

Where r, and 7} denotes usable torque and frictional torque respectively.

Assuming 7} constant and compensating it through the proposed circuit,

Eq. (2.11) becomes:

14

T„=T, (2.12)

If the electrical losses of the motor are neglected, the electrical power

supplied to it and the mechanical power developed are given by EI and

T^co respectively.

Under the steady state condition, it can be written as:

EI = T„co (2.13)

Where, E is the supply voltage applied to the motor and / being the

resulting current in it.

Since, supply voltage, E and angular velocity, a are constants, Eq.(2.13)

may be expressed as:

T„al (2.14)

From Eq. (2.10) and (2.14), one can directly express

la^i (2.15)

From the above equation it is clear that the current of the dc shunt motor

is directly proportional to the viscosity of the liquid under test.

The current / is converted into a proportionate voltage, V^ by allowing

the current to pass through the resistor;?^, for the measurement of

viscosity as shown in Fig. 2.3. Thus,

K=IR, (2.16)

15

IK pot

lOK lOK M/V 1

Figure 2.3 Proposed circuit for the measurement of liquid viscosity.

16

A 12 V dc supply is connected to the dc shunt motor for its operation as

shown in the same circuit. As it is readily seen from Eq. (2.16) that the

voltage, V^ is proportional to the current, / of the dc shunt motor. The

Voltage, V^ corresponding to the frictional torque is obtained from the IK

potentiometer. It is subtracted from V^ and amplified using the

instrumentation amplifier (AD624, Analog Devices). Hence, the output

voltage, F„ of the circuit can easily be understood to be proportional to

the viscosity of the liquid.

2.3 EXPERIMENTAL SETUP

The schematic representation of the experimental setup is shown in

Fig.2.1. It consists of a closed cylinder made of stainless steel having

diameter of 40 mm and a height of 40 mm. It is completely filled with

20ml of the sample under test. The rotating disk has the radius and

thickness of 5 mm and 0.5 mm respectively. The temperature is

maintained constant at a desired level, in the range 20 °C to 60 °C, with

the help of the Peltier cooler/heater (TB-127-1, 0-2,5 Kryotherm, Russia).

The magnitude of the current passing through TEM was used to maintain

or control the temperature of the oil.

17

The dc shunt motor rotates the disk at a constant speed of 900 rpm in the

cylinder. The speed of the motor is measured using a digital tachometer

(RC-lOO, Selectron). The temperature of the oil is recorded by a two-

terminal integrated circuit temperature sensor (AD590, Analog Device).

The output voltage, V^ of the proposed circuit indicated in Fig. 2.3, is

proportional to the viscosity of the liquid and is measured using an

electronic voltmeter (DMM2002, Keithley). Five replications at each

temperature were carried out and their average calculated to minimize the

unforeseen errors.

The experimental set up is utilized to test different vegetable oils viz;

coconut, groundnut, palm and sunflower oils. The same viscosity

measurements were also carried out by the Redwood viscometer

specification number 1 (MSW-527, Macro Scientific) for the sake of

comparison of the results.

2.4 EXPERIMENTAL RESULTS

The experimental results are obtained using the experimental setup of

Fig. 2.1 and the circuit of Fig. 2.3 in addition to Redwood viscometer.

These results are shown in the form of different graphs.

18

The variation of the observed kinematic viscosity with temperature, for

different vegetable oils, using the Redwood viscometer is shown in

Fig.2.4. During these observations a precise control of temperature is

maintained. It can be observed from the characteristics of Fig. 2.4 that the

kinematic viscosity decreases with increase in temperature, for each type

of oil. It is further to be observed from the same figure, that the groundnut

oil has the highest viscosity while the coconut oil, the minimum, at a

given temperature. For the remaining oils viz; Palm oil and sunflower oil

have the viscosities lying between the groundnut oil and the coconut oil.

The variation of the output voltage, V„ of the proposed circuit, at different

temperatures, for various types of vegetable oils is shown in Fig. 2.5. It

can be seen that the variation of these curves is identical to those of

Fig.2.4. Thus, the output voltages of Fig. 2.5 can be correlated with the

viscosity of oils shown in Fig. 2.4. This variation is depicted in Fig. 2.6. It

can readily be observed that it is a linear variation, among the voltage and

the viscosity of oils. As it is well known, that the linear variation is a

desirable feature in instrumentation and hence, the present scheme can be

used to measure viscosity of liquids from the observed voltage of the

proposed circuit. Therefore, one can easily and quickly measure the

viscosity of the required liquid, simply by the observation of the output of

19

^o

o o

I c

20 25 30 35 40 45

Temperature (°C)

50 55 60

20

Figure 2.4 Variation of Redwood viscosities of vegetable oils with temperature.

Groundnut oil

Palm oil

Sunflower oil

Coconut oil

25 30 35 40 45 50 55

Temperature (°C) Figure 2.5 Variation of output voltage of vegetable oils with

temperature.

60

20

0.2 0.4 0.6 0.8

Kinematic viscosity (x 10"* mVs)

Figure 2.6 Output voltage versus observed viscosity.

21

the circuit, without bothering for the difficulties involved with the

different types of viscometers being in use.

22

CHAPTER III


NATURAL MILK

3.1 INTRODUCTION

The story and use of milk goes back to the beginning of civilization itself

Cattle were domesticated even in prehistoric times and milk was one of

the most essential of all foods. As milk is one of the most complete single

foods available in nature for health and promotion of growth, the cow is

considered as a sacred animal in India.

Milk is the normal secretion of the mammary glands of mammals. Its

purpose in nature is to provide nourishment for the young ones of the

particular species producing it. Human has learnt the art of using milk

and milk products as a food for his well being. Thus, an increase in the

milk producing function of the animals, best adapted as a source of milk

for him. The cow is the principal source of milk for human consumption

in many parts of the world, other animals being used as source of milk for

human beings are buffalo, goat, sheep, camel, mare, etc. In India major

source of milk is the buffalo.

Milk is the complex mixture of lipids, carbohydrates, proteins, and many

other organic compounds and inorganic salts dissolved or dispersed in

23

water. Some of these compounds such as the carbohydrates, lactose, and

most of the salts and vitamins are soluble in water. Other ingradients such

as the lipids, proteins, and dicalcium phosphate are dispersed through the

water in the colloidal or near colloidal state.

The lipid is composed primarily of fat, although there are also small

amounts of phospholipids, sterols, the fat soluble vitamins A and D,

carotenes and xanthophylls. The lactose is the only carbohydrate present

in the milk, obtained from cow or other species. The ash of the milk

contains all of the minerals but, not necessarily in the same form [18].

The composition of milk obtained from buffalo is, water (82.14%), fat

(7.44%), protein (4.78%), lactose (4.8%) and ash (0.83%) [27].

The composition of the milk can be altered by the removal of some of its

ingredients or by an addition of various substances usually with

fraudulent intent or as a means of escaping legislative regulations of

standard milk quality. The most common form of adulteration is the

addition of synthetic milk. Synthetic milk is an excellent imitation of

natural milk. In synthetic milk, fat and nitrogen components are

mimicked by vegetable oil and urea respectively and then the detergents

are added to make it frothy. This mixture is so expertly prepared that the

specific gravity of the concocted milk is the same as that of the natural

buffalo milk. This mixture is used to produce adulterated milk. Such milk

24

can be processed into "value added" products which bring in a bigger

profit. A recent Indian Council of Medical research (ICMR) report has

suggested that such adulterated items can even lead to cancerous effects

on the human system and hence, gradual impairment of the body.

Based on the above mentioned significance, a large number of Scientists

are involved in the study of the detection of these adulterants and their

methods of measurements. These methods include determination of fat

and total solids by chemical or physical analysis, estimation of sediment

by forcing milk through filter pads and noting the residue left,

determination of bacterial count etc. [4-5].

However, most of these measurements methods are expensive and time

consuming, as the milk samples need to be transferred to the laboratory

for their testing.

The present chapter describes a method for the determination of the

amount of the adulteration of natural milk with synthetic milk. For the

sake of experimentation, the synthetic milk is prepared in the laboratory,

by emulsifying vegetable oils with appropriate amount of detergent and

urea. A number of samples of the natural milk mixed with synthetic milk

are analyzed by the method of electrical admittance spectroscopy. A

significant variation is observed between the values of conductance

measured at 100 kHz and 8 °C, with different degrees of adulteration.

25

This phenomenon is utilized to detect the adulteration of milk with

synthetic milk, using the electronic Conductance method described in the

next article.

3.2 THE CONDUCTANCE MEASUREMENT METHOD

The electrical admittance between two electrodes, immersed in an

electrolyte can be modeled using series and parallel combination of

capacitors and conductance [28] as shown in Fig. 3.1.

The capacitance Cj represents the double layer capacitance of the

electrode/electrolyte interface, while the series conductance G^ represents

the bulk electrolyte conductance. The geometrical capacitance, Q is the

capacitance formed between the electrodes separated by the electrolyte.

At high jfrequencies, the electrical model reduces to a parallel

combination of G^ and Q as C can be treated as a short circuit [6-7].

26

Electrode 1

o—

Electrode 2

o

Figure 3.1 Electrical model of an electrolyte.

AA/V

Figure 3.2 Conductance measuring circuit.

27

The conductance, G^ can be measured by an operational amplifier circuit

shown in Fig. 3.2. The Op Amp is utilized in the circuit because of its

several desirable characteristics.

Thus, the output voltage, V^ of the circuit shown in Fig. 3.2 can be

expressed as:

K = -^v^ (3.1)

Selecting Zj as a resistance of fixed value whereas, Z, corresponds to the

impedance of the electrolyte i. e, Z, = l^

Employing Eq. (3.1) and keeping the input voltage, F; constant the output

voltage, V^ is found proportional to G^_


The schematic diagram of the experimental set up is shown in Fig. 3.3. It

consists of a cylinder of diameter 40mm and height of 40mm, containing

milk sample and housed in a heat insulator. The thermoelectric module,

TB-127-1,0-2,5 (Kryotherm, Russia) is used for controlling the

temperature at a desired level.

The construction of a typical thermoelectric module (TEM) is shown in

Fig. 3.4. It consists of a number of thermocouples, made of p-type and

28

D.C. 12V 6 A/AT

€y s /

Electrodes

Milk Sample

^ ^ TEM 1 ^ ; ^

Heat Sink

Fan

Figure 3.3 Schematic diagram of the experimental set-up.

n- type semiconductor

D.C. Source

Figure 3.4 Cross section of a typical TEM.

p- type semiconductor

29

n-type semiconductors, connected in series and sandwiched between two

Alumina ceramic plates. When dc current flows through TEM, it causes

temperature difference between TEM sides. As a result, one TEM face,

will be cooled while its opposite face is heated up. If the heat generated

on the TEM hot side is effectively dissipated into heat sinks and further

into the surrounding environment by fanning of heat sinks, then, the

temperature on the TEM cold side will be much lower than that of the

ambient. The TEM's cooling capacity is proportional to the current

passing through it. The sensing device consists of a pair of platinum

electrodes on glass wands 5mm x 5mm with a separation of 5mm.

Samples for testing were prepared by adding different quantities of

synthetic milk to the natural milk. The synthetic milk was prepared by

mixing 9 gm refined oil, 0.6 gm detergent and 0.8 gm urea in 500ml of

tap water. Samples of 25 ml were used in the measurement system, with

different percentage of adulteration. These samples were put in the

cylindrical container and a temperature of 8 °C was maintained by TEM.

This temperature was measured and verified using AD590 temperature

sensor. At the noted temperature, the bulk electrolyte conductance, G

and the geometrical capacitance, Q were measured between the

electrodes [29]. These measurements were made using the LCR Bridge,

30

HP 4284 A (Hewlett Packard, USA), at a voltage of 1.0 V r.m.s with

varying frequency from 20Hz to IMHz.


The experiments were performed to obtain G andQ, using the procedure

explained in the last article.

The variation of the capacitance, Q with frequency for different

adulterations is shown in Fig. 3.5. There is a large variation in the value

of Cj at a lower frequencies for different samples. It can also be noted

that it decreases with frequency and saturates above 1 kHz, at a value of

about 60pF.

Fig. 3.6 shows the measurement results for the conductance, G^ of the

milk samples at different frequencies, ranging from 20 Hz to 1 MHz at 8

°C temperature. From the figure, it is evident that the conductance varies

considerably upto the frequency of 100 kHz but, remains almost constant

above this frequency. It can also be observed from the same figure that

the value of the conductance decreases with the increase in the

concentration of the synthetic milk at a given frequency. The main reason

for such a variation is due to the salt content in the natural milk.

31

—•— natural milk

- • - 7 5 % milk/25% synthetic

- A - 5 0 % milk/50% synthetic

—X—25% milk/75%synthetic

X synthetic milk

l.OE+Ol l.OE+02 l.OE+03 l.OE+04 l.OE+05 l.OE+06

Frequency (Hz) Figure 3.5 Variation of Cb with frequency at different

adulteration.

2.5

2 •

V2

O

•i o

1.5

0.5

0

natural milk

synthetic milk

l.OE+Ol l.OE+02 l.OE+03 l.OE+04

Frequency (Hz)

l.OE+05 l.OE+06

Figure 3.6 Variation of G5 with frequency at different adulteration.

32

The measurement of G^ is carried out at 100 kHz and its variation with

the percentage of synthetic milk is depicted in Fig. 3.7. It can be

concluded from the figure that the conductance decreases with increase in

the concentration of synthetic milk.

Fig. 3.8 exhibits the changes in the conductance with temperature, for

different samples of the natural milk with the varying concentration of the

synthetic milk. It is evident from the figure that the conductance

increases with increase in temperature for a selected sample of the milk.

The other point to be observed from the characteristics is that their slope

decreases with increase in the concentration of the synthetic milk. Hence,

precise confrol of temperature is required to obtain accurate measurement

results.

Fig. 3.9 shows the variation of the output voltage, F„ of the circuit with

the percentage concentration of the synthetic milk. The measurements

were carried out for the 1 V r.m.s. input to the circuit, at a frequency of

100 kHz and maintaining the temperature at 8 °C.

33

0 20 80 40 60 Percentage of syntetic milk

Figure 3.7 Variation of conductance with percentage concentration of synthetic milk.

100

2.5

1/3

a

o 3

T3 C o U

0.5

natural

6 8 Temperature (°C)

10

Figure 3.8 Temperature dependance of conductance at 100 kHz for different samples.

12

34

10 20 30 40 50 60 70

Percentage of synthetic milk

80 90 100

Figure 3.9 Output voltage with percentage concentration of synthetic milic.

35

CHAPTER IV


HONEY

4.1 INTRODUCTION

Honey is the natural complex food product produced by bees from nectar

of plants and also from honeydew. It is a unique sweetening agent that

can be used by humans without processing. Bee honey has significant

nutritional and medicinal benefits. It is a rich source of readily available

sugars, organic acids, various amino acids and an additional source of

many biologically active compounds.

Normally, honey contains 12.4 - 20.3% moisture and 60.7 - 77.8%

sugars, of which about 0 - 2% may be sucrose, 25.2 - 35.3% glucose, and

33.3 - 43% fructose and less than 0.25% of ash.

Honey has always been an easy target of adulteration for economic gains.

Being a natural product, the composition of honey is highly variable.

Honey adulteration has evolved from the basic addition of cane sugar and

water to specially produced syrups for which the chemical composition

approximately reproduces that of natural honey. Therefore, there is a

need, for the development of more sophisticated methods to detect honey

adulteration.

36

A number of methods exist to check the adulteration, one of which

commonly used is the pollen analysis. It can demonstrate the addition of

syrup by the microscopic detection of cane sugar annuli or parenchyma,

or starch grains [8]. This technique provides very good results [30]. But

the ultrafilteration of the honey, limits the applicability of this method for

the determination of the purity/adulteration [31].

The other method available in the literature is based on the stable carbon

isotope ratio analysis (SCIRA). This method is based on the difference in

isotopic carbon composition that depends on the origin of the plant. The

creation of database on the isotopic contents of the honeys (mostly from

C3 plants) has revealed that these contents are relatively uniform [9]. It

was thus, possible to detect the addition of a com or cane sugar syrup

from C4 plants. But, this method is useful only if the adulteration is about

20%. Few studies concerning adulteration detection in honeys by

chromatographic methods have also been reported [10-11]. However,

these methods have the drawbacks of slow testing and expensive

experimental set up.

The proposed electronic technique to be discussed in the following article

is based on the variation of the dielectric properties of the food materials.

Various factors which can influence the dielectric properties of foods are

moisture, ash, electromagnetic waves and the physical state of food [32].

37

It is well known that the value of the capacitance of the capacitor depends

on its geometry and the physical properties (dielectric constant) of the

material placed between the plates. Thus, the capacitive methods can be

used for the determination of the composition of binary mixtures of non

conducting fluids where they differ in their dielectric constants. The

present technique involves the measurement of the capacitance of the

mixture (adulterated honey) with the variation of its dielectric constant,

depending on the percentage of adulteration.

Later on the variable capacitor referred to above is connected in the

circuit of a relaxation oscillator. The change in capacitance modulates the

output frequency of the oscillator. The frequency of the output signal is

measured using the digital counter. Thus, the output frequency of the

circuit is a measure of the adulteration of the honey.

4.2 THE CAPACITANCE BASED TECHNIQUE

A parallel-plate capacitor with plate area 'a' and plate separation 'd',

filled with a dielectric material, is shown in Fig. 4.1 and its capacitance,

C is given by [33]:

C = e,s^y^ (4.1)

38

Plates

Dielectric (Honey)

Figure 4.1 Dielectric based capacitive transducer.

DD

R, •AAAr

AAAr

Output frequency

Figure 4.2 Capacitance to frequency conversion using Relaxation oscillator.

39

where, e, is the dielectric constant of the material (Honey in this case)

between the plates and s^ is the permittivity of the free space.

If such a capacitor is connected in the circuit of a relaxation oscillator

shown in Fig. 4.2, it is converted into a period - modulated output signal

[34-35]. This oscillator relies on an RC circuit, formed by the Resistor R^

and Capacitor C and a comparator as a Schmitt trigger. The period T, of

the output signal is proportional to the Capacitance, and may be

expressed as:

T = RC\n V -V V V -V V

_ DD ' TH ' TL

(4.2)

The threshold voltages, V^.^ and ¥•,.„ of the Schmitt-trigger comparator are I

given by:

Where, V^^ is the fixed dc voltage.

If we select R^,R2and R^ of equal value, then F„ and r,„ take the

following forms:

Vr,=Voo/^ and (4.5)

VrH-2V,j3 (4.6)

40 ^

A substitution of F^ and V^„ from Eq. (4.5) and (4.6) in Eq. (4.2) results

in:

T = R,C\n4 or f = /j^c\n4 (^"^^

where, f is the frequency of the output signal.

If R^ is kept constant, it is evident from Eq. (4.8) that the frequency f, of

the modulated output signal is inversely dependent on the capacitance , C

used in the circuit.

4.3 EXPERIMENTAL METHOD

The capacitor for experimentation was formed by a pair of individual

platinum electrode on glass wands with square shape having dimensions

of 5mm X 5mm and a separation of 5mm. The charging resistor

R^ = \00kn was used in the circuit and the IC 356 was used as a Schmitt

trigger.

Pure honey was adulterated with different quantities of syrup to obtain a

number of samples. These samples were mixed thoroughly and kept at the

room temperature. For each test, approximately 2 g of the honey sample

was placed as a dielectric material between the plates of the capacitor.

The measurement of the capacitances so formed were performed with the

help of HP 4284 A, an LCR apparatus from Hewlett Packard, USA. The

41

variation of frequency, /o f the output signal shown in Fig. 4.4 was

recorded by a digital frequency counter.

4.4 MEASUREMENT RESULTS

The measurement results of the capacitances of the adulterated honey

samples are presented in Fig. 4.3. It can readily be observed from the

graph that the capacitance of the sample increases with the increase in the

adulteration of the honey.

The charging resistor, R^ is selected aslOOAQ for the circuit of Fig. 4.2.

The variation of the measured capacitance C is shown in Fig. 4.3. It

varies between 20 pF and 500 pF for adulteration from 0 to 100 percent.

As per the Eq. (4.8) and the experimental setup of Fig. 4.2, the

measurement of the relaxation oscillator frequency with percentage

adulteration is also shown in Fig. 4.4. It can be observed from the

variation that the frequency of the output signal decreases from 308 kHz

to 12.34 kHz for increase in adulteration from 0 to 100 percent.

42

0 10 20 30 40 50 60 70 80 90 100

Percentage honey adulteration

Figure 4.3 Variation of Capacitance with adulteration.

10 20 30 40 50 60 70

Percentage honey adulteration

80 90 100

Figure 4.4 Variation of frequency with adulteration.

43

CHAPTER V

ESTIMATION OF THE ADULTERATION IN

PETROL AND DIESEL

5.1 INTRODUCTION

The importance of petrol and diesel in the present world is well known to

everyone. Thus, their purity play an important role in functioning of the

appliances viz; vehicles, airplanes and other machines. Hence, it becomes

necessary to check their adulteration as it may affect the performance and

even may damage the appliances in the worst possible case.

Fiber optic sensors offer several advantages compared to conventional

non-optical sensors. It provides the possibility of sensor technology that

is light weight, small size, potentially multiplexable, immune to

electromagnetic interference (EMI), without electromagnetic

susceptibility (EMS), and at the same time, it does not require electrical

current at the sensing point [36].

Most commonly used commercial automotive fuels available on the

Indian subcontinent are petrol and diesel. These are generally adulterated

with kerosene, as the price of kerosene, distributed through public

44

distribution system is kept low due to social and economical

considerations.

Adulterated fuels make exhaust gases more poisonous, worsening the

pollution crisis and causing acute respiratory infections and other

ailments. When Kerosene is mixed with petrol, it does not bum

completely and releases more cancer-causing hydrocarbons, nitrous

oxides and carbon monoxide instead of the less-harmful carbon dioxide

released when pure petrol is used [37]. Adulteration of diesel with

kerosene decreases diesel's lubricating function, leading to faster wear

and tear of the pistons and thus, requires higher maintenance costs. In

addition, the soot particles carried by diesel exhausts also have unbumt

and harmful hydrocarbons from the kerosene.

Kerosene being the most popular adulterants for petrol and diesel, is

much similar in chemical structure to petrol and diesel and thus mixes

with almost no aberration in the properties of automotive fuel [38-39].

A number of methods have been proposed in the literature for measuring

adulteration of petrol and diesel, by kerosene viz; the filter test, testing

through specific gravity, viscosity, odor based method [12], ultrasonic

technique [13], titration technique [14-16] etc. The specific gravity

measurement suffers significant inaccuracy in the measurement, whereas

the viscosity measurement method has the drawback of generating the

45

same viscosity of the adulterated sample by adding a small amount of

high viscosity lubricating oils. The method described in the present

chapter is very simple, compact and portable as compared to the methods

already available to check the adulteration.

In the optical fiber, the light is guided by the inner medium of higher

refi"active index (core), but a small percentage of the field travels in the

cladding. The evanescent field or wave is an effect experienced by light

at boundaries with a change in refractive index. If the cladding is

removed, the evanescent wave is able to interact with the measurand,

providing the basis for sensing. For the fluids obeying the Lambert-Beer

law of absorption, the evanescent absorbance depends linearly on both

exposed fiber length and the fluid concentration [40-41].

This chapter deals with an electronic technique to determine the

adulteration of petrol and diesel caused by kerosene. An LED placed at

one end of the fiber provides sufficient radiant energy over the

wavelength region where absorption is to be measured. The light is

guided inside an optical fiber through the principle of total internal

reflection. The cladding of an optical fiber is removed over a small length

of the fiber. Thus, evanescent wave is able to interact with the measurand,

providing the basis for sensing. The light received at the other end of the

fiber is converted into a proportional current using a photodiode. This

46

current is further converted into a proportionate output voltage using a

current to voltage converter. The resulting voltage can be measured using

a sensitive digital voltmeter. Later on the reading of this voltmeter can be

calibrated in terms of the percentage of adulteration.

5.2 THE FIBER OPTIC METHOD

The experimental set-up of the proposed electronic technique to

determine the adulteration is shown in Fig. 5.1. It consists of 5V constant

dc supply connected to an LED. The light emitted by the LED is

proportional to the forward current. Light emitting diodes are designed to

produce coherent light at 630 nm wavelength with a very narrow

bandwidth.

Silicon photodiode is being used as the photo detector in the circuit. The

current of the photo detector is proportional to the intensity of the

incident light falling on it. The photo detector is in the photovoltaic mode,

which offers lower noise and therefore, is better suited for measurement

and instrumentation applications. The Op Amp's input impedance being

very high, the photo diode current flows through the feedback resistor R.

This current is converted into a proportional voltage given by:

K = iLxR (5.1)

47

M+

c

o

a

tn

n

T

a\ o o 2 3 . 3

"h-<3> 1—=< H

48


The bulk absorbance of the petrol and diesel at different adulteration

levels is measured with ELICO SL 164 Double beam UV-VIS

spectrophotometer at 630 nm wavelength. The 1.0 cm cuvette was used to

measure the absorbance relative to petrol. The MFOE 71, 9508, Mexico,

LED was used which provide the radiation at the wavelength of 630 nm.

The length of the optical fiber used was 30 cm with a core diameter of

1mm from which cladding of 6 cm was removed from the central region.

The material of the core is polymethylmetacrilate (PMMA), with a

refractive index of 1.492. The cladding is made of fluorinated polymers

with refraction index of 1.417. The photo detector used is MF0D71,

9432, Mexico, which converts the light intensity into a proportionate

current.


The bulk absorbance of petrol and diesel at different adulteration levels is

measured at 630 nm of wavelength. The absorbance measured is with

respect to pure petrol and diesel. The variation of bulk absorbance with

increase in the percentage of kerosene in petrol and diesel is shown in

Fig. 5.2. It can be observed that the absorbance increases with increase in

kerosene adulteration.

49

0 10 20 30 40 Percentage adulteration with kerosene

50

Figure 5.2 Variation of bulk absorbance of petrol and diesel with kerosene adulteration.

0.16

10 20 30

Percentage adulteration with kerosene

40 50

Figure 5.3 Output voltage for percentage adulteration with kerosene.

50

It is also to be noted from the same figure that the absorbance for petrol is

higher as compared to diesel for the same adulteration with kerosene.

The variation of the output voltage for each value of the percentage

adulteration with kerosene in petrol and diesel is measured using the

proposed electronic circuit and is shown in Fig. 5.3. The output voltage

decreases almost linearly with increase in the percentage of kerosene in

petrol and diesel. It can also be observed that the value of the output

voltage is higher for petrol as compared to diesel for the same

concentration of kerosene.

51

CHAPTER VI

DISCRIMINATION OF VEGETABLE OILS

6.1 INTRODUCTION

Lipids are one of the large groups of organic compounds which are of

great importance in the selection of food. The lipids present in the food

are readily digested and utilized in the body. They are widely distributed

and almost every natural food contains considerable amount of them.

Much of our discussion in the present chapter is confined to the prepared

edible fats and oils which are available in market in a fairly pure state.

Research is going on at a higher level to discriminate different vegetable

oils so that fraud of these oils can be checked in the market which may

cause serious harm to health. Adulteration involves addition of cheaper

oils in the pure ones. The most common adulterants found in virgin olive

oil are refined olive oil, OPO, synthetic olive oil glycerol products, seed

oils (such as sunflower, soy, maize and rapeseed) [42-46] and nut oils

(such as hazelnut and peanut oil) [46-48]. In some cases, besides the

economic fraud, adulteration may cause serious health hazards.

Several techniques are available in the literature for the discrimination of

vegetable oils. These include colorimetric reactions, determination of

52

iodine value, saponification value, density, viscosity, refractive index and

ultraviolet absorbance [17]. However, they are time-consuming and

require sample manipulation. Gas and liquid chromatography are the

techniques that are being used at present for oil analysis. This technique

involves extraction and preconcentration, which make the overall analysis

also time-consuming. Therefore, chromatographic methods cannot be

used for real time in situ analysis. Moreover, chromatographic methods

are expensive, as they require solvents of high purity far anialytic

separation and sample extraction. Spectroscopic [49] methods present an

alternative to chromatography. However, it suffers the disadvantage of

lack of selectivity.

The colour of fats and oils is due to presence of numerous pigments. An

orange-red or yellow pigmentation is usually caused by the presence of

carotenoids. The darkening, which some oils show on limited oxidation is

caused by the oxidation of tocopherols, the vitamin E substance present in

them. The green color in the oil is due to the presence of chlorophyll.

When the oil is made from a green plant products, some of the

chlorophyll will be carried along and results in green color of the oil.

Brown pigments are usually present in oils prepared from rotten or

damaged plant products which are obtained from the disintegration of

protein and carbohydrate molecules [18]. These compounds have a

53

marked influence on the oil quality. For instance, tocopherols and

carotenoids affect the oxidative stability of oils, whereas chlorophylls are

responsible for oil photo oxidation [50].

In this chapter we present an electronic technique for the discrimination

of vegetable oils. Vegetable oils viz; castor, olive, sunflower, mustard,

and groundnut oils are analyzed by emission of monochromatic light at

different wavelengths of 635nm, 565nm, 470nm and 430nm. A fi-action

of the incoming light is absorbed by the oil sample, as a result, light of

lower intensity emerges out of the oil, which is measured using an

electronic circuit described in the following article.

6.2 THE OPTICAL TECHNIQUE

The proposed electronic technique for determining the adulteration of the

vegetable oils is shown in Fig. 6.1. It consists of +5 V constant supply fed

to an LED. Monochromatic light from LED was passed through the oil

sample contained in the polysterene cuvette. The light passed through the

sample was detected by the photoconductor which changes its electrical

resistance. This change in the electrical resistance of the photoconductor

changes the frequency of the voltage controlled oscillator circuit.

The voltage controlled oscillator 566 IC, has circuitry to generate signals

square-wave and triangular-wave. The frequency of these signals is set

54

/v

by an external resistor R^ and capacitor C and thenmriecril^T&na

dc voltage Vc.

A center operating frequency, /„of the voltage controlled circuit is:

fo = 2 (V^-K^

R,C, V* (6.1)

Where V* is the +12 dc voltage, with the practical circuit value

restrictions that Fcshould be within range oiVAV* and V^ and R^ =\QkD.

andC, = 220pF are selected. The frequency of the output square wave can

then be varied from 22.1kHz to 227.2kHz.

The resistor divider R^and photoconductor cell sets the modulating

voltage which falls properly in the voltage range of VA V* and V*. The

control voltage, V^ is given as:

^ R. ^ V. = '3 V^ (6.2)

The resistance of the typical cell can change over wide range from about

20kQ to few kilo ohms.

When the photoconductor cell is illuminated by a light beam, it has a

resistance of 20kQ and the control voltage is 9.6F, resulting in an upper

output frequency of S\.UHz. When the light beam is interrupted, the cell

has resistance of 20kQ and the control voltage output is 11.7 V, giving

rise to a lower output frequency of 22.1kHz.

55

510 ohm < ' i

+5V

V c "

+ 12V

• R3 Photo

conducto:

riTi

Figure 6.1 Circuit diagram of the proposed technique.

56


The studies were performed on five commercial available edible oils

including castor, olive, sunflower, mustard and groundnut oils. The

samples were analysed without any prior treatment. An oil sample of 4ml

was placed in a polystyrene cuvette. Light of wavelengths, 635nm,

565nm, 470nm and 430nm was passed through a polystyrene cuvette

containing the sample oil. Some of the incoming light was absorbed by

the sample. As a result, light of lower intensity strikes a photoconductor.

The amount of light that passed through the sample was measured by an

electronic circuit which produces square wave of variable frequency,

proportional to the intensity of light beam. The frequency of the output

signal was measured using a digital frequency counter.


The digital frequency counter output obtained for various oil samples at

different wave lengths is shown in Fig. 6.2.

From Fig. 6.2 it is observed that at 635nm wavelength, the output

frequency for all the oil samples are quite close to each other. At 565nm,

the output frequencies were close to one another and it was same for

castor oil and sunflower oil. At 470nm the output frequency for

groundnut, castor and olive oil are poorly spaced as well as groundnut

57

• Castor oil • Olive oil A Sunflower oil X Mustard oil X Ground nut oil

400 450 500 550 600 650

Wavelength (nm)

Figure 6.2 Electronic frequency counter output for different oil samples.

58

and castor oil were having the same frequency. At 430nm wavelength,

the separation of all oil classes was good.

59

CHAPTER VII

CONCLUSIONS

7.1 INTRODUCTION

The objective of this thesis is to develop electronic techniques for

studying the characteristics of natural fluids as the adulteration and

impurities in the natural fluids affect the health of human beings,

performance of vehicles and machines in industries etc. Thus, a number

of techniques are already available in the literature which require their

testing in the laboratory and need skilled staff and consume appreciable

time. To overcome these drawbacks a number of useful transducer based

electronic circuits have been designed, fabricated and tested. The

proposed techniques are utilized for testing different types of fluids and

their results are compared with the available methods. It has been found

that our measurement results are very close to those obtained from the so

called standard methods already available at present. Moreover, the

proposed electronic techniques in the thesis are instantaneous or require a

few minutes time as compared to the available techniques which require

hours of sample preparation and their testing. The test results presented in

the various chapters of the thesis fulfill the objective successfully.

60

7.2 INVESTIGATIONS OF THE THESIS

The thesis includes the testing of the adulteration of milk, honey, petrol

and diesel and vegetable oils using different techniques.

The Viscosity measurement technique for liquids with temperature

control has been presented in Chapter II. The viscosity is measured

simply by observing the output voltage of the proposed circuit which can

be calibrated in terms of the liquid viscosity. The measured viscosity of

the vegetable oils is also compared with that obtained by Redwood's

viscometer. The results of both the methods are close to each other. The

proposed technique has several advantages over the Redwood's

viscometer.

The testing of the adulteration of milk is carried out by the measurement

of its conductance at different frequencies varying between 20 Hz to

IMHz and at a constant temperature of 8 °C. This phenomenon of the

conductance variation is exploited to detect the adulteration of milk with

synthetic milk. The proposed method would find applications in food

processing industries. Thus, a portable device based on the proposed

method can be made for an on road measurement of adulteration in milk.

The other useful liquid for nutrition and medicine under test is honey.

The analysis of the honey samples is based on its dielectric properties.

Thus, a parallel plate capacitor is made use for testing honey with

different percentage of adulteration, kept as dielectric and measuring its

capacitance. The variation of the capacitance is found to be significant

with the adulteration of honey. The results of this method indicate that the

method is quite simple and quick and hence, suitable for large scale

industrial monitoring of honey samples.

The significance of purity of petrol and diesel is known to every body.

The discussed technique is based on the evanescent wave to measure the

adulteration of petrol and diesel. The adulteration is created by adding

different amounts of kerosene, a very cheap and common contaminant.

The presented calibration graphs, showing the variation of the output

verses percentage contamination are found to be linear, an important

feature for instrumentation and measurement. The proposed method

would be useilil in automotive and petrochemical industries due to its

simple design, safety with inflammable fuels. This method can also be

used for an in-field analysis and monitoring of the quality of petrol and

diesel.

The last electronic technique is discussed for the discrimination between

different types of vegetable oils. The technique involves the use of

different wavelengths generated by LED. However, the best results are

obtained at the wavelength of 430nm. It is clear from the results

presented in the form of graphs between frequency and different types of

62

vegetable oils that the method provides a very useful tool for the

discrimination of vegetable oils. The technique provides rapid

identification of vegetable oils in additipn to the avoidance of consumable

reagents and of extensive sample pre-treatment. The electronic circuitry

involved gives an insight to develop a portable instrument for such

measurement and discrimination of natural fluids.

7.3 FUTURE SCOPE

Modem trend is to use electronic transducers in industrial measurements

for the assessment, monitoring, and control of food quality and safety,

since they offer rapid measurement and control and have low costs. Thus,

there is a lot of future scope in this area for research. Some of them are

mentioned below:

• There seems a wide scope for use of odor based transducers

(electronic noses) for the detection of adulteration in different types of

vegetable oils, honey, milk, diesel and petrol etc.

• The proposed electronic circuits may be modified and can be

simulated in portable adulteration measuring instruments for different

types of fluids discussed in the present work. Thus, a possibility of

replacing the presently used techniques and meters which are

63

expensive, time consuming and requires skilled staff for their

operation.

• The other proposed future work could be to discriminate the source of

milk from the milk sample viz; cow, goat, sheep, camel, mare, mice

etc. This may involve the work of modification of the discussed

circuits of the present work and the investigation of new electronic

sensors.

• Another interesting problem would be to investigate electronic

techniques for identifying honey from different floral, viz; jamun,

aonla, soapnut, gurige, beetlenut, neem terminilia etc. This is

important because the source of honey determines the taste and the

composition of it which may be useful for different medical and

nutritional applications.

• In this thesis, the application of the proposed technique for the

discrimination of the vegetable oils has been discussed. To determine

the percentage of adulteration of vegetable oils using this technique

could be taken up as a future task.

To sum up, there is a wide scope for research on the subject of electronic

transducers and their applications for detecting and determination of the

percentage adulteration in fluids. Some of which are significant because

of their nutritional values and others for applications in machinery.

64

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