ISSN 1974-9821
Vol. 7 N. 1
February 2013
International Review on
Modelling and Simulations
T
(IREMOS)
Contents:
IN
An Enhanced Ultra Capacitor Interface Circuit Based Bidirectional Soft Switching Converter
by B. Stalin, T. S. Sivakumaran
1
16
Three-Phase Shunt Active Filter with Compensation of Reactive Power
by A. Ouchatti, A. Abbou, M. Akherraz, A. Taouni
22
A Comparative Study of Modular Axial Flux Podded Generators
for Marine Current Turbines
by Sofiane Djebarri, Mohamed Benbouzid, Jean Frédéric Charpentier, Franck Scuiller
30
A New Sensorless Control Design of Induction Motor
Based on Backstepping Sliding Mode Approach
by A. Bennassar, A. Abbou, M. Akherraz, M. Barara
35
Development of Fuzzy Logic Controller for DC-DC Converter in Electric Vehicle
by Mardhiah Saripudin, Muhamad Mansor
43
Models for Evaluating Energy Savings Achieved by Energy Storage System in Urban Railway
by Sung-Dae Kim, Kyu-Hyoung Choi
51
Structural Behavior of a Ballasted Small Railway Track Under Static and Dynamic Loadings
by Waluyo Adi Siswanto, Sam Tsae Yun, Wahyu Mulyo Utomo
59
Techno-Economic Analysis of a Photovoltaic-Fuel Cell Grid-Connected Hybrid Energy System
by Malious Sheilla, Chee Wei Tan, Cheng Siong Lim
65
Geometrical Approximation of the Overhead Power Line Conductors
by T. Modrić, S. Vujević, T. Majić
76
Robust Adaptive Backstepping Control for Wind Energy Systems with Uncertain PMSGs
by F. Grouz, L. Sbita
83
Active Disturbance Rejection Control for DFIG Based Wind Farms
Under Unbalanced Grid Voltage
by Ali Boukhriss, Tamou Nasser, Ahmed Essadki, Abdellah Boualloch
95
R
EP
R
Design and Realization of Maximum Boost Switched Inductor Z-Source Inverter
for Three Phase On-Line UPS
by K. Chitra, A. Jeevanandham, Nimitha Ashok
(continued on inside back cover)
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations
(IREMOS)
Editor-in-Chief:
Santolo Meo
Department of Electrical Engineering
FEDERICO II University
21 Claudio - I80125 Naples, Italy
santolo@unina.it
Editorial Board:
IN
T
Brunel University
Univ. of Western Brittany- Electrical Engineering Department
Univ. of Auckland – Department of Mechanical Engineering
Univ. of Zagreb - Faculty of Electrical Engineering and Computing
Univ. of L'Aquila - Department of Electrical and Information Engineering
Univ. of Ontario Institute of Technology
FEDERICO II Univ., Naples - Dept. of Electrical Engineering
Univ. of Kiel
Technical Univ. of Sofia - Electrical Power Department
National Cheng-Kung Univ. - Department of Mechanical Engineering
Andong National Univ. - School of Mechanical Engineering
Technical Univ. of Budapest
Tsinghua Univ. - Department of Mathematical Sciences
Univ. de Haute Alsace IUT de Colmar
FEDERICO II Univ., Naples - Dept. of Electrical Engineering
Univ. of Pretoria - Dept.of Mechanical & Aeronautical Engineering
Institut de Mathématiques et de Modélisation de Montpellier
Indian Institute of Technology, Kanpur - Mechanical Engineering
"Gh. Asachi" Technical University of Iasi
Slovak Univ. of Technology - Faculty of Mechanical Engineering
Aristotle Univ. of Thessaloniki
Jiangsu Univ. - Department of Mathematics
Kobe Univ. - Division of Mechanical Engineering
Technische Univ. Berlin - Institute for Energy Engineering
Brunel University - School of Engineering and Design
R
(U.K.)
(France)
(New Zealand)
(Croatia)
(Italy)
(Canada)
(Italy)
(Germany)
(Bulgaria)
(Taiwan)
(Korea)
(Hungary)
(China)
(France)
(Italy)
(South Africa)
(France)
(India)
(Romania)
(Slovak Republic)
(Greece)
(China)
(Japan)
(Germany)
(U.K.)
EP
Marios Angelides
M. El Hachemi Benbouzid
Debes Bhattacharyya
Stjepan Bogdan
Cecati Carlo
Ibrahim Dincer
Giuseppe Gentile
Wilhelm Hasselbring
Ivan Ivanov
Jiin-Yuh Jang
Heuy-Dong Kim
Marta Kurutz
Baoding Liu
Pascal Lorenz
Santolo Meo
Josua P. Meyer
Bijan Mohammadi
Pradipta Kumar Panigrahi
Adrian Traian Pleşca
Ľubomír Šooš
Lazarus Tenek
Lixin Tian
Yoshihiro Tomita
George Tsatsaronis
Ahmed F. Zobaa
The International Review on Modelling and Simulations (IREMOS) is a publication of the Praise Worthy Prize S.r.l..
The Review is published bimonthly, appearing on the last day of February, April, June, August, October, December.
R
Published and Printed in Italy by Praise Worthy Prize S.r.l., Naples, October 31, 2013.
Copyright © 2013 Praise Worthy Prize S.r.l. - All rights reserved.
This journal and the individual contributions contained in it are protected under copyright by Praise Worthy Prize S.r.l. and the
following terms and conditions apply to their use:
Single photocopies of single articles may be made for personal use as allowed by national copyright laws.
Permission of the Publisher and payment of a fee is required for all other photocopying, including multiple or systematic copying,
copying for advertising or promotional purposes, resale and all forms of document delivery. Permission may be sought directly
from Praise Worthy Prize S.r.l. at the e-mail address:
administration@praiseworthyprize.com
Permission of the Publisher is required to store or use electronically any material contained in this journal, including any article or
part of an article. Except as outlined above, no part of this publication may be reproduced, stored in a retrieval system or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written
permission of the Publisher. E-mail address permission request:
administration@praiseworthyprize.com
Responsibility for the contents rests upon the authors and not upon the Praise Worthy Prize S.r.l..
Statement and opinions expressed in the articles and communications are those of the individual contributors and not the
statements and opinions of Praise Worthy Prize S.r.l.. Praise Worthy Prize S.r.l. assumes no responsibility or liability for any
damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained herein.
Praise Worthy Prize S.r.l. expressly disclaims any implied warranties of merchantability or fitness for a particular purpose. If
expert assistance is required, the service of a competent professional person should be sought.
International Review on Modelling and Simulations (I.RE.MO.S.), Vol. 7, N. 1
ISSN 1974-9821
February 2014
A Semi-Cylindrical Capacitive-Based Differential Sensing System
for Water Content In Crude Oil Measurement
Maher Assaad1, Aslam M. Zubair2, Tong Bon Tang2
Abstract – A capacitive sensor based measuring system for water content in crude oil is
IN
T
presented. The non intrusive capacitive sensor is made of two semi-cylindrical electrodes which
are mounted on outside of the glass tube. The tube is filled with sample under test. The capacitive
variation is measured by taking advantage of big dielectric permittivity difference of oil and water.
The semi-cylindrical capacitive sensor has ability to detect small capacitance variation (pF) and
these variations can be converted into voltage by proposed differential interface circuit. The
interface circuit is based on differential sensing technique. Such technique allows the removal of
unwanted signals (e.g. temperature, background noise and systematic offset) because they affect
both sensors in a similar manner. It however will not auto-compensate for the degradation in
sensitivity. Hence, increased accuracy and linearity is achieved by differential sensing technique.
Both simulation and actual hardware implementation confirmed the proposed system design. The
system is experimentally tested for 0-30% water content in oil and achieved resolution of 0.39%.
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved.
Keywords: Capacitive Sensor, Water Content, Interface Circuit, Crude Oil, Differential Sensing
Vrm
(Vsm)
Vrf (Vsf)
Zf
R
Zi1 (Zi2)
Cr (Cs)
r (s)
Rf (Cf)

Sinousoidal input signal with frequency 
Operational amplifier op-1 (op-2) output
signal in the reference (sample) sensor path
Multiplier output signal in the reference
(sample) sensor path
Filter output signal in the reference (sample)
sensor path
Capacitance to voltage converetr (CVC)
feedback impedance
Impedance of reference (sample) capacitor
Capacitance of the reference (sample) sensor
Phase of signal Vr (Vs)
Feedback circuit resistance (capacitance)
Instrumentation amplifier gain
EP
Vin
Vr (Vs)
To overcome the congenital limitations of previous
systems, a new differential capacitive sensor based
measurement system for water content in oil is proposed.
The capacitance of a capacitor depends on area of
electrode, distance between the electrodes and dielectric
constant of material between electrodes. The capacitive
sensors are widely used for measurement of several
quantities in different applications such as pressure
sensing [4], position sensing [5], humidity measurement
[6], liquid level sensing [7], liquids two phase flow
measurement [8]-[20], electronic tongue system [21] and
human blood cells measurement [22], are few of them
[27], [28].
The dielectric permittivity varies from material to
material. By utilizing the advantage of these dielectric
variations, two phase (liquid-liquid, liquid-gas etc.) void
fraction measurement can be performed by capacitive
sensors. In [8], oil fraction is measured in two phase oilwater flow by using a single pare of concave electrodes
mounted outside of the pipe walls. The single ended
capacitance to voltage conversion technique is used in
interface circuit of the system. The phase percentage
measurement is performed in [9] by using capacitive
sensor. The electrodes mounted inside and outside of
pipe walls. The capacitance of the sensor mainly depends
on volume of two phases. The two phases tested was
water-oil, oil-gas and water gas. In [10], air-water two
phase flow measurement is performed by using ring and
concave electrode capacitive sensors. To analyze the
capacitance variations with different flow rates,
capacitance meter is used. The operating frequency was
1MHz and relative error was 4%.
R
Nomenclature
I.
Introduction
During the extraction, transportation and refining
process of crude oil, online determination of water
content is always a major problem. To measure water
content in crude oil, the most commonly used analytical
method involves distillation, centrifugation and electrical
dewatering [1].
Those methods give accurate results but are suitable
for offline detection and take considerable time for each
measurement.
There are also some online measurement methods,
namely density, microwave, capacitive, ray, radio
frequency and shortwave absorption [2], [3] but they
have limited measurement range and accuracy.
Manuscript received and revised January 2014, accepted February 2014
213
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
Maher Assaad, Aslam M. Zubair, Tong Bon Tang
The complete system architecture explanation is
provided in Section 2. The results are discussed in detail
in Section 3, Section 4 is about discussion and
conclusion is made in Section 5.
II.
System Architechture
The system is explained in three major parts i.e.
capacitive sensor, the interface circuit and data
acquisition and display unit.
IN
T
A. Capacitive Sensor Design
The sensor is designed with semi-cylindrical
electrodes mounted outside of a glass tube. The water-oil
sample is filled in glass tube surrounded by two semicylindrical electrodes. The capacitance of the sensor
depends on dielectric permittivity of medium exist
between electrodes.
The capacitive sensor for measurement of water
contents in crude oil requires high sensitivity to increase
the measurement resolution. To obtain a high resolution
sensor, single pair, two pair and three pair semicylindrical electrode configurations are designed and
tested experimentally. Different electrode configurations
are shown in Fig. 2. The relative capacitance change of
the sensor is measured by LCR meter when it is filled
with pure oil and pure water respectively.
EP
R
The [11] used helical electrode capacitive sensor for
water-air two phase measurements. The capacitance
changes are measured in term of change in phase of input
signal of 1MHz by interface circuit. The error in
measured value is 1.5%. The air-water two phase
measurements are performed in [15]. The two phase
components were water and gas in stationary state. The
change in output frequency proportional to capacitance
variation is observed by interface circuit. The error
observed was 5%. In the proposed design, capacitive
measurement technique is also used for water in oil
measurement.
In this paper, a measurement system for water content
in crude oil is proposed. The block diagram of the
system is shown in Fig.1.
The system consists of two semi-cylindrical capacitive
sensors; one of them is filled with pure crude oil acting
as a reference sensor and the other as a measurement
sensor filled with a mixture of crude oil and water, an
interface circuit and liquid crystal display (LCD) panel.
The interface circuit of the system is based on
differential sensing technique. The use of differential
sensing technique allows us to remove effects of
unwanted inputs (e.g. temperature, background noise and
systematic offset) because these affect sensors equally
[23], [24]. Time-dependent sensor drift common to both
capacitive sensors could also be removed simultaneously,
eliminating the need for periodic recalibration. The both
sensors are excited with a common sinusoidal voltage
(Vin), having frequency (f) and generates a fine dc
voltage (Vdc) at the output of two low pass filter (LPF) of
interface circuit. The output of two LPF is proportional
to capacitance of measurement and reference sensor
respectively.
The output of interface circuit is the difference of the
two capacitance measurements, a metric of the water
content in the crude oil. The data acquisition unit consists
of microcontroller and LCD unit to display. The output
dc voltage of interface circuit is calibrated in percentage
water content in oil.
The calibration is performed by properly
programming of microcontroller.
Fig. 2. Semsicylindrical sensor electrode configurations
R
TABLE I
CHARACTERISTICS OF SEMI-CYLINDRICAL CAPACITIVE SENSOR
WITH DIFFERENT ELECTRODES CONFIGURATIONS
One pair of
Two pairs of
Three pairs of
Senor electrodes
semi-cylindrical semi-cylindrical semi-cylindrical
configuration
electrodes
electrodes
electrodes
Capacitance, C (pF)
9.39
14
23.47
Sensor’s sensitivity
4.87
2.85
1.39
(∆C/C)
The results of the sensitivity test are shown in Table I.
It is cleared from the Table I that single electrode
paired semi-cylindrical capacitive sensor has highest
sensitivity. Although other two designs have high initial
capacitance but relative change in capacitance is low as
compared to one electrode pair semi-cylindrical
capacitive sensor. Therefore, we have selected one pair
semi-cylindrical capacitive sensor for our particular
application.
Fig. 1. Block diagram of the system
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 7, N. 1
214
Maher Assaad, Aslam M. Zubair, Tong Bon Tang
The experimental measurements are taken by using a
low frequency LCR meter for capacitance measurement
of the sensor.
The electrodes are mounted outside of the glass tube
to make it non invasive to sample under test. The sensor
is made of two semi-cylindrical electrodes as shown in
Fig. 3. The soft copper foil is mounted on the outer side
of the glass tube. The actual capacitance (Ca) due to
sample is in series with glass tube wall capacitance (Cw).
The total capacitance (Ct) of sensor can be expressed
as:
CC
(1)
Ct  a w
Ca  Cw
The glass wall capacitance is dependent to dielectric
of glass and Ca is proportional to dielectric of sample
filled in glass tube. The actual permittivity (εa) of two
liquids is determined by [9], which mainly depends on
volume percentage of two phases in tube and is given by:
T
Vw w  Vo  o
Vt
(2)
R
where Vw is the volume of water in tube, εw is dielectric
permittivity of water, Vo is oil volume in tube, εo is
dielectric permittivity of oil and Vt is the total volume of
the sample.
The plot of water percentage in oil and its affect on
actual permittivity of sample is shown in Fig. 4(a). The
capacitance of the sensor having two semi-cylindrical
electrodes of same size, separated by a distance is
calculated in [17]. This can be written as:
IN
a 
(a)
Figs. 4. (a) The effect of water on actual permittivity of sample
(b) water concentration vs. Sensor capacitance
(3)
The experimental and calculated results are shown in
Fig. 4(b). The error between calculated values by
MATLAB and experimental value is 0.108 which is
probably because of fringing capacitance effect and wires
capacitances. Two sensors with same specifications are
designed. The copper electrodes are mounted on outside
of glass specimen tube.
The diameter of tube is 12mm, length is 100mm and
its capacity is 10ml maximum. A soft copper adhesive
foil of thickness 65micron is used for electrodes. The
length of each electrode is 90mm and minimum spacing
between electrodes is 4mm. The designed capacitive
sensor has initial capacitance of 9.39pF with pure oil as
dielectric material.
The capacitance of the sensor varies with respect to
operating frequency. The effect of frequency on sensor
capacitance is shown in Fig. 5. At low frequencies
capacitance is always high but for high frequencies the
capacitance reduces and will not be much affected further
with increase in frequency. The reference and
measurement sensors are excited by a common
sinusoidal source. The sensor signals are then fed to
differential interface circuit for further processing.
R
EP
n

  o a A
1
Ca   2 o a A  

2R
i 0
 d   i  1 d 
(b)
Fig. 3. Design of the semi-cylindrical capacitive sensor
where A is the unit area of the electrode, εo is the
dielectric permittivity of free space, εa is actual
permittivity of sample inside glass tube, d is minimum
distance between the electrodes, R is the radius of the
tube and ∆d is an increment distance between semicylindrical concave electrodes.
The calculated capacitance values with respect to
water concentration are obtained by using (2) and (3).
B. Interface circuit
The second principal part of the system is interface
circuit of the system.
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 7, N. 1
215
Maher Assaad, Aslam M. Zubair, Tong Bon Tang
The interface circuit receives signals from both
sensors, extracts information from them and converts it
into an equivalent DC voltage.
The differential interface circuit of the system is
further divided into two sections; one of them is for
reference signal processing and other is for measurement
signal processing. Each individual section is consists of
capacitance to voltage converter, a multiplier stage and a
low pass filter. The difference of outputs of both sections
is taken by a difference amplifier and output is fed to
display unit for further processing. The interface circuit
is shown in Fig. 6. The sensors are excited by a common
sinusoidal voltage source Vin, with frequency f. The
resultant sensor signals obtained from both sensors are
fed to each respective capacitance to voltage converter
(CVC) which converts it in to a voltage whose amplitude
is modulated by sensor capacitance. The feedback
impedance (Zf) is the same for both operational
amplifiers (i.e. op-1 and op-2) which consists of parallel
combination of Rf and Cf. The OPs act as capacitance to
voltage converters which control the system sensitivity.
Vr  
Zf
Zi1
Vin
(4)
Vin
(5)
and:
Vs  
Zf
Zi 2
where Zi1 is the impedance of reference capacitor (Cr)
and Zi2 is impedance of measurement capacitor (Cs).
From the circuit:
where:
Rf
1  j C f R f
T
Zf 
j Cr
and Z i 2  1
IN
Z i1  1
jCs
From (4) and (5) the CVCs outputs become:
 R f Cr
Vr  

R
1 Rf C f

2

2
 R f Cs
Vr  

1 Rf C f
A sin t  r 
(6)
A sin t   s 
(7)
EP
where φr and φs are the phase shifts of Vr and Vs signals
and given by:
Fig. 5. The effect of frequency on sensor capacitance
 1
  r   s  tan1 
 Rf C f





(8)
R
Assuming the sensors are excited by a common ac
voltage source Vin. Let Vin = Asinωt, the CVCs outputs
are given by:
Fig. 6. The differential interface circuit of the system
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 7, N. 1
216
Maher Assaad, Aslam M. Zubair, Tong Bon Tang
The high frequency and high speed multiplier, AD835
is used for multiplication of two signals. Mathematically
multipliers outputs can be written as:
where:
K  Const. 
Vrm  Vr  Vin
Vrm  
 R f Cr A2

1 Rf C f

2

1 Rf C f
1
1

 2 cos   2 cos  2t     (9)



The output of multiplier is fed to low pass filters. The
cut off frequency of low pass filter is adjusted 15Hz.
The LPF removes high frequency components from
outputs of multiplied signal. So, high frequency
components of (9) and (10) are filtered out by a first
order LPF.
The outputs of LPF become:
 R f Cr A 2

1 Rf C f
Vsf  

2
 R f C s A2


(11)
1
 cos 
2
An instrumentation amplifier (INA103) is used to take
difference of both outputs of two low pass filters.
The instrumentation amplifier provides more stable
results then a general amplifier. The output of
instrumentation amplifier (IA) with a gain  is:


R
Vo   Vsf  Vrf  K  C s  Cr 
III. Experiment Results
The proposed interface circuit has been simulated for
many values of sensor capacitance by using
PSPICE/Orcad software (version 9.2.3) [25].
For simulation setup, two simple capacitors are used as
sensing elements. The values of capacitors were selected
on the basis of actual values of sensors with air dielectric.
The reference capacitance value was kept constant and
the value to measurement sensor was gradually increased
to a certain range. The simulation results showed good
linearity behaviour between input capacitance change and
output voltage.
(12)
EP
1 Rf C f
2
1
 cos 
2
R
Vrf  
C. Data Acquisition and Display
The data acquisition and display unit consists of a
microcontroller (PIC-16F877) and a 16x2 LCD display.
The microcontroller is programmed to calibrate and
convert data from dc voltage to percentage of water
content. The microcontroller reads data on its analog
input pin and compares with reference voltage.
The 10bits ADC of PIC16F877 is used in 8bit mode to
obtain desired resolution. Using an 8b ADC, the system
resolution is100/28 = 0.39% (percentage of water content
per crude oil sample). The output data of microcontroller
is displayed on a 16x2 LCD in terms of water percentage.
T

1 Rf C f
1
1

 2 cos   2 cos  2t     (10)


2
1
 cos 
2
IN
Vsm  

2
The (13) highlights the main advantage of the
proposed system, i.e. the output voltage is linearly
proportional to the difference between the capacitance of
the reference sensor (RS) and the capacitance of the
sensor for sample measurement (MS). As Cr is a
constant, the output voltage is a direct measure of Cs thus
the water content in crude oil.
Vsm  Vs  Vin
 R f C s A2
 R f A2
(13)
Signal generator
LCR meter
Digital Osciloscope
DC supply
Sensors
Circuit Board
Fig. 7. The experimental setup with sensors, interface circuit and measuring instruments
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 7, N. 1
217
Maher Assaad, Aslam M. Zubair, Tong Bon Tang
From (13), Vo(design) = 0.09 (Cs-Cr) for A=0.5V,
=7.24, Rf=1MΩ and Cf=10pF, where the coefficient
‘0.09’ represents the sensitivity of the proposed system in
V/pF.
From Fig. 8(b), we could derive similar expression for
the actual measurements, which gives:
Vo(measurement)=0.086(Cs-Cr)
(14)
T
Hence, the actual sensitivity of the proposed system is
0.086V/pF. This gives an error of 4.6% from the
theoretical calculation; this error is probably due to
inaccurate values of discrete components, instruments
inaccuracy or resistance of the wires.
The Fig. 9(a) shows the effect of water on the output
voltage of interface circuit and added water vs. measured
water graph is shown in Fig. 9(b).
The good linear relationship between the added and
the measured water content, albeit at a systematic error
of 0.017 (Ideally y=x).
Discussion
IN
IV.
The proposed system has been tested by simulation
and experimentally to validate the basic idea and
investigate the system performance.
It is cleared from Fig. 8 that the results of calculation
and experiment are very consistent to theoretical model.
The slightly lower sensitivity obtained in the actual
hardware implementation is probably due to inaccurate
values of discrete components or calibration issues of
equipment. Table II summarizes the overall system
design. The advantages of the proposed system are:
 The system has a very simple structure suitable for
online measurement, and is low cost and portable, as
opposed to the conventional system which includes
complex tools for distillation, centrifugation and
dewatering [1].
 Any unwanted noise and systematic offsets including
sensor drift can be canceled out by the difference
amplifier (assume negligible degradation in sensor
sensitivity).
 For different types of crude oil, recalibration is not
required.
 The resolution of the proposed system is 0.39%,
compared favorably with 3% obtained by [3] and
1.35% by [26].
 The measurement error is 1.7%, better than [10], [12],
[14].
R
EP
R
After a successful verification of interface circuit by
simulation on PSPICE,experimental test has been carried
out. The proposed interface circuit has been implemented
on a breadboard and tested under laboratory conditions.
The Fig. 7 shows experimental setup, designed semicylindrical sensors along with system prototype.
The prototype of the system has been built using
discrete components. The excitation signal of 1Vp-p with
frequency of500 kHz is applied to the sensors. The
feedback parameters of both capacitance to voltage
coveters were Rf=1MΩ and Cf=10pF.
The analog multiplier IC AD835 is used for
multiplication of sensor signal with input source signal.
The AD835 gives very fine result of multiplication on the
system operating frequency (500 kHz). The 1st order LPF
is consist of RC circuit, with adjusted cut off frequency
to 15 HZ. It gives fine dc voltage with negligible
oscillations. The difference of both LPF output signals is
taken out by INA103 instrumentation amplifier, with a
gain of 7.24 to make it properly readable for
microcontroller. In order to evaluate the performance of
the system initially both sensors were filled with pure
crude oil. To make sure the oil is free from water;
distillation process is performed by using distillation
apparatus. There was a slightly difference of capacitance
between two sensors. To remove this minor difference, a
small valued variable capacitor is connected in parallel to
reference sensor. After removing capacitance difference
of both sensors, water is added up in measurement sensor
only with certain percentage. The system has been tested
for 0-30% of water in oil. The results of experiments are
summarized is Figs. 8.
(a)
A. Non Idealities
There are certain factors which can affect the
performance of the system. To increase system
efficiency, one must take care of various parameters i.e.
1. The water is not soluble in oil therefore water drops
sink down towards bottom of the tube because of
high density. Therefore it may cause improper
detection of small concentration of water. Make sure
water lies between the electrodes instead of bottom.
(b)
Figs. 8. (a) The effect of water percentage on (Cs-Cr)
(b) dc output voltage vs. (Cs-Cr)
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 7, N. 1
218
Maher Assaad, Aslam M. Zubair, Tong Bon Tang
(a)
(b)
Figs. 9. (a) The affect of water on output voltage. (b) added water vs. Measured water
System of the Water Content in Crude Oil. Proc. ICMTMA, 3, 904907.
[3] Castle G.S.P., Roberts J. (1974). A microwave instrument for the
continuous monitoring of the water content of crude oil. Proc.
IEEE , 62 (1), 103- 108.
[4] K. Mochizuki, T. Masuda, and K. Watanabe. (1998). An interface
circuit for high accuracy signal processing of differentialcapacitance transducers. IEEE Transaction on Instrumentation and
Measurements, 47, 823–827.
G. Brasseur. (1998). A capacitive 4-turn angular-position sensor. IEEE
Transaction on Instrumentation and Measurements, 47, 275–279.
[5] Cirmirakis. D., Demosthenous. A., Saeidi. N., Donaldson. N.
(2013). Humidity-to-Frequency Sensor in CMOS Technology
With Wireless Readout. IEEE Sensors Journal, 13(3), 900-908.
[6] Bera, S.C., Ray. J.K., Chattopadhyay, S. (2006). A low-cost
noncontact capacitance-type level transducer for a conducting
liquid. IEEE Transactions on Instrumentation and Measurement,
55(3), 778-786.
[7] Marco Demori, Vittorio Ferrari, Domenico Strazza. (2009). A
sensor system for oil fraction estimation in a two phase oil-water
flow. Procedia Chemistry, 1(1), 1247-1250.
[8] M.S.A. Abouelwafa, E.J.M. Kendall. (1980). The use of
capacitance sensors for phase percentage determination in
multiphase pipelines. IEEE Transaction on Instrumentaion and
Measurements, 29 (1), 24–27.
[9] Ahmed, W.H. (2006). Capacitance Sensors for Void-Fraction
Measurements and Flow-Pattern Identification in Air-Oil TwoPhase Flow. IEEE Sensors Journal, 6(5), 1153,1163.
[10] J.J.M. Geraets, J.C. Borst. (1988). A capacitance sensor for twophase void fraction measurement and flow pattern identification.
Int. J. Multiphase Flow 14 (3), 305–320.
[11] J. Tollefsen, E.A. Hammer, (1998). Capacitance sensor design for
reducing errors in phase concentration measurements. Flow Meas.
Instrum. 9 (1), 25–32.
[12] J.K. Keska, B.E. Williams, (1999). Experimental comparison of
flow pattern detection techniques for air–water mixture flow. Exp.
Thermal Fluid Sci. 19, 1–12.
[13] A. Jaworek, A. Krupa. (2004). Gas/liquid ratio measurements by
RF capacitance sensor. Sensors and Actuators A: Phys. 113 (2),
133–139.
EP
R
2. If sensor electrodes are not properly shielded, then
electrostatic effect may disturb the value of the
capacitance.
3. Noise: when dealing with small signals, then
atmospheric noise also affects the sensor capacitance.
4. Thanks to differential sensing, many of them are
canceled out by differential sensing technique.
When doing calibration of the system, It is very
difficult to deal with small signals because lab equipment
itself cannot properly differentiate between instrument
noise and information signal. By overcoming these issues,
the efficiency of the system can be increased.
IN
T
TABLE II
SUMMARY OF THE CHARACTERISTICS OF DIFFERENTIAL CAPACITIVE SENSOR BASED INTERFACE CIRCUIT FOR AN ACCURATE MEASUREMENT
OF WATER CONTENT IN CRUDE OIL
Sensor geometry
Semi-cylindrical
Methodology for water contents measurement Differential capacitive sensing technique
Methodology of Interface Circuit
Differential odulation/demodulation Technique
Capacitive Resolution
pF- Range
Testing
PSPICE Simulation and Experiment
Fluid Used
Dulang crude oil
Detection range
0% to 30%
Measurement error
1.7%
Application
Petroleum Industry
V.
Conclusion
R
The experimental results demonstrated the good linear
behavior of the proposed system, making it an attractive
option for accurate measurement of water content in crude
oil. The semi-cylindrical capacitive sensor is sensitive
enough to detect small Pico-Farad variation and interface
circuit also has ability to convert these small changes into
voltage. The differential sensing technique made accurate
measurements possible. The proposed design is simple
and it can also be used to monitor water contamination in
other petroleum products as well.
References
[1]
[2]
Fingas M., Fieldhouse B. (2012). Studies on water-in-oil products
from crude oils and petroleum products. Elsevier, Mar. Pollut. Bul
64 (2), 272-283.
Sun R., Ji N., Guo L., Tian Y., Chen X. (2010). The Measurement
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 7, N. 1
219
Maher Assaad, Aslam M. Zubair, Tong Bon Tang
Authors’ information
1
Department of Electrical, Electronic and Communication Engineering,
American University of Ras Alkhaimah, Ras Alkhaimah, U.A.E,
corresponding author
E-mail: maher.assad@aurak.ae
2
IN
T
Universiti Teknologi PETRONAS, Department of Electrical and
Electronics Engineering, 31750 Tronoh, Perak, Malaysia.
R
EP
R
[14] A. Jaworek, A. Krupa. (2010). Phase-shift detection for
capacitance sensor measuring void fraction in two-phase flow.
Sensors and Actuators A: Physical, 160(1–2), 78-86.
[15] H. Caniere, C. T’Joen, A. Willockx, M. De Paepe. (2008).
Capacitance signal analysis of horizontal two-phase flow in a small
diameter tube. Exp. Thermal Fluid Sci. 32, 892–904.
[16] Chiang C.-T., Huang Y.-C. (2006). A semi-cylindrical capacitive
sensor with interface circuit used for flow rate measurement. IEEE
Sensors Journal, 6(6), 1564-1570.
[17] W.H. Ahmed, B.I. Ismail. (2008). Innovative techniques for twophase flow measurements, Recent Patents Elect. Eng. 1, 1–13.
[18] A.L. Stott, R.G. Green, K. Seraji. (1985). Comparison of the use of
internal and external electrodes for the measurement of the
capacitance and conductance of fluids in pipes. J. Phys. E: Sci.
Instrum. 18, 587–592.
[19] Jiamin Ye, Lihui Peng, Weirong Wang, Wenxing Zhou. (2011).
Helical Capacitance Sensor-Based Gas Fraction Measurement of
Gas–Liquid Two-Phase Flow in Vertical Tube With Small
Diameter. IEEE Sensors Journal, 11(8), 1704-1710.
[20] N. Angkawisittpan, T. Manasri. (2012). Determination of Sugar
Content in Sugar Solutions using Interdigital Capacitor Sensor.
Measurement Science Review. 12(1), 8-13.
[21] Siyang Zheng, Mandheerej S. Nandra, Chi-Yuan Shih, Wei Li, YuChong Tai. (2008). Resonance impedance sensing of human blood
cells. Sensors and Actuators A: Physical, 145–146, 29-36.
[22] Reverter, F. Casas, O. (2010). Interfacing Differential Capacitive
Sensors to Microcontrollers: A Direct Approach. IEEE
Transaction on Instrumentation and Measurement, 59(10), 27632769.
[23] F. M. L. van der Goes and G. C. M. Meijer. (1996). A novel lowcost capacitive-sensor interface. IEEE Transactions on
Instrumentation and Measurement, 45(2), 536-540.
[24] Assaad M., Aslam M. Z. (2012). An interface circuit design based
On differential capacitive sensors for accurate measurement of
water contents in crude oil. Proceeding IEEE ICCAS, 263-266.
[25] Chen X.G., Gu D.W., Qu Y. (2006). Real-time estimation of oil
quantity in crude oil tanks. IEEE Proceeding Science Measurement
Technology, 153(3), 108-112.
[26] Rezai-Rad, G.A., Akbarizadeh, G., A new readout circuit structure
for SAR satellite imaging sensors, (2010) International Review of
Electrical Engineering (IREE), 5 (1), pp. 282-290.
[27] Rimminen, H., Linnavuo, M., Sepponen, R., Human identification
and localization using active capacitive RFID tags and an electric
field floor sensor, (2010) International Review of Electrical
Engineering (IREE), 5 (3), pp. 1061-1068.
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved
International Review on Modelling and Simulations, Vol. 7, N. 1
220
International Review on Modelling and Simulations
(IREMOS)
(continued from outside front cover)
106
Optimal Load Shedding for Radial Distribution Systems with and without DGs
Using Particle Swarm Optimization Algorithm
by Mageshvaran R., Jayabarathi T., Siva Prasad Reddy S., Leela Rajesh S., Rama Prabha D.
114
A Novel Dissociated Current Control Technique for Harmonic Minimization in Non-Linear Loads
by T. Parithimar Kalaignan, J. Senthilkumar, Y. Suresh
125
A Solution to the Profit Based Unit Commitment Problem
Using Integer-Coded Bacterial Foraging Algorithm
by T. Venkatesan, C. Muniraj
132
T
Fault Detection and Control Loop Reconfiguration for WECS with PMSG Speed Sensor Fault
by F. Grouz, L. Sbita
IN
A New Approach for Solving Hydrothermal Unit Commitment and Scheduling
for Generating Companies Using Particle Swarm Optimization
by S. Padmini, R. Jegatheesan, Subhransu Sekhar Dash, S. Hemanth
142
152
Design of Super-Capacitor Based Frequency Control Ancillary Services with the Computation
of Ancillary Service Requirement Assessment Indices
by N. D. Sridhar, I. A. Chidambaram
160
Firefly Algorithm Based Optimization of Strategic Bidding to Maximize Profit
and Benefit of Competitive Electricity Market
by K. Asokan, R. Ashokkumar
175
Modelling and Simulation of a Variable Step Size Algorithm for a Power Simulator
by K. Keerthivasan, K. Geetha, V. Sharmila Deve
185
Modelling and Simulation of Interference Cancellation Receiver
for MIMO Multicarrier CDMA Based Cognitive Radio
by S. Mohandass, G. Umamaheswari
196
Forces of Internal Combustion Heat Engines
by Florian Ion T. Petrescu, Relly Victoria V. Petrescu
206
A Semi-Cylindrical Capacitive-Based Differential Sensing System for Water Content
in Crude Oil Measurement
by Maher Assaad, Aslam M. Zubair, Tong Bon Tang
213
R
EP
R
Renewable Energy Based Shunt Compensator for Power Quality Improvement Using P-Q Control Theory
by Aravindan P., Sanavullah M. Y., Vijayakumar G.
Abstracting and Indexing Information:
Academic Search Complete - EBSCO Information Services
Cambridge Scientific Abstracts - CSA/CIG
Elsevier Bibliographic Database SCOPUS
Index Copernicus (Journal Master List): Impact Factor 6.55
Autorizzazione del Tribunale di Napoli n. 78 del 1/10/2008
T
IN
R
EP
R
1974-9821(201402)7:1;1-S
Copyright © 2014 Praise Worthy Prize S.r.l. - All rights reserved