Chapter 2

Impedance Spectroscopy
and Experimental Setup

2.1 Introduction

The objective of this chapter is to introduce the measuring instruments and soft-
ware programs used for the experimental setup. It provides the reader a detailed
insight of, electrochemical impedance spectroscopy basics and data representa-
tion along with highlighting the methodology of measurement data collection. It
explains all the hardware and software used to collect the impedance data and the
models involved in analyzing the acquired information. It also describes the inter-
facing of the measuring instruments with LabVIEW program to obtain a stand-
alone automated measurement system. It provides an account of the significant
applications of impedance spectroscopy method for characterization of sensors
and material under test (MUT). The objectives are to measure and character-
ize the developed sensors according to EIS models and methods. Mathematical
methods like complex non-linear least square curve fitting were used to deduce
equivalent circuit to the electrochemical cell under test. The parameters obtained
from the measuring instruments are frequency, f, impedance, Z and phase angle.
Mathematical methods used to interpret these into real and imaginary parts in the
complex plane for analysis of impedance characteristics are also discussed.

2.2 Electrochemical Impedance Spectroscopy

Electrochemical Impedance Spectroscopy (EIS) has seen a huge boost in popular-

ity in recent time due to its extraordinary sensitivity. It is used to evaluate electri-
cal properties of materials and their interfaces with surface-modified electrodes
[1]. This method has been widely used to study of electrochemistry [2, 3], bio-
medical applications [4, 5], material science [6] and others. J. Ross Mcdonald in
[7] describes the EIS as a part of Impedance measurement using AC polarography
involving electrochemical reactions. The response of an electrochemical cell to
a low amplitude sinusoidal perturbation as a function of frequency and has been

© Springer International Publishing Switzerland 2016 21

A.I. Zia and S.C. Mukhopadhyay, Electrochemical Sensing: Carcinogens
in Beverages, Smart Sensors, Measurement and Instrumentation 20,
DOI 10.1007/978-3-319-32655-9_2
22 2  Impedance Spectroscopy and Experimental Setup

reported to estimate the dielectric properties of milk [8], meat inspection [9], quality
testing in leather [10], Saxophone reed inspection [11], detection of contaminated
seafood with marine biotoxin [12], food endo-toxins [12–16], evaluate electrical
properties of drinks, and water [17]. EIS involves measurements and analysis of
materials involving ionic conduction in solid and liquid electrolytes. Ionically con-
ducting glasses and polymers, fused salts, and nonstoichiometric ionically bonded
single crystals have been used for impedance measurements where conduction can
involve motion of ion vacancies and interstitials. EIS is also conducted to study of
fuel cells, rechargeable batteries, and corrosion. Another category of IS applies to
dielectric materials: solid or liquid non-conductors whose electrical characteristics
involve dipolar rotation, and to materials with predominantly electronic conduction
[18]. System Impedance may be measured using various techniques. The most cited
impedance measurement techniques are given as follows.

2.2.1 AC Bridges

This is the oldest of all the techniques initially used for the measurement of dou-
ble-layer parameters, principally of the hanging mercury drop electrode. It has
also been used to measure the electrode impedance in a faradaic reaction to evalu-
ate the dynamic processes at the electrode. Although this method is slow, yet pro-
vides a magnificent precision of measurements.

2.2.2 Lissajous Curves

Formation of elliptical figures as a result of the simultaneous application of the

applied AC voltage and resulting AC current to a twin beam oscilloscope is called
Lissajous curves. Analyzes of Lissajous curves produced on twin channel oscilloscope
screens was used to perform impedance measurements and had been an accepted
method for impedance spectroscopy prior to the advent of modern EIS instrumenta-
tion. The measurement time involved in using this technique (often up to many hours)
is long enough for a chemical cell to cause drift in its system parameters. The cell can
change through adsorption of impurities, oxidations, degradations, temperature vari-
ations, etc. These curves have been used to determine the impedance, but frequency
limitations and sensitivity to noise has limited the use of this technique. Figure 2.1
shows the formation of Lissajous figures as a consequence of two out of phase signals.

2.2.3 Fast Fourier Transforms (FFT)

The Fast Fourier Transforms is a mathematical method to evaluate the system

impedance. Taking the Fourier transform of the perturbation signal in time domain
2.2  Electrochemical Impedance Spectroscopy 23

Fig. 2.1  Formation
of Lissajous figure

and generation of corresponding frequency domain data using a computerized

algorithm is referred as FFT. FFT provides a fast and efficient algorithm for com-
putation of the Fourier transforms. In practice, only limited length data is trans-
formed, causing the broadening of the computer frequency spectrum, commonly
called ‘leakage’. Another problem called ‘aliasing’ is linked with the presence of
the frequencies larger than one-half of the time domain sampling frequency.

2.2.4 Phase Sensitive Detections (PSD)

Phase sensitive detection is used in lock-in amplifiers interfaced with precision

potentiostats for system impedance measurements. It contains one time-independ-
ent component, depending on the phase difference between two signals and pro-
portional to the amplitude of the measured AC signal. The output signal is applied
to a low-pass filter that averages the signal component having frequencies above
the cut-off frequency. The disadvantage of the lock-in technique is that it retains
the combination of harmonic frequencies present in the input signal.

2.2.5 Frequency Response Analysis (FRA)

Frequency Response Analyzers are hi precision instruments that determine the fre-
quency response of the standardized system. The operation of FRA is based on
interpreting correlation of the studied signal with the reference perturbation. The
measured signal is multiplied by the sine and cosine of the reference signal of the
same frequency and integrated over one time period. Real and imaginary parts of
24 2  Impedance Spectroscopy and Experimental Setup

the measured signal are recovered, strictly rejecting all harmonics. The advantage
of the correlation process is a reduction of noise, but it is achieved at the cost of
attenuation of the output signal.
Among a number of methods available for impedance measurements, FRA has
become a de facto standard for EIS. FRA is a single sine-wave input method in
which a small amplitude (5–15 mV) AC sine wave of a given frequency is over-
laid on a dc bias potential, applied to the working/excitation electrode and meas-
urement of resulting AC current is made. The system remains pseudo-linear at
low-amplitude AC potential. The process is repeated for the desired frequency
range, and impedance is computed for five to ten measurements per decade change
in frequency. In order to ensure the system linearity, stability, and repeatability, this
method is rendered viable only for a stable and reversible system in equilibrium.
For this reason, instantaneous impedance measurements are mandatory for non-
stationary systems [19]. A non-linear system will contain harmonics (noise) in the
measured current response. The drift in the measured system parameters is often
observed if the system loses its steady state during the measurement time. The elec-
trochemical cell can change through adsorption, oxidation, coating degradation and
temperature variations; to list, these are a few major factors affecting the steady-
state condition of the system under test. EIS is used to deduce the changes taking
place in the electrochemical system in general and observe the changes in the con-
ductance and capacitance at the sensing surface, interface, and layers, in particular.
Next section discusses the fundamental concepts of impedance spectroscopy.

2.2.6 Electrochemical Impedance Spectroscopy;

Theory and Analyses

In practice, electrochemical cells are an example of complex non-linear systems.

The relationship between current and voltage is highly non-linear. Pseudo-linearity
of the electrochemical system is achieved by considering a small linear part of the
I-V curve as shown in Fig. 2.2.
Pseudo-linearity is quite useful because; cell’s substantial non-linear response
to Direct Current (DC) potential is not observable as current is measured at excita-
tion frequency; the measured current is independent of harmonics. If the system is
non-linear, the current response of the system will be deformed by the harmonics.
The system under test must remain in steady-state throughout the testing time; this
is another stringent condition that may affect system linearity. With the advent of
hi precision fast FRAs and computing systems, this problem could be catered for.
For example, it takes only 88 ms for Hioki 3522-50 to measure impedance, at a
particular frequency, without compromising the accuracy of 99.95 % while operat-
ing at slow mode; refer to Hioki 3522-50 specification sheet shown in Table 2.1.
In a pseudo-linear electrochemical cell, the impedance can be measured by
applying a low-amplitude AC perturbation, Et, and measuring the phase shift
appearing in consequent alternating current flowing through the sensor with
2.2  Electrochemical Impedance Spectroscopy 25

Fig. 2.2  I-V curve for a

non-linear system. Pseudo-
linearity of the system is
achieved by considering a
small part of the curve

reference to the applied signal. The magnitude of the occurring phase shift
depends on the impedance offered to the electron flow by nature of the electro-
lyte, diffusion, electrode kinetics and chemical reactions happening inside the cell.
Figure 2.3 shows a phase shift ɵ in the received, current signal with reference to
the applied potential perturbation.
Impedance (Z) is a measure of the circuit characteristics to impede the flow of
electrons through the circuit, measured in Ohm when exposed to periodic electri-
cal perturbations. The reciprocal of impedance is called admittance, denoted by Y
and measured in Siemens (S). Mathematically, impedance is expressed as a com-
plex number comprising of resistance and reactance. Resistance is a static prop-
erty of the system and is independent of the incident Alternating Current (AC)
frequency. It is represented by the real part of the compound number, denoted as
Re, Zreal, or Z′. On the other hand, reactance is purely frequency dependent and
appears in capacitors and inductors consequent to the applied AC frequency.
Reactance is represented by the imaginary part of the complex impedance and is
symbolized by Rim, Xc or Zc″ for capacitive reactance and XL or ZL″ for inductive
reactance, respectively. The basic Ohm’s law in Eq. 2.1 defines the resistance R in
term potential, V, and current I as;
V
R= (2.1)
I
whereas, Ohm’s law for alternating current defines impedance Z in terms of time-
dependent alternating potential Et, and current It as:
Et
Z= (2.2)
It
26 2  Impedance Spectroscopy and Experimental Setup

Table 2.1  Hioki Hi Precision LCR 3522-50 and 3532-50 Specifications

Specifications
3522-50 3532-50
Measurement |Z|, |Y|, θ, Rp (DCR), Rs (ESR, |Z|, |Y|, θ, Rp, Rs (ESR), G,
parameters DCR). G, X, B, Cp, Cs, Lp, Ls, D, Q X, B, Cp, Cs, Lp, Ls, D, Q
Measurement ranges: 10.00 mΩ–200.00 MΩ (depending on measurement frequency and
|Z|, R, X signal levels)
θ −180.00° to +180.00°
C 0.3200 pF–1.0000 F 0.3200 pF–370.00 mF
L 16.000 nH–750.00 kH
D 0.00001–9.99999
Q 0.01–999.99
|Y|, G, B 5.0000 nS–99.999 S
Basic accuracy Z: ± 0.08 % rdg. θ ± 0.05°
Measurement frequency DC, 1 MHz–100 kHz 42 Hz–5 MHz
Measurement signal 10 mV–5 V rms/10μA–00 mA rms
levels
Output impedance 50 Ω
Display screen LCD with backlight/99,999 (full 5 digits)
Measurement time Fast: 5 ms Fast: 5 ms
(Typical values for Normal: 16 ms Normal: 21 ms
displaying |Z|) Slow 1: 88 ms Slow 1: 72 ms
Slow 2: 828 ms Slow 2: 140 ms
Settings in memory Max. 30 Sets
Comparator functions HI/IN/LO settings for two measurement parameters; percentage,
Δ%, or absolute value settings
DC Bias External DC bias ± 40 V max. (option)
External printer 9442 printer (option)
External interfaces GP-IB or RS-232C (Options), external I/O for sequencer use
Power source 100, 120, 220 or 240 V(± 10 %) AC (selectable), 50/60 Hz
Maximum rated power 40 VA approx 50 VA approx

Fig. 2.3  Phase shift in
current It as a response to
excitation-potential Et in a
linear system
2.2  Electrochemical Impedance Spectroscopy 27

The excitation signal can be expressed as a function of time;

Et = E0 sin ωt (2.3)
where Et is the potential difference at time t, E0 is the amplitude of the voltage
signal at t = 0, and ω is the angular frequency given by (ω = 2πf) expressed in
radians/second and frequency, f, in hertz.
For a linear system, the response signal It, has a phase shift,θ, with amplitude of
I0 which can be expressed by:
It = I0 sin(ωt − θ) (2.4)
An expression in Eq. 2.2 for Ohm’s Law can be used to calculate the impedance of
the system given by;

Et E0 sin ωt
Z= =
It I0 sin(ωt − θ )
sin(ωt)
Z = Z0 (2.5)
sin(ωt − θ )

The impedance, Z, now can be expressed in term of a magnitude of Z0 and a phase

shift, θ. Equation 2.5 can also be expressed in term of Euler’s relationship given
by;
ejθ = cos θ + jsinθ (2.6)
√
where j = −1 (‘j’ is preferred by electrochemists instead of ‘i’)
The impedance, Z, can be expressed in term of potential, E, and current
response, I, given by;
Et = E0 ejωt (2.7)

It = I0 ej(ωt−)θ (2.8)
Therefore the impedance, Z;

Et E0 ejωt
Z(ω) = = = Z0 ejθ (2.9)
It I0 ej(ωt−θ)

Z(ω) = Z0 (cosθ + jsinθ ) (2.10)

The impedance now is in the form of real part (Z0 cosθ) and imaginary part (Z0
sinθ) represented as follows:
ReZ = Z ′ = Zreal = Z0 cos θ (2.11)

Z ′′ = Zimag = Z0 sin θ (2.12)

28 2  Impedance Spectroscopy and Experimental Setup

The raw data for all measured frequencies in EIS experiments comprises of the
real and imaginary components of potential difference E′ and E″ and the real
and imaginary components of current I′ and I″ respectively. The phase shift (ɵ)
and total impedance (Z) are the two basic parameters calculated out of the raw
data using equations given in Table 2.3. For data analysis purpose, the calculated
impedance characteristics are expressed as Nyquist plot and Bode plot.

2.2.7 ‘Nyquist’ and ‘Bode’ Plots for Impedance

Data Analysis

Nyquist plot also known as Cole-Cole plot is one of the most critical and popu-
lar formats for evaluating electrochemical parameters like electrolytic solution
resistance (Rs), electrode polarization resistance (Rp) and double layer capaci-
tance (Cdl), etc. These parameters shall be discussed in detail in the following sec-
tions. Nyquist plot represents Z′(ω) and Z″(ω) in a complex plane. Among several
advantages of Nyquist plot; calculation of solution resistance by extrapolating the
curve to x-axis; observable effects of solution resistance; emphasis on the series
circuit; comparison of the results of two or more separate experiment, are a few
major advantages. One major disadvantage of Nyquist plot is that information on
frequency is lost which makes the calculation of Cdl complicated.
Bode plot represents absolute Z(ω) and phase angle θ(ω) in the frequency
domain. Since frequency appears at one of the axes, the effect of the spectrum on
the impedance and phase drift is obvious. Rs, Rp, Cdl and frequency values, where
phase shift θ(ω) is maximum/minimum, can be evaluated using Bode plot. This
format is desirable when data-scatter prevents adequate fitting of the Nyquist plot.
Due to these edges, researchers declare Bode plot as a clearer description of elec-
trochemical cell’s frequency-dependant behavior compared to Nyquist plot.
A flow diagram developed by McDonald [18], shown in Fig. 2.4, has been fol-
lowed by analysis of the electrochemical research on detection of hormones and
EDCs presented in this thesis. In order to understand the significance and methods
to extract electrochemical cell’s parameters, Randle’s electrochemical cell model
was used to deduce equivalent circuit for the electrochemical cell under test.
Complex Nonlinear Least Square (CNLS) curve fitting technique was applied to
extract equivalent circuit and component parameters.

2.2.8 Randle’s Electrochemical Cell Equivalent

Circuit Model

This model was introduced by Randle in ‘Discussion of the Faraday Society’ in

1947 [20]. The model provides the account of mixed kinetic processes taking
2.2  Electrochemical Impedance Spectroscopy 29

Fig. 2.4  Flow chart for

the measurement and
characterization of a material-
electrode system by EIS [18]

place at the electrode-electrolyte interface. These processes include the fast mass
transfer reaction, slow-paced charge transfer reaction, and diffusion processes at
the interface. A double layer capacitance is observed at the interface due to the
presence of Outer Helmholtz Plane (OHP) and Inner Helmholtz Plane (IHP) at the
electrode surface as shown in Fig. 2.5.
The Randle’s cell includes double-layer capacitance, Cdl, solution resistance,
Rs, charge/electron transfer resistance, Rct and ZW as shown Fig. 2.6 in the electro-
chemical cell equivalent circuit deduced in [20].
The expression for the absolute impedance as a function of frequency is given
as;

Rct 2C
jωRct dl
Z(ω) = Rs + 2 C2
− 2 R2 C 2 (2.13)
1 + ω2 Rct dl 1 + ω ct dl

where the real part (Z′) is given by;

Rct
Z ′ (ω) = Rs + 2 C2 (2.14)
1 + ω2 Rct dl
30 2  Impedance Spectroscopy and Experimental Setup

Fig. 2.5  Kinetic processes
taking place at electrode-
electrolyte interface (Randle’s
cell model)

Fig. 2.6  Randle’s
electrochemical cell
equivalent circuit model

and the imaginary part (Z″) is given by;

2C
ωRct dl
Z ′′ (ω) = − 2 2 2 (2.15)
1 + ω Rct Cdl

The impedance spectra from the experimental results depicted electrode and elec-
trolyte are related by a mixed kinetic and diffusion processes at the electrode
surface which causes a polarization at the interface. Rct is, therefore, sometimes
referred as polarization resistance, denoted as Rp, in EIS literature. The value of
‘charge transfer resistance Rct, r polarization resistance Rp′ can be calculated from
Bode or Nyquist plot. The rate of an electrochemical reaction can be strongly
influenced by diffusion of reactants towards, or away from the electrode-electro-
lyte interface. This situation can exist when the electrode is covered with adsorbed
solution components or a selective coating. An addition element called Warburg
impedance, ZW, appears in series with resistance Rct. Mathematically Warburg
impedance is given by;
σw
ZW = √ (2.16)
jω
where, σw is called Warburg diffusion coefficient. It appears that the character-
istic of the Warburg impedance is a straight line with a slope of 45° at a lower
frequency. This refers to low-frequency diffusion control because the diffusion
2.2  Electrochemical Impedance Spectroscopy 31

of reactants to the electrode surface is a slow-paced process which can happen at

low frequencies only. At higher frequencies, however, the reactants do not have
enough time to diffuse. The slope of this line gives Warburg diffusion coefficient.
The Nyquist plot in Fig. 2.7 shows the diagonal line of diffusion process (Warburg
impedance) at low frequency. The charge transfer process at higher frequency is
illustrated by a single time constant semi-circle curve.
The Nyquist plot for a Randle’s cell is always a semicircle due to an RC paral-
lel equivalent circuit. The solution resistance Rs also referred as ‘uncompensated
solution resistance’ denoted as ‘RΩ’ in EIS literature can be calculated by high-fre-
quency intercept on the real axis. High-frequency intercept lies closer to the ori-
gin of the plot. In Fig. 2.7 it could be read as 25 kΩ. The real axis value at the
other (low frequency) intercept is the sum of solution and polarization resistance.
The low-frequency intercept could be read by interpolating the semi-circle to the
real axis. (In Fig. 2.7 it reads as 325 kΩ). The diameter of the semicircle is, there-
fore, equal to the polarization resistance (300 kΩ in this case). Figure 2.8 shows the
absolute impedance, Z, versus frequency and phase angle in degree with respect
to the applied frequency, f in Hz. The two plots combined together are referred as
Bode plot. Figure 2.9 shows a combined Bode plot for an electrochemical system
with Z (absolute) plotted on the primary y-axis and phase (degree) plotted along
the secondary y-axis. Frequency is plotted on the x-axis. This format of Bode plot
is a useful alternative to calculating solution resistance (Rs or RΩ), polarization
resistance (Rp or Rct) and Cdl. Furthermore, log(Zabs) versus log(ω) plot sometimes
allow a more efficient extrapolation of the data from higher frequencies.

Fig. 2.7  Nyquist plot for

Randle’s electrochemical cell
model [19]
32 2  Impedance Spectroscopy and Experimental Setup

Fig. 2.8  Bode plot for

Randle’s electrochemical cell
model [19]

Fig. 2.9  Extraction of
intrinsic parameters from
bode plot [19]

2.3 Experimental Setup

The experiment setup mainly consisted of Hi-precision Hioki 3522-50 LCR meter,
Hioki 4-terminal probe 9140, digital thermometer and humidity tester interfaced
through RS232 to a tailor-made LabVIEW program executing on a desktop data
2.3  Experimental Setup 33

Fig. 2.10  Laboratory test bench with Hioki Hi Precision LCR and data acquisition system

acquisition computer. The temperature, humidity, and inert atmosphere controls

were achieved by placing the sensor inside a desiccator, whenever required, to per-
form the testing under stringent environmental conditions. MicroSuite Laboratory,
a research facility available to the School of Engineering and Advanced
Technology, Massey University, Palmerston North was used to conduct all set of
experiments. Figure 2.10 shows the main experimental setup and the block dia-
gram of the laboratory setup and apparatus used for this research in addition to
other in-lab available facilities for heating, cooling, auto enclave, chromatography,
microscopy, and spectrophotometry, etc.

2.3.1 Equipment and Instrumentations

The high precision LCR meter Hioki 3522-50 and 3532-50 have been used to
obtain test parameters’ measurements in order to perform investigation electro-
chemical impedance spectroscopy from 1 to 5 MHz range as required. The techni-
cal specifications of the high-performance set of test equipment LCR meter Hioki
3522-50 and 3532-50 are given in Table 2.1. Figure 2.11 shows the front panel of
Hioki high precision LCR meter 3522-50.

2.3.2 Fixture and Test Probe Connections

The standard fixture is a four-wire type Hioki 9261 which can be used for all
test frequencies from DC to 5 MHz. Figure 3.3 shows Hioki 9140 4-terminal test
probe with crocodile clip termination which can be used for testing in a range of
1 MHz–100 kHz. There are two sets of terminals connecting the sensor to the test
34 2  Impedance Spectroscopy and Experimental Setup

Fig. 2.11  Hioki (Japan) 3522-50 LCR Hi-tester

Fig. 2.12  Connecting LCR3522-50/3532-50 to the 9262 test fixture and developed interdigital

sensing system

equipment. The outer set of terminals, named HCUR and LCUR on the front panel,
are used to measure the current flowing through the sensor, whereas, the inner set
of terminals, appointed as HPOT and LPOT, measure the potential across the sensor
at any instant of time. Detail description is shown in Fig. 2.12. Table 2.2 displays
the details of fixture connection with shielding to the device under test (DUT).

2.3.3 RS-232C Interface for 3522-50/3532-50 LCR Hi Tester

An RS-232C was used to interface Hioki LCR3522-50 to a desktop/laptop com-

puter in order to develop an automatic data acquisition system. Use of the interface
made it possible to control all the functions of the LCR3522-50/3532-50 using soft-
ware algorithm. The graphical user interface was developed in Labview software to
input setting parameters except power on/off. The program consisted of commands
and queries made by the data acquisition computer system to the interfaced instru-
ment. A command sent is a set of instructions or data to setup the test conditions
2.3  Experimental Setup 35

Table 2.2  Hioki Hi Precision LCR test terminals description

Test Terminal Description
HCUR Carries the signal current source. Connected to the excitation electrodes
of the interdigital sensor
HPOT Detected high voltage sense terminal. Measure potential difference at any
instant of time
LPOT Detected low voltage sense terminal
LCUR Test Current detection terminal
GUARD Connected to the GND input to minimize noise

Table 2.3  LCR testing parameters and calculation equations

Parameter Series equivalent circuit mode Parallel equivalent circuit mode
Z

|Z| = V/I(= R2 + X2 )
Y

|Y| = 1/|Z|(= G2 + B2 )
R Rs = ESR = ||Z|cosθ| Rp = |1/|Y|cos∅|(=1/G)
X X = ||Z|sinθ|
G G = ||Y|cos∅|
B B = ||Y|sin∅|
L Ls = X/ω Lp = 1/ωB
C Cs = 1/ωX Cp = B/ω
D D = |1/ tan θ| |
Q Q = |tan θ| = (1/D)

communicated to the LCR meter, whereas query is a set of data or status informa-
tion requested from the LCR meter. The LCR transmitted the measured/calculated
parameters in response to the queries made by the data acquisition computer. The
software echoed back the received automatic measurements of the required param-
eters’ data on the computer monitor via a graphical user interface in addition to writ-
ing/saving it in Microsoft Excel worksheet in ‘xls’ format. Table 2.3 provides the
details of the parameters measured and calculated by LCR3522-50/3532-50 using
the mathematical equations mentioned against each parameter. The data acquisi-
tion computer system was used to analyse further the saved information to study the
impedance characteristics of the developed sensors and material under test.

2.3.4 Conclusions

The experimental setup, instrumentation, program and measurement methods

have been discussed in this chapter. High precision LCR meter’s interface with
the LABVIEW program has been established in order to erect a stand-alone auto-
matic measurement system. Details of the experimental setup, connection cables,
36 2  Impedance Spectroscopy and Experimental Setup

instruments settings, and program interface were explained in the chapter. The
basic theory of measurement method using Impedance Spectroscopy (IS) has also
been discussed to enlighten the reader with the basic measurement methodol-
ogy. The setup has been built to a stage where it could be interfaced with a smart
sensing transducer that could fetch the information from the electrochemical cell,
interpret it into required electrical signal so that valuable information about the
kinetic processes taking place inside the cell could be extracted. Development of a
sensitive, selective and reliable sensor was the most important part of this research
project. The details of the development of the smart sensor are discussed in the
following chapter.

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