Impedance Measurement Technique Research Articles

Can Electrochemical Impedance Spectroscopy be Replaced by Direct Current Techniques in Battery Diagnosis?

Electrochemical impedance spectroscopy (EIS), a conventional and alternating-current-(AC)-based technique for impedance measurement, is commonly used in battery diagnosis. However, it requires expensive equipment and demanding operating conditions and is complex and model-dependent in data analysis. Recently, novel direct current (DC) analytics have emerged as an alternative to EIS. They are simple yet powerful, being capable of revealing impedance information that traditionally could only be obtained through EIS and determining Li-ion diffusion coefficient. Besides, a complete EIS spectrum can be predicted based on constant current charging curves in the support of machine learning methods. This work highlights the similarities and discrepancies between DC techniques and EIS in the electrochemical analysis of Li-ion batteries. Looking ahead, DC techniques may be a promising substitute for EIS in future battery diagnosis, requiring simplified equipment while offering a deep understanding of battery impedance and its underlying electrochemical processes.

Frequency Scanning of Weakly Damped Single-Phase VSCs With Chirp Error Control

The chirp sweep is a go-to wide-band impedance measurement technique when speed and simplicity are of main concern. Additionally, the time-frequency trait of chirp scans provide unique benefits for systems exhibiting frequency couplings - a phenomenon often encountered in single-phase VSCs. Unfortunately, time domain interpretation of chirp responses are inaccurate if the VSC-based system exhibits weak damping, as the transient response induced by the chirp cannot be safely neglected. We quantify this error for linear(ised) time-invariant and time-periodic systems, with impedance representations of scalar transfer functions and harmonic transfer functions, respectively. An observer termed the Multiple Chirp Reference Frame Filter is proposed which enables real-time estimation of the harmonic transfer functions and their corresponding chirp errors. By controlling the relative errors to negligible values, the chirp exhibits low rate around resonances and high rate elsewhere. An experimental admittance sweep of a single-phase STATCOM operated by dispatchable Virtual Oscillator Control, consolidates the proposed approach as a simple frequency scan technique for weakly damped and frequency coupled systems.

High-temperature impedance properties of Sr1-xCaxTiO3 ceramics for lead-free capacitor applications

ABSTRACT Lead-free Sr0.6Ca0.4TiO3 ceramic was prepared by solid-state reaction route. X-ray diffraction technique showed the phase purity and identified the orthorhombic perovskite structure. Scanning Electronic Microscopy observation evidenced homogeneous morphology and dense microstructure. Electrical conduction and dielectric relaxation mechanisms at high temperature have been studied by complex impedance measurement techniques over a wide range of frequencies and temperatures, from 100 Hz to 1 MHz and from 573 K to 783 K. Fitting of impedance measurements allowed us to study grains and grain boundaries electrical characteristics and their contribution to the conduction and dielectric relaxation processes in the ceramic. Electrical conduction in grains is due to oxygen vacancy jumps for temperatures below 733 K and to polarons above 763 K. Electrical DC conductivity in grains and grain boundaries is mainly due to oxygen vacancies. Impedance measurements and relaxation time distribution function calculations show non-Debye-type relaxation effects for both grains and grain boundaries.

Non-Destructive Evaluation of Thermal Aging in EPDM Rubber Using Electromagnetic Techniques.

This study investigates the use of eddy-current technology and impedance spectroscopy in sensing the change in rubber properties after it is exposed to accelerated thermal aging. The thermal aging process, by application of temperature and pressure over time, of ethylene propylene diene monomer (EPDM) rubbers containing both carbon black (CB) and graphene are investigated. Both eddy-current sensing and electrical impedance measurement techniques were used for electromagnetic analysis. Both methods measure the in- and out-of-phase responses as a function of excitation frequency at room temperature. The measurements were performed before and after the aging process. The electrical percolation threshold was detected in the rubber samples by varying the CB content from 0 to 40 wt%. In the rubber sample containing 30 wt% CB, 0-5 wt% of the CB was replaced with graphene flakes. The substitution of graphene for CB in the EPDM rubber formulation provided an enhanced eddy-current and electrical impedance response. The findings demonstrate the feasibility of employing electromagnetic analysis techniques to investigate the extent of aging.

Injection Amplitude Guidance for Impedance Measurement in Power Systems

Impedance measurement techniques based on small-signal injections in AC power system have been well-developed but a gap in the analysis is that the selection of an injection amplitude is based only on experience. This letter develops an analytical process to analyse the noise existing in power systems and thereby determine the minimum injection amplitude according to an allowable error. The process is based on knowledge of stochastic processes and statistics, where the Monte Carlo method is also employed to simplify the process. A power hardware-in-the-loop system with a grid-following inverter is employed in experimental verification of the results.

Broadband measurements of the surface impedance in ferromagnetic wires as a boundary condition for scattering problems

In the cm-wave range, the skin depth is comparable to the micron radius of ferromagnetic wires and thus their magnetic and conductive properties will influence the scattered electromagnetic field. Solving the scattering problem by considering the complicated internal magnetic structure of the wire becomes unpractical. There is thus a need to develop hybrid methods when the external problem of scattering on an inclusion is solved together with the experimental impedance conditions on its surface. Herein, we propose an accurate broadband impedance measurement technique operating up to GHz. The printed circuit board measurement and calibration cells designed in this work allow flexibility in choosing external stimuli such as magnetic field, tensile stress, and heat. The experimental impedance can be then used as the boundary condition in electromagnetic simulations making it possible to model, predict and design wire-based composites using numerical solvers such as CST Studio Suite.

Direct Measurements of Ionic Transport Behavior of Dual-Layer Porous Electrodes

To improve power and cycling performance of lithium-ion batteries, dual-layer or porosity-gradient electrodes have been proposed. By engineering a higher porosity close to the separator, the intention is to improve ion transport where it is most impactful. In this research, MacMullin numbers of two dual-layer anode samples are tested using an impedance measurement technique developed previously. To characterize the microstructure of each layer independently, we developed an improved transmission-line model that accounts for each layer’s properties.Virtual experiments using COMSOL Multiphysics to simulate impedance measurements are used to examine and improve the accuracy of the numerical inversion procedure. The results for the two dual-layer anodes studied show that MacMullin numbers follow expected trends, though the anodes are quite different from each other.

Probing Deep Lung Regions using a New 6-electrode Tetrapolar Impedance Method.

Probing deep regions of the lung using electrical impedance is very important considering the need for a low cost and simple technique, particularly for the low and medium income countries. Because of complexity and cost, Electrical Impedance Tomography is not suitable for this envisaged application. The simple Tetrapolar Impedance Measurement (TPIM) technique employing four electrodes is the age old technique for bioelectrical measurements. However, it has its limitations in respect of organ localisation and depth sensitivity using skin surface electrodes. Recently, a new 6-electrode TPIM with two current electrodes but two pairs of appropriately connected potential electrodes positioned on the front and back of the thorax, proposed by one of the authors, came with a promise. However, this work gave a qualitative proposal based on concepts of physics and lacked a quantitative evaluation. In order to evaluate the method quantitatively, the present work employed finite element method based COMSOL Multiphysics software and carried out simulation studies using this new 6-electrode TPIM and compared the results with those from 4-electrode TPIM, with electrodes applied either on the front or at the back of the thorax for the latter. Initially, it carried out a sensitivity distribution study using a simple rectangular volume conductor which showed that the 6-electrode TPIM gives better depth sensitivity throughout the lung region. Next it used a near life like thorax model developed by another of the authors earlier. Using this model, extensive studies were carried out to quantify the overall sensitivity over a target lung region, the contribution of the target lung to the total measured impedance, and several other parameters. Through these studies, the 6-electrode TPIM was established on a stronger footing for probing deep regions of the lungs.

A Novel Calibration-Free Remote Antenna Impedance Measurement

Connecting the antenna under test (AUT) to a network analyzer through a feeding cable is a typical method for determining the input impedance. However, the induced current on the feeding cable obstructs precise measurement in the case of electrically small antennas (ESAs). A remote impedance measurement technique is proposed to address the drawbacks of network analyzer-based measurements. First, the AUT is connected to three standard loads, a short, an open, and a matched load consecutively. Then an electrostatic discharge (ESD) is used as an impulsive source to excite the AUT. Concurrently, a probe connected to an oscilloscope captures the impulse responses. Finally, the input impedance of the AUT is determined by extracting complex natural resonances (CNRs) from three impulse responses. Four different antennas are designed and prototyped. Then, using a full-wave simulator, their input impedances are computed and compared to those estimated using the proposed technique. The input impedances obtained by the proposed technique are very consistent with those from full-wave simulations.

Fast Sub-Hz potentiostatic/galvanostatic bio-impedance measurements using chaotic oscillators.

The measurement of bio-impedance spectra at ultra low frequencies (sub-Hz) is known to require a considerably long time with the classical frequency-sweep method or other narrow-band periodic excitation signals. In this work, an impedance measurement technique based on using wide-band chaotic signals is proposed and experimentally validated over the frequency range [Formula: see text]. The technique was tested in both potentiostatic and galvanostatic modes, first using commercial components and then using an enhanced Howland current pump designed and fabricated in a 65nm CMOS technology. The accuracy of the proposed technique was assessed on fruit samples compared to measurements conducted using a research-grade Biologic VSP-300 electro-chemical station.

Quantitative study of tumor angiogenesis in three-dimensional matrigel barrier using electric impedance measurement technique

Tumor angiogenesis refers to the development of new blood vessels in tumors and is a vital indicator of cancer metastasis which is the major cause of cancer-related deaths. Study of tumor angiogenesis is critical for the development of potential therapeutic strategies of suppressing cancer metastasis. In the current work, a microfluidic device has been developed and was composed of 2 reservoirs connecting with a Matrigel-filled microchannel. The microchannel was mimicked as a biological barrier and embedded with measurement microelectrodes. New blood vessels were successfully induced to extend along the microchannel. Meanwhile, real-time impedance measurement was conducted to quantitatively monitor the tumor angiogenesis process. The results revealed the extension speed of new blood vessels was proportional to chemical induction level, i.e., VEGF165 concentration. Moreover, tumor angiogenesis was shown to be induced by the VEGF released from cancer cells and significantly correlated to the number of cancer cells. In addition, anti-VEGF suppressor was quantitatively evaluated to study the suppression efficacy of tumor angiogenesis. The current microfluidic device provides a promising tool to study tumor angiogenesis in 3D biological barrier. The impedance technique offers reliable and quantitative evidences for evaluating drug efficacy. Development of tumor angiogenesis analytical platform can potentially lead to develop novel therapeutic strategies of suppressing cancer metastasis.

High-P–T impedance measurements using a laser-heated diamond anvil cell

The electrical conductivity (EC) of minerals found on Earth and throughout the solar system is a fundamental transport property that is used to understand various dynamical phenomena in planetary interiors. High-pressure and high-temperature (P-T) EC measurements are also an important tool for observing phase transitions. Impedance measurements can accurately measure the EC of a nonmetallic sample. In previous measurements under static conditions using a laser-heated diamond-anvil cell (LHDAC), only direct current resistance is measured, but this method overestimates the bulk sample resistance. Moreover, the previous methodology could only be applied to nontransparent samples in an LHDAC using infrared lasers, limiting the range of measurable composition. To the best of our knowledge, no in situ high-P-T EC measurements of transparent materials have been reported using LHDAC techniques. We developed a novel impedance measurement technique under high-P-T conditions in an LHDAC that applies to transparent samples. As a validation, we measured the EC of Mg0.9Fe0.1SiO3 bridgmanite up to 51GPa and 2000K and found that the results are consistent with those of previous studies. We also measured the EC values of sodium chloride to compare with those of previous studies, as well as those of cubic boron nitride and zirconia cement to quantify how well they insulate under high P-T conditions. This is the first report of the impedance and EC measurements of transparent minerals in an LHDAC, which allows the measurement of Fe-poor/-free materials, including the major constituents of the interiors of gas giants and icy planets, under extreme conditions.

Measurement of Extreme Impedances with the S Parameters

High frequency measurement of extreme impedances, such as the Equivalent-Series-Resistance (ESR) of an ultra high-Q capacitor, can be performed with specific and costly instrumentation whose principle is generally based upon a coaxial resonant line or a resonant cavity [1]. A cost-effective solution for measuring impedances at high frequencies is the classical One-Port reflection technique that can be performed with a Vector Network Analyzer (VNA). In [2], only this technique was considered, and the analysis was limited to a relative error of 10%; nevertheless, this work showed that the reflection technique is unsuited for measuring extreme impedances. In [3], all of the impedance measurement techniques that can be performed with a VNA are presented and compared. This analysis confirmed the limitations of the reflection technique and showed the abilities of the transmission technique for measuring extreme impedances. Unfortunately, these comparisons were based on absolute errors of the measured impedance (ΔZ) that are not significant for an engineer who needs to select the best method. Moreover, in [2], [3], the analyses are not extended to the negative resistances, and the resistance's sign inversion error is not considered.

Electromechanical impedance-based embeddable smart composite for condition-state monitoring

In the present study, an alternating current (AC) based electro-mechanical impedance (EMI) technique was employed to evaluate the performance of smart cementitious composite-based impedance sensor (SCC- i S) over a frequency range, and then was employed as embeddable sensor for monitoring and assessing the health of concrete structure. For this purpose, a method for developing SCC-iS by reinforcing the carboxylic group (COOH-) multi-walled carbon nanotube (COOH-MWCNT) in the cementitious composite matrix is described. The optimal CNT concentration in SCC- i S was obtained based on the AC impedance measurement technique over a specified frequency range. After finding the optimal CNT concentration in SCC- i S, their piezoresistive behaviour (in terms of change in electrical impedance or electrical conductance) was examined using an electro-mechanical impedance measurement approach under uniaxial compressive loading. Finally, the developed sensor is employed as an embedded sensor for damage monitoring of structures under flexural loading. The acquired electrical impedance- and conductance- responses from the SCC- i S were utilized to evaluate the occurrence and progression of damage in real-time. The damage metric and the shift in frequency band were used to quantify the level of damage in the structures. From the experimental study, 0.50 wt% CNT concentration is found to be optimum for developing the efficient SCC- i S. Under the uniaxial compressive loading, the electrical variation in impedance (EVZ) and electrical variation in conductance (EVC) in SCC- i S exhibit excellent correlation with compressive strain and are capable of detecting the damage. The acquired signals from embedded SCC- i S show the effectiveness and sensitivity (in both qualitative and quantitative terms) for damage monitoring of structures; even they are capable of tracing the early-stage damage initiation in concrete structures. The electrical conductance spectra within a specified frequency range show a leftward shift, indicating the degradation in stiffness of concrete structure. Overall, the developed SCC- i S is the first of its kind and is found to be very effective and durable for real-time monitoring of structures, especially in the aggressive environment. • Development of smart nanoengineered composite using functionalized CNT. • Embedded sensors for capturing the electro-mechanical impedance (EMI) signature. • Sensor characterization and evaluation of piezoresistive behavior in frequency bands. • Demonstration for damage monitoring of structures under flexural loading. • Damage metric and shift in frequency band for accurate damage quantification.

Investigation of ground impedance measurement techniques up to 1 MHz frequency in urban dense power substations

Investigation of ground impedance measurement techniques up to 1 MHz frequency in urban dense power substations

MOF-based sensor platforms for rapid detection of pesticides to maintain food quality and safety

Pesticides are primarily used in agriculture to increase crop yield because of their highly lucrative, stable structure and agricultural benefits such as eliminating fungi, plant diseases, pests and insects to regulate the growth of crops. Apart from their rebel design and agricultural benefits, pesticides have severe toxicity to a variety of other living organisms. Therefore, developing effective pesticide detection systems is an ongoing challenge. Multiple technologies that for the rapid, easy, sensitive, and selective detection of these neurotoxic compounds are in demand. This paper reviews the recent advances in sensing assays based on the metal-organic framework (MOF) structure for pesticide detection. We have reviewed state-of-the-art optical biosensors for in-place sensing that have the advantages of a simple protocol, simple manipulation, super sensitivity, wide linear range, and cost-effectiveness. These biosensors use chemiluminescence with a short sensing time and a highly sensitive luminescence sensor that enables real-time detection by easy smartphone pairing. For profitable platforms, the obstacles related to sample preparation and equipment cost can be overcome by employing electrochemical sensors. The intensity, impedance, and potential difference measurement techniques used in these biosensors allow for low detection limits and observable durations in water, agricultural, and food samples containing high levels of pesticides.

Structural, thermal, and electrochemical studies of biodegradable gel polymer electrolyte for electric double layer capacitor

A quasi-solid-state supercapacitor is fabricated using a biodegradable gel polymer electrolyte (GPE), and graphene nano-platelets (GNPs) capacitive electrodes. The GPE film comprises biodegradable polymer cellulose acetate (CA), ionic liquid, 1-ethyl-3-methylimidazolium thiocyanate (EMImSCN) and dopant salt potassium thiocyanate (KSCN). The polymeric gel films are prepared using the standard “solution cast technique” and characterized by using X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermogravemetric analysis (TGA), Impedance spectroscopy, and Linear sweep voltammetry techniques. The synthesized GPE exhibits maximum room temperature ionic conductivity ∼1.2 x 10−3 S cm−1 and an electrochemical stability window of ∼2.4 V. The electrical double layer capacitor (EDLC) is configured by sandwiching the GPE film between two graphene nanoplatelets (GNPs) electrodes. The performance of the EDLC cell is evaluated in terms of specific capacitance, rate, and pulse power by using cyclic voltammetry, and electrochemical impedance measurement techniques.

An Auto Adjustable Transimpedance Readout System for Wearable Healthcare Devices

The objective of this work was to design a versatile readout circuit for patch-type wearable devices consisting of a Transimpedance Amplifier (TIA). The TIA performs Current to Voltage (I–V) conversion, the most widely used technique for amperometry and impedance measurement for various types of electrochemical sensors. The proposed readout circuit employs a digitally controllable feedback resistor (Rf) technique in the TIA to improve accuracy, which can be utilized in a variety of electrochemical sensors within a current range of 0.1 µA–100 µA. It is designed to accommodate multiple sensors simultaneously to track multiple target analytes for high accuracy and versatile usage. The readout circuit consists of low power operational amplifier (op–amp) and digital circuit blocks, is designed and fabricated with Magna 0.18 µm Complementary Metal Oxide Semiconductor (CMOS) technology, which provides low power consumption and a high degree of integration. The design has a small size of 0.282 mm2 and low power consumption of 0.38 mW with a 3.3 V power supply, which are desirable factors in wearable device applications.

In situ key aging parameter determination of a vehicle battery using only CAN signals in commercial vehicles

In this article, an on-line impedance measurement technique for a battery pack is demonstrated and proofed, using only the already existing sensors and accessible bus data in an electrified vehicle. A sufficient amount of AC harmonics in the DC-link current, for the identification purposes, is created in normal driving conditions. Fourier analysis is used to process the data and extract the impedance information. It is found that the proposed on-line method can accurately measure the battery pack impedance at a low frequency range (5 Hz to 10 mHz) with 40 Hz sampling frequency in the bus data. A key impedance value in the electrochemical impedance spectroscopy can be captured clearly in different conditions, which can be used to track the battery state of health. A recorded current waveform during an on-road test is reproduced by a state-of-art battery tester in a lab and the obtained results are compared with impedance values measured by a classic potentiostat. The results from the on-road test have an excellent agreement with lab measurements.

Dual-Modality Volume Measurement Integrated on a Ventricular Assist Device.

Ventricular assist devices (VADs) are implanted in patients suffering from end-stage heart failure to sustain the blood circulation. Real-time volume measurement could be a valuable tool to monitor patients and enable physiological control strategies to provide individualized therapy. However, volume measurement using one sensor modality requires re-calibration in the critical time post VAD implantation. To overcome this limitation, we have integrated ultrasound and impedance volume measurement techniques into a cannula of an apical VAD. We tested both modalities across a volume range from 140-420 mL using two differently sized and shaped biventricular silicon heart phantoms, which were subjected to physiological pressures in an in-vitro test bench. We compared results from standard calibrated measurements with calculations found by a quadratic optimization for the single modality and their combination (dual-modality) and validated the results using twofold cross-validation. The dual-modality approach resulted in most favorable limits of agreement (LOA) of -0.83 ± 1.54% compared to -13.88 ± 5.90% for ultrasound and -43.45 ± 10.28% for electric impedance, separately. The results of the dual-modality approach were as accurate as the standard calibrated measurement and valid over a large range of volumes (140-420 mL). In this in-vitro study, we show how a dual-modality ventricular volume measurement of ultrasound and electric impedance increases the robustness and renders calibration obsolete. Ventricular volumes could be measured accurately in the critical period post VAD implantation despite ventricular remodeling.