Impedance Measurement Technique Research Articles

A Magnetic-Sensing-Based Wide-Bandwidth Grid Impedance Measurement Technique With Small Perturbation Injection

Grid impedance is an important parameter in the impedance-based stability analysis method for analyzing the interaction between the power electronic inverters and the power grid. However, the existing measurement technique is deteriorated by narrow-bandwidth sensors, large perturbation injections, and inaccurate response components extraction based on the fast Fourier transform (FFT) algorithm. To overcome these problems, a magnetic-sensing-based wide-bandwidth grid impedance measurement technique with a small perturbation injection is proposed in this article. A novel impedance extraction algorithm based on the quadrature delay estimator (QDE) is developed to overcome the spectral leakages and frequency aliasing effect of the existing FFT-based impedance extraction algorithm. The proposed grid impedance measurement technique is implemented on a digitally controlled inverter system, and its effectiveness is verified through the experimental results.

Reconstruction of half-space boundary impedance and sound source direct radiation based on reflection coefficient estimation

When implementing the reconstruction of the sound field directly radiated from a source located in a half-space, the half-space basis functions with boundary impedance as a parameter, need to be formulated. And the boundary impedance is usually obtained via <i>in situ</i> sound impedance measurement techniques. In the reconstruction method based on the expansion in half-space spherical wave basis functions, a hologram surface and a single reference microphone placed in the near-field are used to collect sound pressures. The sound pressure at the reference microphone is first reconstructed and the error of the reconstructed pressure relative to the measured pressure is then calculated. The sound pressure reflection coefficient corresponding to the minimum error is chosen as the measure of the reflection coefficient at the measurement point. Thus, this method is applicable to reconstructing the directly radiated sound pressures without the knowledge of boundary impedance, free from the in situ sound impedance measurement techniques necessary for conventional methods. The purpose of this work is to discuss the various parameters affecting the accuracy of reconstruction. Moreover, the boundary impedance is reconstructed based on the estimation of the reflection coefficient, so that a sound impedance measurement technique implemented via the near-field acoustical holography is proposed. By taking the spherical source for example, numerical simulations are conducted to verify the proposed method of reconstructing the boundary impedance and the directly radiated sound pressures. The influences of reference microphone coordinate, the effective flow resistivity of the boundary, and the rate of decrease of porosity with depth of the boundary on the accuracy of reconstruction are quantitatively analyzed.

Reconstruction of half-space boundary impedance and sound source direct radiation based on reflection coefficient estimation

When implementing the reconstruction of the sound field radiated directly from a source located in a half-space, the half-space basis functions need to be formulated with boundary impedance as a parameter. The boundary impedance is usually obtained via <i>in situ</i> acoustic impedance measurement techniques. In a reconstruction method based on expansion in half-space spherical wave basis functions, a hologram surface and a single reference microphone placed in the near-field are used to collect sound pressures. The sound pressure at the reference microphone is first reconstructed and the error of the reconstructed pressure relative to the measured pressure is then calculated. The sound pressure reflection coefficient corresponding to the minimum error is chosen as the estimated value of the reflection coefficient at each of the measurement points. Thus, this method is applicable to reconstructing the directly radiated sound pressures without knowledge of the boundary impedance, without the <i>in situ</i> acoustic impedance measurements necessary for conventional methods. The purpose of this work is to discuss the various parameters affecting the accuracy of reconstruction. Moreover, the boundary impedance is reconstructed based on the estimation of the reflection coefficient. In this way, an acoustic impedance measurement technique implemented via the near-field acoustical holography is proposed. Taking the source to be spherical, numerical simulations are conducted to verify the proposed method of reconstructing the boundary impedance and the directly radiated sound pressures. The influences of reference microphone coordinates, the effective flow resistivity of the boundary, and the rate of decrease of porosity with depth of the boundary on the accuracy of reconstruction are quantitatively analyzed.

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

Practical Implementation of a Novel Output Impedance Measurement Technique for EIT System While Attached to a Load.

A novel method for measuring the output impedance of current sources in an EIT system is implemented and tested. The paper shows that the proposed method can be used at the time of operation while the load is attached to the EIT system. the results also show that performance of the system improves when the shunt impedance values from the proposed technique are used to set the adaptive sources as opposed to the shunt impedance values acquired through open circuit measurements.

An Overview of Acoustic Impedance Measurement Techniques and Future Prospects

In order to progress in the area of aeroacoustics, experimental measurements are necessary. Not only are they required for engineering applications in acoustics and noise engineering, but also they are necessary for developing models of acoustic phenomenon around us. One measurement of particular importance is acoustic impedance. Acoustic Impedance is the measure of opposition of acoustical flow due to the acoustic pressure. It indicates how much sound pressure is generated by the vibration of molecules of a particular acoustic medium at a given frequency and can be a characteristic of the medium.The aim of the present paper is to give a synthetic overview of the literature on impedance measurements and to discuss the advantage and disadvantage of each measurement technique. In this work, we investigate the three main categories of impedance measurement techniques, namely reverberation chamber techniques, impedance tube techniques, and far-field techniques. Theoretical principles for each technique are provided along with a discussion on historical development and recent advancements for each technique.

An oxide coating impedance measurement during micro-arc oxidation

The impedance instrument converter of oxide layers formed by micro-arc oxidation (MAO) is developed. It allows continuous non-destructive testing of electric parameters of the synthesized coatings (resistance and capacitance) and electrolyte conductivity to assess the degree of degradation. The instrument converter consists of a generator, a measuring circuit, a repeater and has a digital output. The modified ammeter-voltmeter method is used as the impedance measurement technique. High accuracy of resistance, capacitance and conductivity measurements (the total relative error is no more than 0.5%) is achieved by performed functional and metrological analysis of the converter measurement channels, as well as metrological tests.

Accurate Online Battery Impedance Measurement Method with Low Output Voltage Ripples on Power Converters

The conventional online battery impedance measurement method works by perturbing the duty cycle of the DC-DC power converter and measuring the response of the battery voltage and current. This periodical duty cycle perturbation will continuously generate large voltage ripples at the output of power converters. These large ripples will not easily be removed due to the high amplitude and wide frequency range and would be a challenge to meet tight output regulation. To solve this problem, this paper presents a new online battery impedance measurement technique by inserting a small switched resistor circuit (SRC) into the converter. The first contribution of this work is that the perturbation source is moved from the main switch to the input-side of the converter, so the ripples are reduced. The analysis and experimental results of the proposed method show a reduction of 16-times compared with the conventional method. The second contribution tackles the possible change of the battery state of charge (SOC) during the online battery measurement process, which will inevitably influence the impedance measurement accuracy. In this proposed method, battery impedance at multiple frequencies can be measured simultaneously using only one perturbation to accelerate measurement speed and minimize possible SOC change. The experimental impedance results coincide with a high-accuracy laboratory battery impedance analyzer.

Electrical Properties in Large Frequency and Temperature Ranges of Sr0.6Ca0.4TiO3 Ceramics

Abstract: Lead-free Sr0.6Ca0.4TiO3 (SCT) ceramic was prepared by the solid state reaction route. X-Ray diffraction technique showed the phase purity and identified the orthorhombic perovskite structure of the material. Scanning Electronic Microscopy observation evidenced homogeneous morphology and dense microstructure for the ceramic. The dielectric and conductivity properties of the sample were studied using complex impedance measurement technique in a wide range of frequencies and temperatures: from 100 Hz to 1.8 GHz and from 25°C to 550°C. The ceramic exhibits a stable dielectric permittivity and low dielectric losses in frequency and temperature up to 200°C. This is very interesting in view of developing high-quality lead-free ceramic capacitors for applications requiring high temperatures; for example, in cars. The increase in dielectric permittivity for temperatures higher than 200°C may be related to oxygen vacancies that are heat-activated in the material. Dielectric losses show the existence of a dielectric relaxation at low temperatures and low frequencies. Conductivity measurement investigated at high temperatures show on one hand high AC conductivity values attributed to the high temperature jumping process and on the other hand two electrical conductivity mechanisms above 400° C in the material. Keywords: Strontium calcium titanate, Ceramic, Structure, Dielectric properties, Conductivity.

Piezoelectric‐based hoop‐type interface for impedance monitoring of local strand breakage in prestressed multi‐strand anchorage

In this study, a piezoelectric-based interface technique for impedance measurement is presented to monitor local strand breakage in multi-strand anchorage systems. Firstly, a hoop interface-based impedance measurement model is designed based on stress behaviors of the multi-strand anchorage. Coupled dynamic behaviors between the lead zirconate titanate (PZT) interface and the target tendon anchorage are interpreted to determine sensitive frequency ranges under local strand breakage. Next, a prototype of the PZT interface is designed to fit into the target multi-strand anchorage to monitor the stress variations induced by local strand breakages. Dynamic characteristics of the PZT interface are numerically analyzed to sensitively catch impedance signals in predetermined frequency ranges. Finally, a series of damage scenarios are tested on a full-scale multi-strand anchorage system to evaluate the feasibility of the PZT interface for monitoring a series of strand-breakage cases. Impedance responses of the PZT interface prototype are analyzed to determine damage-sensitive frequency ranges. Linear tomography of root-mean-square-deviation (RMSD) indices is utilized to localize damaged strands.

Application of Laser-Ultrasonic Technique of Acoustic Impedance Measurement with Signals Detection by Backward-Mode Scheme for Porosity Content Evaluation in CFRP Laminates

The aim of this work is the development and experimental implementation of the laser-ultrasonic method for CFRPs porosity assessment with one-side access to an investigated object. The scheme with the laser thermooptical generation and backward-mode piezoelectric detection of longitudinal acoustic waves is used. The proposed method is based on the measurement of the acoustic impedance of a composite specimen by using the value of the integral of the ultrasonic pulse reflected from an immersion layer-specimen interface. The existence of the relationship between the porosity content, ultrasound velocity, and material’s density allows one to assess the porosity of CFRPs by the measured acoustic impedance. The proposed method does not require plane parallelism of the input and output surfaces of the studied objects, as well as measuring the thickness of the object. This allows studying CFRP structures with complex shapes. This method may be of use for various types of composite materials, regardless of acoustical waves propagating features related to a periodical material’s structure. CFRP specimens with three reinforcement schemes and different average volume porosity contents were investigated. It is shown that the local porosity distribution in the studied CFRPs is nonuniform along the fiber stacking plane. The porosity content obtained by the laser-ultrasonic method was checked using the X-ray computer tomography. The porosity values, averaged from the laser-ultrasonic measurement results, coincide with the X-ray tomography data within the error limits. The method can be useful for quality control of obtained composite structures with the aim of modernization of technology processes and selecting optimal production conditions and also for the detection of changes in composite structures during their operation or during fatigue testing processes.

REAL-TIME MONITORING OF CELL CULTURES WITH NICKEL COMB CAPACITORS

The aim of the study was to present a method for assessing the condition of cell culture by measuring the impedance of cells cultured in the presence of nickel. For this purpose, an impedance measurement technique using nickel comb capacitors was used. The capacitor electrodes were made using a thin film magnetron sputtering. In the experimental part, the culture of cells of mouse fibroblasts on the prepared substrate was performed. The cell culture lasted 43 hours and showed that the presented technique allows it to be used to analyze the effect of nickel on cells.

Extraordinary performance of semiconducting metal oxide gas sensors using dielectric excitation

Semiconducting metal oxides are widely used for gas sensors. The resulting chemiresistor devices, however, suffer from non-linear responses, signal fluctuations and gas cross-sensitivities, which limits their use in demanding applications of air-quality monitoring. Here, we show that conventional semiconducting metal oxide materials can provide high-performance sensors using an impedance measurement technique. Our approach is based on dielectric excitation measurements and yields sensors with a linear gas response (R2 > 0.99), broad dynamic range of gas detection (six decades of concentrations) and high baseline stability, as well as reduced humidity and ambient-temperature effects. We validated the technique using a range of commercial sensing elements and a range of gases in both laboratory and field conditions. Our approach can be applied to both n- and p-type semiconducting metal oxide materials, and we show that it can be used in wireless sensor networks, and drone-based and wearable environmental and industrial gas monitoring. Semiconducting metal oxide gas sensors with a linear response, broad dynamic range and high baseline stability can be created with the help of a dielectric excitation technique.

Linear gas sensing with dielectric excitation

An impedance measurement technique based on dielectric excitation in oxide semiconductors can provide a highly linear sensing signal over a wide range of gas concentrations.

An Improved Controlled-Frequency-Band Impedance Measurement Scheme for Railway Traction Power System

Railway traction power system (TPS) impedance affects the stability and operation performance of connected power electronics devices (i.e., electric trains) with the closed-loop control system. In order to identify the detailed TPS impedance, the wideband-response-based impedance measurement technique has become attractive for its fast execution time and accuracy, especially the chirp-based technique for its bilateral controllability of injected wideband disturbance. However, for the reason that the disturbance device is directly powered by the measured system, the fundamental component separates some harmonic clusters in the frequency domain and leads to unsatisfactory uniformity of the injected wideband disturbance. In this article, a segmented-chirp-based technique is proposed to eliminate this phenomenon caused by the fundamental component, where the chirp signal is segmented and carried on the fundamental only when the amplitude is relatively smooth on top (or bottom), which facilitates a uniform wideband distribution to keep a good measurement accuracy. Meanwhile, the presented modular disturbance circuit with a flexible topology can better adapt to the various industrial engineering conditions. Finally, the detailed measurement results based on the simulation and downscaled experimental system validate the effectiveness of the proposed measurement scheme.

A Face-Shear Mode Piezoelectric Array Sensor for Elasticity and Force Measurement.

We present the development of a 6 × 6 piezoelectric array sensor for measuring elasticity and force. The proposed sensor employs an impedance measurement technique, sensing the acoustic load impedance of a target by measuring the electrical impedance shift of face-shear mode PMN–PT (lead magnesium niobate–lead titanate) single crystal elements. Among various modes of PMN–PT single crystals, the face-shear mode was selected due to its especially high sensitivity to acoustic loads. To verify the elasticity sensing performance, gelatin samples with different elastic moduli were prepared and tested. For the force measurement test, different magnitudes of force were loaded to the sensing layer whose acoustic impedance was varied with applied forces. From the experimental results, the fabricated sensor showed an elastic stiffness sensitivity of 23.52 Ohm/MPa with a resolution of 4.25 kPa and contact force sensitivity of 19.27 Ohm/N with a resolution of 5.19 mN. In addition, the mapping experiment of elasticity and force using the sensor array was successfully demonstrated.

A Low Cost, Rapid Impedance Measurement Technique Suitable for Li-ion Health Diagnosis in Battery Energy Storage Systems

Battery energy storage is becoming a vital part of green energy systems. Prediction of the state of health of energy storage systems is difficult as it relies on a number of parameters. Pseudo Random Binary Sequence (PRBS) excitation of energy storage batteries has been shown to be a valid method of battery parameter identification for lead acid batteries [1]. The purpose of this work is to validate PRBS test data from a 3Ah LiFePO4 cell forming part of an EV battery-pack cell against Electrochemical Impedance Spectroscopy (EIS) data obtained from an industry-standard potentiostat (Solartron 1480). PRBS results are obtained in under 200 seconds on easily reproducible equipment which can be built into a green energy battery management system, while the EIS process takes over two hours on prohibitively expensive laboratory equipment. This work validates PRBS as a fast and portable method of obtaining the impedance spectrum of Lithium Ion cells, which can then be used to obtain information about SoH of the BESS.

Rapid impedance spectroscopy using dual phase shifted chirp signals for electrochemical applications

Impedance is an important diagnostic feature finding applications in material science, analytical chemistry, understanding biological systems etc. This is particularly true for diagnosis of electrochemical systems such as fuel cells and storage batteries. However the conventional technique for impedance measurement, i.e. Electrochemical Impedance Spectroscopy (EIS), is time intensive and requires sophisticated instrumentation making it unsuitable for online applications. This paper introduces a novel technique that makes use of two high bandwidth and short duration signals having dissimilar phases to estimate impedance. A unique class of signal, viz. the dual phase shifted chirp signal, which comprises two identical chirp signals having a known phase difference, is used to obtain the impedance profile. The technique is validated through both, simulation as well as experiments. The results obtained from this work are in correspondence with those obtained through conventional EIS, albeit in a minuscule fraction of time and with meagre instrumentation. The proposed technique will pave way for a quick and cost effective alternative to EIS and allow for impedance measurement during operation.

Spatially resolved electrical impedance methods for cell and particle characterization.

Electrical impedance is an established technique used for cell and particle characterization. The temporal and spectral resolution of electrical impedance have been used to resolve basic cell characteristics like size and type, as well as to determine cell viability and activity. Such electrical impedance measurements are typically performed across the entire sample volume and can only provide an overall indication concerning the properties and state of that sample. For the study of heterogeneous structures such as cell layers, biological tissue, or polydisperse particle mixtures, an overall measured impedance value can only provide limited information and can lead to data misinterpretation. For the investigation of localized sample properties in complex heterogeneous structures/mixtures, the addition of spatial resolution to impedance measurements is necessary. Several spatially resolved impedance measurement techniques have been developed and applied to cell and particle research, including electrical impedance tomography, scanning electrochemical microscopy, and microelectrode arrays. This review provides an overview of spatially resolved impedance measurement methods and assesses their applicability for cell and particle characterization.

Voltage-Dependent Capacitance Extraction of SiC Power mosfets Using Inductively Coupled In-Circuit Impedance Measurement Technique

The voltage-dependent capacitances of silicon carbide power metal–oxide–semiconductor field-effect transistors ( mosfets ) affect the switching characteristics and have a direct impact on the electromagnetic compatibility (EMC) performance of the power conversion circuit. To predict and mitigate the potential impact on EMC in the early design phase, the capacitances have to be obtained accurately. In this paper, a novel method is proposed based on an inductively coupled in-circuit impedance measurement technique. The proposed method extracts the voltage-dependent capacitances of a mosfet under its actual biased voltage without making any direct electrical contact, and hence eliminates potential safety hazards. Once the inductive probes are characterized, there is no need to re-calibrate the setup prior to each measurement, and therefore, it simplifies the whole measurement process. The accuracy of the extracted voltage-dependent capacitances for the SiC power mosfet has been validated experimentally.