Transfer Impedance Measurements Research Articles

Transfer impedance measurement of shielded cables with mismatched loads

Transfer impedance measurement of shielded cables with mismatched loads

Design of Transfer Impedance Measurement Fixture of EMI Gaskets Up to 18 GHz

To achieve the transfer impedance measurement of electromagnetic interference (EMI) gaskets, a fixture useful up to 18 GHz is developed based on the SAE ARP1705C standard. The radial size of the coaxial section of the fixture is shaped from the perspective of its characteristic impedance and suppression of higher-order modes. Subsequently, a parametric analysis is performed to examine the sensitivity of critical dimensions, and the study analyzes the key factors affecting the voltage standing wave ratio (VSWR) of the fixture and its 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega$</tex-math> </inline-formula> resistor. Based on the preceding analysis, two solutions are proposed to improve the VSWR: reducing the length of the 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega$</tex-math> </inline-formula> resistor and modifying the shape of the coaxial outer conductor. The ultimate outcome of the transfer impedance measurement fixture yields a VSWR lower than 2.6:1, up to 18 GHz. The functionality of the fixture is demonstrated through the measurement of two gaskets, showcasing its practical utility in engineering applications.

Optimisation of an Electrical Impedance Sensor for Use in Microfluidic Chip Electrophoresis

Label-free measurements using impedance sensing could enable microfluidic chip electrophoresis (ME) to be used in point-of-care (POC) diagnostics. However, impedance sensing methods reported in this field need considerable optimisation. GOAL: Develop a novel design process for optimising tetrapolar electrical impedance measurement (TEIM) sensor performance in ME applications through a systematic investigation a) of the impact of a TEIM sensor’s design parameters on its performance in ME and b) of the relationship between the above parameters with those of the microfluidic channel and the sample to be sensed. METHODS: 3D FEM sensitivity simulations, verified experimentally, were carried out to study the impact of sensor and channel parameters on the measured impedance and their interrelationship. Subsequently, the impact of sensor parameters on sensing a sample band’s conductivity and size was investigated. RESULTS: The impact of channel dimensions on transfer impedance measurements is significant. The non-linearity reported for transfer impedance measurement of volume conductors can be manipulated by appropriate sensor parameter design. The sensor performance can be optimised by designing electrode length and measurement electrode distance in relation to the channel height and sample band length, respectively. The sensor performance is not affected by the injection electrode distance. CONCLUSION: There is a relationship between sensor, channel and band parameters and this warrants establishing a systematic design process of TEIM sensors in ME. SIGNIFICANCE: This paper presents a novel approach to optimising the design of TEIM sensors in ME potentially providing significant performance improvements and thus allowing for label-free POC electrophoresis diagnostics.

Improved Alternative Method for Fast and Simple Transfer Impedance Measurements

The transfer impedance of coaxial cables has been under investigation for many decades. Since this parameter is highly relevant in electromagnetic compatibility (EMC) many theoretical models and various test procedures exist. The method proposed in this letter employs a direct line injection using the magnitudes and phases of two s-parameter, namely reflection coefficient and forward gain, in order to determine the transfer impedance reliably and swiftly. Extracting the transfer impedance requires little post processing and the test setup consists only of a simple adapter and the cable under test. This method also allows to account for different lengths of cables as will be outlined and does not require any alteration of the cable under test. It may be used for ready-made cables with molded, crimped or soldered connectors as well as for open-ended samples of cables. The method presented here extends the model used and the usable frequency range considerably compared to previous work on this alternative approach.

N-SrTiO3 nanoparticle/BiOBr nanosheet as 0D/2D heterojunctions for enhanced visible light photocatalytic dye degradation

A novel 0D/2D heterojunction N-SrTiO3/BiOBr (NSTO/BiOBr) was constructed by uniform dispersing of N-SrTiO3 nanoparticles on BiOBr nanosheets through a facial one-step precipitation method. All the synthesized NSTO/BiOBr composite photocatalysts with different N-SrTiO3 content were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflection spectroscopy (UV–Vis DRS), photoluminescence (PL) spectra, photocurrent response, electrochemical impedance spectra (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption. The visible light rhodamine B degradation results revealed that the formation of 0D/2D heterojunction NSTO/BiOBr results in improved photodegradation activity as compared with N-SrTiO3 and BiOBr, and NSTO/BiOBr with the 18% weight percentage of N-SrTiO3 is most effective among all the NSTO/BiOBr nanocomposites. The activity comparison of 18% NSTO/BiOBr with that of pure NSTO and BiOBr also conforms to their corresponding photoelectric response and electron transfer impedance measurements. Finally, RhB degradation mechanism over NSTO/BiOBr composite catalyst were proposed.

Evaluation of Surface Transfer Impedance of Coaxial Cables

This paper presents a set of measurements in order to experimentally study transfer impedance of coaxial cable RG 213. Both the transfer impedance (Zt) and the Shielding Effectiveness (SE) are essential in the considerations of the EMC project. In this context, this work presents a procedure to measure the transfer impedance of two coaxial cables RG 213 under the same conditions and compare the measurements with theoretical references. The results of transfer impedance (Zt) measurements and theoretical references are quantified through the Feature Selective Validation technique.

Research on Time-Domain Transfer Impedance Measurement Technology for High Frequency Current Transformers in Partial Discharge Detection of Cables

We focus on the high frequency current method which is widely applied in the partial discharge (PD) detection of cables. Aiming at guaranteeing the accuracy of this method, we study an innovative time-domain technology for effectively measuring the transfer impedance of the high frequency current transformers (HFCTs). The proposed technology called pulse injection method obtains the system response under the excitation of the wide-band instantaneous pulse signal. Firstly, by studying the working principle of HFCTs, we summarize that the bandwidth of the selected signal acquisition device should be at least 100MHz to ensure measurement accuracy. Secondly, Gauss pulse and square wave pulse are generated to determine the effects of different sources. The measurement results indicate that Gauss pulse is more suitable for pulse injection method, and the rise time should be under 10 ns to improve the starting frequency of oscillation distortion. Finally, the transfer impedance curves of five types of HFCTs are acquired by both pulse injection and traditional point-frequency methods. The measurement results show a remarkable consistency between two methods. However, pulse injection method requires the simpler operation and has a higher resolution, obviously improving the measurement efficiency and better displaying the details of the transfer impedance curves.

A lumped-element model of the chinchilla middle ear.

An air-conduction circuit model was developed for the chinchilla middle ear and cochlea. The lumped-element model is based on the classic Zwislocki model of the same structures in human. Model parameters were fit to various measurements of chinchilla middle-ear transfer functions and impedances, using a combination of error-minimization-driven computer-automated and manual fitting methods. The measurements used to fit the model comprise a newer, more-extensive data set than previously used, and include measurements of stapes velocity and inner-ear sound pressure within the vestibule and the scala tympani near the round window. The model is in agreement with studies of the effects of middle-ear cavity holes in experiments that require access to the middle-ear air space. The structure of the model allows easy addition of other sources of auditory stimulation, e.g., the multiple sources of bone-conducted sound-the long-term goal for the model's development-and mechanical stimulation of the ossicles and round window.

On Sensitivity in Transfer Impedance Measurements.

The term sensitivity is sometimes misused when discussing volume impedance measurements. This is a critique of the name of the quantity sensitivity, as well as pointing out how the term easily can be misinterpreted. To resolve the issue, a shift of focus towards volume impedance density, which is a more useful quantity, is proposed. A new parameter, perceptivity, is introduced. Perceptivity is useful tool for characterization of measurement systems, to objectively compare systems, and to formulate instrument specifications.

Transfer Impedance Measurement of Shielded Cables Through Localized Injection

This letter presents a method to determine experimentally the transfer impedance of electrically short shielded cables up to 100 or 150 MHz (depending on the cable length). The proposed method aims to create a disturbance along the cable shield with a localized injection device as for instance a toroidal magnetic probe. Two different experimental setups referred as “scalar” and “vectorial” setups are proposed. The validations are performed on cables of known transfer impedance with respect to other experimental techniques and theoretical formulations. The presented results exhibit the advantages and drawbacks of both setups with respect to the existing experimental methods.

Modified coaxial wire method for measurement of transfer impedance of beam position monitors

The transfer impedance is a very important parameter of a beam position monitor (BPM) which relates its output signal with the beam current. The coaxial wire method is a standard technique to measure transfer impedance of the BPM. The conventional coaxial wire method requires impedance matching between coaxial wire and external circuits (vector network analyzer and associated cables). This paper presents a modified coaxial wire method for bench measurement of the transfer impedance of capacitive pickups like button electrodes and shoe box BPMs. Unlike the conventional coaxial wire method, in the modified coaxial wire method no impedance matching elements have been used between the device under test and the external circuit. The effect of impedance mismatch has been solved mathematically and a new expression of transfer impedance has been derived. The proposed method is verified through simulation of a button electrode BPM using cst studio suite. The new method is also applied to measure transfer impedance of a button electrode BPM developed for insertion devices of Indus-2 and the results are also compared with its simulations. Close agreement between measured and simulation results suggests that the modified coaxial wire setup can be exploited for the measurement of transfer impedance of capacitive BPMs like button electrodes and shoe box BPM.

Phase division multiplexed EIT for enhanced temporal resolution

Objective: The most commonly used EIT paradigm (time division multiplexing) limits the temporal resolution of impedance images due to the need to switch between injection electrodes. Advances have previously been made using frequency division multiplexing (FDM) to increase temporal resolution, but in cases where a fixed range of frequencies is available, such as imaging fast neural activity, an upper limit is placed on the total number of simultaneous injections. The use of phase division multiplexing (PDM) where multiple out of phase signals can be injected at each frequency is investigated to increase temporal resolution. Approach: TDM, FDM and PDM were compared in head tank experiments, to compare transfer impedance measurements and spatial resolution between the three techniques. A resistor phantom paradigm was established to investigate the imaging of one-off impedance changes, of magnitude 1% and with durations as low as 500 µs (similar to those seen in nerve bundles), using both PDM and TDM approaches. Main results: In head tank experiments, a strong correlation (r > 0.85 and p < 0.001) was present between the three sets of measured transfer impedances, and no statistically significant difference was found in reconstructed image quality. PDM was able to image impedance changes down to 500 µs in the phantom experiments, while the minimum duration imaged using TDM was 5 ms. Significance: PDM offers a possible solution to the imaging of fast moving impedance changes (such as in nerves), where the use of triggering or coherent averaging is not possible. The temporal resolution presents an order of magnitude improvement of the TDM approach, and the approach addresses the limited spatial resolution of FDM by increasing the number of simultaneous EIT injections.

Improved design and in-situ measurements of new beam position monitors for Indus-2

Beam position monitors (BPM) are important diagnostic devices used in particle accelerators to monitor position of the beam for various applications. Improved version of button electrode BPM has been designed using CST Studio Suite for Indus-2 ring. The new BPMs are designed to replace old BPMs which were designed and installed more than 12 years back. The improved BPMs have higher transfer impedance, resonance free output signal, equal sensitivity in horizontal and vertical planes and fast decaying wakefield as compared to old BPMs. The new BPMs have been calibrated using coaxial wire method. Measurement of transfer impedance and time domain signals has also been performed in-situ with electron beam during Indus-2 operation. The calibration and beam based measurements results showed close agreement with the design parameters. This paper presents design, electromagnetic simulations, calibration result and in-situ beam based measurements of newly designed BPMs.

Uncertainties in coaxial cable transfer impedance

The Electro-Magnetic Compatibility (EMC) design of aircraft and spacecraft has to consider the shielding effectiveness of metal braids around wires and cable bundles. The EMC design is usually supported by modeling and measurement of the transfer impedance of representative samples of metal braids. In practice it turns out that results of modeling tools and measurements are not always in good agreement, in particular for the higher frequencies in the MHz region. It appears that both modeling tools and measurement methods are subject to uncertainties. The objective of the present paper is to investigate these uncertainties. Therefore, a sensitivity analysis is applied to an analytical transfer impedance model. Results indicate that the determination of the average height between the carriers of a braided shield is a critical quantity to obtain accurate transfer-impedance predictions at high frequencies. Moreover, a multi-conductor transmission line (MTL) model for the line injection method as set-up for transfer impedance measurements is presented. This MTL model is used to analyse the sensitivity of termination loads and permittivities, and to show the differences in resonance effects on transfer impedance measurements caused by impedance mismatches and by differences in propagation speeds inside and outside the coax under test. Finally, uncertainties in the measurement set-up are discussed. Finally, uncertainties in the measurement set-up are discussed. Finally, uncertainties in the measurement set-up are discussed.

Imaging fast electrical activity in the brain during ictal epileptiform discharges with electrical impedance tomography

Electrical Impedance Tomography (EIT) is an emerging medical imaging technique which can produce tomographic images of internal impedance changes within an object using non-penetrating surface electrodes. It has previously been used to image impedance changes due to neuronal depolarisation during evoked potentials in the rat somatosensory cortex with a resolution of 2 ms and <200 μm, using an epicortical electrode array. The purpose of this work was to use this technique to elucidate the intracortical spatiotemporal trajectory of ictal spike-and-wave discharges (SWDs), induced by electrical stimulation in an acute rat model of epilepsy, throughout the cerebral cortex. Seizures lasting 16.5 ± 5.3 s with repetitive 2–5 Hz SWDs were induced in five rats anaesthetised with fentanyl-isoflurane. Transfer impedance measurements were obtained during each seizure with a 57-electrode epicortical array by applying 50 μA current at 1.7 kHz to two electrodes and recording voltages from all remaining electrodes. Images were reconstructed from averaged SWD-related impedance traces obtained from EIT measurements in successive seizures. We report the occurrence of reproducible impedance changes during the initial spike phase, which had an early onset in the whisker barrel cortex and spread posteriorly, laterally and ventrally over 20 ms (p < 0.03125, N = 5). These findings, which confirm and extend knowledge of SWD initiation and expression, suggest that EIT is a valuable neuroimaging tool for improving understanding of neural circuits implicated in epileptic phenomena.

Transfer impedance simulation and measurement methods to analyse shielding behaviour of HV cables used in Electric-Vehicles and Hybrid-Electric-Vehicles

Abstract. In the power drive system of the Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs), High Voltage (HV) cables play a major role in evaluating the EMI of the whole system. Transfer impedance (ZT) is the most commonly used performance parameter for the HV cable. To analyse and design HV cables and connectors with better shielding effectiveness (SE), appropriate measurement and simulation methods are required. In this paper, Ground Plate Method (GPM) with improvements has been proposed to measure ZT. Use of low-frequency ferrites to avoid ground-loop effects has also been investigated. Additionally, a combination of analytical model with a circuit model has been implemented to simulate limitations (frequency response) of the test setup. Also parametrical studies using the analytical model have been performed to analyse the shielding behaviour of HV cables.

Measurement and modelling the sensitivity of tetrapolar transfer impedance measurements

Finite element method (FEM) modelling of a small disk in a homogeneous saline medium showed that the sensitivity distribution for tetrapolar transfer impedance measurements was dependant on the ratio, σdisk/σsaline, and not absolute conductivity values. In addition, the amplitude of the negative sensitivity regions between the drive and receive electrodes decreased non-linearly with σdisk/σsaline for σdisk/σsaline < 1, eventually becoming zero. This non-linear behaviour determined the limit of the assumption of a small change in conductivity in Geselowitz’s lead theorem with 0.5 <σdisk/σsaline <1.5 for the measurements reported. The modelling supported the design of a sensitivity measurement system using an insulating support and a metal disk in a saline filled tank. Measurements were shown to give good agreement with sensitivity predictions from Geselowitz's lead theorem. Replacing the homogeneous medium in the FEM model with layers of different conductivity parallel to the plane of the electrodes changed the sensitivity distribution when the thickness of the layers adjacent to the electrodes were less than ½ the electrode spacing. A layer of greater conductivity over a layer of lesser conductivity next to the electrodes gave a peak in the sensitivity distribution and extended regions of negative sensitivity further into the tissue.

Alternate methods for transfer impedance measurements of shielded HV-cables and HV-cable-connector systems for EV and HEV

The commonly used Transfer Impedance, ZT, measurement methods for shielded cables and connectors for high voltage applications in Electric and Hybrid Electric Vehicles might be difficult to handle and reproducibility might be low. Alternative methods to measure ZT are required. In this article, the methods, Ground Plate Method and Capacitive Voltage Probe Method are introduced. The methods do not require special setups and can handle even large cable-connector systems. Performance has been investigated by comparisons to ZT measurements using well established methods, i.e. Triaxial- and Line-Injection-Method. Performance and limitations of the proposed methods for both cable and cable-connector systems are discussed. Measurement results were compared to analytical formulas for ZT. It could have been shown that accuracy of proposed, easier to apply and more flexible alternative methods is in the same range as Triaxial- and Line-Injection-Method. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:359–366, 2016.

EN50289 동축케이블 전달 임피던스 측정 방법을 이용한 통신 케이블의 차폐 효과 분석

EN50289 동축케이블 전달 임피던스 측정 방법을 이용한 통신 케이블의 차폐 효과 분석

Correlation of Liquid Volume in Stomach to Electrical Transfer Impedance Measurements Using FIM

The present work is directed to the measurement of the absolute volume of secreted acid in the stomach using 6-electrode FIM. Stomach acid is important because it has diagnostic applications in diarrhoeal diseases and in anaemia. Through a simplified resistance model this work has predicted that the variation in (Ze-Zs)/Ze with volume of liquid in stomach should be much greater than that of Zs/Ze . The simple resistance model has also predicted that the normalised change in measured transfer impedance (Ze-Zs)/Ze will be proportional to the volume of liquid in the stomach provided the resistivity of the liquid and the depth of stomach from the frontal skin surface is constant. Both these have been verified through real life measurement on two human subjects. This means that the measured transfer impedance change can indeed be related to the volume of saline in stomach. Together with depth information obtained using anatomical markers, it may be possible to obtain the absolute volume using FIM non-invasively. DOI: http://dx.doi.org/10.3329/bjmp.v6i1.19761 Bangladesh Journal of Medical Physics Vol.6 No.1 2013 66-74