Electrical Measurement Method Research Articles

Electrical measurement method of static friction force on rough surface

Friction plays a key role in the assessment of the safety and stability of mechanical systems (such as superconducting magnet quench explosion, aerospace vehicle bearing wear, etc.). Due to the closeness of the interfaces in engineering structures and the randomness of the contact surfaces, existing methods for measuring static friction force are unable to measure it at the contact interfaces of engineering structures under service conditions. In this paper, a new method for measuring the static friction force at the interface based on electrical signals is proposed. This method enables the measurement of the static friction force at interfaces of complex engineering structures under service conditions solely through electrical signals. The results indicate that the contact resistance gradually decreases with the increase in tangential load during the static friction stage until a monotonic behavior of macroscopic sliding occurs. The evolution of contact resistance is linked to the evolution of the real contact area, and this monotonic behavior can be explained as the deformation form of contact points. The accuracy of the proposed electrical measurement method is verified by comparison with experimental results (with an error of less than 9%). The indirect measurement method of friction force proposed in this paper can effectively measure the static friction force at the interfaces of engineering structures under service conditions, and it is expected to be applied to the detection of friction performance at engineering structure interfaces in extreme service environments.

Photodetector array for measuring the spatial–temporal distribution characteristics of electric field in oil–pressboard insulation based on the Kerr electro‐optic effect

AbstractAccurate measurement and effective analysis of the space electric field and charge characteristics within the oil–pressboard insulation structure of converter transformer are essential for achieving precise insulation structure design. Presently, most electric field measurement methods relying on the Kerr electro‐optical effect are limited to single‐point measurements. Given the complexity of converter transformer insulation structures, including their large scale and the use of various materials, existing technologies and findings struggle to provide comprehensive electric field observations within the oil–pressboard region. After leveraging the Kerr electro‐optic effect, a high‐precision 32‐unit photodetector array has been developed to achieve regional measurements of spatial‐temporal electric field in oil–pressboard insulation. The array boasts a measurement spatial resolution of 1.4 mm2 and a sensitivity of 0.15 kV/mm, ensuring measurement accuracy exceeding 96.50%. Through practical measurements of the spatial electric field distribution within the oil–pressboard insulation under direct current voltage, the non‐uniform distribution of the electric field is effectively captured in oil. Notably, the maximum deviation in field strength at different positions within the transformer oil can reach 18.5%. Moreover, as the applied voltage increases, the unevenness coefficient of the field strength gradually rises, peaking at 1.19, which signifies a progressive expansion in the area affected by electric field distortion. By conducting tests to assess the dispersion of volume resistivity in samples from various positions within large sheets of pressboard, the variation in volume resistivity of materials is posited as one of the contributing factors to the non‐uniform distribution of electric field within the oil. The detailed accomplishments aim to provide essential technical and theoretical support for optimising insulation structure design of converter transformers.

Temperature rise detection in GaN high-electron-mobility transistors via gate-drain Schottky junction forward-conduction voltages

An electrical measurement method for the junction temperature and thermal resistance of GaN high-electron-mobility transistors (HEMTs) is discussed. It is based on the forward voltage drop across the gate-drain Schottky diode. During measurement of this temperature-sensitive parameter, the source is left floating while the drain is grounded. Previous studies have shown that the hot spot in GaN HEMTs is near the gate side, close to the drain. The forward voltage drop across the gate-drain diode yields higher and more consistent temperatures relative to those using the forward voltage drop across the gate-source Schottky diode. This method could potentially provide more accurate data for thermal management and reliability analyses of GaN-based HEMTs. The maximum temperature of the sample was 44.8 °C on the grate-drain side and approximately 40.5 °C on the gate-source side when the sample exhibited 3.44W thermal power consumption for 1 min. Hence, the proposed method is practical and instructive.

Non-destructive characterization of pore structure and chloride diffusion coefficient of cementitious materials with modified non-contact electrical resistivity method

The intricate pore structure of cement-based materials passively influences chloride ion transport and mechanical properties. Existing non-contact electrical resistivity measurement (NC-ERM) methods lack precision for rigorous studies. the NC-ERM was upgraded in this research, which is suitable for assessing the pore structure and transport characteristics of hardened cementitious substrates. The results obtained from this method closely correspond to those obtained from CEMHYD3D, Mercury intrusion porosimetry (MIP), and other methods. Additionally, the impact of mixture proportions on the resistivity, pore structure parameters, and chloride ion diffusion coefficient of cementitious materials is discussed. With an increase in sand ratio and sand-to-stone ratio, the resistivity exhibits an initial rise followed by a decline. Chloride diffusion of 5 wt% NaCl-saturated specimens is 1.2–1.3 times higher than 3.5 wt% NaCl. This study provides a novel non-destructive, convenient and accurate method for characterising the pore structure and testing the transport properties of cementitious materials.

Dual resistance Janus PDA/patterned PVDF membrane for membrane distillation with early wetting detection using electrochemical impedance spectroscopy

Membrane distillation (MD) is highly efficient in separating and removing water pollutants; however, it is susceptible to membrane wetting and fouling especially when treating low-surface tension pollutants such as oils and surfactants. To address these limitations, we fabricated a Janus polydopamine (PDA)/patterned polyvinylidene fluoride (PVDF) membrane with anti-wetting and anti-fouling properties via non-solvent- and vapor-induced phase separation. In the MD test with a NaCl feed solution with hourly sodium dodecyl sulfate injection, the Janus membrane with the hydrophobic patterned PVDF layer significantly delayed membrane wetting with only a slight trade-off in flux - an 8.6 % decrease in water vapor flux. Also, in the MD test using a NaCl feed solution containing 1000 mg L−1 of canola oil, the hydrophilic PDA layer of the Janus membrane effectively prevented the interaction between oil and the membrane surface. The wetting progression of the Janus membrane was systemically monitored using electrochemical impedance spectroscopy to identify the mechanism of its wetting behaviour and to detect and analyse the different wetting stages (i.e., non-wetting, partial wetting, and full wetting). Therefore, unlike conventional electrical conductivity measurement methods, the wetting front estimated using EIS enabled a more precise wetting detection during the DCMD operation.

On-line monitoring of membrane fouling based on an improved electrical measurement method.

On-line monitoring of membrane fouling is essential in the water treatment process. Drawbacks such as low-sensitivity and off-line limitations limit the application of existing methods. An on-line monitoring method based on Electrical Resistance Tomography (ERT) sensors is put forward in this paper. The Particle Swarm Optimization with Simulated Annealing (PSO-SA) algorithm is used in optimizing the topologies of finite element models in order to decrease the ill-posedness of sensitivity matrices. The deep denoising extreme learning machine with an auto-encoder model and the K-singular value decomposition algorithm are used in ERT reconstruction to improve imaging quality. The lift-wavelet is adopted in measuring the permeate flux to improve measuring accuracy. The ERT pixel values of the membrane module and the result of flux are used to analyze the fouling status. The results of membrane fouling experiments demonstrate the following: (1) Based on the local ERT pixels, the "two stage" phenomenon of membrane fouling can be observed. (2) In the early stage, the fouling distribution of the localized membrane module is consistent with its ERT pixels. (3) The deposition process of foulants for the localized membrane module is synchronized with the variation of ERT pixels. (4) The integrity of the membrane module can be detected according to the ERT pixels. Therefore, the novel method can effectively reflect the membrane fouling process, especially in the early stages of membrane fouling.

Status of X-ray Acoustooptics at the Institute of Microelectronics Technology Russian Academy of Sciences

The electrical measurement method, scanning electron microscopy method and high-resolution X-ray diffraction method have been used to investigate the process of the surface acoustic wave (SAW) propagation in a LiNbO3 ferroelectric crystal. Measurement of the amplitude-frequency response provides information on the losses in the acoustoelectronic device during the process of the SAW propagation. The scanning electron microscopy method permits to visualize the SAW on the surface of piezoelectric crystals in the real-time mode and to observe diffraction phenomena in acoustic beam. The X-ray diffraction method is sensitive to the crystal lattice distortions by surface acoustic wave and allows determining the SAW amplitudes.

Application of the van der Pauw method for electrical conductivity measurements at high temperatures using an insulating compressing ring.

High quality data on the high temperature electrical properties of ceramics, particularly oxides, is of great value for material selection, design, and modeling for a broad range of emerging applications. Utilizing the mismatch in the coefficient of thermal expansion between two materials, a purely mechanical method for establishing electrical contact in the van der Pauw geometry to measure the bulk resistivity of ceramic disks at high temperatures is presented. Measurements of a reference material, 20 mol. % Gd-doped cerium oxide, are presented up to 1000 °C. The viability of electrical measurements up to a maximum temperature of 1600 °C is also considered. Measurements are performed using multiple techniques and compared to literature values finding excellent agreement. The approach described in this work enables the van der Pauw method to be applied to many ceramic materials over a wide range of temperatures and environments.

Verification of the Electrical Impedance Method for Measuring the Humidity of Silicate Material

Measuring humidity in building materials is of great importance in assessing the condition of materials and also in building diagnostics, as the presence of humidity affects their physical and thermal insulation properties. In the construction industry, the use of non-destructive electrical measurement methods for testing the physico-chemical properties of materials is common and especially the electrical conductivity of materials is significantly affected by humidity.

Trajectory monitoring method based on optical sensing spectral energy and adaptive threshold

Distributed optical fiber sensing technology is widely used in structural health monitoring, security systems and other fields. The traditional monitoring method of electrical measurement can ensure monitoring accuracy of train trajectory, while this method is easily affected by thunderstorm weather. In order to simultaneously improve the anti-interference ability and monitoring accuracy, this paper proposes a trajectory monitoring method based on optical sensing spectral energy and adaptive threshold. This method only needs to monitor the backward Rayleigh scattering optical signal of a redundant communication fiber, and perform Fourier transform and spectral energy operation to analyze vibration signals of the entire line. An adaptive threshold algorithm is utilized to autonomously locate fiber position of the train and form a spatial–temporal trajectory map. The method proposed in this paper is a passive monitoring method using optical sensing, which greatly improves system’s ability to resist electromagnetic interference, reduces the monitoring cost of the entire system, and effectively ensures the positioning accuracy. Experimental results demonstrate the effectiveness, safety, and accuracy of the train trajectory monitoring method based on optical sensing spectral energy and adaptive threshold.

Influence of Overlying Strata Movement on the Stability of Coal in Fully Mechanized Top-Coal Caving Mining

Overlying strata movement has an important effect on the stability of coal along goaf. In order to study the impact of overlying strata movement on the stability of coal during fully mechanized top-coal caving mining, a simulation experiment was conducted on the Liuxiang Coal Mine using digital image correlation (DIC) and stress electric measurement methods. The characteristics of overlying strata movement, stress concentration and deformation evolution of coal, and interlayer sliding between coal and rock are analyzed. The following conclusions could be drawn. The movement of overlying strata can be classified into two stages: the first stage is characterized by vertical displacement, while the second stage is characterized by horizontal displacement. In the first stage, the vertical movement of overlying strata causes the vertical stress concentration of the coal. In the second stage, the horizontal movement causes frictional sliding between coal and rock, which produces a shearing effect on the coal. Under these two effects, the coal along goaf gradually reaches its strength limit, and local deformation occurs, and the micro-cracks are further concentrated and fused in this area. When macro-cracks are formed, occur and expand unstable, the elastic energy is released suddenly, which will lead to dynamic disasters such as rock bursts.

Fabrication of silver/silver-tetracyanoquinodimethane heterogeneous nanowires using nanoskiving method

In this study, silver/silver-tetracyanoquinodimethane nanowires with excellent microstructure quality are prepared by combining the nanoskiving method with the solution reaction method, and their electrical properties are tested. The perpendicular cutting direction and larger cutting thickness are beneficial to the acquisition of complete and less deformed silver nanowires. Silver/silver-tetracyanoquinodimethane heterogeneous nanowires can be precisely prepared at small droplet concentration, small droplet volume, and 60 s reaction time. The continuity, dimensions, and formation mechanism of nanowires are characterized by atomic force microscope and scanning electron microscope. Raman spectroscopy and transmission electron microscope revealed the successful formation and core-shell structure of silver-tetracyanoquinodimethane nanowires. The electrical properties of silver/silver-tetracyanoquinodimethane heterostructure nanowires show a typical Schottky barrier using a two-point electrical measurement method. This work lays a solid foundation for promoting the engineering application of silver nanowires and silver/silver-tetracyanoquinodimethane heterogeneous nanowires.

Yeraltı Raylı Sistem İnşaatlarındaki Jeoteknik İncelemeler ve Geoteknik Uygulamalar: Halkalı-Yeni Havalimanı Metro Hattı Örneği

In this study, geological researches carried out before the construction of underground rail systems and geotechnical application methods preferred during the construction were examined within the scope of Halkalı-İstanbul Airport metro project. The metro line consists of a total of 66.2 km long underground tunnels, 31.3×2 km main line and 1.8×2 km repertorium connection line. 1006 soil and 1230 rock samples were collected for the main line whose geological research was carried out with 198 core drillings with a total length of 9588.5 m. The results of the laboratory tests on the samples and the field tests carried out in the boreholes were obtained. In addition, a total of four two-dimensional inverted solution resistor underground sections were obtained by using the Multiple Electrode Electrical Resistance Tomography measurement method in the middle of two lines (Line-1 Km. 61+440 – 61 +660 /Line-2 Km: 61 +400 - 61+620), in the Olympic Stadium station (Km: 62+215 – 62 +490) and in the TBM route (Line-2 Km: 62 +835 – 63+050). The geological sections obtained from the drillings and the geophysical sections obtained by the electrical resistivity method were compared.

Measurement Technique and Result Analysis of Helicopter Rotor Blade Structural Vibration Load

The measurement of helicopter rotor blade structural load amid flight has always been the difficulty in flight test. In this paper, the principle of the existing blade structural load measurement method (electrical measurement method) was analyzed, and the problem of physical decoupling in the use of this method was expounded. As a weak signal measurement, the electrical measurement method also has electromagnetic interference problems, which will affect the flight test period of blade structural load measurement. Therefore, a numerical decoupling measurement method based on fiber Bragg grating (FBG) was proposed. Then, the new method was applied and verified in the load equation modeling test and the flight test under the real atmospheric environment was carried out. Through comparing and analyzing the measured data of the new method and the electrical measurement one, the correctness of the FBG data decoupling method was validated. The results indicate that the method proposed in this paper can effectively improve the efficiency of blade load equation modeling engineering and has good application value.

Study on structural damage evolution of excavated slope subjected to earthquake and rainfall using electrical resistivity measurement

Earthquake and rainfall are two major factors contributing to the slope failures. To examine the evolution of slope structural damage and the failure mechanism during the shaking and rainfall process, a model test of excavated slope subjected to earthquake and rainfall has been performed. The evolution of structural damage within the slope is considered as the changing process of porosity and crack development. The unique relation between of porosity and resistivity of unsaturated soil is utilized to reveal the spatial-temporal variation of slope structural damage by electrical resistivity measurement method. The testing results show that the shaking induced cracks appear on the surface of upper soil layer at the mid-height of slope model, and the structural damage could be both accumulated on the surface and inside the slope under seismic motion. The damaged area provides preference infiltration path for rainwater flow in the following raining process, resulting in the rapid increase of water content of slope interior. The sliding body extends and develops upwards to the slope crest under rainfall condition. The failure patten suggested by the structural damage parameter is verified by the dynamic response of slope model. The structural damage parameter using resistivity is able to show the spatial-temporal evolution of structural damage inside the slope quantitatively, and reflect the porosity change of soil under continuous earthquake and rainfall conditions. The evolution of structural damage reveals that the dynamic failure mode of excavated slope under earthquake and rainfall is the upwards-developed retrogressive sliding of upper soil layer. The evaluating method using resistivity measurement is particularly promising for field test of slope where it can be used to monitor the structural damage change of soil mass subjected to complex environment conditions.

A New Electrical Resistance Measurement Method of Carbon Fiber-Reinforced Polymer Tubes Based on C⁴D Technique

This work introduces the capacitively coupled contactless conductivity detection ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{C}^{{4}}\text{D}$ </tex-math></inline-formula> ) technique into nondestructive testing (NDT) of carbon fiber-reinforced polymer (CFRP) and proposes a new resistance measurement method of CFRP tubes. The proposed method does not require direct contact between the electrodes and the carbon fiber. Therefore, the electrical resistance of CFRP can be measured without the treatments required by traditional electrical methods that may lead to surface or structural damage. The equivalent circuit model of the new method is established, and the challenges are analyzed. Simulation and experiment are conducted with woven fabric CFRP tubes to verify the feasibility of the proposed method, including the range of workable frequency, the effectiveness of the circuit model, and the capability of damage detection. Research results show that a relatively high working frequency is required to accurately measure the interested resistance and sense the resistance change. By selecting a workable frequency, the effectiveness of the circuit model is verified. Research results indicate that the stray capacitance between the electrodes has little effect on resistance measurement, and the capacitor–resistor–capacitor model is still applicable. Research results also verify the feasibility of the proposed method for damage detection. It is able to sense the resistance change resulted from the damage of CFRP, either the conductivity changes in simulation or actual cutting damage in experiment.

Resistance-frequency eddy current method for electrical conductivity measurement

In eddy current measurements of electrical conductivity, adverse effects from lift-off effects are inevitable, especially for relatively large lift-offs. In this work, a new method of electrical conductivity measurement, the resistance-frequency eddy current method, is proposed. The method uses an LC resonator as the measurement probe and characterizes the conductivity of the measured material by exploiting the physics that the ratio of the resonant frequency to the resonant resistance of the probe is linearly related to the logarithm of the conductivity. Furthermore, a two-dimensional resistance-frequency plane (RF plane) consisting of resonant frequency and resonant resistance is established. The resistance frequency lift-off curves in the RF plane have good linearity in the med-high lift-off range, which can be used to eliminate lift-off effects. Experimental results show that the proposed method can perform conductivity measurements in the med-high lift-off range of 1 mm to 2.5 mm independent of lift-off, with relative errors within 5 %. Therefore, the proposed method is particularly suitable for conductivity measurements in the med-high lift-off range, especially for metallic materials with thicker surface coatings.

A Novel Transient Electric Field Measurement for Low Kerr Constant Liquid Dielectrics Based on Concave Spherical Mirror Conjugate Structure

This article proposes a Kerr effect electric field measurement method based on a concave spherical mirror conjugate structure (CSM CS) for a transient electric field in low Kerr constant liquid dielectrics. The accuracy of transient electric field measurement can be greatly improved in a limited space by multiple small-angle reflections. To verify the effect of the proposed structure, the electric field distribution is measured in propylene carbonate (PC) with a high Kerr constant at a switching overvoltage. The measurement results show that the electric field error of a PC under an extremely low electric field is only about 2%. The novel structure improves the electric field measurement accuracy of a liquid with a high Kerr constant. Then, the whole device is applied to the transformer oil, and the accuracy of the measured electric field is also greatly improved. At the same electrode size, the sensitivity of measuring the electric field with the proposed structure is three times that without it. The analysis results show that the introduction of the proposed structure has little effect on the electric field measurement. The proposal and application of the proposed CSM CS further expand the electric field measurement range based on the Kerr effect and improves the electric field measurement accuracy.

Trampoline-Shaped Micro Electric-Field Sensor for AC/DC High Electric Field Measurement

The measurement of high electric field is widely used in applications such as power grid, electrical equipment, space launch, petroleum industry, and meteorological monitoring. Traditional electric field measurement methods, such as field mills, are bulky and cause electric field distortion. In this article, we presented a trampoline-shaped microelectric field sensor (E-sensor) based on microelectromechanical system (MEMS). The micro E-sensor uses the effect of electrostatic induction, which generates force that drives the vibration of a piezoresistive film and converts the electric field into a differential voltage signal. The presented E-sensor can measure both ac and dc high electric fields with relatively high resolution and wide range. Through experimental measurement, the device exhibits an ac resolution of 172 V/m/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> and a linear measurable electric field range of 312 V/m to over 700 kV/m. The presented E-sensor has good performance with mm-level size and low cost, which could be mass produced for broad applications.

Estimation of Electron Density and Temperature by Continuum Spectrum in a Moving Atmospheric-Pressure Nonthermal-Equilibrium Argon Plasma Bullet

A moving atmospheric-pressure nonthermal-equilibrium argon plasma bullet was investigated by emission spectrum and plasma current. Moving plasma changes spatially and temporally. Therefore, it is necessary to consider the time variation of plasma in measurement. Thus, the validity of the electron density estimated by the two types of optical and electrical measurement methods was examined. The electron density and temperature are estimated from the analysis of continuum spectrum (CS). Moreover, the electron density was also estimated from the relationship between the current and the propagation velocity of the plasma luminescence. The plasma current was estimated from the power-line currents with and without plasmas. The propagation velocity of the plasma luminescence was measured by applying the time-of-flight (ToF) method on the observed emission intensity. The electron density estimated from the analysis of CS is comparable to that estimated from the effective peak plasma current. Consequently, the analysis of CS is applicable to a moving plasma bullet.