Resistance Measurement Technique Research Articles

A Low-Power Impedance-to-Frequency Converter for Frequency-Multiplexed Wearable Sensors.

We propose a low-power impedance-to-frequency (I-to-F) converter for wearable transducers that change both its resistance and capacitance in response to mechanical deformation or changes in ambient pressure. At the core of the proposed I-to-F converter is a fixed-point circuit comprising of a voltage-controlled relaxation oscillator and a proportional-to-temperature (PTAT) current reference that locks the oscillation frequency according to the impedance of the transducer. Using both analytical and measurement results we show that the operation of the proposed I-to-F converter is well matched to a specific class of sponge mechanical transducer where the system can achieve higher sensitivity when compared to a simple resistance measurement techniques. Furthermore, the oscillation frequency of the converter can be programmed to ensure that multiple transducer and I-to-F converters can communicate simultaneously over a shared channel (physical wire or virtual wireless channel) using frequency-division multiplexing. Measured results from proof-of-concept prototypes show an impedance sensitivity of 19.66 Hz/ Ω at 1.1 kΩ load impedance magnitude and a current consumption of [Formula: see text]. As a demonstration we show the application of the I-to-F converter for human gesture recognition and for radial pulse sensing.

Optimizing Thermoelectric Performance of Hybrid Crystals Bi2O2Se1-xTex in the Bi2O2X System.

In addressing the global need for sustainable energy conversion, this study presents a breakthrough in thermoelectric materials research by optimizing the Bi2O2Se1-xTex system in the Bi2O2Se/Bi2O2Te pseudobinary series. Leveraging the principles of innovative transport mechanisms and defect engineering, we introduce tellurium (Te) doping into Bi2O2Se to enhance its thermoelectric properties synergistically. With the help of various advanced characterization tools such as XRD, SEM, TEM, XPS, FTIR, TGA, LFA, and DSC, combined with relevant resistance and density measurement techniques, we conducted an in-depth exploration of the complex interactions between various factors within thermoelectric materials. We recognize that the balance and synergy of these factors in the thermoelectric conversion process are crucial to achieving efficient energy conversion. Through systematic research, we are committed to revealing the mechanisms of these interactions and providing a solid scientific foundation for the optimal design and performance enhancement of thermoelectric materials. Finally, the advantage coefficient (ZT) of the thermoelectric material has been significantly improved. The crystallographic analysis confirms the formation of a continuous series of mixed crystals with varying Te concentrations, adhering to Vegard's law and exhibiting significant improvements in electrical and thermal conductivities. The Bi2O2Se1-xTex crystals, particularly the Bi2O2Se0.6Te0.4 composition, demonstrate a peak ZT of 0.86 at 373 K. This achievement aligns with recent advancements in defect-enabled mechanisms and band convergence and sets a new standard for high-performance thermoelectrics. The study's findings contribute significantly to the ongoing quest for efficient thermal-to-electrical energy conversion, offering a promising avenue for future sustainable energy technologies.

Electrical, optical and dielectric properties of polyvinylpyrrolidone/graphene nanoplatelet nanocomposites

In this study, polyvinylpyrrolidone (PVP) nanocomposite films containing GnP in four different volume fractions (φ = 0.00, 2.00, 4.08, and 5.91) were prepared by the solution casting method. UV–Vis absorbance spectroscopy, reflectance spectroscopy, and two-point probe resistivity measurement techniques were used to examine the optical, electrical, and dielectric properties of these films. Optical band gap energies of the PVP/GnP nanocomposites were obtained using the most commonly used Tauc, Kubelka-Munk (K-M), Absorbance Spectrum Fitting (ASF), and Derivative (DM) methods. The results obtained by Tauc, K-M, and ASF methods were found to be consistent with each other. In addition, basic optical parameters such as Urbach energy (Eu), refractive index (n), optical conductivity (σopt) and dielectric constant (ε) of the PVP/GnP nanocomposites were investigated. As the GnP volume fraction increased in the nanocomposites, the electrical conductivity, Eu, n, σopt and ε increased whereas Eg decreased. These nanocomposites produced by varying the GnP volume fraction are promising for using optics, electricity, optoelectronics, and many other industrial applications.

Investigation of time variations of redox reactions in SrRuO3 through interface-sensitive resistance measurements

We used an interface-sensitive resistance measurement technique to observe the time evolution of the early stages of redox reactions at the interface between the metallic oxide SrRuO3 and a silver epoxy electrode at around room temperature (∼280–320 K). On exposure to a reducing gas (CO or H2), the interface resistance gradually increased. The time variation functions of the resistance increases for CO and H2 were similar, although the magnitude was greater for H2 than for CO. After substitution of O2 for the reducing gas, the interface resistance decreased to almost the initial value, i.e., that before exposure to a reducing gas. The resistance variations can be well explained by the time variations of the oxygen deficiency at the SrRuO3 interface and subsurfaces as a result of reduction or oxidation. We regarded the reactions as pseudo-first-order reactions and evaluated the rate constants of the SrRuO3 redox reactions at a SrRuO3–Ag interface. For the reduction (resistance increase) process, a single exponential component was enough to fit the data, which suggests that the reduction proceeds successively from outside to inside the bulk. Adsorption of oxygen atoms in the oxidation (resistance decrease) process involved several rate constants, at least up to three exponential components, depending on the prior degradation by a reducing gas. The effective activation energy of each redox reaction was evaluated from an Arrhenius plot.

Modeling and Validation Studies on Solidification of Sodium Nitrate and LiCl‐KCl

AbstractTernary alloy fuel will be used as driver fuel for future fast reactors. Reprocessing of this spent alloy fuels will be carried out by pyrochemical reprocessing which is based on molten salt electrorefining at high temperature. During electrorefining, fission products get accumulated in the electrolyte along with some actinides in the form of their chlorides. The presence of fission products in the salt will add to the radioactivity levels and hence have to be stripped off. Melt crystallization is pursued to remove fission products from contaminated salt and to reuse the purified salt for electrorefining. Numerical modeling and experimental studies on tracking the phases during solidification of molten sodium nitrate salt were carried out. The numerical predictions closely matched with the experimental results. A resistance measurement technique was developed to accurately track the solidification interface so as to validate the numerical predictions.

Electronic, nanomechanical and smart reversible phase transition behaviours of sputtered titanium oxide-vanadium oxide composite thin films

Crystalline vanadium oxide-titanium oxide (VO-TO) composite thin films of 197 nm are developed on quartz and silicon substrates by RF magnetron sputtering technique. A thorough structural investigation of deposited thin films is carried out by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. Differential scanning calorimetry (DSC) and temperature-based sheet resistance measurement techniques reveals the Smart (i.e., reversible) phase transition behaviour of VO-TO films at about 45 °C. Further selective depth analysis by XPS on the VO-TO films shows the variation of the Ti doping amount along the thickness. The top region of VO-TO thin film possess lower Ti species, while beyond 50 nm thickness from the surface possess comparatively rich Ti species. This graded Ti species along the depth also results in the variation of nanomechanical properties along the depth as confirmed by nanoindentation. The simulation through the finite element approach is also carried out to depict the experimental results of nanoindentation. The nanohardness and modulus of the presently developed VO-TO composite film were measured as 6.7 GPa and 158.7 GPa, respectively at 50 nm depth. Beyond 50 nm, nanohardness and modulus were 5.6 GPa and 116.6 GPa, respectively. Further, finite element simulation predicted yield stress value of 3.52 GPa at 50 nm depth whereas higher yield stress of 4.68 GPa was predicted beyond 50 nm.

C -axis transport in UTe2 : Evidence of three-dimensional conductivity component

The recently discvoered topological spin-triplet superconductor UTe${}_{2}$ is thought to have anisotropic electronic band structure, yet measurements of normal-state electrical transport anisotropy have remained elusive. In this study, the authors develop and employ a generalized Montgomery resistance measurement technique to fully characterize the absolute transport anisotropy of UTe${}_{2}$, finding that the $c$-axis resistivity is surprisingly not quantitatively anisotropic, but rather qualitatively different from $a\ensuremath{-}b$ plane resistivities.

Silver-coated copper particles as a new raw material for manufacturing electrical contacts

Electrical contacts were prepared from copper, silver, and silver-coated copper (Cu@Ag) powders by cold-press and sintering. Then, they were used in an electrical circuit and evaluated their performance under AC (7 A, 6000 switchings) and DC (10 A, 20 A, 200 switchings) currents. The microstructure, phase structure, thermal stability, and electrical resistance of the contacts were studied using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), and two-point electrical resistance measurement techniques. Results showed that the electrical resistance of copper contacts after 6000 switchings under AC current reaches from the initial value of 0.1 to 0.7 Ω. However, the electrical resistance of the silver and Cu@Ag contacts remained unchanged close to 0.1 Ω under the same conditions. The electrical resistance of copper contacts under 10 A-DC current increased from 0.11 Ω to 18 kΩ after 200 switchings, while the electrical resistance of the air and argon-sintered Cu@Ag contactsafter 200 switchings in the same conditions increased from 0.11 to 0.14 and 0.18 Ω, respectively. Increasing the DC current from 10 to 20 A increased the final electrical resistance of the copper contact from 18 kΩ to 35 kΩ and increased the electrical resistance of the Cu@Ag contact (sintered in air) from 0.18 Ω to 0.93 Ω after 200 switchings. Increasing the DC current from 10 A to 20 A did not affect the electrical resistance of the Cu@Ag contact sintered in argon. The study of microstructure of the contacts showed that surface of the copper contact oxidizes and cavities and micro-cracks appear on it during switchings. The Cu@Ag contacts sintered in argon were more resistant against oxidation than other contacts under switching.

Are Liquid Metals Bulk Conductors?

Stretchable electronics have potential in wide-reaching applications including wearables, personal health monitoring, and soft robotics. Many recent advances in stretchable electronics leverage liquid metals, particularly eutectic gallium-indium (EGaIn). A variety of EGaIn electromechanical behaviors have been reported, ranging from bulk conductor responses to effectively strain-insensitive responses. However, numerous measurement techniques have been used throughout the literature, making it difficult to directly compare the various proposed formulations. Here, the electromechanical responses of EGaIn found in the literature is reviewed and pure EGaIn is investigated using three electrical resistance measurement techniques: four point probe, two point probe, and Wheatstone bridge. The results indicate substantial differences in measured electromechanical behavior between the three methods, which can largely be accounted for by correcting for a fixed offset corresponding to the resistances of various parts of the measurement circuits. Yet, even accounting for several of these sources of experimental error, the average relative change in resistance of EGaIn is found to be lower than that predicted by the commonly used bulk conductor assumption, referred to as Pouillet's law. Building upon recent theories proposed in the literature, possible explanations for the discrepancies are discussed. Finally, suggestions are provided on experimental design to enable reproducible and interpretable research.

Temperature dependent striction effect in a single crystalline Nd2Fe14B revealed using a novel high temperature resistivity measurement technique

We studied the temperature dependence of resistivity in a single crystalline Nd2Fe14B using a newly developed high temperature probe. This novel probe employs mechanical pin connectors instead of conducting glue/paste. From warming and cooling curves, the Curie temperature was consistently measured around T c = 580 K. In addition, anomalous discrete jumps were found only in cooling curves between 400 and 500 K, but not shown in warming curves. More interestingly, when the jumps occurred during cooling, the resistivity was increased. This phenomenon could possibly be due to a temperature dependent striction effect induced by the re-orientation of magnetic domains well below the Curie temperature. Further microscopic study is needed to confirm this effect.

Performance analysis of constant current heated antagonistic shape memory alloy actuator using a differential resistance measurement technique

This work presents the development of a precise, constant current heating mechanism for an antagonistic shape memory alloy (SMA) actuator. The actuator was developed using a pair of SMA wires arranged in an antagonistic configuration. SMA possesses a unique phase-dependent, resistance variation property which is called self-sensing. This phenomenon is observed during thermal phase transition. A constant heating current was employed to measure combined differential resistance (ΔR) which provides insignificant hysteresis and linear relationship with displacement. ΔR eventually helps to determine the present position of the actuator for sensorless feedback control. The aim is to remove additional external sensors, reducing actuator footprint and interface complexity using the proposed study. The performance analysis of the actuator was evaluated under constant current by the tracking trajectory of reference signals. The tracking results confirmed the improvement in operating bandwidth by a reduction in displacement. The heating module mainly consisted of a low pass filter, operational amplifier with a current sense feedback mechanism that regulates the heating current in proportion to PWM signals. The result shows a significant 21% variation in the observed value of ΔR (1.200–0.254 Ω) between the major–minor loops. The study confirms linearity and maintains similarity by highest correlation 0.9508 during open-loop, which further improves to 0.9891 in close feedback reference tracking with an error band ±0.05 mm.

Progress and Monitoring Opportunities of Skid Resistance in Road Transport: A Critical Review and Road Sensors

Skid resistance is a significant feature that provides consistent traffic safety management for road pavements. An appropriate level of Skid resistance describes the contribution that the pavement surface makes to tire/road friction, and the surface of the road pavement can reduce vehicle operation cost, traffic accidents, and fatalities, particularly in wet conditions. Wet conditions decrease the level of the skid resistance (pavement friction), and this may lead to serious struggles related to driving on the road pavement (e.g., skidding or hydroplaning), which contributes to higher crash rates. The knowledge of skid resistance is essential to ensure reliable traffic management in transportation systems. Thus, a suitable methodology of skid resistance measurement and the understanding of the characterization of the road pavement are key to allow safe driving conditions. This paper presents a critical review on the current state of the art of the research conducted on skid resistance measurement techniques, taking into account field-based and laboratory-based methodologies, and novel road sensors with regard to various practices of skid resistance, factors influencing the skid resistance, the concept of the minimum skid resistance and thresholds. In conclusion, new trends that are relevant to data collection approaches and innovative procedures to further describe the data treatment are discussed to achieve better understanding, more accurate data interoperability, and proper measurement of skid resistance.

Effect of MWCNT addition on the optical band gap of PVA/CS transient biocomposites

In recent years, as a result of increasing environmental concerns, biodegradable materials have gained great attention. With the rapid development of electronic technology, the importance of innovation and development of low-cost, sustainable, transient bioelectronics materials is increasing. In this research, the preparation of Poly(Vinyl Alcohol) (PVA), Chitosan (CS), and Multi-Walled Carbon nanotube (MWCNT) biocomposite films have been described. The solution mixing, ultrasonic mixing, and spin coating techniques were used to prepare the PVA/CS/MWCNT biocomposite thin films. UV–Vis absorption spectroscopy and two-point probe resistivity measurement techniques were used to study the optical and electrical properties of the biocomposite thin films. Optical band gap energies ( Eg) of PVA/CS/MWCNT biocomposites were obtained using the Tauc and Absorbance Spectrum Fitting (ASF) methods. Results obtained with both methods were found to be exactly the same. Experimental results have shown that with increasing MWCNT concentration, electrical conductivity (σ) increases from 1.75x10−16 S to 2.94x10−3 S, and Eg decreases significantly. At the same time, the fundamental optical parameters such as band tail (Urbach) energy ( Eu), refractive index ( n), absorption ( α), and extinction ( k) coefficient of the PVA/CS/MWCNT biocomposites were investigated in the UV-VIS range. The improvement observed in the optical and electrical properties of PVA/CS/MWCNT biocomposite films shows that these composites could be used as bioelectronics materials.

Crystallographic direction related spin current transmission in MgO(001)/Fe0.79Si0.21(001)/Pt(111) epitaxial bilayers

Spin-pumping and spin-orbit torque efficiencies in ferromagnetic/heavy metal bilayers, which usually consist of the polycrystalline grains, are related to the spin current transmission from ferromagnets to heavy metals and vice versa, respectively. In this work, epitaxial ${\mathrm{Fe}}_{0.79}{\mathrm{Si}}_{0.21}(001)/\mathrm{Pt}(111)$ films were fabricated to investigate the spin-pumping efficiency and spin-orbit torque efficiency by ferromagnetic resonance and harmonic Hall resistance measurement techniques, respectively. Ferromagnetic resonance results show that the incremental magnetic damping constants in epitaxial ${\mathrm{Fe}}_{0.79}{\mathrm{Si}}_{0.21}(001)/\mathrm{Pt}(111)$, compared with those of the epitaxial ${\mathrm{Fe}}_{0.79}{\mathrm{Si}}_{0.21}(001)/\mathrm{Al}{\mathrm{O}}_{x}$ reference sample, depend on whether the external magnetic field is applied along the in-plane easy or hard axes of ${\mathrm{Fe}}_{0.79}{\mathrm{Si}}_{0.21}$. The Pt thickness-dependent anisotropic damping constant was ascribed to the anisotropic spin current absorption in epitaxial Pt(111) layer. When electric currents were applied along the easy and hard axes of ${\mathrm{Fe}}_{0.79}{\mathrm{Si}}_{0.21}$ in epitaxial ${\mathrm{Fe}}_{0.79}{\mathrm{Si}}_{0.21}(001)/\mathrm{Pt}(111)$ bilayers, a large difference between spin-orbit torques generated from Pt(111) was observed by a harmonic Hall resistance measurement method. Both of the results suggest that spin current transmission efficiency is related to the anisotropic spin Hall effect of epitaxial Pt(111) layer due to the different spin-orbit interaction energies along the different crystallographic directions of Pt.

Designing efficient soil resistivity measurement technique for agricultural wireless sensor network

SummaryThis paper presents the study and method for measuring the electrical properties of the agricultural soil using a wireless sensor network to counter the dynamic changes in electrical properties of soils under variable rainfall and flood conditions. Soil moisture and nutrients can be correlated with the resistance of soil, which is the essential electrical property of the soil. Resistivity can help us to classify different agricultural soil types and can be used for real‐time monitoring of crop fields. The diverse resistivity soil patterns may help to classify the physical, chemical and biological properties of soil. In our research work, we have taken soil from different districts of Madhya Pradesh state and classified it based on resistivity. We have also designed a low‐cost resistivity sensor module with a mathematical justification of the results. The new sensor module has been tested on different soil samples of Madhya Pradesh, and wireless sensor network (WSN) has been proposed to collect and process the data for application in the agriculture fields. The paper also describes the challenges and the various methodologies for the measurement of soil resistivity and moisture using the Internet of Things (IoT) architecture.

Room-temperature reduction at SrRuO3–metal interface in hydrogenous atmosphere detected by interface-sensitive resistance measurement

Using interface-sensitive resistance measurement techniques, we detected the reducing reaction precursor at the interface between the metallic oxide SrRuO3 and the electrodes under a hydrogenous atmosphere at room temperature. The interface resistance between this polycrystalline oxide and the electrodes (metallic pads or wires) clearly increased with the hydrogen present even at room temperature. In contrast, for bulk SrRuO3, no increase in resistance was found. The rate of increase of the interface resistance depends on the electrode material, for example, that of SrRuO3–Ag is larger than that of SrRuO3–Cu, and the rate is related to the propensity for bulk oxide to reduce; Ag2O is easier to reduce than CuO. The origin of the increase in interface resistance is posited to be the partial deficiency of oxygen in SrRuO3. Our experiments suggest that the reduction at the interface of SrRuO3 occurs at relatively low temperatures (room temperature) compared with the bulk reducing temperature of ≈200°C previously reported. In addition, electrode materials control the reducing reaction at the interface.

Oxygen diffusion study in manganite films near room temperature

In this report we have studied the resistance relaxation due to oxygen diffusion around room temperature into the perovskite oxide manganite film of two different classes of paramagnetic insulating system. One (Y0.5Ca0.5MnO3) has ∼2.3 times larger A-site cationic disorder than the other (La0.85Sr0.15MnO3). Both are grown on LaAlO3 (LAO) substrate. Electrochemical method has been used to oxidise the film surfaces at room temperature and isothermal resistance measurement technique was applied to study the dynamic motion of oxygen diffusion. Experiment shows that Debye/non-Debye diffusion factor is inversely temperature dependent i.e. temperature increment helps non-Debye process. Non-Debye process is favourable in less A-site cationic disordered system.

Delineation of Heavy Mineral Bearing Placers by Electrical Resistivity and Radiometric Techniques Along Coastal Odisha, India

The distribution of heavy minerals in the beach placer deposits of the eastern coastal areas of India is investigated using electrical resistivity and radiometric methods. A combination of electrical resistivity and radioactivity measurement techniques was utilized for the first time to delineate heavy mineral bearing zones along the beach. The objective of this study was to delineate the spatial and vertical extension and also to locate the existence of concealed pockets of heavy minerals. A total of seven resistivity and radioactivity profiles, both parallel and perpendicular to the coastline, were measured. The radiometric measurements were performed both in the field and in the laboratory using a portable Geiger-Muller (GM) counter and a high-purity germanium detector (HPGe), respectively. A zone with inverted resistivity values from 0.1 to 1.1 Ωm and depths extending to approximately 20 m from the surface was interpreted as the heavy mineral bearing zone. The surficial exposures of heavy mineral bearing placers were located by integrating the results of the resistivity and radiometric techniques. The zones with high conductivity and high radioactivity values were identified as the heavy mineral bearing placers containing monazite. Good agreement was observed between the resistivity and the radioactivity data for the very shallow deposits of heavy mineral placers. In general, the area shows a patchy distribution of heavy minerals along the coast.

The Slice-Resistivity method to measure the chloride ion diffusion coefficient of cementitious materials

Most of the existing experimental and research methods for the diffusion of chloride ions in cement-based materials use an applied electric field test method with electrodes, which are unable to eliminate the effect of polarization. In this study, the relationship between resistivity and chloride ion diffusion coefficient (CIDC) is established by the Nernst-Einstein equation. Based on the non-contract electrical resistivity measurement technique, the resistivity of cement-based material is measured by the Slice-Resistivity method, in which the chloride ion diffusion coefficient can be obtained with no polarization effect. In the experiments undertaken, the chloride ion diffusion coefficients of samples with 0.3, 0.4, 0.5 water-cement ratios and aggregate volume fractions of 12%, 22% were calculated at 3, 7, 14 and 28 days ages. It was found that the size of the slices has no influence on the results; however a decrease of the water-cement ratio as well as an increase of aggregate volume would lower the chloride ion diffusion coefficient. According to the experimental results and the Bruggeman model, a new general equation describing the relationship between w/c, curing time, aggregate volume and the chloride ion diffusion coefficient is proposed. In addition, simulation based on the homogenization method is applied to predict the equivalent chloride ion diffusion coefficient of the samples added aggregate. The results show that the simulation results are consistent with the experimental results, especially for 14 and 28 days.

Identification of aquifer layer using method of geo-electric resistivity in Tampabatu Village, Ampana Tete Sub-districts

The study was conducted using geo-electric method to identify the groundwater aquifer layer and depth which is below the surface based on the resistivity value. The purpose of this research is to know the aquifer which is identified by 3 point of measurement expanse. The research method used is geo-electric resistivity method and measurement technique used is Vertical Electrical Sounding (VES) with Schlumberger configuration. Data processing using Progress Version 3.0 software is performed to obtain the distribution of the earth surface subsurface type resistance. Based on the results obtained aquifer coating on the resistivity value ranged from 30 Ωm-58 Ωm with the value of formation factor 2-3 which is a free aquifer layer and aquifer medium. The aquifer layer is detected at a depth of ± 12.08 m up to ± 100 m below ground level (bgl).