Two-channel impedance spectroscopy for the simultaneous measurement of two samples

We describe a dielectric relaxation technique, which allows one to obtain a very accurate comparison of the behavior of two different samples. The key feature is the simultaneous impedance measurement on two capacitors that can share a common center electrode, implying that the same voltage is applied to both samples and that only a single gain/phase analyzer is required. The capabilities of this technique have been examined by comparing the dynamics of protonated and deuterated 1-propanol samples using this dual-channel analyzer in the frequency range of 10(-2)-10(6) Hz and in the temperature range of 110-160 K, after calibrating the system using the same sample in both, channel 1 and channel 2. For many supercooled liquids, the high sensitivity of the dielectric relaxation behavior on temperature prevents a meaningful comparison of nearly identical dynamics on the basis of two separate measurements. Based on this dual-channel method, we observe that a deuterated 1-propanol sample displays small but systematic deviations from the relaxation spectra of its protonated counterpart, which would not be observable in separate dielectric measurements. Many other applications can be envisioned where simultaneous or differential impedance measurements are advantageous.     

Note: electrode polarization of Galinstan electrodes for liquid impedance spectroscopy

Electrode polarization is a significant obstacle in the impedance measurements of ionic liquids. An atomically smooth electrode surface could potentially reduce unwanted impedance contributions from electrode polarization. Liquid metal electrodes were formed by adhering Galinstan to acrylic plates in a parallel-plate capacitor arrangement. Electrode polarization was compared to a similar cell with stainless steel electrodes. The impedance of salt and protein solutions (β-lactoglobulin) was measured from 40 Hz to 110 MHz. Because of oxide layer formation, the performance of the Galinstan electrode is significantly different than the theoretical ideal.     

Inductive impedance transducer for recording displacements of ferromagnetic and nonferromagnetic conductive objects

The paper describes an inductive magnetic transducer for on-line recording of translations and vibrations. The transducer consists of an iron cored sensor coil and simple accompanying circuitry. The main features which are peculiar to the present transducer are (a) facility for linearizing the voltage versus displacement characteristic for certain regions of distances, (b) ability to measure vibrations and translations of both ferromagnetic objects and nonferromagnetic conductive objects, (c) relative simplicity of circuitry, and (d) the fact that only passive components are used for the transducer and an output voltage enhancement is attained by the employment of resonance. The paper is introduced by a comprehensive review of various types of magnetic transducers.     

Alternating current impedance spectroscopy measurement under high pressure

A microcircuit was designed and fabricated on a diamond anvil cell for alternating current impedance spectroscopy measurement under high pressure. Sputtered molybdenum film on a diamond anvil was used as an electrode, maintained the contact between the sample and the electrode stable, and reduced the electrode effect on the impedance measurement. By the empty cell and short circuit tests, the parasitic capacitive impedance from the sample chamber wall was observed to be larger than 10(5) Ω at a frequency lower than 1.0 MHz and could be ignored for samples with higher conductivity. The wire inductance was only 1.0 μH and just appeared at frequency higher than 20 kHz, which could be subtracted from measured impedance for the samples with higher impedance than several hundred ohms. Using this apparatus, the impedances of the II-VI group cadmium sulfide were measured. The pressure dependence of the grain interior conductance of CdS crystal was obtained, which reflected that the phase transitions of CdS under high pressure are the same as the single crystal measurement results.     

导电板上方涡流检测探头阻抗的快速计算与仿真

采用一种基于Maxwell方程组、矢量磁位和空间解域截取的级数展开快速计算方法,导出级数形式的导电板上方通电线圈阻抗变化表达式;通过设定适当的解域截取半径和级数求和项数,可以在保证计算精度的同时提高计算速度。在多种线圈激励频率下,分别采用级数展开法与有限元仿真法,对线圈的阻抗变化进行了计算,两种方法的计算结果非常吻合,相互验证了两种涡流检测计算模型的正确性。     

Characterization of thermoelectric elements and devices by impedance spectroscopy

This article describes a new measurement technique that utilizes impedance spectroscopy for the characterization of thermoelectric materials and devices. Two circuit models were developed and used to help explain the impedance spectroscopy data using transmission line theory and a coupled electrothermal model. Two testing configurations have been investigated including one based on a sinusoidal source (ac lock-in technique) and one based on a pulsed wave source. Methods for reducing the measurement times for this technique are discussed. In addition, the influence of radiation losses on this measurement technique has also been analyzed to further understand the limitations of this technique at higher temperatures.     

Novel impedance cell for low conductive liquids: determination of bulk and interface contributions

A plane capacitor cell with variable gap has been designed in order to detect the complex permittivity of low conductive liquids (up to 500 microS/cm) and the impedance of the sample-electrode interface. The novelty of the cell consists of the simultaneous presence of the field uniformity ensured by a guard ring, an adjustable gap between 300 microm and 6.75 mm (the electrode axial motion avoiding any rotation), and the immersion of the capacitor in the sample reservoir. The size of the capacitor electrodes and the gap values have been tested via the capacitance detection of the in-air cell at 1 kHz. The sample measurements have been performed by scanning the frequency range between 15 Hz and 2 MHz at four different capacitor gap values. In the paper a method to directly extract the bulk complex permittivity and the interface impedance versus frequency is presented. It is based on the assumption that the interface contribution is independent of the electrode gap, as confirmed (within the measurement accuracy) from measurements on all samples investigated. As samples of interest, we have chosen two certified electrolytic conductivity standards, KCl aqueous solutions having conductivity traceable to SI units; and two polymer latex aqueous dispersions of microspheres. Regarding KCl solutions, the conductivity measurements are compatible with the reference values within the specified uncertainty; the measured permittivities are consistent with the literature. For all samples, we have recovered the expected result that the interface impedance mainly affects the low frequency range (f<10 kHz).     

Temperature-stable parallel-plate dielectric cell for broadband liquid impedance measurements

A liquid impedance cell for broadband impedance measurements up to 110 MHz is presented. The design incorporates temperature control and minimizes parasitic capacitance and inductance. The cell is simple to fabricate and uses chemically resistant materials, stainless steel, and Teflon. This dielectric cell can be used in a variety of liquid measurements, particularly those related to impedance measurements of biological objects in solution. Temperature control is illustrated in measurements of the permittivity of deionized water from 5 to 55 °C. Numerical fitting procedures employed on the relaxation curves indicate good agreement with previous studies on beta-lactoglobulin and hen lysozyme. Titration capability is demonstrated through dielectric titration of hen lysozyme and beta-lactoglobulin.     

Spatially resolved low-temperature spectroscopy on niobium bulk samples

Using a low-temperature STM, simultaneous measurements of the surface topography and of spatial variations in the current-voltage characteristics have been performed on poly-crystalline niobium bulk samples. A special electronic set-up was developed which allows the tip bias to be swept at a constant tip position. From the resulting I(V) curves the actual magnitude of the superconducting energy gap is derived. The comparison of the surface morphology and gap distribution permits the detection of possible correlations between local variations in the superconductivity and in the topography. Upon the application of an external magnetic field, local variations of the gap are observed which have no topographic counterparts. This latter observation might indicate the existence of isolated vortices.     

A dual analyzer for real-time impedance and noise spectroscopy of nanoscale devices

This paper introduces a simple portable dual analyzer which allows real-time ac-impedance measurements and noise spectroscopic analysis simultaneously, employing one or two data acquisition systems together with a low noise current-to-voltage preamplifier. The input signal composed of numerous selected frequencies of sinusoidal voltages with a dc bias was applied to a device under the test (DUT): single walled carbon nanotube field effect transistors (SWCNT-FETs). Each frequency component, ranging from 1 to 46.4 kHz, was successfully mapped to a Nyquist plot using the background of the electrical noise power spectrum. It is, thus, clearly demonstrated that this dual analyzer enables the real-time ac-impedance analysis and the frequency response of the carrier transport in the SWCNT-FETs as a DUT.     

Assessing the tribocorrosion behaviour of Cu and Al by electrochemical impedance spectroscopy

This study is focused on the interests and limits of Electrochemical Impedance Spectroscopy, to establish the electrochemical behaviour of a tribosystem between Cu and Al, in acid solution. The calculated capacitance, in high-frequency range, partially allows understanding the double layer state of body in the contact. The Potential of Zero Charge (PZC) was calculated for Cu sample and it was associated with a potential range for Al. PZC value of each material is discussed as a key parameter of sliding contact. During tests of wear, the EIS results are related to the evolution of adsorbed water molecules.     

基于太赫兹波谱的液体极性测量

太赫兹波能与极性液体的氢键发生强烈的共振吸收作用,分子极性越大,吸收作用越强。基于此特性,在0.2～1.0 THz波段利用太赫兹时域光谱技术对甲醇、乙醇、正丙醇、正丁醇四种一元醇液体的极性进行检测研究。根据测量得到的四种液体太赫兹波谱数据,得出了液体的极性与其太赫兹波谱的关系式,再利用此关系式求得四种液体的计算值。通过对四种液体极性的标准值和计算值比对,验证了所得液体极性求取公式的有效性。研究结果表明,四种不同液体的时域光谱因分子的极性差异有显著的不同,所用的液体极性测量方法能够对液体的极性进行快速有效的检测与鉴别,可为其他液体极性的检测提供参考。     

Design and analysis of flow measurement of conductive liquid and transmission via optical channel

Measurement and transmission of flow rate of a conducting liquid through a pipe line is generally done by using electromagnetic flow meter which consists of a large electromagnet and a pair of sensing electrodes along with electronic system and involves large cost and size. In the present paper, a very simple flow sensing system for a conducting liquid is proposed and this system does not require any electromagnet and involves very low cost. Moreover in modern instrumentation system the signal transmission through optical communication system is being more preferred where the transmitted signal does not suffer from measurement error due to electromagnetic interference. So an MZI based optical communication technique has been described in the present paper. The proposed technique consists of only four insulated conducting electrodes in contact with the flowing liquid along with an electro-optic system for signal conditioning and transmission of the measured signal to a remote location. The performance of the sensor and the transmission system has been analyzed in the form of a bridge network with bridge arms represented by lumped parameter polarization impedances among the electrodes. The theoretical equations explaining the operation of the bridge network with a stabilized sinusoidal ac source and MZI based electro-optic system have been derived. A proto type unit has been designed, fabricated and its function has been studied experimentally and the experimental results are reported in the paper. A very good linear characteristic under streamline condition of the proposed unit has been observed with very good repeatability and very small uncertainty of measurement. The graphical abstract is shown below.     

Hyperspectral photoacoustic spectroscopy of highly-absorbing samples for diagnostic ocular imaging applications

Photoacoustic spectroscopy has been used to measure optical absorption coefficient and the application of tens of wavelength bands in photoacoustic spectroscopy was reported. Using optical methods, absorption-related information is, generally, derived from reflectance or transmittance values. Hence measurement accuracy is limited for highly absorbing samples where the reflectance or transmittance is too low to give reasonable signal-to-noise ratio. In this context, this paper proposes and illustrates a hyperspectral photoacoustic spectroscopy system to measure the absorption-related properties of highly absorbing samples directly. The normalized optical absorption coefficient spectrum of the highly absorbing iris is acquired using an optical absorption coefficient standard. The proposed concepts and the feasibility of the developed diagnostic medical imaging system are demonstrated using fluorescent microsphere suspensions and porcine eyes as test samples.     

液态一元醇的太赫兹时域光谱研究

太赫兹波可以与极性液体中的氢键网络产生强的相互作用,作用越强吸收越强。鉴于此性质,利用太赫兹时域光谱技术对甲醇、乙醇、正丙醇在0.1~1THz波段内的太赫兹光谱进行了检测,发现其吸收光谱随分子极性的差异有显著的区别,并从中提取出了一元醇的吸收系数、折射率、介电常数等光学参数。在此基础上还利用对样品介电常数敏感的微孔金属片,通过产生的共振峰漂移进一步对不同一元醇进行了检测,结果表明太赫兹光谱技术结合微结构器件在液态化学及生物样品检测方面有潜在的应用价值。     

采用电化学交流阻抗等测试方法研究聚氨酯涂层在海水腐蚀环境中的失效机理

本文采用电化学交流阻抗谱研究聚氨酯涂层在3.5%氯化钠溶液浸泡作用下的性能变化,用FTIR对涂层失效前后的组成进行分析,用SEM研究涂层表面形貌变化,用能谱研究腐蚀产物的成分,对聚氨酯涂层在腐蚀环境中的失效机理进行详细的研究和分析。     

Note: Radio frequency surface impedance characterization system for superconducting samples at 7.5 GHz

A radio frequency (RF) surface impedance characterization (SIC) system that uses a novel sapphire-loaded niobium cavity operating at 7.5 GHz has been developed as a tool to measure the RF surface impedance of flat superconducting material samples. The SIC system can presently make direct calorimetric RF surface impedance measurements on the central 0.8 cm(2) area of 5 cm diameter disk samples from 2 to 20 K exposed to RF magnetic fields up to 14 mT. To illustrate system utility, we present first measurement results for a bulk niobium sample.     

Single HeLa and MCF-7 cell measurement using minimized impedance spectroscopy and microfluidic device

This study presents an impedance measurement system for single-cell capture and measurement. The microwell structure which utilizes nDEP force is used to single-cell capture and a minimized impedance spectroscopy which includes a power supply chip, an impedance measurement chip and a USB microcontroller chip is used to single-cell impedance measurement. To improve the measurement accuracy of the proposed system, Biquadratic fitting is used in this study. The measurement accuracy and reliability of the proposed system are compared to those of a conventional precision impedance analyzer. Moreover, a stable material, latex beads, is used to study the impedance measurement using the minimized impedance spectroscopy with cell-trapping device. Finally, the proposed system is used to measure the impedance of HeLa cells and MCF-7 cells. The impedance of single HeLa cells decreased from 9.55 × 10(3) to 3.36 × 10(3) Ω and the impedance of single MCF-7 cells decreased from 3.48 × 10(3) to 1.45 × 10(3) Ω at an operate voltage of 0.5 V when the excitation frequency was increased from 11 to 101 kHz. The results demonstrate that the proposed impedance measurement system successfully distinguishes HeLa cells and MCF-7 cells.     

Gene expression programming for automatic circuit model identification in impedance spectroscopy: Performance evaluation

Circuit/model identification is applied to impedance spectroscopy when there is no prior knowledge of the inner workings of the sensor or process under analysis. This paper presents a performance assessment of gene expression programming for automatic circuit model identification in impedance spectroscopy. The main objective of this work is to improve gene expression programming specific implementation details, with pre-embedding knowledge regarding circuit simplification rules, in order to improve its performance for circuit identification in impedance spectroscopy. Three different versions of gene expression programming are presented, discussed and analyzed. Insight is given into the inner workings of gene expression programming while highlighting the proposed changes in the three versions. The performance of the improved algorithm is analyzed through numerical simulated impedance data. It is further validated by the successful application to measurements of a real sensor along with a study of its performance on measured data.     

Study on carrier mobility measurement using electroluminescence in frequency domain and electrochemical impedance spectroscopy

In this paper, the two methods, electroluminescence in frequency domain and electrochemical impedance spectroscopy, have been applied to investigate the carrier mobility in single layer polymer light-emitting diode employing the polymer MEH-PPV (Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) as the light-emitting layer. The carrier mobility μ is 1.64 × 10⁻⁶ cm²/V s under the electric field 8.3 × 10⁵ V/cm measured by the method of electroluminescence in frequency domain. The electrochemical impedance spectroscopy results indicate that the carrier mobility μ is 1.08 × 10⁻⁶ cm²/V s under the electric field 7.5 × 10⁵ V/cm. A significant advantage of the two methods is that both of them can be applied to measure the carrier mobility in the thin film.