Simple Electrical Model Research Articles

Field trials on covercrete monitoring sensors

This paper details the application of in situ electrical measurements to study cover-zone performance and presents the initial results from a long-term field exposure study. Field data are presented from a marine test site, an urban exposure site and a roadside test site. A range of formalisms are exploited to allow ease in data interpretation and a simple electrical model is used to show the interrelationship between electrical properties of concrete, pore structure, degree of pore saturation and ionic ingress. Measurements, to date, indicate that the sensor arrangement embedded within each of the test specimens is behaving as anticipated from previous laboratory studies. Water absorption, ongoing hydration and pozzolanic activity are detected within the cover zone and, in the case of the marine site, ionic ingress is detected in one of the sets of test specimens.

Field trials on covercrete monitoring sensors

This paper details the application of in situ electrical measurements to study cover-zone performance and presents the initial results from a long-term field exposure study. Field data are presented from a marine test site, an urban exposure site and a roadside test site. A range of formalisms are exploited to allow ease in data interpretation and a simple electrical model is used to show the interrelationship between electrical properties of concrete, pore structure, degree of pore saturation and ionic ingress. Measurements, to date, indicate that the sensor arrangement embedded within each of the test specimens is behaving as anticipated from previous laboratory studies. Water absorption, ongoing hydration and pozzolanic activity are detected within the cover zone and, in the case of the marine site, ionic ingress is detected in one of the sets of test specimens.

Modeling and characterization of deep trench isolation structures

In this paper, we present a simple equivalent electrical circuit model and sidewall interface characterization results for a deep trench isolation structure. The trench structures used in the study consisted of n-silicon/undoped trench/n-silicon. The trenches were filled with undoped polycrystalline silicon and the trench sidewall was lined with thermal oxide and a deposited silicon nitride. The capacitance–voltage characteristics across the trench were measured and compared against the model predictions. The circuit model includes the effect of the space-charge region and recombination–generation currents in the undoped polycrystalline silicon trench fill material. The Terman method was used to extract the silicon/oxide sidewall interface density and the mid gap value was found to be less than 10−10#/cm2-eV.

A Capacitance Probe and a New Model To Identify and Predict the Capacity of Columns Equipped with Structured Packings

A new probe based on the measurement of the electrical capacitance has been developed to measure liquid holdup in columns equipped with structured packings. The main advantages of this new probe are that it is nonintrusive, it allows fast and online measurements, and it can be used for laboratory-scale columns as well as for industrial applications. The probe is designed to measure local liquid holdup and it can therefore be used to evaluate the presence of the liquid hold-up gradient inside each packing element in the column. Evaluation of the liquid hold-up gradient is helpful to identify locations inside the packing element where flooding begins and to suggest packing design modifications. The relation between electrical capacitance and liquid holdup closely follows the predictions obtained using simple electrical models. The experimental results obtained with the probe have enabled a simplified model to be tuned to predict capacity limits of columns equipped with structured packings.

A hard-tube pulser of 60 kV, 10 A for experiment and modeling in plasma immersion ion implantation

This paper describes an experiment and modeling in plasma immersion ion implantation using a high-voltage pulsed power system. This consists of a high-voltage pulse generator that uses a hard tube switch. The reason for using this type of circuit category in the Plasma Immersion Ion Implantation (PIII) facility rather than a previously used pulse-forming network (PFN) circuit configuration is stated. The experimental results of the application of this device to a glow discharge PIII are also discussed. In order to assess these results, a simple electrical model describes the plasma as a resistive load in parallel with a capacitance taking into account the pulse rise-time distortion caused by a long connecting coaxial cable. Plasma parameters for PIII processing, such as ion average implantation current and plasma sheath thickness, are calculated from the experimental settings.

Characterization of Zircaloy-4 oxide layers by impedance spectroscopy

Two Zircaloy-4 type alloys with different tin contents (0.5 and 1.2 wt%) have been oxidized in autoclave (400°C in steam) for several durations (1–140 days). The film has been characterized by electrochemical impedance spectroscopy (EIS). Several soaking times have been investigated (up to 40 days). The Cole–Cole representation has been used to display and study the data. A simple electrical model has been derived from the observed spectra: the electrical circuit includes two RC loops in series, whose capacitances are frequency dispersed. It is thoroughly related to the layer structure. It has been shown that even before the kinetic transition, the film is constituted of three parts: an inner layer which is compact, an outer layer subdivided in an external region immediately soaked by the electrolyte, and an internal one in which electrolyte diffusion processes can take place. The kinetic transition is interpreted in terms of an abrupt `compacity' change, both layers degrading at this point. The alloy with high tin content exhibits higher dispersive properties of the oxide layer formed on it, in correlation with its faster oxidation kinetics.

Characterization of Three-Dimensional Tissue Cultures Using Electrical Impedance Spectroscopy

Electrical impedance spectroscopy was used to characterize the cell environment of multilayered cell cultures (MCCs), a culture system in which cells are grown on a permeable support membrane to form a thick disc of cells with tumor-like properties. Cultures were grown using SiHa tumor cells as well as V79 wild-type cells and V79/DOX cells cultivated to exhibit multidrug resistance. Electrical impedance measurements were made on MCCs over a frequency range of 0.1 kHz to 1 MHz. Data analysis using a simple electrical model for the cell environment yielded estimates for parameters related to the intra- and extracellular resistance and net membrane capacitance, which were then related to MCC thickness. The extracellular fraction and tortuosity of the MCCs were determined in separate experiments where the rate of diffusion and the equilibrium level of C 14-inulin, which does not penetrate the cell membrane, was measured within MCCs. Impedance measurements predicted the barrier to diffusion posed by the extracellular space of MCCs to be roughly two times greater than that inferred from the C 14-inulin experiments. However, the relative ranking of the three cell types used to grow MCCs was similar for the two methods. Results indicate that impedance spectroscopy is well suited for use in characterizing the MCC cell environment, offering a fast, nondestructive method for monitoring cell culture growth and integrity.

Analysis of the fluxgate response through a simple spice model

In this paper, harmonics content of sinusoidal excited fluxgate sensors response is analyzed by means of a simple electrical model developed for SPICE. The model construction is detailed and it is applied to the simplest fluxgate sensor. Well known characteristics of these sensors are confirmed through the simulations, while new useful outcomes are discussed. In particular it is found that the 4th harmonic response has, in analogy to that of the 2nd one, a linear range which is of greater sensitivity independent of the shape of the BH curve. Second and 4th harmonic responses present a negative slope region. Using a previously developed 2nd harmonic fluxgate magnetometer, some preliminary experimental results are obtained confirming the appearance of the negative slope region at its output.

Dielectric characterization of ferroelectric thin films deposited on silicon

This paper describes some experimental results concerning the dielectric characterizations of PZT, PT and BT ferroelectric thin films deposited on silicon. Firstly, the ferroelectric properties of these films are checked, notably the high dielectric constant values. Secondly, assuming a simple electrical model, we derive from impedance measurements the conductivity of the platinum deposited as a bottom electrode.

Two-dimensional simulation of conducted currents characteristics in electrical discharges

In this paper, a simple general electrical discharges circuit model for electrical discharge current waveform simulation in overvoltaged air gaps is presented. A macroscopic circuital method of simulation utilizing the standard SPICE network simulator, based on a two-dimensional (2-D) nonlinear impedances network has been proposed. The structure of the simulation framework is designed to take into account the electrode geometries in a straightforward way. A study of conducted current waveform for different electrode geometries has been done. Experimental data have been used to validate the simulation results.

Effects of diffraction on the sensitivity of needle-type ultrasonic receivers

The low-frequency sensitivity of piezoelectric receivers usually is assumed to be represented accurately by the −3-dB cutoff frequency fco=(2πRiCi)−1, where Ri is the loading (e.g., amplifier) resistance and Ci is the total capacitance. For typical needle-type hydrophones such as used in medical ultrasound exposimetry, fco is less than 50 kHz. However, theoretical studies have shown that diffraction effects at the needle tip can cause a low-frequency rolloff in sensitivity at frequencies much higher than that predicted by this simple electrical model. To examine this effect, broadband frequency response measurements of several needle-type hydrophones were made in the frequency range 0.2–2 MHz. The active sensor material was polyvinylidene fluoride, and needle diameters ranged from a few tenths of a millimeter to approximately 1 mm. In all cases the sensitivity decreased with decreasing frequency, with the −3 dB points all lying above 400 kHz. Such behavior calls the use of these devices into question when accurate knowledge of the pressure waveform is required, particularly with regard to measuring the peak rarefactional pressure in pulsed waveforms displaying significant finite amplitude distortion.

Current noise of trimmed thick‐film resistors: measurement and simulation

An investigation of laser‐trimmed thick‐film resistors’ current noise was carried out. A large number of samples from two pastes with different P‐ and L‐cuts were prepared. The noise spectrum of the trimmed resistors was measured to obtain a relationship between the current noise and the cut parameters. A simple but comprehensive electrical model for the simulation of the current noise of trimmed resistors is also presented. The results from the noise simulation agree with the measured data.

200 MHz optical signal modulation from a porous silicon light emitting device

The light emission frequency response of an extremely stable Schottky (Al-porous silicon) light emitting device is presented. The construction steps, critical for device stability, are also presented. The device, when it is reverse biased in breakdown conditions, shows a white light emission visible in normal daylight. The emission mechanism is supposed to be the radiative transition of hot electrons generated in the breakdown process. The optical signal modulation has been measured up to 200 MHz and a simple electrical model is presented in order to explain the dynamic behavior of the device. The device speed seems to be limited by the junction capacitance rather than by an intrinsic physical limit of the emission mechanism.

Electroluminescent Displays

AbstractThis paper will review the electrical and optical properties of both monochrome and color electroluminescent (EL) displays. A simple electrical model for thin film electroluminescent (TFEL) device operation will be presented and used to describe the luminance and power consumption of TFEL devices. The basic material characteristics desirable for EL phosphors will be described. Progress in the development of monochrome and color EL displays will be presented including TFEL and Active Matrix EL devices and phosphors.

Electrochemical impedance of pits. Influence of the pit morphology

The evolution of the impedance of a AISI 430 steel electrode affected by pitting corrosion was studied. Open pits were obtained in sulfuric acid solution containing sodium chloride and closed pits were formed in pure sodium chloride solution. Some changes affecting the shape of the impedance diagrams during the development of pits could be related to geometrical effects due to the morphologies of the pits. The results obtained with open pits are explained by the increase in the roughness induced by their development. With closed pits, the electrode impedance behaves like the impedance of a porous electrode. A simple electrical circuit model is proposed to account for the evolution of the impedance diagrams.

Pollution performance of 110 kV metal oxide arresters

Pollution test results of single-unit 110 kV metal oxide surge arresters with porcelain housing according to the solid layer and salt fog methods are presented. During 6 hours of testing, the internal and external charge and maximum temperature along the varistor column were measured. The formation of single stable dry bands on the housing was often observed especially during salt fog tests. In such cases, the varistor temperature can reach about 70/spl deg/C. The simple electrical model of the arrester enabling calculations of voltages and currents as a function of arrester and pollution parameters is shown.

Deposited thin-film wear sensors: materials and design

Vacuum deposited thin-film sensors have been developed for monitoring wear and temperature in a variety of bearing applications. The sensor typically consists of one or more metallic or insulator films. This lamination sputtered thin-film resistance elements and thermoelectric elements with appropriate insulators is deposited directly on the bearing surface. The thin-film package can be designed to have wear behavior similar to that of the bearing materials, and to have a small surface area that conforms to the bearing contour. The wear sensor monitors the regression of the surface, i.e. the loss of material due to wear, in the range 0.1–10 μm (or more) over the small area that the sensor occupies. The thermoelectric sensor monitors local temperature. The effect of the materials and fabrication on the properties of the sensors are described as they effect the electrical response and the wear characteristics. Desired properties needed by the conducting film component include adequate electrical conductivity, adhesion to the insulating layers, low ductility, adequate toughness, and hardness. The critical properties of the insulating film component were found to be adhesion, low conductivity, strength, and hardness. Test results were obtained for sliding ring and block tests in both air and oil-lubricated environments. For conducting films, aluminum, platinum, tantalum, and type K + and K − thermoelectric alloys were studied and are reported here. Copper and two metal silicides were also evaluated. For insulating films, results on aluminum oxide, tantalum oxide, and borosilicate glass are reported. The substrate block material was 304 stainless steel. It was found that the electrical performance of the conducting films in the sensor package can be described using a simple electrical resistance model.

The Problem of the Top Cell for the Micromorph Tandem

ABSTRACTA detailed study of the influence of different materials for the amorphous top cell on the stabilized efficiency of amorphous silicon/microcrystalline silicon (”micromorph”) tandem cells is presented. The authors investigate different amorphous i-layer materials which are applied in cells with varying thicknesses. It is shown that it is preferable to optimize the top cell in order to obtain a high current rather than a high voltage.A simple optical and electrical model is presented which allows one to predict the optimum optical bandgap of the i-layer material of the top cell and to determine its optimum thickness for maximum stabilized efficiency. By means of this model it is shown that the optimum top cell for a total cell current of 26 mA/cm2 should contain an about 2500 Å thick i-layer with an optical gap Eo4 ≃ 1.8 eV. The model furthermore shows that it is desirable to obtain slightly bottom-limited conditions after degradation in order to maximize the output power.A stabilized efficiency of 10.7 % for a micromorph tandem cell has been confirmed by an independent measurement (FhG-ISE). Another such cell yields a stabilized efficiency of 11.2 % as measured in our laboratory.

Modelling of bonding pads and their effect on the high-frequency-noise figure of polysilicon emitter bipolar junction transistors

This paper presents detailed experimental results on the input impedance of bonding pads, and a simple electrical model that accurately describes the impedances of these pads as a function of frequency for five different types of pad structures. It also describes the effects of the bonding pads on the minimum high-frequency-noise figure (NFMIN) of polysilicon emitter npn bipolar junction transistors as functions of collector current density and emitter areas. It was found that for devices with larger emitter areas (AE > 48 μm2) and relatively low base resistance (RB < 30 Ω), the effects of the same bonding pads on the noise figure was not as pronounced as for the smaller area devices with larger base resistances. For a device with AE = 3.2 μm2 operating at 1 GHz, biased with a collector density of 0.15 mA μm−2, neglect of the effects of the bonding pads results in too low NFMIN (by 1–2 dB) when calculated values were compared to measurements. Finally, for devices with the same emitter areas, bonding pads with smaller impedance results in a larger NFMIN compared to measurements on similar transistors with pads of larger impedances.

A 100 kV 10 A high-voltage pulse generator for plasma immersion ion implantation

The design of a high-voltage pulsing system for a plasma immersion ion implantation (PIII) facility is presented. A list of requirements, which have to be fulfilled by a high-voltage pulse generator to get best results and a optimum operation of the PIII system, is given. A simple electrical model of the plasma is presented which describes the plasma as a capacitive–resistive load. The model parameters are determined to fit experimental results. The requirements for the pulse generator can be fulfilled well using a pulse generator design which employs a hard tube switch. A pulse generator design is presented which is especially optimized for PIII systems. The hard tube control is especially optimized for obtaining voltage rise times as short as possible.