Ac Bridge Research Articles

2117 交流ブリッジ回路による櫛歯アクチュエータの駆動とそのセンサ応用(要旨講演,一般セッション:マイクロナノメカトロニクス)

2117 交流ブリッジ回路による櫛歯アクチュエータの駆動とそのセンサ応用(要旨講演,一般セッション:マイクロナノメカトロニクス)

A Novel Approach to Modeling and Simulation of NTC Thick-Film Segmented Thermistors for Sensor Applications

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper describes the design, modeling, simulation, and fabrication of thick-film segmented thermistors. These thermistors were printed on alumina using negative temperature coefficient 3K3 paste, composed of nanometer powder. Their room temperature resistance was measured versus the number of segments and electrode surface value for the fixed layer thickness and electrode spacing. After that, very large thermistors were printed to serve as both the powerful self-heaters and the heat loss sensors in the thermistor volume air flow meter and anemometer. For an application in AC bridges, impedance Z(f) and insertion loss S21 [dB] of the same largest segmented thermistor were measured using network analyzer HP8752A. Impedance modeling was performed using simple equivalent electrical circuit with circuit parameters estimated by fitting procedure (traditional approach), as well as using a commercial electromagnetic simulation program microwave office (MWO, novel approach). This was followed by the modeling of electrical current distribution over a number of segments done within the MWO. The results obtained from simulations and measurements were mutually compared. </para>

Single- and multi-sine DFT demodulation with an application to precision capacitive sensors

This paper presents a comparative study of digital methods to improve the signal to noise ratio in ac bridge measurements and other applications requiring demodulation of amplitude-modulated signals. Three types of discrete Fourier transform (DFT) based algorithms are analyzed. The algorithms considered are single-sine conventional DFT, single-sine running DFT, and multi-sine running DFT. We report on a case study using a field programmable gate array (FPGA) to monitor the output signal from a typical ac bridge with variable capacitive sensors in two arms. Theoretically, both the single- and multi-sine running DFT algorithms are shown to provide improved ripple noise performance over the conventional single-sine DFT approach. Additionally, in the presence of a high noise background, theoretical calculations indicate that the multi-sine running DFT provides a factor of 2 improvement in signal to noise ratio compared to the single-sine conventional DFT. Experimental results also show a moderate improvement in ripple noise, but not at the level predicted by the theory. Finally, the method for running multi-sine reported can be used for any periodic basis function. As a result, higher complex basis functions, particularly those with orthogonal properties, such as those that can be generated from a Fourier series or functions that contain continuous spectra (wavelets for example), could also be used.

Electrical conductivity of niobium-containing oxide-fluoride melts

The effect of Nb2O5 on electrical conductivity of metals based on CaF2 and CaF2-30% Al2O3 at T = 1500–1900 K in an oxidizing atmosphere is investigated using an ac bridge at the frequency 5 kHz. It is found that, as the Nb2O5 concentration increases from 0 to 25%, the electrical conductivity of the melts decreases, while the activation energy of electrical conductivity increases monotonically. The data obtained agree with viscosity investigations and indicate that niobium is the complexing agent in oxide-fluoride melts.

Modelling and Simulation of Adaptive Digital AC Bridge for Impedance Measurements

This paper proposes an innovative and efficient method for balancing an adaptive digital AC bridge employing a closed-loop control system to measure the impedance of passive networks. A neoteric method that uses Widrow-Hoff's least mean square (LMS) algorithm is adopted to minimize the error and to reduce the complexity of computation. The MATLAB-SIMULINK package is used for the dynamic simulation of digital AC bridge. By using this modelling, we have achieved higher accuracy, reproducibility, and faster convergence. The digital AC bridge is balanced by controlling the in-phase and quadrature component of the complex voltage. The stability of the bridge is controlled by the parameter μ, which also determines the adaptation rate. This paper also explains the various methodologies used for simulation reporting the results.

Systematic Approach for the Linearization and Readout of Nonsymmetric Impedance Bridges

This paper presents a general concept for the linearization of impedance bridges with circuit components changing in only one polarity. A feedback loop using a transadmittance amplifier, which is properly designed and matched to the nominal value of the bridge components, reduces nonlinearity from 9% to 0.4% over plusmn20% of bridge imbalance. The method can be applied for dc or ac bridges, and the linearization can conveniently be integrated with the readout circuit, resulting in a highly linear sensor readout. In addition to the linearization of the bridge transfer function itself, the method can be applied for the linearization of a range of transducers with a hyperbolic transfer function

The theoretical principles of the construction of variational quadrature ac bridges

New approaches to constructing quadratic bridges, based on a variational calibration and correction of the measurement error and the wide use of digital signal processing, which enable high metrological characteristics of the apparatus to be obtained for small dimensions and low cost, are proposed.

Intelligent phase correction in automatic digital ac bridges by resilient backpropagation neural network

The present paper describes the development of an ANN based phase correction system which has been employed in conjunction with a real automatic digital ac bridge. The proposed ANN-based phase corrector has been developed using backpropagation learning employing resilient backpropagation (popularly known as RPROP). Significant improvements have been obtained in the proposed phase correction system for measuring impedance and reported in the paper.

Modelling and Simulation of Universal Digital AC Bridge Using Ann Technique

Bridges are the measuring devices used for accurate measurement of impedance. As such, there is no universal bridge circuit that measures impedance of all types of passive components. Moreover, the bridges available cannot be used for high-frequency impedance measurements. This paper proposes an automatic digital AC bridge model, which is considered to be universal and suitable for high-frequency impedance measurement up to 1MHz. In this adaptive digital AC Bridge, balancing is achieved by means of Artificial Neural Network based on stochastic gradient search algorithm. Among the various gradient search techniques, the Widrow-Hoff's Least Mean Square (LMS) technique has been chosen as it involves less computational burden. The digital AC bridge operations have been verified by simulation. The simulated system was tested for measuring impedances of pure and impure inductors, capacitors, resistors, and a series combination of an inductance and a capacitance. The effects of various parameters like supply voltage, reference resistance, learning rate, and sampling rate were considered to investigate the performance of universal high-precision AC Bridge, and the results are reported. This model is advantageous over the traditional heuristic methods in terms of higher accuracy, faster convergence, and greater reproducibility and reliability.

Interleukin-13 Is the Key Effector Th2 Cytokine in Ulcerative Colitis That Affects Epithelial Tight Junctions, Apoptosis, and Cell Restitution

Interleukin-13 Is the Key Effector Th2 Cytokine in Ulcerative Colitis That Affects Epithelial Tight Junctions, Apoptosis, and Cell Restitution

Sci‐YIS Fri ‐ 05: Design and testing of a new sealed water calorimeter for electron beams

The Electron Sealed Water (ESW) calorimeter is a new device designed for measurements in clinical electron beams. This work presents the calorimeter design, preliminary measurements and evaluation of correction factors. The calorimeter contains a 30×30×20 cm3 water phantom surrounded by a cooling system to allow for operation at 4°C. Two thermistor probes measure temperature change inside a glass vessel filled with high‐purity nitrogen‐saturated water. Correction factors for glass perturbation were calculated using Monte Carlo simulations. Corrections for thermal conduction were simulated using Femlab software. Resistance of the thermistor probes was measured using a lock‐in amplifier and an AC bridge circuit. Measurements were done for 6, 9, 12, 16 and 20 MeV electron beams from a Varian Clinac 21EX. Irradiations of 667 MU were done at 1000 MU/min for an irradiation time of 40 s. Measurements were also taken with a PTW Roos ion chamber inside the calorimeter phantom. For 30 runs, the standard error on the mean temperature change was less than 0.2% for all energies. When normalized to the 12 MeV measurements, values of k′R‐50 for the Roos chamber calculated from calorimeter measurements for the 9, 16 and 20 MeV beams agreed with TG‐51 values within 0.7 %. Water calorimetry in electron beams has previously been regarded as unfeasible as high dose gradients were thought to provoke unmanageable temperature gradients. Using the ESW calorimeter, we have shown for the first time that reproducible measurements can be performed in electron beams with energies as low as 6 MeV.

WE‐D‐T‐617‐06: Development of a Sealed Water Calorimeter for Clinical Electron Beams

Purpose: The purpose of this project is to develop a water calorimeter for use in clinical electron beams to directly determine absorbed dose to water. This work presents the design of the Electron Sealed Water (ESW) calorimeter, preliminary measurements and evaluation of correction factors. Method and Materials: The calorimeter contains a 30 × 30 × 20 cm3 water phantom surrounded by a cooling system to allow for operation at 4°C. Two thermistor probes measure the temperature change inside a glass vessel filled with high‐purity nitrogen‐saturated water. Correction factors for the glass perturbation were calculated using Monte‐Carlo simulations. Corrections for thermal conduction were simulated using Femlab finite element modeling software. Resistance of the thermistor probes was measured using a lock‐in amplifier and an AC bridge circuit. Measurements were done for 6, 9, 12, 16 and 20 MeV electron beams from a Varian Clinac 21EX with a 10 × 10 cm2 applicator at 105.5 cm SSD with the thermistor probes positioned at dref. Irradiations of 667 MU were done at 1000 MU/min for an irradiation time of 40 s. Measurements were also taken with a PTW Roos ion chamber inside the calorimeter phantom. Results: The standard error on the mean temperature change for each energy was less than 0.2%. Reproducibility for measurements on separate occasions was 0.2%. When normalized to the 12 MeV measurements, values of k'R‐50 for the Roos chamber calculated from calorimeter measurements for the 9, 16 and 20 MeV beams and agreed with TG‐51 values within 0.7 %. Conclusion: Water calorimetry in electron beams has previously been regarded as unfeasible as high gradients were thought to provoke unmanageable temperature gradients. Using the ESW calorimeter, we have shown for the first time that reproducible measurements can be performed in electron beams with energies as low as 6 MeV.

Non-destructive observation of electrically detected magnetic resonance in bulk material using AC bias

DC bias is normally found in conventional measurements of electrically detected magnetic resonance (EDMR). Usually, electrodes are formed on the sample surface to make ohmic contacts for detecting changes in the electrical characteristics of the sample material. Thus, destructive procedures are required to detect the EDMR signal of bulk material with such methods. An AC bias detection technique was developed to allow the non-destructive EDMR measurement of bulk materials. An AC bridge circuit was constructed to detect the change in impedance of the sample, which when changed by ESR, an unbalanced AC voltage can be detected. By detecting this AC bias, it is possible to cancel the effects, such as Shottky barriers, that disturb the ohmic contact between the electrodes and a sample material. Further, the AC bias current penetrates the thin surface layer of a sample such as silicon oxide, which normally obstructs a DC current. This method was utilized using conductive rubber contacts for non-destructive EDMR measurements of part of a silicon wafer. EDMR spectra observed were the same as those obtained by the conventional method of using DC bias detection.

High precision calibration of ac current-to-voltage converters

A two-stage transformer, built as a current comparator with a shielded magnetic core, is used to make a novel ac bridge for calibration of ac shunts for large currents and other ac current-to-voltage converters. A fine adjustable reference transresistance is made by current transformation and a non-reactive precision resistor connected to the secondary. By using an auxiliary transformer and resistor, all four two-stage transformer secondary terminals are brought to ground potential and consequently both magnetizing and capacitive errors are kept below one part per million.

Adsorption of n-Butanol on Pb–Ga in Aqueous Solutions: Effect of Metal on the Adsorption of Organic Compounds in the Absence of Metal–Water Chemisorption Interaction

The potential dependence of the differential capacitance is measured by an ac bridge at 420 Hz and 32°C at Pb–Ga/H2O interface in 0.05 M Na2SO4 solutions containing n-butanol in different concentrations. Adsorption parameters for n-butanol are determined using a regression analysis and compared with those for Hg, Tl–Ga, and Bi–Ga. As follows from this comparison, though there is no chemisorption interaction between these metals and water, the energy of n-butanol adsorption at these metals depends on the metal nature. The Pb–Ga data fit a common correlation dependence of the electronic capacitance of different electrodes (Cm–1)phys on the energy of the n-butanol molecules adsorption thereon in the absence of a metal–water chemisorption interaction. This finding evidences that the dependence of the energy parameters for the adsorption of organic compounds on the metals' electronic properties, when characterized by (Cm–1)phys, is of general nature.

Initial NIST AC QHR Measurements.

We demonstrate that dc quantized Hall resistance (dc QHR) guideline properties and dc and ac QHR values can be measured without changing sample probe lead connections at the QHR device, and report ac QHR values that converge to the dc QHR value when using four-terminal-pair ac QHR measurements. This was accomplished during one cooldown using single-series and quadruple-series connections outside the sample probe. The QHR was measured from 0 Hz to 5500 Hz in 1:1 ratio at 20 µA to ±1 part in 107 uncertainties with a poor-quality QHR device. A good device would allow an order of magnitude smaller uncertainties over this frequency range. We exchanged positions of the QHR device and reference resistor in the bridge and remeasured the resistance ratios to remove dominant ac bridge effects.

Unequalized Currents in Coaxial AC Bridges

In a coaxial ac bridge with imperfect current equalization, the comparison of two standard resistors shows a linear frequency dependence. Unequalized currents load the magnetic cores in the coaxial bridge and result in effective loss factors of certain capacitances of the compared resistors. To avoid this systematic effect in any coaxial bridge used for the precise calibration of impedance standards, a correct arrangement of current equalizers is absolutely necessary.

A Descriptive Approach to Analyzing Passive Four-Armed AC Bridge Circuits

A descriptive analysis is applied to alternating-current circuits, which is extended to the most complicated subclass of measurement circuits: passive four-armed bridge ones. General relations are derived between parameters of the measurement specimen and those of the bridge circuit, together with synthesis rules for these circuits that inexplicitly incorporate those relations. The results completely formalize synthesizing passive bridge circuits and reduce the treatment to choosing between possibilities.

The modified Rankine balance: A highly efficient, low-cost method to measure low-temperature magnetic susceptibility in rock samples

In this article, we present a method to measure the relative changes in the magnetic susceptibility of rock samples in the low-temperature range (−200 °C to +20 °C). The method differs from other experimental methods currently used in that it requires—in contrast to ac bridges, the most widely used devices—very little sophisticated laboratory equipment: A high-precision laboratory balance, a Pt-100 thermoelement and a computer with standard input/output interface and analog/digital processing capabilities, as well as a few rare earth magnets, are the only devices needed in addition to standard laboratory equipment. A Dewar container and a few plexiglass panes can either be handcrafted in the workshops of any larger research institute or are commercially available at little cost. The results of our measurements reveal that the temperature-varying magnetic properties of rock samples can be reliably observed.

Instrumentation & Measurement Pocket Book, Third Edition

The book is divided into four parts: `Systems', `System Components', `Measurements' and `Microprocessor Based Systems'.