Impedance analyzers

A common known method to get eddy-current informations about material flaws is the measurement of real- and imaginary part of the complex impedance of a coil in absolute circuit. The measurement, shown in this paper, are done with an impedance analyzer (HP4192A). The device measures the serial inductance L, and the serial resistance Rs of the complex impedance with an auto-balance bridge measurement circuit [5]. 

Two different formed coils with the same outer diameter of winding scan a material edge. One coil is a pot-core coil, the other is wound around a cylinder core. The impedance analyzer measures the complex impedances of the coils. 

The determined eddy-eurrent parameter is the inductance of the eomplex impedance measured by impedance analyzer at j=100 kHz. Therefore the impulse response function from chapter 4.2.1. is used for calculation. The depth of the cracks is big in comparison to coil size. For presentation the measured and pre-calculated data are related to their maxima (in air). The path X is related to the winding diameter dy of the coil. 

HP Operational and service manual. Model 4192A. LF Impedance Analyzer. 

While somewhat complicated, Bott, A. W., Electrochemical impedance spectroscopy using the BAS-Zahner IM6 and lM6e impedance analyzers . Current Separations, 17, 53-59 (1998), is a helpful introduction to the subject, and also mentions computer simulations. 

Alberti et al. investigated the influence of relative humidity on proton conductivity and the thermal stability of Nafion 117 and compared their results with data they obtained for sulfonated poly(ether ether ketone) membranes over the broad, high temperature range 80—160 °C and RHs from 35 to 100%. The authors constructed a special cell used in conjunction with an impedance analyzer for this purpose. Data were collected at high temperatures within the context of reducing Pt catalyst CO poison-... 

The Impedance Analyzer was controlled by a 9836 Hewlett-Packard computer which also controlled the time-tempe ture of the press. Measurements at frequencies from 5 to 5 x 10 Hz were taken at regular Intervals during the cure cycle and converted to the complex permittivity. Further details of the experimental procedure has been given elsewhere [10]. 

Most often, the electrochemical impedance spectroscopy (EIS) measurements are undertaken with a potentiostat, which maintains the electrode at a precisely constant bias potential. A sinusoidal perturbation of 10 mV in a frequency range from 10 to 10 Hz is superimposed on the electrode, and the response is acquired by an impedance analyzer. In the case of semiconductor/electrolyte interfaces, the equivalent circuit fitting the experimental data is modeled as one and sometimes two loops involving a capacitance imaginary term in parallel with a purely ohmic resistance R. 

In particular, VF2/F3E copolymers have also been the subject of extensive research [6,17,96]. As an example to illustrate the dielectric behavior of these copolymers, the temperature dependence of the real and the imaginary part of the complex permittivity at two different frequencies (1 and 100 kHz) are shown in Figs. 23a and 23b respectively. The measurements correspond to the 60/40 copolymer. The data have been collected by using a sandwich geometry with gold evaporated electrodes [95]. Frequencies of 103 and 106 Hz have been used by employing a 4192 A HP Impedance Analyzer. From inspection of Fig. 23b... 

Commercial impedance analyzers offer equivalent circuit interpretation software that greatly simplifies the interpretation of results. In this Appendix we show two simple steps that were encountered in Chapters 3 and 4 and that illustrate the approach to the solution of equivalent electrical circuits. First is the conversion of parallel to series resistor/capacitor combination (Fig. D.l). This is a very useful procedure that can be used to simplify complex RC networks. Second is the step for separation of real and imaginary parts of the complex equations. 

Dielectric response data were taken on a Czochralski-grown very pure crystals of sisniCc (size 0.5 x 5 x 5 mm3) with probing electric-field amplitudes of 200 V/m applied along the polar c axis. A wide frequency range, 10-5 < / < 106 Hz, was supplied by a Solartron 1260 impedance analyzer with a 1296 dielectric interface. Different temperatures were chosen both... 

The measurements in an impedance spectroscopy test of a simple electrolyte are normally obtained in the hertz to some megahertz frequency range with an impedance analyzer for this purpose impedance spectroscopy as a methodology is similar with DS (see Section 8.6.2). 

In impedance spectroscopy, the analyzer measures the response of the test sample, normally in the form of a cylindrical wafer with a radius of about 8-12 mm and a width of around 1-3 mm, which is included between the plates of a parallel capacitor sample holder (see Figure 8.17) [132], The impedance analyzer measures the capacitance, C, and the conductance, G, of the capacitor. The capacitance is related as follows (see Chapter 4) (see Equation 4.41)... 

The measurements were obtained in the frequency range from 100 Hz to 1MHz with the help of a Hewlett Packard impedance analyzer applying a constant bias voltage of 0 V and a modulating voltage of 500 mV [133], Then, the real (Zr) and imaginary (/,) parts of the complex impedance were calculated from the measured impedance. 

Hewlett-Packard Co., Palo Alto, CA Manual for HP4192A Low-Frequency Impedance Analyzer... 

The TFM method was further validated by comparison of the measured R and XL with steady state data with an HP4192A Impedance Analyzer for the same crystal in contact with aqueous sucrose solutions (Fig. 12.6). 

Measurement of calibrated capacitors can also be used to determine instrument limitations. Figure 36 shows a plot of the variation in measured capacitance versus known capacitance for a commercial impedance analyzer system (110). 

The conductivity of sintered pellets was obtained from two-probe impedance spectroscopy. Platinum electrodes were applied on both surfaces of pellets by coating platinum paste and then firing at 850°C for 0.5h. Measurements were made with an computer-interfaced impedance analyzer (GenRad 1689 Precision RLC Diglbridge) over a frequency range of 12-10 Hz in the temperature range of 500°C-800°C. Each sample was measured in air and H2 atmospheres, respectively. 

The electrochemical properties of the prepared materials were evaluated using coin-t e cells. The positive electrode consisted of 80 wt% oxide powder, 10 wt% carbon, and 10 wt% poljwinylidene difluoride (PVDF) binder on aluminum foil. The negative electrode was either metallic lithium or carbon on copper foil. The electroljde was 1 M LiPFe in a 1 1 mixture of ethylene carbonate (EC)/diethyl carbonate (DEC). The coin cells were galvanostatically cycled at 2.8 4.3 V. The a.c. impedance of the cointype cells was measured in the frequency range of lOmHz-lOOKHz using an impedance analyzer (BAS-ZAHNERIM6). 

Ionic Conductivity. The electrical conductivity measurements were performed using a Hewlett Packard model 4192 impedance analyzer under computer control, using a conductance cell similar to that described by Pauly and Schwan (5). The conductivity measurements were essentially constant between 1-100 kHz, ruling out electrode polarization or other artifacts. In 0/W microemulsions, no appreciable dielectric relaxation effects are expected or observed below 1 GHz (U. 

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