No abstract

The paper presents the family of three analyzers allowing to measure impedance in the range of 10 Ω<|Z x |<10 GΩ in a wide frequency range from 10 mHz up to 100 kHz. The most important features of the analyzer family are: miniaturization, low power consumption, low production cost, telemetric controlling and the use of an impedance measurement method based on digital signal processing (DSP). The miniaturization and other above-mentioned features of the analyzers were obtained thanks to the use of the newest generation of large-scale integration chips: e.g. "system on a chip" microsystems (AD5933), 32-bit AVR32-family microcontrollers and specialized modules for wireless communication using the ZigBee standard. When comparing metrological parameters, the developed instrumentation can equal portable analyzers offered by top worldwide manufacturers (Gamry, Ivium) but outperforms them on smaller dimensions, weight, a few times lower price and the possibility to work in a distributed telemetric network. All analyzer versions are able to be put into medium-volume production.

No abstract

No abstract

A comprehensive description of impedance of electrochemical systems has been presented, along with the assumptions of the method used. In this method, a multisinusoidal current excitation signal is used. The changes of potential of both the electrodes and the potential difference between these electrodes are all registered simultaneously as a function of time. The proposed method offers the possibility of separately determining the instantaneous value of impedance of each electrode as well as the impedance of a twoelectrode system. The short-time Fourier transform of time registers allow the determination of changes in the measured impedance values over time. The method has been successfully verified with an electrical equivalent circuit simulating a non-stationary two-electrode system. The values of the impedance of particular components during operation of the fuel cell under a changing load have been obtained.

This paper presents a virtual instrument for measuring the impedance parameters of high impedance objects (|Z x | 10 G ). A method of component identification of multi-element two-terminal networks has been developed on the basis of bilinear transformation. The method is dedicated to parameter identification of different kinds of anticorrosion coatings. During the identification, the vector measurement of the object impedance is necessary at a few selected frequencies, equal to the number of elements under identification. The analysis of optimal frequencies selection is presented ensuring minimal identification error. The test results from the implemented algorithm are shown. The results proved the possibility of shortening the anticorrosion coating performance testing time by several orders in relation to the traditional impedance spectroscopy technique. A digital signal processing technique has been used in the virtual instrument for determination of the orthogonal parts of the measurement signals. It allows us to achieve a wide range of measurement frequencies, especially very low, from 1 MHz to 100 µHz. In order to measure impedance in the range 100|Z x | 10 G with an error not exceeding 2.5%, an input circuit based on a current-to-voltage converter has been used.The use of modern electronic components combined with digital signal processing techniques resulted in a low-cost instrument for measurement parameters allowing widespread use in impedance spectroscopy for many technical objects.

In this paper the method of fast impedance spectroscopy of technical objects with high impedance (|Z x | ≥ 1 GΩ) is evaluated by means of simulation and a practical experiment. The method is based on excitation of an object with a sinc signal and sampling the response signals proportional to current flowing through and voltage across the measured impedance. The object's impedance spectrum is obtained with the use of continuous Fourier transform on the basis of linear approximations between samples in two acquisition sections, connected with the duration of the sinc signal. The method is first evaluated in MATLAB by means of simulation. An influence of the sinc signal duration and the number of samples on impedance modulus and argument measurement errors is explored. The method is then practically verified in a constructed laboratory impedance spectroscopy measurement system. The obtained acceleration of impedance spectroscopy in the low frequency range (below 1 Hz) and the decrease of the number of acquired samples enable to recommend the worked out method for implementation in portable impedance analyzers destined for operation in the field.

No abstract