Improvement of the fast impedance spectroscopy method using square pulse excitation

Published in: Proceedings of the 14th Joint International IMEKO TC1 + TC7 + TC 13 Symposium : "Intelligent quality measurements - theory, education and training" ; in conjunction with the 56th IWK, Ilmenau University of Technology and the 11th SpectroNet Collaboration Forum ; 31. August - 2. September 2011, JenTower Jena, Germany. - Ilmenau : Univ.-Bibliothek, ilmedia, 2011. URN: urn:nbn:de:gbv:ilm1-2011imeko:

Using A Particular Sampling Method for Impedance Measurement

The paper presents an impedance measurement method using a particular sampling method which is an alternative to DFT calculation. The method uses a sine excitation signal and sampling response signals proportional to current flowing through and voltage across the measured impedance. The object impedance is calculated without using Fourier transform. The method was first evaluated in MATLAB by means of simulation. The method was then practically verified in a constructed simple impedance measurement instrument based on a PSoC (Programmable System on Chip). The obtained calculation simplification recommends the method for implementation in simple portable impedance analyzers destined for operation in the field or embedding in sensors

System for wireless monitoring of quality of anticorrosion coatings on objects difficult-to-reach

W artykule przedstawiono zminiaturyzowany analizator impedancji przeznaczony do spektroskopii impedancyjnej powłok antykorozyjnych obiektów trudnodostępnych znajdujących się w terenie (np. na stalowych konstrukcjach mostu). Przewidziano jego pracę w systemie z komunikacją bezprzewodową opartą na standardzie Bluetooth, w odległości do 100 m od komputera sterującego. Realizuje on pomiary impedancji w zakresie 10 Ω |Zx| 10 G Ω na częstotliwości pomiarowej z przedziału 0,01Hz 100 kHz. W konstrukcji analizatora zastosowano oryginalne rozwiązanie wykorzystujące dwa specjalizowane mikrosystemy AD5933. Błąd względny pomiaru modułu impedancji mieści się w przedziale š1 %, a bezwzględny argumentu š1°.The paper presents a miniaturised impedance analyzer for impedance spectroscopy of anticorrosion coatings on objects difficult-to-reach located directly in the field (e.g. on the steel construction of the bridge). The analyzer is designed to be used in a system with wireless communication based on the Bluetooth standard on the distance up to 100 m from a controlling computer. It measures impedance in a range of 10 Ω |Zx| 10 G Ω at the measurement frequency in a range of 0,01Hz 100 (10 frequencies in each decade). The analyzer construction is based on original solution using two specialized microsystems (SoC) AD5933 eliminating the need of calibration measurement which is necessary in the configuration proposed by the manufacturer. The tests of the realized analyzer prototype were performed. To do this, the reference RC two-terminal network of configuration and component values representing typical equivalent circuit of the anticorrosion coating in the early stage of exploitation was used. The relative error of the impedance modulus measurement is in the range of š1 %, whereas the impedance argument absolute error is in the range of š1°. The important advantage of the proposed solution based on SoC is reduction of power consumption down to ca. 0,7 W, which is very profitable in case of the impedance analyzer designed to work directly in the field

Using A Particular Sampling Method for Impedance Measurement

The paper presents an impedance measurement method using a particular sampling method which is an alternative to DFT calculation. The method uses a sine excitation signal and sampling response signals proportional to current flowing through and voltage across the measured impedance. The object impedance is calculated without using Fourier transform. The method was first evaluated in MATLAB by means of simulation. The method was then practically verified in a constructed simple impedance measurement instrument based on a PSoC (Programmable System on Chip). The obtained calculation simplification recommends the method for implementation in simple portable impedance analyzers destined for operation in the field or embedding in sensors

Floating-point laboratory A/D converter based on DAQ card

W artykule przedstawiono zrealizowany przetwornik a/c typu "floating-point" na bazie karty akwizycji danych typu PCI-6221 uzupełnionej o wzmacniacz wejściowy o programowanym wzmocnieniu. Opisywany przetwornik jest podstawą ćwiczenia w laboratorium studenckim. W skład ćwiczenia wchodzi dodatkowo program symulacyjny pozwalający zapoznać się z ideą pracy przetworników typu "floating-point", a następnie przejść do realizacji przetwornika w systemie na bazie karty akwizycji danych.The paper presents the performed floating-point A/D converter based on PCI-6221 DAQ card with the added input programmable gain amplifier. The converter is a main object in a student lab. The laboratory exercise additionally contains a simulation program, which allows us to familiarize with an idea of floating-point converters and then follow up with the converter based on DAQ card

Portable impedance analyzer using phase-sensitive detector

W artykule przedstawiono prototyp analizatora impedancji, w którym zastosowano dwa mikrosystemy AD5933 do wydzielania składowych ortogonalnych sygnałów pomiarowych w zakresie częstotliwości od 0,01 Hz do 1 kHz i detektory fazoczułe dla częstotliwości z przedziału 1 kHz - 100 kHz. Przyjęte rozwiązanie pozwoliło wyeliminować błędy pomiaru argumentu impedancji wprowadzane przez AD5933 w górnym zakresie częstotliwości. Uzyskany błąd względny pomiaru modułu impedancji mieści się w przedziale š1%, a bezwzględny argumentu š1° w całym zakresie częstotliwości.The paper presents a prototype of an impedance analyzer in which two AD5933 microsystems (Fig. 1) for determination of measurement signal orthogonal parts in the frequency range from 0,01 Hz up to 1 kHz and phase-sensitive detectors for the frequency range 1 kHz ? 100 kHz (Fig. 2) are employed. The phase-sensitive detectors (Fig. 3) were realized using operational amplifiers (AD8065) whose gain was changed from -k to +k and vice-versa, depending on the state (shorted or open) of switches (ADG451) driven by the reference signal. Separate generators AD9833 were used for generation of the excitation signal of the measured impedance and the reference signal. The generators were synchronized by means of the common signal used also by the phase-sensitive detectors. The assumed solution allowed eliminating the impedance argument errors caused by AD5933 in the high frequency range (Fig. 5), while simultaneously minimizing the time required for impedance spectroscopy of the object under test. The relative error of the impedance modulus measurement is in the range of š1%, and the absolute error of the impedance argument is in the range of š1° (Fig. 4)

High impedance spectroscopy analyzer using DSP

W artykule przedstawiono opracowany i wdrożony do produkcji seryjnej analizator do spektroskopii wysokoimpedancyjnej. Dzięki zastosowaniu obwodu wejściowego w postaci sondy pomiarowej (2 i 3 zaciskowej) analizator umożliwia pomiary w zakresie 100 &Omega; < |Zx| < 100 G&Omega;. Do wyznaczania składowych ortogonalnych sygnałów pomiarowych wykorzystano technikę cyfrowego przetwarzania sygnałów. Pozwoliła ona na pomiary w szerokim zakresie częstotliwości od bardzo niskich 100 &Mu;Hz do 1 MHz. Analiza rzeczywistych parametrów sond, umożliwiła wyznaczenie zależności korygujących wyniki pomiaru, które zaimplementowane w oprogramowaniu analizatora, zwiększyły dokładność pomiaru impedancji.The paper presents the developed high impedance spectroscopy analyzer which was putted into production. The analyzer allows to measure in the range of 100&Omega; < |Zx| < 100 G&Omega; thanks to the usage of the input circuitry in form of the measurement probe (2 and 3 terminal). The digital signal processing technique was used to determine orthogonal parts of the measurement signals. This allows measuring in a wide frequency range from very low 100 &Mu;Hz up to 1 MHz. The analysis of the real-life parameters of the probes made possible evaluation of correction formulas which were implemented in analyzer software and increased accuracy of the impedance measurement

Fast High-Impedance Spectroscopy Method Using Sinc Signal Excitation

In this paper the method of fast impedance spectroscopy of technical objects with high impedance (|Zx| ≥ 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

Fast high-impedance spectroscopy method using sinc signal excitation

In this paper the method of fast impedance spectroscopy of technical objects with high impedance (|Zx| ≥ 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

High impedance analyzer using DFT for phase-sensitive detection

W pracy przedstawiono metodę pomiaru impedancji opartą na próbkowaniu sygnałów oraz wyznaczaniu ich parametrów z zastosowaniem algorytmów cyfrowego przetwarzania sygnałów. Zastosowano dyskretną transformację Fouriera do wyznaczania składowych ortogonalnych sygnałów pomiarowych. Przeprowadzono analizę dokładności pomiaru impedancji uwzględniającą rozdzielczość przetworników a/c, amplitudę sygnału pomiarowego, liczbę zebranych próbek w czasie pomiaru oraz stosunek składowych ortogonalnych impedancji mierzonej. Wyniki badań symulacyjnych pozwoliły na zrealizowanie analizatora do spektroskopii wysokoimpedancyjnej w szerokim zakresie częstotliwości od bardzo niskich 100 &Mu;Hz do 1MHz.The paper presents the impedance measurement method based on signal sampling and determining their parameters with the aid of algorithms of digital signal processing. The Discrete Fourier Transform was used to determine orthogonal parts of measurement signals. The analysis of measurement accuracy was performed taking into account the resolution of the AD converters, measurement signal amplitude, the number of acquired samples during the measurement process and the ratio of orthogonal parts of the measured impedance. The results of simulations have allowed to make high impedance analyzer working in a wide frequency range starting from 100?Hz to 1MHz