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.
The paper presents the family of three analyzers allowing to measure impedance in the range of 10 Ω<|Zx|<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.
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.
Varistors are commonly used elements which protect power supply networks against high-voltage surges or lightning. Therefore, quality and endurance of these elements is important to avoid losses when an expensive laboratory equipment would not be protected from random overvoltages. Additionally, excessive leakage currents generate serious costs due to high energy consumption. The paper presents shortly properties of varistors that comprized different ZnO grain types and can have various quality which changes continuously during exploitation (due to exposition to overheating and overvoltage pulses). Therefore, it is important to monitor varistors during their ageing (causing changes within their microstructures). A few methods of varistor property diagnosis were considered and compared with the methods currently applied in laboratory or industry applications. A new measurement (diagnostic) system that can monitor varistors during ageing and can be widely applied in power networks is presented. The proposed system fulfills requirements of the industrial customers which demand various methods for power line protection. The proposed system can be simply developed into a more advanced wireless diagnostic system of long power supply lines.