An universal coaxial multiplexer for switching one measurement device between several measurement points is described. The coaxial multiplexer consists of independent switch modules (channels), which are controlled via optical fibres. The off-state isolation of multiplexer was measured to be better than -185 dB at 1 kHz. Properties of the multiplexer enable to use it in automation of high precision 2-TP and 4-TP coaxial a.c. bridges or other precise measurement applications.
The paper describes the experimental study of a two-phase sine wave generator intended for use in an impedance metrology. It is based on a 20-bit digital-to-analog converter (DAC) based on the R-2R architecture. Some tests for evaluation of the generator were carried out. The excellent parameters of the DAC made possible achieve a very good stability of the complex voltage ratio which is about ± 0.25 part in 10 6 for the amplitude ratio and less than ± 0.25 µrad for the phase difference.
Some details about digital balanced and unbalanced impedance comparators are presented in this article. A method of measuring an impedance ratio using the digital unbalanced comparator is described. Considerations about measurement errors connected with an experimental comparator setup are included. The research results are in an agreement with the theoretical assumptions.
This paper deals with modern wireless transmission systems. It focusses on real implementation of recursive least squares (RLS) channel equalizer into the system of software defined radio (SDR), in order to minimize the distance between the signal and SNR transmitting channel noise and then reduce the error rate of bit error rate (BER) transmission. The authors aimed to conduct a real measurement using universal software radio peripheral (USRP). Experimental results suggest that researched RLS equalizer embodies better BER values in comparison to commercially most common equalizers of the...
This paper presents the analysis results of experimental research of bidirectional switches based on thyristor SCR and transistor IGBT in a coil circuit of the electrodynamic actuator. A broader scope of application of the IGBT due to an oscillating frequency of the coil current has been shown because at small-capacitance of capacitor bank switching difficulties have arisen in the application of the SCR.
The article presents a method for calibration of strain gauge amplifiers with improved uncertainty in low voltage ratio range. The method is based on linearity check of amplifier using resistance circuit and combinatorial calibration method in combination with traditional strain gauge bridge simulators.
Giant Magnetoimpedance (GMI) sensors are a new family of magnetic sensing devices that show potential to detect ultra-weak magnetic fields. Recent studies demonstrated that phase-based GMI magnetometers can achieve very high sensitivities. This work aims at the development of an enhanced GMI magnetometer, based on a high resolution digital phase reading electronic circuit that makes use of the Dual Mixer Time Difference method, to read the impedance phase variations of GMI samples.
The International Electrotechnical Commission issued in 2010 a revision of the standards IEC 60060, describing how to calculate amplitude and time parameters used to evaluate high voltage tail chopped lightning impulse waveforms. However, the need for a full reference lightning impulse, in addition to the tail chopped impulse, creates difficulties for the tests and processing of the waveforms. This paper proposes an alternative method that precludes the need for the reference impulse.
The subject of the publication is a portable device for measurements of impedance magnitude in the range of 25 Ω ÷ 2.5 kΩ, with the phase angle of -90 ÷ 0°, within the frequency band of 100 Hz ÷ 100 kHz. Small measuring current, 10 ÷ 100 µA, allows for the use of miniature sensors for the measurement of sample with volume as small as several mm³. The device was designed specifically for local measurements of electrical conductivity in biological objects.
The presented innovative magnetic testing method utilises the fact, that each commercially available electromagnet can not only be used as an actuator, but also comprises internal sensor functions. This allows a huge application variety in the fields of non-destructive testing and condition monitoring of electromagnetic systems during production and within the application in the field.