The paper compares four methods (zerocrossing with pre-filtration, integrated zero crossing, windowed and interpolated FFT, and dynamic parameter estimation with pre-filtration) of instantaneous power-line frequency estimation from the point-of-view of their sensitivity to higher-order harmonic content and to the additive noise and from the point-of-view of their response time. Comparison is based on computer simulations.
The paper presents the computerized multichannel system for monitoring and testing the dynamic processes in electrical and hybrid drives. The system operates "on line" in very short response time on telemetric base. It provides the continuous measurements of the following parameters: rotary speeds, torques and electrical currents and tensions. The measurement date is stored in the computer so it allows further "off line" analysis and conversion. This way the galvanic connections are avoided between wires and transducers. The wireless connections provide wide frequency band, good accuracy,...
In this paper we present a frequency-meter based on the method of reciprocal frequency-meter. For the implementation of the frequency-meter we have used an FPGA and a microcontroller. We have measured frequencies between 0.05 Hz and 10MHz. The measuring ranges are: 0.05 Hz to 0.5 Hz, 0.5 Hz to 5 Hz and 5 Hz to 10 MHz. The measurement times for the corresponding ranges are: 20 to 10 s, 2 to 1 s and 0.2 to 0.1 s respectively. The base error of the frequency-meter is 2·10 -6 .
In this paper we present a digital generator which produces sine-wave signals with variable frequency. The shape of the signal is stored in memory. The modification of the frequency is achieved by changing the number of samples used to generate a period. The digital circuitry of the generator is implemented using a field programmable gate array (FPGA) and a microcontroller. Experimentally we have generated sine-wave signals with frequencies between 1÷100 kHz and analysed their content in harmonics. Finally we present some possibilities for optimising the generator.
Various error sources cause linearity errors which degrade the performance of D/A converters. The paper presents a non-linear model to describe multiplying D/A converters. A Walsh transformation based diagnostic tool is used to determine the model parameters. Based on this model, a calibration scheme is derived, in order to compensate the non-linear behaviour of the converter. Practical applicability of the proposed method is shown by measurements performed on a custom designed test circuit.
This paper describes the development, under a graphical programming environment, of a software application to control a modified Wheatstone bridge for measurement and calibration of high value standard resistors. Intuitive panels allow an easy user interface to control the bridge (three high performance measurement equipment and a variable DC voltage source), through a GPIB bus and on screen indications to all non-automatic operations. The user can graphically preview the intermediate results and decide to accept or refuse the data. The data can then be used to calculate the temperature and...
In the paper the analytical evaluation of theuncertainty on signal parameter estimation in frequency domain is dealt with. Two different and widely diffused algorithms able to compensate the spectral leakage effects due to asynchronous sampling are considered. The combined uncertainties on the final results (tones frequency, amplitude, and phase) due to the propagation of the uncertainty on the input samples are analytically evaluated. Simulation tests are then carried out in order to validate the obtained formulas.
Architecture and properties of the virtual probes created by the analog modules of the IEEE Std 1149.4 test bus are presented. Capabilities of the bus co-operated with the CIM 97 Multidiatest Measurement System in the area of the analog signal were investigated on the examples of the resistance, capacitance and inductance measurement. Application of the bus, when access to analog nodes of the circuits is limited and the analytical method is needed for supporting of testing, is discussed.
We propose a method for measuring the phase angle between two low-frequency sinusoids. In this method, we integrate one signal between a zero crossing of this signal and a zero crossing of the other signal. Two different integrals are performed, where each integral is a function of the amplitude and frequency of the integrated signal and the phase angle between the two signals. The phase angle is obtained through simple algebraic manipulations.
The objective of this work is to describe a versatile multifunction electrical digital meter based on personal computer; it has been developed for incorporation into a laboratory testing system. The meter uses two 12-bit A/D. The A/Ds are connected to parallel printer port of PC. The work was developed for Measurement of power. Using a programming language Turbo C++ was calculated: rmsVolts, rmsAmps, volt-amps, Reactive Power, Phase angle, frequency, Active power, watts-hour, resistance, capacitance and period. The values are shown at the monitor as a 4-digit display. The accuracy of meter...