Slobodan S. Milovancev

Low frequency stochastic true RMS instrument

A stochastic instrument for true RMS measurement in the low-frequency range is presented. Variable accuracy is achieved by varying the measuring time of the instrument. Inaccuracy of 0.1% of full scale is demonstrated. A complete theory of operation of the instrument is developed and the explicit dependence of measurement error on the measured signal shape is given. Simulations and experimental results strongly confirm the described theory. Simple hardware structure allows easy implementation of parallel measurement.

Digital Stochastic Measurement of a Nonstationary Signal With an Example of EEG Signal Measurement

This paper presents a method of digital stochastic measurement (DSM) of nonstationary signals. The method is based on stochastic analog-to-digital (A/D) conversion and accumulation, with a hardware structure based on a field-programmable gate array and a low-resolution A/D converter. The characteristic of previous implementations of DSM was the measurement of stationary signal harmonics. This paper shows how DSM can be extended and also used when it is necessary to measure the time series of nonstationary signals. An electroencephalography signal is selected as an example of a real nonstationary signal, and its DSM is tested by simulations and experiments. Tests are done without adding noise and with adding a noise-varying signal-to-noise ratio (SNR) from 10 to -10 dB. The results of simulations and experiments are compared versus theory calculations, and the comparison confirms the theory. The presented method provides control of the measurement uncertainty even at low SNR values, by controlling the sample rate of the used A/D converter. This enables designers of measurement systems to choose fast A/D converters with low resolution to achieve higher measurement accuracy.

A new approach to voltage measurements in power systems

In the paper a new scheme for power line voltage measurement is suggested. It uses coreless measurement transformer because it is precise, linear and assures galvanic separation of measuring instrument from high input voltage as well. Theoretical linearity is calculated and it is the most important property of the device. The amplitude and phase linearity limits are significantly lower then 16-bit limit.

A precision power amplifier for calibration systems

A simple design for a precision, high-voltage and high-current amplifier is given. A pair of such amplifiers is implemented in the ac voltage, current, power and phase angle calibration system in Federal Bureau for Measures and Precious Metals in Belgrade, Serbia. The measurement results of output stability, as the most important parameter in metrology applications, are presented.

General method for quantization error predetermination in digital measurement system

Digital measurement instruments and systems have the quantization error as a systematic error, since there is no way to eliminate it. The standard intention is to hold it below tolerable limit. The paper deals with the method how to predetermine quantization error if the A/D converter word length, the numeric processor word length, the D/A converter word length and the measurement data processing algorithm are given.