E. Zelenskiy, Y. Kononov, V. Rudnev
THE LINEAR STATE ESTIMATION ALGORITHM TO IMPROVE THE ACCURACY OF MEASUREMENTS OF THE INSTANTANEOUS VALUES OF CURRENTS AND VOLTAGE IN ELECTRIC NETWORKS

The paper presents an algorithm which allows to reduce measurements’ inaccuracy of an instantaneous values of currents and voltages in electrical networks. The considered approaches are used in the prototype stand for the non-sinusoidal power flows modeling based on LabVIEW programming environment using the facilities of modules NI-9225 and NI-9227. Experiment was performed to model non-sinusoidal load flow on the prototype stand for a simple AC 10 kV closed network.

Y. Kononov, M. Ospishchev, V. Rudnev, S. Mikhaylov
THE EFFECT OF GPS-SIGNAL QUALITY ON TIMING ACCURACY OF SEA 9724 AND NI 9467 GPS MODULES SYNCHRONIZATION

The work results from the research of PPS-signals mistiming derived from SEA 9724 and NI 9467 GPS receiver modules. Effect of the number of satellites being tracked and tracking time has been studied. The mistiming value does not exceed PPS 0.1 µs at number of satellites greater than 5 for SEA 9724 and greater than 3 for NI 9467. It is proposed to use the value of co-ordinates as the initial information which will allow oscillating PPS at the number of satellites fewer than 4.

Pavel Ripka
ELECTROMAGNETIC RESPONSE OF SOIL

The possibility of measuring both time-domain and frequency-domain response on small soil samples would allow one to predict the influence of such soil on various types of mine detectors without field trial. We have measured the time-domain soil response on standard cylindrical samples. The time response to abruptly removed magnetic field is similar to 1 / t^x, where x is between 1.1 and 1.3. We have also measured frequency-domain response in the 400 Hz to 480 kHz band by various independent methods and compared with values calculated from the time response. This study shows that for soils with high content of nanoparticles the complete frequency characteristics should be measured instead of traditional two-point measurement.

Luis S. Rosado, Filipe A. Cardoso, Susana Cardoso, Telmo G. Santos, Pedro M. Ramos, Paulo P. Freitas, Moisés Piedade
COMPARISON OF SPIN VALVE AND MAGNETIC TUNNEL JUNCTION MAGNETO RESISTIVE SENSORS IN EDDY CURRENT TESTING PROBES

This paper compares two different magneto resistive sensor technologies used on the same configuration of eddy current testing probe. Two dimensional testing results on a friction stir welding aluminum joint were used to compare spin valve and magnetic tunnel junction sensors. These results showed that, magnetic tunnel junction sensors, provided a significant improvement on the signal to noise ratio and signal amplitude over spin valves.

Dragana Popovic Renella, Sasa Spasic, Sasa Dimitrijevic, Marjan Blagojevic, Radivoje S. Popovic
AN OVERVIEW OF COMMERCIALLY AVAILABLE TESLAMETERS

The Hall-effect based Teslameters (also called Gaussmeters) are the mostly applied instruments for measuring DC and AC magnetic flux densities in modern science and industry. This paper gives an overview of commercially available Teslameters at the high-end performance level. The Teslameters have been evaluated by following characteristics that are published by suppliers: probe dimensions, magnetic field sensitive volume, accuracy, magnetic resolution, measurement range, frequency bandwidth, temperature coefficient sensitivity, and price/performance ratio.
The Teslameter that best matches the measurement needs in various application fields incorporates a 3-axis integrated Hall probe, analog electronics based on the spinning-current technique, an analog-to-digital converter, an embedded computer, and a touch-screen display. The 3-axis Hall probe is a single silicon chip integrating both horizontal and vertical Hall magnetic sensors and a temperature sensor. The spinning-current eliminates most of the Hall probe offset, low-frequency noise, and the planar Hall voltage. The errors due to the Hall sensor non-linearity and the variations in the probe and electronics temperatures are eliminated by a calibration procedure. The errors due to the angular imperfections of the Hall probe are eliminated by a calibration of the sensitivity tensor of the probe. This Teslameter can measure magnetic field vectors from about 100 nT to 30 T, with the spatial resolution of 100 µm, magnetic resolution ±2 ppm of the range, the accuracy 0.002% of the range, a temperature coefficient less than 5 ppm/°C, and angular errors less than 0.1°.