Uglješa Jovanović

Realization and optimization of bus bar current transducers based on Hall effect sensors

In this paper the realization and optimization of two coreless open-loop bus bar current transducers based on a Hall effect sensor are presented. Two types of bus bar are evaluated: flat rectangular and rectangular with a restrictive region in the middle. Both realized transducers are capable of measuring AC and DC currents up to 300 A and 10 kHz frequency with nonlinearity less than 0.3% in the entire range. Several methods for resolving issues with the skin effect and stray magnetic fields are presented along with the experimental test results. Some of the presented methods are novel and have never been evaluated.

Low-cost wireless dust monitoring system

In this paper a prototype of wireless system for dust density measurement is presented. The system is developed with inexpensive commercially available components and can measure dust density up to 0.5mg/m3. The system is modular and consists of a base station connected to a PC via USB communication and an autonomous sensing node equipped with an optical dust sensor GP2Y1010AU0F. A virtual instrument made in LabVIEW is created to monitor the system operation, data acquisition and data storage.

A Matlab/Simulink 3D model of unsymmetrical ultrasonic sandwich transducers

Ultrasonic sandwich transducer is a half-wave resonant structure which oscillates in thickness direction. This paper presents a new Matlab/ Simulink model of a prestressed unsymmetrical ultrasonic sandwich transducer, which is modeled by applying three-dimensional (3D) Matlab/Simulink models of piezoceramic rings and metal endings derived from the piezoceramic ring model. With the cascade connection of the piezoceramic rings model with metal endings model, a complete model of ultrasonic transducer is obtained. Using this model one may determine any transducer transfer function, whereat is taken into the account the external medium influence, as well as the influence of the thickness and radial modes of each transducer component. The electromechanical equivalent circuit of the hammer transducer, which represents onedimensional (1D) model, is also derived and presented in this paper. The comparisons between experimental and theoretical results are quite good and validate the new analytical 3D design approach.