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Optical rotary encoders generate nonlinear sine and cosine signals in response to a change of angular position that is being measured. Due to the nonlinear shape of encoder output signals, encoder sensitivity to very small changes of angular position is low, causing a poor measurement accuracy level. To improve the optical encoder sensitivity and to increase its accuracy, an improved linearization circuit based on pseudo-linear signal generation and its further linearization with the two-stage piecewise linear analog-to-digital converter is presented in this paper. The proposed linearization circuit is composed of a mixed-signal circuit, which generates analog pseudo-linear signal and determines the first four bits of the final digital result, and the two-stage piecewise linear analog-to-digital converter, which performs simultaneous linearization and digitalization of the pseudo-linear signal. As a result, the maximal value of the absolute measurement error equals to 3.77168·10−5 [rad] (0.00216°) over the full measurement range of 2π [rad].

In this paper the realization and optimization of a novel coreless folded bus bar current transducer based on a Hall effect sensor are presented. The proposed transducer utilizes the bus bar folded in the shape of a Cyrillic letter “ $${\Pi }$$ ” to suppress impact of the skin effect, and it is capable of measuring AC and DC currents up to 250 A at 10 kHz frequency with nonlinearity less than $$\pm 0.5\%$$ in the entire current range. Methods for suppression of the skin effect impact and impact of stray magnetic fields are presented along with the experimental test results. Some of the proposed methods are novel and have never been evaluated.

A three-dimensional (3D) model of a high-power ultrasonic, composite, unidirectional transducer is proposed in this paper. The proposed 3D Matlab/Simulink model of the composite transducers predicts the thickness and the radial modes of oscillation as well as their mutual couplings. This longitudinal, prestressed, asymmetrical, piezoelectric transducer, which consists of two active piezoelectric layers, front, back and central oscillating metal mass, is realized. Due to its special structure, the central mass is not bounded using a bolt and performs unidirectional piston motion as compression and expansion occur in cycles keeping the axial dimension of the transducer roughly constant because of mutually opposite polarization of active elements. The electromechanical equivalent circuit of the transducer, representing one-dimensional (1D) model, is derived first and is also presented in this paper, while the resonance frequency equation is obtained analytically. Few composite transducers are designed and manufactured. Their resonance frequencies are measured and compared with the analytically obtained results for a large number of electrical connection combinations. In order to demonstrate the capabilities and limitations of the 1D model, comparison with the results from the 3D model are made. Results show that the measured frequencies are in good correspondence with the analytically obtained from 1D model only for the thickness modes and from the 3D model for the thickness and the radial modes of oscillation and their mutual coupling.

Deformation of the natural magnetic earth field by introducing ferromagnetic objects and electrical devices leads to the creation of an anomalous magnetic field in which a person resides. The longest period of time a person resides in bed is in a static position, and according to scientific facts, the magnetic field change has significant impact on health. The paper calculates the magnetic field in a real bed with a ferrite structure and a mattress with ferrite springs. The author also presents the latest scientific findings on the health effects of staying in enhanced magnetic field for longer rest periods during night breaks.

The paper provides an overview of coreless open-loop current transducers based on Hall effect sensor CSA-1V. Depending on the implementation method and current range, the presented transducers are divided in the four groups. The transducers are capable to measure AC and DC currents ranging from several tens of miliamperes up to several hundreds of amperes. Methods for resolving issues with the skin effect and stray magnetic fields are also presented including the experimental test results. Some of these methods are novelty and have never been presented in literature.

A low-cost teslameter based on a Hall effect sensor MLX90242 is proposed in this paper. The proposed teslameter is built around a PIC18F4550 microcontroller and it can measure magnetic flux density in the range between -55 mT and 55 mT. Temperature stability of measurements originates from the MLX90242 sensor itself. In order for the proposed transducer to be accurate, it has undergone a calibration procedure using a highly accurate teslameter employed as reference instruments and high-quality variable-field electromagnet. The proposed teslameter can store measurements on a PC via built-in USB communication. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III43014]

This paper reviews the realization of a simple wireless measurement system for measurement of UV radiation based on a photodiode as a sensor. The realized system was designed to be a constituent part of a photovoltaic tracking system and the associated weather station both currently developed at the Faculty of Electronic Engineering in Nis. The development of system hardware is presented as well as the calibration of the realized system and the test results obtained in the laboratory before and after calibration.

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.