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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.

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.