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This paper presents the development and characterization of an electric power generator device using a piezoelectric material made of Lead Zirconate Titanate (PZT). The device was built like a mechanical structure in which were coupled eight piezoelectric cells subjected to cyclical loads of traction and compression, which work as electricity generator. For the experimental characterization, a system...
Shape memory alloys (SMA) have been the subject of several studies due to their excellent physical and mechanical properties. For this reason, a wire SMA is used in various applications as thermomechanical actuators that are subject to repeated thermal cycling in a range of temperatures and variable loads. The mechanical stability is a fundamental behavior that need to be understood to project well...
This paper presents a non-uniform sampling analog-to-digital converter (ADC) architecture using an adaptive level-crossing technique. The architecture can be dynamically configured through three parameters that allow the user to match the ADC to the signal to be acquired or to application constraints. When applied to sparse signals, this architecture outperforms uniform sampling architectures. In...
With the purpose of realizing an integrated circuit and knowing that the capacitors generally use less space than resistors in the integration process, we propose an architecture of a pulse-width programmable linear amplifier that uses a switched capacitor instead of resistors. This architecture was obtained from modifications of a programmable gain amplifier developed in previous work. The proposed...
In this article, we examine different architectures of analog-to-digital converters (ADCs) and propose a flexible architecture based on sampling by crossing levels and adaptive quantization step, aiming at reducing the energy required to convert and process specific signals. The proposed architecture has parameters which can be configured by the user, in order to adapt the conversion process to the...
In this paper, a data fusion proceeding was developed based on the Maximum Likelihood Estimation technique (MLE), considering the variables to be fused, having symmetric triangular probability distributions. This procedure was utilized to the wind speed measurement by means of indirect measure of the ultrasonic time-of-flight (ToF), fusing two independent measurements obtained by threshold detection...
An architecture of a programmable gain integrating amplifier is presented. The circuit operates using two clock phases for sampling and amplification and the gain is defined by the ratio between the pulse-width of a control signal and the integrator time constant, which is defined by a resistor and capacitor. The proposed architecture also has configuration switches that enable its use in the modes...
In this paper, we analyze the propagation of uncertainties in a programmable gain amplifier. The circuit is based on a superregenerative configuration and its gain is set by the duty-cycle of a digital signal. The uncertainty analysis allows for better component specifications in the circuit design, identifying the sources of uncertainties that play major role on the final gain uncertainty.
In this paper some considerations about the application of nanocrystalline alloys in toroidal cores for current transformers used for measurement purposes are presented. Based on the electromagnetic properties of these materials, such as high relative magnetic permeability, magnetic flux density saturation, high resistivity and low hysteresis losses are discussed. Also, will be discussed how the former...
A method for measuring multi-level fluid, based on ultrasonic echo detection by means of the wavelet transform (WT), is presented. The Wavelet Transform provides a tool for analyzing the time frequency evolution of transient signals. This highlights the excellent performance shown by the WT as a powerful tool for the analysis of echoes in a noisy environment. A mother wavelet is utilized to obtain...
In this paper, the effect of dc amplifier input offset voltage on the static and dynamic performances of a generic constant-temperature thermoresistive-sensor-feedback circuit (CTC) is reviewed. A negative-feedback automatic control circuit for the input offset voltage is proposed in order to assure a stable operation of the CTC and to obtain optimal response time. Experimental evaluation results...
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