1,721,067 research outputs found
Guest editorial: Opportunities and threats in providing remote access to manufacturing-related environments
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The Huang Hilbert Transform for evaluating the instantaneous frequency evolution of transient signals in non-linear systems
No full textTraditional approaches for the analysis of transient signals are generally based on the apriori knowledge of the system under test for choosing a preliminary set of waveforms; consequently, they use a mathematical algorithm to decompose the signal itself into a suitable combination of the chosen waveforms. Conversely, this work is aimed to investigate the possibility of extracting the features of transient signals through the evaluation of their instantaneous frequency evolution. For this aim, the Huang Hilbert Transform (HHT) has been exploited (i) to decompose the input signal into a set of Intrinsic Mode Functions (IMFs), (ii) to extract the IMFs analytical signals, (iii) to evaluate their amplitude and phase evolutions, (iv) to compute the instantaneous frequency of the input signal and (v) to extract the signal information searched for. In order to evaluate its performance, the proposed approach has been firstly applied to a synthesized signal with known instantaneous amplitude and frequency evolution. Successively, in order to assess the reliability of HHT results with signals acquired on experimental circuits, the current flowing in an actual RLC circuit during its free natural oscillation has been analyzed. With the aim of analyzing the performance gained also in the presence of evident non-linearities, a saturable inductor has been introduced in the test circuit. Also in this case, by comparing the achieved results with those shown by different traditional approaches, great advantages have been experienced in terms of accuracy. Furthermore, beyond the accurate frequency representation, the experimental results evidenced the intrinsic ability of the proposed approach to extract meaningful information related to the knowledge of the underlying process. Finally, it is worth noting that the results reported in this paper requested no apriori knowledge about the signal/process under test
Low-cost prototype for the electronically compensation of Current Transformers
No full textIn this paper, a novel method for the compensation of
commercial current transformers (CTs), based on the insertion of
a series analog circuit at the secondary winding is proposed. The
method allows the enhancement of existing transformers which
can, thus, reach the 0.2 ratio error and a phase error lower than
the measurement sensitivity, only by means of the insertion of a
low-cost circuit. The feasibility of the method has been preliminarily
verified by applying the model of the compensating circuit
to the actual signal acquired at the transformer terminals. Successively,
the circuit has been realized and applied to a commercial
CT. Experimental tests, aiming at assessing the compensation
performance, have been conducted by varying the magneto-motive
force at both industrial and higher frequencies
Transient analysis in non-linear systems through the Huang Hilbert Transform
No full textThe paper deals with the use of the Huang Hilbert Transform (HHT) for the analysis of transient signals in non linear circuits. Differently from traditional methods that decompose a signal as the sum of apriori adopted waveforms, HHT procedure decomposes the signal of interest in oscillatory modes aposteriori determined, in dependence on the signal characteristics, giving, thus, a better information about the physical characteristics of the observed system. The performance of the proposed analysis method has been evaluated by applying the HHT to the current acquired from an actual RLC circuit during its free natural oscillation. The circuit involves a saturable inductor, therefore the HHT capability of providing physically meaningful information accounting for both non stationarity and non linearity has been appreciated
Performance assessment of Field Programmable Analog Arrays
No full textField Programmable Analog Arrays (FPAAs) are reconfigurable analog modules introduced on
the electronic market in the last decade. Their operation and, in particular, their programmability
is achieved owing to the use of switched capacitors technology. At least in principle, they seem
to be a very attractive and powerful tool to design analog circuits whose parameters have to be
tuned to signal variations as in carrying out sensor conditioning systems. But the aim of exploiting
their possibilities in the field of metrology requires complete characterization and performance
assessment of the involved building blocks.
With this goal, in the paper, the metrological characterization of the most commonly blocks
to be used in analog conditioning circuits, such as amplifiers and filters, is performed. These
blocks have been characterized in terms of both frequency response and step response and the
obtained experimental results have been compared with those expected from theoretic analysis.
Concluding remarks are then deduced to furnish practical hints in the use of FPAAs in measurement
applications
Field Programmable Analog Arrays for conditioning ultrasonic sensors
No full textThis paper proposes the use of field programmable analog arrays (FPAAs) as adaptive conditioning blocks for ultrasonic sensors. The uncertainty achievable through this technique, in fact, results very sensitive to the measurement conditions, due to the attenuation affecting the echo during its propagation. Indeed, FPAAs emulate analog circuits whose characteristics have to be dynamically tuned according to different operating conditions.
Actually, the signal provided by the ultrasonic sensor is properly processed in order to improve the overall measurement accuracy. In this paper, the prototype of a distance meter based on time-of-flight (TOF) measurement is presented in order to evidence the advantages gained by FPAA features in processing the sensor output to compensate echo attenuation and distortion versus target distance.
The prototype working is supervised by a digital signal controller (DSC) whose tasks are: 1) driving the ultrasonic transducer; 2) performing the echo acquisition; 3) tuning on the fly the FPAA features; 4) evaluating the TOF; 5) measuring the target distance; and 6) delivering the final result to the end user.
This paper is completed by the results achieved in a number of experimental tests allowing interesting considerations to be drawn. In particular, the experiments confirm the prototype reliability and effectiveness also with ultrasonic echoes characterized by very low signal-to-noise ratios
An E-Learning portal for Electrical and Electronic Measurement courses employing remote instrument control
No full textIn the paper the realization of an E-learning portal for Electrical and Electronic Measurement courses is presented. The main focus is the implementation of a remote laboratory, to enable students at home to perform experimental activities through the Internet network. The authors illustrate, as case-study, a Web-based measurement station to acquire conducted interferences emitted by a Variable Speed Drive (VSD), which consists of Pulse Width Modulation (PWM) inverter, asynchronous three-phase motor, and histeresys brake axially tied to the motor.
Students log on a Web site realized through HTML pages and published through LabVIEWTM G Web server; they can activate the test circuit, set its working conditions, carry out the measurement procedures, and process the results. That is accomplished through a PC that receives client requests through CGI programs, controls the measurement instruments through IEEE 488 interface bus and programs realized in LabVIEWTM software and, eventually, presents the measurement results to the client on an HTML page
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