1,720,960 research outputs found
Sensori e Interfacce per l'Industria e la Biomedica
No full textThe design and development of sensor readout circuits are fundamental to modern signal processing systems. This research study focuses on investigating, designing, and analyzing novel circuits for sensor interfacing, especially for industrial and biomedical fields. A broad range of original oscillator-based and bridge-based conditioning circuits are discussed and analyzed. A significant contribution is the exploration of second-generation voltage conveyor oscillators, for which 34 novel VCII-based sinusoidal oscillator circuits have been discovered. Among these, 30 schemes are single-frequency oscillators, while the remaining 4 can also be used as variable-frequency oscillators. These circuits are particularly suitable for resistive and capacitive sensor interfacing. For the case in which these VCII interfaces have to be implemented on an integrated circuit, the design of a new low-voltage, low-power VCII topology in 150 nm CMOS technology is also presented. This design aims to represent a valid alternative to commercial VCII when low-power battery-powered portable applications are of concern, as is often the case. Concerning bridge-based interfaces, this research study also presents a novel bridge interface specifically designed for a research-level biomedical sensor used for NaCl concentration measurement. Differently from other solutions reported in the literature, the proposed interface has the advantage that it can also be used with non-purely resistive or capacitive sensors, such as the one considered here. Experimental and simulation results are reported for all the proposed solutions. These validate the theoretical treatment of the analysis performed and provide insight about the circuit performance. The obtained results confirm the suitability of the proposed schemes for implementing sensor interfaces meant to be used with several industrial and biomedical sensors in a broad range of applications
Variable Frequency Oscillator-Based Resistive Sensor Interfaces Using VCII
No full textThis work deals with the realization of oscillator-based resistive sensor interfaces using a second-generation voltage conveyor (VCII). In particular, novel configurations of sinusoidal variable frequency oscillators (VFO) are presented and analyzed in detail. As discussed, the oscillation frequency can be tuned by varying a single resistor in the circuit. To the authors’ best knowledge, this is the first reported case of sinusoidal single-resistor controlled oscillators (SRCO) using VCII. Thanks to this property, the circuit is a very ideal candidate for implementing an electronic interface for resistive sensors. A theoretical analysis of the circuits is conducted to discuss their operation and outline the design process. Finally, simulated and experimental results using commercially available components are presented to validate the theoretical analysis and assess the circuit performance as resistive sensor interfaces
The Implementation of Single VCII-based RC Sinusoidal Oscillators: 28 Novel Configurations
No full textA VCII-based RC Sinusoidal VFO as Capacitive Sensor Interfaces
No full textIn this paper, a novel configuration of a sinusoidal variable frequency oscillator is presented. The circuit employs a single second-generation voltage conveyor as active element, so enjoys all the advantages of the current-mode approach. The circuit can be designed to have its oscillation condition independent of the value of one of its capacitances in a certain range. Due to this extremely attractive property, the circuit may be used as an electronic interface for capacitive sensors. A theoretical treatment of the circuit is provided to demonstrate its feasibility and to show the design process. Finally, both simulated and experimental result using off-the-shelf components are provided to validate the theoretical treatment and investigate the circuit performance as a capacitive sensor interface
A Survey on Current-Mode Interfaces for Bio Signals and Sensors
Get PDFIn this study, a review of second-generation voltage conveyor (VCII) and current conveyor (CCII) circuits for the conditioning of bio signals and sensors is presented. The CCII is the most known current-mode active block, able to overcome some of the limitations of the classical operational amplifier, which provides an output current instead of a voltage. The VCII is nothing more than the dual of the CCII, and for this reason it enjoys almost all the properties of the CCII but also provides an easy-to-read voltage as an output signal. A broad set of solutions for relevant sensors and biosensors employed in biomedical applications is considered. This ranges from the widespread resistive and capacitive electrochemical biosensors now used in glucose and cholesterol meters and in oximetry to more specific sensors such as ISFETs, SiPMs, and ultrasonic sensors, which are finding increasing applications. This paper also discusses the main benefits of this current-mode approach over the classical voltage-mode approach in the realization of readout circuits that can be used as electronic interfaces for different types of biosensors, including higher circuit simplicity, better low-noise and/or high-speed performance, and lower signal distortion and power consumption
A Novel AC Wheatstone Bridge-Based Analog Interface for RC Biosensor Applications
No full textIn this paper, a novel electronic interface circuit for RC biosensor applications is proposed and analyzed. The circuit is based on the self-balancing Wheatstone bridge, which allows for a larger dynamic range with respect to traditional bridge methods. Differently from similar previously proposed solutions that operate with purely resistive or capacitive sensors, the circuit is meant to be used with a biosensor that has a more elaborated RC equivalent circuit. In particular, it is shown that, under certain conditions discussed in the text, the system is able to measure the resistance value of the equivalent circuit of this sensor. The operation of the circuit is described in detail, as well as the results and measurements performed on a practical discrete-component implementation of the circuit
Localization of Personnel in Industrial Environments Using Passive RFID Tags
No full textThis paper presents the realization of a wireless monitoring systems for usage in industrial environments. The systems operates in a closed space, monitoring users positions, accesses to the room, and environmental parameters. Differently from other previously proposed solutions which use active tags, the proposed system operates by monitoring the position of an user in closed space through a matrix of RFID readers and passive tags. In this way, the users do not have to worry about periodically recharging the batteries for their tag, as happens in the active tag use case. A closed test space has been divided in a matrix of position tracking sectors for testing purposes, each covered by one RFID reader. The information is made available locally through a Graphical User Interface (GUI), and remotely using an Internet of Things (IoT) webserver. The system is described in detail in all its parts, from the nodes hardware and firmware, to the GUI and remote platform integration
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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