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Wolfgang Holzapfel, Nejat Mahdavi, Martin Suske
INERTIAL GRADE LASER ACCELEROMETER-PRACTICABILITY AND BASIC EXPERIMENTS

A novel laser accelerometer is introduced, its physical principle and main characteristics are explained, and preliminary experimental results are presented. The accelerometer utilizes two Nd:YAG laser crystals and a common proof mass which operate in push-pull mode. The main advantages of the described laser accelerometer are wide measuring range which covers 9 decades up to 100 m/s², very high linearity over measuring range and excellent dynamics (20 kHz bandwidth). In comparison to servo accelerometers, these results represent a high-performance sensor. The measurement uncertainty and precision analysis have been carried out according to GUM guidelines. The analysis shows that the relative uncertainty in sensitivity of the laser accelerometer amounts to 10-6.

Andrea Cataldo, Bahram Nabet, Adriano Cola, Amerigo Trotta
HMSM PHOTODETECTORS FOR HIGH-SPEED APPLICATIONS

In this paper we describe the characterization of a family of optical devices based on heterojunction and heterodimensional structures and we investigate their static and dynamic properties. Such devices are good candidates, due to their high performance, for utilization as the sensing element for the realization of sensors in the fields of telecommunications, remote sensing, LIDAR and medical imaging. First, we present a Heterostructure Metal-Semiconductor-Metal (HMSM) photodetectors that employ a uniformly doped GaAs/AlGaAs heterojunction for the dual purpose of barrier height enhancement and creating an internal electric field that aids in the transport and collection of the photogenerated electrons. In this first family of devices, two doping levels are compared showing the direct effect of the aiding field due to modulation doping. Subsequently, we analyse a novel Resonant-Cavity-Enhanced (RCE) HMSM photodetector in which a Distributed Bragg Reflector (DBR) is employed in order to reduce the thickness of the absorption layer thus achieving good responsivity and high speed as well as wavelength selectivity. Current-voltage, photocurrent spectra and highspeed time response measurements point out the better performance of this last family of detectors, as they can operate in tens of Giga-Hertz range with low dark current and high responsivity. Particularly, the I-V curves show a very low dark current (around 10 picoamps at operative biases) and the photocurrent spectrum shows a clear peak at 850 nm wavelength. Combination of very low dark current wavelength selectivity, and compatibility with high electron mobility transistors makes these devices especially suitable for the above-mentioned applications.

Christof Bosbach, Tilo Pfeifer, Frank Depiereux
ABSOLUTE DISTANCE MEASUREMENT WITH MINIATURIZED

White light interferometry or coherence radar is a well known and established measurement technique for years. But especially the field of production technology and medical technology need measurement systems with continuously increasing performance. This paper demonstrates, how the use of special optical components for higher measurement frequencies and the miniaturizing of the sensor tip can enlarge the application fields for this system. First, the fundamental aspects of white light interferometry are presented and lead to the new concept of a distance measurement system. It is shown how the inset of a special stepped mirror in the detection interferometer increases the measurement frequency and how the sensor is miniaturized using a Fabry-Perot interferometer.

Remigiusz J. Rak, Pawel Pyszlak
THE DESIGN OF A WEB-BASED VIRTUAL LABORATORY – SELECTED PROBLEMS

Virtual Instruments, as well as networked and distributed measurement systems, are the natural tools, which can be used in a modern didactic process for creating virtual laboratories offered by a group of Universities. In the paper the solution of the experimental model of the remote access to the measurement laboratory is presented. The project aims at designing the complete PC-based Virtual Instrument (VI) as a platform for acquisition, processing, presenting and distributing data throughout a global network. Computer network based measurement and automation is dramatically affecting traditional academic research and teaching. It makes researchers more productive, and improves the way students learn.

Bojan Erjavec, Janez Šetina
DESIGN OF HELIUM PERMEATION REFERENCE LEAKS WITH GENERATED FLOWS BELOW 10-14 mol/s

The calibration of helium permeation reference leaks below 10-14 mol/s is presented. The reference leak is based on the known construction with a He reservoir and a permeable glass tube leak element. The leak rate is determined in situ using the rate of pressure rise method. The reference leak is equipped with a small calibration volume containing a miniature Ti-getter pump to reduce the residual pressure rise due to outgassing and a spinning rotor gauge (SRG) to measure the rate of He pressure rise. In vacuum metrology, the SRG has been recognized as a transfer standard due to its inertness, high resolution and excellent long-term stability. The He leak rate ranging from 4,0×10-17 mol/s to 1,0×10-14 mol/s, measured at the reference leak temperature of 23°C, is linearly dependent on the He fill pressure ranging from 4,6 Pa up to 1120 Pa. Multiple He flow measurements in the 10-15 mol/s range show that a measurement uncertainty less than 2% can be achieved.

J.C. Campo, M. A. Pérez, F. J. Ferrero, M. González, J.C. Viera, C. Blanco
LABORATORY COURSE OF ELECTRONIC INSTRUMENTATION BASED ON THE TELEMETRY OF SEVERAL PARAMETERS OF A REMOTE CONTROLLED CAR

A new laboratory course in electronic instrumentation based on the telemetry of the temperature, revolutions per minute and acceleration of a remote controlled car is described in this paper. The main objective of the course is to cover the disciplines involved in Instrumentation, that is, sensor use, analog and digital design, microcontrollers, data acquisition and software, within a framework that provides highly motivating work.

Artur Cardoso, Aurélio Campilho
LEARNING THE BASICS OF ANALOGUE-TO-DIGITAL CONVERSION - AN EXPERIMENTAL APPROACH

This paper describes a set of computer-based experiments, based in LabVIEW, designed to help engineering students learn the basic concepts of analogue-to-digital conversion, such as quantization and sampling. The course was taken by Electrical and Computer Engineering students at the Electrical and Computer Engineering Department of the Faculty of Engineering of the University of Porto. A broader aim of this pedagogical experiment was to increase the students’ motivation and to increase their learning effectiveness.

Tomáš Sysala, Petr Dostál, Petr Bláha
THE MEASURING, MONITORING AND CONTROL SYSTEMS FOR THE REAL MODEL IN EDUCATION

This paper is focused on education in the field Measurement and control of technological processes. In one part of this field students obtain theoretical knowledge in an application of commercial systems for measurement, visualisation and control of technological processes. The data are measured by a programmable controller (PLC) and as the superior systems the system InTouch, Wizcon and ContolWeb2000 were used. All systems were tested on the real equipment. The programmable controller controls the surface of two communicating vessels and at the same time is a data source for master applications that are designed for the systems InTouch, Wizcon and ContolWeb2000.

C. De Lazzari, M. Darowski, E. D'Avino, F. Clemente, R. Mimmo, M. Guaragno, G. Tosti, G. Ferrari, A. Menichetti
IN VIVO AND NUMERICAL SIMULATION STUDIES ON HAEMODYNAMIC PARAMETERS AND CARDIOPULMONARY INTERACTION

In the paper the results of clinical and simulation studies on main haemodynamic parameters were compared. Cardiac output, arterial, atrial and venous pressures were measured in vascular patients during spontaneous breathing and artificial ventilation. Computer simulator was used to model a human cardiovascular system and calculate values of haemodynamic parameters in steady states. Changing intrathoracic pressure, from negative to positive values simulated cardiopulmonary interaction during spontaneous breathing and controlled ventilation. The results of the studies presented in the paper proved that numerical simulation is a very suitable and reliable tool to predict trends of haemodynamic parameters changes. Also the potential influence of mechanical ventilatory support on these parameters may by analysed before application of less or more positive airway pressure. It is an important contribution to the safety and efficacy of ventilatory support in these patients in which high intrathoracic pressure may cause a dramatic drop of cardiac output, venous return and arterial pressure.

Shigeru Takayama, Satoshi Miyajima, Eiji Yoneda, Komyo Kariya
EDUCATIONAL TOOL FOR MEASUREMENT ENGINEERING BY VIRTUAL INSTRUMENT

Virtual instrument is the system to operate the task of measurement, data processing, monitoring and system control on one virtual platform. The remarkable characteristics are on the integration and the flexible customization. Therefore, the virtual instrument has been used by researchers and engineers as a professional engineering tool. However, by using various features of virtual world, the virtual instrument is utilized as an educational tool for students to learn measurement principle, measuring object, operation method of system and various topics concerning to the measuring. By using at experiments in education, it is expected that the learning through virtual instrument enhances intuition and motivation of students to measurement engineering. This paper describes the construction and characteristics of the educational tool by virtual instrument.

Page 888 of 891 Results 8871 - 8880 of 8905