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This paper describes the most important factors influencing the aluminum electrolyte capacitor showing, in particular, the effect of temperature on the lifetime of this device. The automation of the measurement system, with the oven interfaced with a PC, was also completed to control all the involved parameters.

Optical machines with a vision system containing a video camera are designed to perform contact-less three-dimensional measurements. They are becoming more widely used in the industrial sector because of the many possibilities for automation they permit and because of the speed and economies in measurement tasks that can consequently be obtained. Within dimensional control these machines introduce significant characteristics of flexibility, savings and reliability. Therefore the purpose is to identify the principal metrological characteristics of such machines and so characterise the metrological traceability of the measurements obtained from them. The aim is to qualify each part of the optical machine as well as on the whole. Previously, no metrological traceability of this equipment has been provided in primary metrology, either at national (SIT—Sistema di Taratura in Italia—Calibration System in Italy) or at international level (EA–European co-operation for Accreditation). For this reason we develop a mathematical model that permits the evaluation of the measurement uncertainties in the use of such a device. The purpose is to obtain the certification of the measurement results furnished by the optical machine in as broad a context as possible. The experimental results of the tests are introduced for validating the proposed method. This paper provides the basis of the expression of the uncertainty of a measurement result obtained using the optical measurement machines and it shows the necessary requirements for the numerical evaluation of such uncertainty.

Heart rate is one of the main physiological variables to monitor the energetic behaviour of observed animals and also to study the influence of the environment around these animals. In 1996 at the University of Florence, the Departments of Animal Biology and Genetic and the Electronic Engineering, started a joint research project monitoring the cardiac activity of animals and building a hardware/software device in order to measure the instantaneous and average heart frequency of animals with a skeletal barrier.

Circulating levels of atrial natriuretic factor (ANF), the education of myocardial contractility (evaluated by ejection fraction, EF) and different pain intensity were assessed in patients with uncomplicated acute myocardial infarction (AMI). We investigated the relationships between ANF, or EF, and pain intensity by identifying appropriate statistical methods and introducing a procedure for pain intensity measurement. Pain in AMI is variable in intensity, often severe and in some instances intolerable, but in over 20% of AMI patients it may be absent. By using plasma ANF concentration and self-report of AMI pain as parameters, we described a statistical method verifying that AMI patients can be categorized into two significantly different groups: pain and no-pain. Pain is a purely personal experience that includes both the original pain sensation (OPS), depending on the intensity of the stimulus, and the individual emotional reaction component (ER). We developed a method to deduce the OPS from the patient's self-report of AMI pain and then devised an instrument which estimates the ER of each patient by applying electrical stimuli of different intensities. The procedure to disclose a significant correlation (not present by using the self-report of AMI pain) between OPS and ANF, or EF in pain patients is described. The inverse correlation found between EF and OPS suggests that the extent of myocardial damage may play a role in AMI pain onset and affect its intensity. However, when ANF concentration exceeds a threshold value, AMI patients reported only an unpleasant sensation; this result indicates that ANF may be involved in preventing AMI pain. The statistical method introduced for the comparison between the regression lines of ANF and EF in pain and no-pain patients showed that the interdependence between ANF and EF is not influenced by pain, confirming that EF is the major trigger for ANF release in AMI.

A basic optical time-domain reflectometry (OTDR) configuration is shown. An optical pulse typically 10-10000 ns long is launched into a test fiber via a directional coupler. The backscatter radiation from the fiber is detected and processed and the backscatter signature displayed. Since the backscatter power is directly related to the fiber loss and its arrival time back at the OTDR to the distance traveled, it is for these two parameters that the OTDR needs primarily to be calibrated. Several methods for carrying this out are described in the IEC 61746 document. In this paper, we present measurements made with the recirculating delay line, which is a passive method among the distance scale calibrating ones.

A symbolic formulation approach is applied to the problem of computing testability features of analog linear networks. The program, SAPTES, obtained by following this approach is presented. The program can be a very useful tool for designers and researchers in the field of linear analog circuits. SAPTES, which is written in LISP and runs on MS-DOS personal computers, is able to compute the testability of linear circuits of rather high complexity (composed of tens of components and nodes). Computational times range from a few tens of seconds to some tens of minutes on medium speed computers. The program is easily transportable to workstations or a mainframe, and, for the mainframe, program performance will considerably increase. >

The offer provided by an electric utility combines many characteristics of a service together with the continuous delivery of electricity as a product. The quality of electricity as a processed material, resulting from a continuous process and having immediate delivery in continuous flow can he adversely affected by the end-use processes of other customers, as well as by the continuous-process reliability. Hence, the guidelines endorsed by ISO Standard 9004-3 for the quality management of processed materials must be suitably tailored in the case of electricity. Problems that must be dealt with to control the characteristics critical to quality of electricity are discussed. In this connection, measurement activities oriented to quality management are considered, mainly to outline unsolved problems.

A method for the performance evaluation of digital measurement instruments based on asynchronous sampling and nonlinear signal conversion is proposed. The authors propose a performance index for the comparison of different asynchronous strategies and develop the analytical form of that index for two sampling techniques, equally spaced and random. The idea is to interpret the instantaneous output of the instrument as a discrete random variable with a uniform distribution over the successive occasions of measurement. Thus, the asymptotic variance of the reading can be a sum of contributions, each of which is obtained by weighting the contributions relative to each spectral component of the signal according to a frequency-dependent coefficient which is assumed to the performance index. >

To investigate the relationship between plasma atrial natriuretic factor (ANF) levels, impaired myocardial contractility and pain intensity in acute myocardial infarction (AMI) we introduced a procedure estimating the pain component not influenced by the individual emotional reaction to stress, i.e., the original pain sensation. We deduced this pain component during AMI by correcting the personal report of AMI pain, quantified on a VAS, with the emotional reaction of each patient estimated by using a custom-built instrument which applies electrical stimuli of different intensities. Twenty-five patients with uncomplicated AMI were studied. According to plasma ANF levels and AMI pain values reported on the VAS, patients were categorized into 2 groups: pain and no-pain. Plasma ANF levels were significantly lower in pain (35.9 ± 2.5 pg/ ml) than in no-pain patients (70.8 ± 3.3 pg/ ml), whereas the ejection fraction (EF) was significantly higher in pain (49.6 ± 1.7%) than in no-pain patients (29.3 ± 1.9%). Within each group, a negative correlation was found between ANF and EF; the corresponding regression lines did not differ significantly in their slopes or intercepts, suggesting that AMI pain does not affect ANF release. The significant negative correlation between original pain sensation and EF found in pain patients indicates that this pain component may be useful to gauge the severity of impaired myocardial contractility during AML Moreover, the much higher plasma ANF levels observed in no-pain patients suggest that ANF may be involved in preventing AMI pain.

A model is developed for the relation between the performance degradation of a component in a step-stress test and the stresses applied during the test. Then a methodology is proposed, based on this model, which uses step-stress testing to estimate the parameters of the model that represents the predominant failure mechanism of the component. Experimental results, obtained by testing a lot of metallic layer resistors and applying the Arrhenius model, are reported.

A hardware prototype of vector spectrum analyzer, which is based on a randomized sampling strategy and associated alias-free digital signal processing (DSP) algorithms, has been fully designed and implemented. The instrument exploits a couple of identical independently programmable digital data acquisition channels, whose synchronization allows to sample the input signal at instants that can be very close along the time axis (tens of picoseconds), against a maximum single-channel average throughput rate of 250 ksamples per second (kSa/s). This architecture has shown to be suitable for the accurate implementation of the randomized periodic sampling with uniform jitter on which the instrument is based. In addition, the design solutions adopted for the sampling command generators, which exploit the interaction between a digital gate signal and a phase-controlled sinusoidal wave, together with the particular analytical definition proposed for the spectral estimators, have allowed to make practically negligible the quantum time according to which the sampling instants are generated. Experimental results are provided, which validate both the alias-free spectrum analysis technique and the capability of the architecture proposed of reliably implementing the analytical benefits deriving from the randomized sampling strategy adopted.

A broad-band digital harmonic vector voltmeter previously proposed and theoretically studied by the authors was implemented by using a special-purpose random sampling strategy to avoid the bandwidth limitations due to the finite conversion time of the S/H-ADC devices. The experimental results showed that the bandwidth of the instrument is limited only by that of the S/H devices of the acquisition channels, according to the theoretical findings. The maximum amplitude error was not greater than 2%.

This paper describes a general purpose high reliable data acquisition system which allows A/D converter testing by histogram and two tone tests for the fault diagnosis on the same board. A reliability analysis has been carried out in order to optimize the project, the components choice and redundancy configuration. The software has been written in Matlab and LabVIEW, with an easy graphical user interface.

In the paper we consider a statistical approach based on the semi-Markov technique for the measurement of the availability performance of a complex electronic system. Considering the system as a combination of items, the approach allows one to evaluate the availability of the overall system, starting from the reliability and maintainability performances of each item.