1,721,193 research outputs found
A system for the measurement of wire-rope defect positions
No full textElectromagnetic tests are nowadays widely employed to early detect defects of metallic wire ropes. Commercial instruments for electromagnetic tests are able to highlight small defects but provide only a rough estimation of their positions. An analysis of the uncertainty contributions that affect the defect position measurements is described in this paper and an improved measurement system is also presented. The system is designed to be employed with commercial instruments for electromagnetic tests and it is composed of a laser-based detector, a digital acquisition system and a personal computer. A specially designed algorithm locates a reference point in the rope and measures the distance between the defects and the reference. Preliminary experimental results obtained with a standard rope are also presente
A Measurement System for Lyophilization Process Monitoring
No full textLyophilization processes are widely employed in the industrial field to preserve several kinds of substances, such as foods and drugs. In some cases, e.g. during the process optimization, the real-time measurement of mass and temperature is important to monitor drying rate and to prevent product damages because of unsuitable temperatures. In these cases sensors and measurement instruments have to be installed inside the vacuum chamber of the freeze dryer, where temperature and pressure can reach -60degC and 1 Pa respectively. This paper deals with the problems related to the measurement of mass and temperature inside freeze dryers and describes a measurement system that has been specifically designed to monitor lyophilization processes
A Low-Cost Optical Sensor for Non contact Vibration Measurements
Full text linkThis paper presents a new noncontact method to measure vibrations by using a low-cost optical approach that is able to provide a submicrometer resolution. The transducer exploits a simple optical setup based on an intensity-detection scheme that is implemented with plastic optical fibers, whereas innovative non demanding spectral data processing allows compensation of the vibrating surface reflectivity and the gains of the measurement chain. The performance of the proposed system has been assessed, through comparison with other techniques, by performing several measurement tests that use targets vibrating at frequencies from a few hertz up to several tens of kilohertz and with different values of reflectivit
Measurement uncertainty issues in freeze-drying Processes
Full text linkThis paper deals with problems that have to be faced when performing mass and temperature measurements of substances subjected to freeze-drying processes. A brief description of a lyophilization process is initially presented and a deep investigation is performed in order to identify the main uncertainty contributions that affect mass and temperature measurements. A measurement system is then described that has been specifically conceived to work inside a freeze-dryer. Experimental results are reported that refer to the metrological characterization of the proposed measurement system and to its use for the monitoring of real freeze-drying processes. Experimental tests are also described that have been conceived to estimate the uncertainty contributions strictly related to this specific applicatio
Outdoor Experimental Laboratory for Long-Term Estimation of Photovoltaic-Plant Performance
Full text linkThis paper describes an outdoor experimental laboratory that has been developed to estimate the performance of photovoltaic (PV) plants in operating conditions. The laboratory includes ten different plants and a data acquisition system that has been specifically conceived to monitor the actual behavior of the plants. The main goals of this laboratory are the comparison among the performance indexes of different PV technologies and the long-term drift estimation of the specifications of the plant components. In this paper, the first results that refer to a time interval of nine months are reported, which allow a comparison among the monitored PV plants to be performed. A description of the data-acquisition system is also provided by focusing attention toward its metrological management, which allows traceable results to be obtained that are qualified in terms of measurement uncertaint
Uncertainty contribution in power measurements due to non-harmonic components
No full textDigital-wattmeter uncertainty specifications are typically provided for sinusoidal signals only. In some cases specifications are provided also in the presence of harmonic components, but the presence of spurious non-harmonic components is never taken into account. This paper describes a simple algorithm, which is able to estimate the uncertainty increase that is related to such components
Impedance measurement technique based on sine-fit
No full textAn impedance measurement system that is based on a voltmeter with digitising capabilities and on a sine-fit processing is proposed in this paper. The system can be arranged by employing standard instruments that are commonly available in calibration laboratories for the measurement of other electrical quantities. Two different solutions are proposed that differ in the used standards. One solution employs a multifunction calibrator that feeds the unknown impedance and a digital multimeter that acquires the voltage signal across the impedance; the other solution employs the same digital multimeter and a standard resistor in order to estimate the current that flows through the unknown impedance. In both cases the acquired samples are processed according to a four-parameter sine-fit algorithm. The system the authors have arranged allows impedance measurements in the frequency range of 40 Hz to 5 kHz to be obtained with expected standard uncertainty of about 0.04 % on the amplitude and of a less than 0.06 º on the phas
Medical measurements and uncertainties
No full textMeasurements in the medical field are peculiar in at least two ways: they deal with a terribly complex object-the patient-and are performed and managed by another terribly complex instrument-the physician. However, they are measurements and, like all measurements, they have their own uncertainty, which can affect any decision regarding the invaluable - object to be measured-the patient. This article, without any claim to be exhaustive, discusses how the uncertainty of a complex clinical measurement can be estimated, how the physician-based instrument affects it, and how it can affect the final diagnosi
A Vision-Based Technique for Lay Length Measurement of Metallic Wire Ropes
Full text linkThe lay length of metallic wire ropes is an important dimensional quantity whose analysis is useful to highlight rope deformations due to distributed damages. This paper describes a measurement system that is based on a video camera and on an offline processing algorithm. The camera acquires an image sequence of the running rope; then, an image processing algorithm extracts the rope contour and measures both the distance among rope strands and the whole distance covered by the rope during the test. A mathematical model of the rope contour has been developed and employed to test the proposed algorithm with simulated data. Field tests have been carried out with the proposed system on a working aerial cableway using a general-purpose camer
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