1,721,194 research outputs found
A magnetic sensor for measuring plastic pellet flow
No full textThe measurement of the flow of a granular material is an important task in several engineering fields. The ability to carry out such measurement in adverse conditions is also required, especially in industrial environments, when it is necessary to work on complex plants and it is important to obtain data about the process without affecting it. This may impose the development of specific sensors and the use of sophisticated signal processing techniques to obtain the required information. This article deals with the design, development, building and characterisation of a magnetic sensor useful for estimating the material flow of granular plastic pellets, based on magnetic marking of the reacting material and analysing the signal obtained by a detection coil while the pellets pass through a suitable magnetic fiel
Measurement of residence time distribution function by means of a non invasive magnetic sensor
No full textIndustrial measurement techniques are often required to work on complex plants where it is important to obtain data on the processes without affecting them. This may impose the development of specific sensors and the use of sophisticated signal processing techniques in order to obtain the required information. The article describes the development and the characterisation of a measurement technique for obtaining the Residence Time Distribution Function of a reactor for post-poli-condensation of Poly-Ethylen-Terephtalate pellets. The adopted measurement technique is based on marking the reacting material by means of iron powder and uses a non-invasive magnetic sensor. Both the development and the characterisation have been carried out using a 'measurement development system' which allows the initial work to be significantly reduced. Although the description is focused on a specific problem, the proposed processing techniques may be used for various problems involving measurements related to the flow of plastic pellets. Finally, a simple complete measurement system, based on the proposed technique, is describe
Using a-priori information to enhance measurement accuracy
No full textThe term "a-priori information" means a piece of information about the investigated reality that is not obtained by the measuring instruments that carry out the measurement, but is known from other sources. A-priori information is commonly used in the design phase of a measurement procedure, but in several cases it is possible to use this "external" information in a direct and more powerful way to validate measurement results or even to correct the results themselves, obtaining in this way a better accuracy. In this article an algorithm is presented which is useful for integrating any available a-priori information within a measurement process to obtain a better accuracy. A method to estimate the uncertainty of the results after the proposed corrections, and some clarifying examples are also presente
An Ultrasonic Sensor for Distance Measurement in Automotive Applications
Full text linkThis paper describes an ultrasonic sensor that is able to measure the distance from the ground of selected points of a motor vehicle. The sensor is based on the measurement of the time of flight of an ultrasonic pulse, which is reflected by the ground. A constrained optimization technique is employed to obtain reflected pulses that are easily detectable by means of a threshold comparator. Such a technique, which takes the frequency response of the ultrasonic transducers into account, allows a sub-wavelength detection to be obtained. Experimental tests, performed with a 40 kHz piezoelectric-transducer based sensor, showed a standard uncertainty of 1 mm at rest or at low speeds; the sensor still works at speeds of up to 30 m/s, although at higher uncertainty. The sensor is composed of only low cost components, thus being apt for first car equipment in many cases, and is able to self-adapt to different conditions in order to give the best result
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
The autodiagnosis system of an intelligent measuring instrument
No full textThe methodological aspects and the design of the automatic self-diagnosis (auto-diagnosis) system of a high-performance measuring instrument for electrical quantities are described. The auto-diagnosis system can recognise not only severe failures which require out-of-service instrument setting, but also slight failures simply affecting accuracy or not basic features; in the latter case, the instrument is set working in degraded conditions. The auto-diagnosis process is performed making reference to the instrument architecture, based on independent and interconnected functional units, and using an analysis technique, called 'extending ring', to detect failing subsystems. The auto-diagnosis system is divided into two main parts, conceived for separate aims: one is named 'off-line full test auto-diagnosis system' and performs, at power up or on user request, a full comprehensive test; the other, named 'on-line auto-diagnosis system', continuously monitors the instrument behaviour while operating normally to reveal failures or error conditions that can derate the whole performanc
Enhancing the ultrasonic sensor performance by the optimisation of the driving signal
No full textThe issue arising from limitations in sensor performance is crucial in most measuring systems, so it is a matter of high interest to define strategies able to optimize a sensor's behaviour. This paper describes a method for determining a sensor driving signal that enhances the sensor capabilities in stimulation-and-response-based measuring systems. The method is based on a signal theory approach and is quite general, enabling the best performance for different kinds of sensors to be obtained, provided that they can be described in terms of transgfer functiions and that the required performance can be represented by suitable functionals. The method's capabilities are shown in an application involving the measurement of the time-of-flight of ultrasonic pulses. A resolution improvement of more than one order of magnitude is achieved with respect to the standard approaches, still employing low-cost low-damping devices
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
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