1,720,977 research outputs found
“Termometria a Fluorescenza per Misure senza Contatto della Temperatura Superficiale di Beni Culturali”
No full textNel campo delle misure per la conservazione dei beni culturali sono spesso necessarie misure di temperatura della superficie dei manufatti. Per effettuare tali misure in genere vengono utilizzate tecniche basate sul contatto fisico tra la sonda e la superficie mentre, sarebbero da privilegiare metodologie senza contatto, a garanzia dell’integrità dei manufatti stessi.
Il metodo che viene proposto consiste nella deposizione sulla superficie in esame di un sottile strato di fosfori termosensibili di cui se ne misura il tempo di vita di fluorescenza. Poiché si tratta di un metodo remoto, senza contatto, indipendente dalle proprietà ottiche della superficie in esame, è immediatamente applicabile alla misura della temperatura superficiale dei manufatti che devono essere costantemente tenuti sotto controllo. Inoltre, le dimensioni ridotte del sensore e di conseguenza la sua bassa capacità termica, fanno sì che tale approccio sia preferibile alle misurazioni per contatto che possono alterare la temperatura originaria del manufatto.
Nel presente lavoro viene presentato il principio di misura della termometria a fluorescenza e i risultati relativi alla sua applicazione alla misura della temperatura superficiale di una lastra di vetro. Vengono infine confrontati i risultati ottenuti con quelli forniti da una sonda per contatto di tipo industriale
Metodi di Misura del Tempo di Vita di Fluorescenza per Sensori di Temperatura a Fibra Ottica
No full textDevelopment of a Heat Pipe-based Hot Plate for Surface-Temperature Measurements
No full textThe development of a flat heat-pipe-based hot plate operating in the
temperature range from ambient to 200 ◦C is presented here. The aim of the designwas
to improve the heat-transfer performance in order to provide almost ideal thermal uniformity
of surface and volume temperature profiles, thereby ensuring a minimal temperature
gradient and a small effective thermal resistance. The device was investigated
to evaluate its performance in view of its potential use as a calibration apparatus for
surface-temperature sensors. An accurate characterization was carried out to estimate
the surface-temperature stability and uniformity under different thermal conditions.
Measurement results showed temperature stability within 0.03 ◦C and uniformity of
the heat-pipe (HP) hot-plate surface better than 0.08 ◦C. As a result of its high thermal
conductivity, a small perturbation (<0.2 ◦C) of the temperature field both on the
surface and inside the device chamber, when a contact probe is applied on its surface,
was obtained. The study of the HP hot plate and the performed tests suggest that such
a device has potential as a calibration apparatus for surface-temperature sensors
“Un Sistema di Riferimento per la Temperatura Superficiale: una Collaborazione tra INRIM e Industria”
No full textTime-and-Frequency-domain Analyses of Fluorescence Lifetime for Temperature Sensing
No full textFluorescence lifetime detection is widely used for sensing physical and chemical quantities. The
measurement accuracy of fluorescence lifetime-based sensing systems, either in time or frequency
domain relies on their capability of detection and analysis of low level signal superimposed to noise.
In this work a quantitative assessment of several data processing and analysis methods for the
estimation of the fluorescence lifetime was carried out by using an experimental arrangement based
on a fiber optic temperature sensor system. A comparison between the various methods was
performed using actual signals from an optical sensing medium. The basic principles of time- and
frequency-domain lifetime measurements were also reviewed and discussed in order to point out the
limit of the cw frequency-domain approach and to suggest a way to overcome it. The investigated
lifetime interval was from 200 to about 2200 s, corresponding to a temperature span of the sensor
of about 300 °C. The results showed that in time domain such as with Marquardt, integration, and
log-fit algorithms a good agreement, with relative differences from 0.2% to 0.5%, can be reached.
Frequency-domain results based on an N-point fast Fourier transform FFT compare favorably with
the previous ones in the long lifetime region resulting in relative differences lower than 0.2% with
larger differences for short lifetimes. For each data processing method, the uncertainty associated
with lifetime estimation was evaluated. Sampling and harmonics effects on the estimation accuracy
for N-point FFTs were also investigated to trade-off between speed and accuracy of the algorithm
in view of its application in real-time detection systems
A Calibration System for Fluorescence Thermography
No full textA temperature reference system for calibrating fluorescence-based sensors was developed. The system is based on a special thermostatic chamber and on an electro-optic system equipped with a fiber-optic scanner. A thin layer of the sensing material to be calibrated can be coated onto a temperature controlled reference surface, which is housed inside the thermostatic chamber. It was designed in such a way as to operate under different conditions (from vacuum to atmospheric pressure) in order to evaluate the effect of the surrounding fluid on the surface temperature measurements. The reference surface can be heated both radially, by a wire wound heater, and axially, by a thermoelectric cooler. Experimental investigations were carried out in the temperature range –50 °C to about 200 °C. The results showed a temperature stability of better than 0.03 °C and a surface temperature uniformity to within 0.02 °C. The system was used to characterize a sensitive phosphor. The phosphor calibration curve was thus obtained, with a single-point repeatability of better than 0.1 °C. The spatial temperature uniformity of the phosphor-coated surface was also investigated by using the built-in fiber-optic scanner in both environments. The results showed a temperature uniformity to within 0.1 °C
Validation of phosphor thermometry for industrial surface temperature measurements
Full text linkSurface temperature measurements are required by the aerospace and automotive industries to guarantee high-quality products and optimize production processes. Accurate and reliable measurement of surface temperature is very challenging in an industrial environment. Surface contact probes are widely used but poorly characterized, while non-contact infrared thermometry is severely hampered by the unknown emissivity of the surface and by problems caused by stray radiation from the background. An alternative approach to the above techniques is phosphor thermometry, used here in a hybrid contact/non-contact approach.
In this work, the development of a lifetime-based phosphor thermometer, its application to industrial surface temperature measurement and its validation are reported in a metrologically sound manner. The phosphor thermometer was initially calibrated by contact on a reference calibrator system at the Istituto Nazionale di Ricerca Metrologica to provide SI traceability to the measurements at the industrial level; the system was later validated by exploiting a metal phase-change method. The robustness of the approach against a strong radiative background was also investigated. A comprehensive uncertainty analysis was carried out, resulting in an expanded uncertainty (k = 2) lower than 1.4 °C over the temperature range from the ambient to 450 °C.
The phosphor-based thermometer was then tested at industrial manufacturing premises to measure the surface temperature of aluminium alloy billets during the pre-heating phase before forging. The phosphor-based approach was compared with radiation and contact thermometry in both static and dynamic measurement conditions. The experimental results proved that phosphor thermometry, besides being a valid alternative to conventional techniques, may offer better performance in an industrial setting
Investigations on Capacitive-based Relative Humidity Sensors and Their Stability at High Temperature
No full textThe performance of high-temperature, polymer-based RH sensors was
investigated in order to evaluate their long-term stability. The work is aimed at understanding
howsevere temperature cycles may alter the characteristics of relative humidity
(RH) sensors, how they impact the measurements, and how they contribute to the
measurement uncertainty. The tests involved 10 high-temperature RH sensor probes
available from five European manufacturers. They were initially calibrated against
suitable humidity standards in the range from 10%rh to 85%rh with air temperatures
from 20 ◦C to 80◦C, and subsequently, they were exposed to air temperature at about
145 ◦C for several cycles, each cycle lasting (50–100) h. After each high-temperature
exposure, a calibration check at 80 ◦C was carried out. The test lasted until the sensor
exposure time exceeded 300 h. The paper presents the characteristics of such probes,
the investigation results, and the comparison of the specified versus the experimental
performances
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