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A MULTICHANNEL FIBRE OPTIC TEMPERATURE MEASUREMENT SYSTEM
No full textA novel approach to monitoring and control temperature in processes where conventional electrical methods are difficult or ineffective, such as in extremely hostile environments, in biological applications, or in presence of strong electromagnetic interference, is based on the use of fibre optics. The intrinsic characteristics of the optical fibres give to fibre optic sensors several unique features.
In food processing applications, such as in microwave or in radiofrequency heating, there is a need of very localised measurements of both surface and bulk temperatures of the foodstuff, which is immersed in an intense electromagnetic field. While for surface temperatures IR thermometry, or thermography, are possible, the inner temperature can be measured only with the insertion of small probes, immune from electrical disturbances, into the bulk. In this situations, fibre optic sensors are often the only viable alternative for temperature measurement
A multi-channel optical fibre temperature system based on fluorescence thermometry was developed as part of a project aimed at identifying unsatisfactory temperature distributions in food heated in a microwave oven. The system consists of a digital fluorescence lifetime thermometer, a 12-channel optical fibre multiplexer and a set of fully dielectric optical fibre probes. A custom analog-to-digital signal processing (A-DSP) circuit for fluorescence lifetime detection was developed and special probes, suitable for microwave oven applications, were constructed
A Multi-channel Optical Fibre Thermometer
No full textAs part of a project aimed at identifying unsatisfactory temperature distributions within foods heated in microwave
ovens, a multi-channel optical fibre temperature system based on fluorescence thermometry has been developed. The
system consists of a digital fluorescence lifetime thermometer, a 12-channel optical fibre multiplexer and a set of fully
dielectric optical fibre probes. A custom analog-to-digital signal processing (A–DSP) for fluorescence lifetime detection
was developed and special probes, suitable for microwave oven applications, were constructed.
The multi-channel thermometer was calibrated by comparison against a platinum resistance thermometer traceable
to ITS-90 in the temperature range 0–150C. The system affords a temperature repeatability to within 0.3 C, with 0.5 s
response time. Overall system performance and probe calibration are reported. Examples of temperature distribution
measurements within food analogues heated in microwave ovens are reported, as well.
2004 Elsevier Ltd. All rights reserved
Multi-channel fibre-optic Thermometer for Microwave Ovens Characterisation Osaka, Japan, 13-18 June 1999
No full textAccuracy and Calibration Considerations for Fiber Optic Temperature Sensors
No full textIn the present work, the performance characteristics of a set of six fiber optic temperature sensors based on the fluorescence lifetime of neodymium-doped glass have been investigated. The experiment is aimed at verifying whether a satisfactory probe-to-probe repeatability and sensor accuracy can be obtained with minimum calibration effort. To accomplish this task the fiber-optic probes were calibrated, in the temperature range 0 degrees Celsius to 250 degrees Celsius, by comparison against a platinum resistance thermometer in a metal block furnace. The experimental set- up consisted of an electro-optical unit for fluorescence excitation and detection and an analog-to-digital signal processing circuit for lifetime measurements. The temperature probes were assembled by placing the Nd-doped glass at the distal end of a silica optical fiber and by splicing the other fiber end to a 1 by 2 wavelength- independent coupler. The calibration results and the temperature repeatability of the Nd:glass probes are reported. The reproducibility of the measurement method, with an optimum calibration function, and the resulting accuracy are discussed
Metrological Performances of the IMGC Two-Temperature Primary Humidity Generator for the Temperature Range -15 °C to 90 °C
No full textThe Platinum-Palladium Thermocouple as Transfer Standard in the Temperature Range 600 °C-1100 °C
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