Optical thermometry

A variety of fiber optic thermometry systems using fluorescence sensors have been discussed or become available over the past years. Most of the earliest systems are based on the temperature-dependent fluorescence intensity of appropriate materials. One such example of an early commercial system is the Luxtron model 1000, shown in Figure 11.2, which utilized europium-activated lanthanum and gadolinium... 

K. A. Wickersheim, Application of fibre optic thermometry to the monitoring of winding temperatures in medium and large power transformers. SPIE Proc. 1584, 3-14 (1991). 

Reliable temperature measurement in a microwave reaction presents a considerable challenge to the experimentalist, as the microwave field directly affects conventional instruments such as thermometers and thermocouples. Although thermocouples may be used if they are suitably shielded and earthed, there is an inevitable perturbation to the microwave field pattern. A number of other methods are available that are appropriate to use at moderate temperatures. A gas pressure thermometer, or a microwave-transparent liquid thermometer, may be used as inexpensive options, whilst thermal imaging and fluoro-optic thermometry, although expensive, provide more reliable, higher precision information. 

Fig. 2 Typical example of phosphor-based optical thermometry system.

Some years ago D. Stuerga designed a microwave reactor, called the RAMO (reac-teur autoclave microonde), which is not a commercial device. The microwave applicator and the reactor are original. The resonant frequency of the cavity can be controlled by varying the position of a plunger. The effective cavity power can be increased by three orders of magnitude. The autoclave is made of polymeric materials, which are microwave transparent, chemically inert, and sufficiently strong to accommodate the pressures induced. The reactants are placed in a Teflon flask inserted within a polyetherimide flask. A fiber-optic thermometry system, a pressure transducer, and a manometer enable simultaneous measurement of temperature and pressure within the reactor. The system is controlled by pressure. The reactor is shown in Fig. 2.32. 

Temperature either by contact thermometry (millisecond experiments only) or surface radiation for optical thermometry, J(t)... 

Thermal microscopy, reflectance thermometry and scanning optical thermometry measurement methods in micro- and nanodevices have been reviewed by Cahill et al. [59]. 

Direct thermal techniques, which include fiber-optic thermometry, theta-JC testing, infrared thermal imaging, and liquid crystal microthermography, either give a direct temperature measurement or a thermal resistance. 

In the fiber-optic thermometry probe technique, a temperahue sensor, consisting of a small amount of a temperature-sensitive material (manganese-activated magnesium fluorogermanate), is mounted on the end of a probe and is placed on the surface of the device under test (DUT). A filtered xenon flash lamp provides a blue-violet light to excite the phosphor on the probe to fluoresce. When excited by this wavelength of light, the phosphor in the sensor exhibits a deep red fluorescence. 

The fiber-optic thermometry probe technique can measure temperatures with accuracies of 0.1°C. Using the smallest probe, this probing technique can measure temperatures of 0.001-in. spot sizes. After the DUT has reached thermal equilibrium, the system can make up to four measurements per second. To accurately measure junction temperature, the device must be unencapsulated and unsealed. The probe is placed on the junction. 

Optical thermometry has already been cited here and upconverters also find their application here. In Ref. [86] the upconversion emission of Y2O3 Er " nanocrystals prepared by the SGM was studied as a function of temperature in... 

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