Pyrometer optical

Above 962°C, the freezing point of silver, temperatures on the ITS-90 ate defined by a thermodynamic function and an interpolation instmment is not specified. The interpolation instmment universally used is an optical pyrometer, manual or automatic, which is itself a thermodynamic device. 

Ash Fusibility. A molded cone of ash is heated in a mildly reducing atmosphere and observed using an optical pyrometer during heating. The initial deformation temperature is reached when the cone tip becomes rounded the softening temperature is evidenced when the height of the cone is equal to twice its width the hemispherical temperature occurs when the cone becomes a hemispherical lump and the fluid temperature is reached when no lump remains (D1857) (18). 

Lyzenga, G.A., and Ahrens, T.J. (1979), Multi wavelength Optical Pyrometer for Shock Compression Experiments, Rev. Sci. Instrum. 50, 1421-1424. 

Optical pyrometers, depending on radiation phenomena, may be used up to the highest attainable temperatures (2,500°— 3,000° C.). 

HREELS experiments [66] were performed in a UHV chamber. The chamber was pre-evacuated by polyphenylether-oil diffusion pump the base pressure reached 2 x 10 Torr. The HREELS spectrometer consisted of a double-pass electrostatic cylindrical-deflector-type monochromator and the same type of analyzer. The energy resolution of the spectrometer is 4-6 meV (32-48 cm ). A sample was transferred from the ICP growth chamber to the HREELS chamber in the atmosphere. It was clipped by a small tantalum plate, which was suspended by tantalum wires. The sample was radia-tively heated in vacuum by a tungsten filament placed at the rear. The sample temperature was measured by an infrared (A = 2.0 yum) optical pyrometer. All HREELS measurements were taken at room temperature. The electron incident and detection angles were each 72° to the surface normal. The primary electron energy was 15 eV. 

We use commercial Ti02 crystals (Pi-Kent) cut and polished to within 0.3° of the (110) face and we prepare them further with cycles of Ar + bombardment and U H V annealing to approximately 950-1100 K, typically 5-10 min for each cycle. The samples are mounted onto tantalum back-plates via strips of tantalum spot-welded to the back-plate. Annealing is performed by high-energy electron bombardment of the back-plate from a hot filament. Temperatures are measured from optical pyrometers (Minolta) focused on the back-plate. The temperatures are not measured directly from the samples because they are translucent and get darker with each sputter/anneal cycle. 

Hot spots as large scale nonisothermalities, which can be detected and measured by optical pyrometers, fiber optic or IR pyrometers, i.e. these are macro scale hot zones. 

Above the freezing point of silver, Tgq is defined in terms of a defining fixed point and the Planck radiation law, and optical pyrometers are frequently used as temperature probes. The Comite Consultatif de Thermometrie gives a thorough discussion of the different techniques for approximation of the international temperature scale of 1990 [2, 4],... 

Various approaches to measuring flame temperature are well described in Gaydon s book on flames (see Appendix C). The best methods are spectroscopic rather than those which use thermocouples. The sodium line reversal method is perhaps the easiest. Sodium is added to the flame and the sodium D lines viewed against a bright continuum source (e g. a hot carbon tube). When the flame is cooler than the source the lines appear dark because of absorption. When the flame is hotter than the tube, the bright lines stand out in emission. The current to the tube, which will have been precalibrated for temperature readings by viewing the tube with an optical pyrometer, is adjusted until the lines cannot be seen. At this reversal point, the flame and tube temperature should be equal. 

The methods of temperature measurement of graphite filaments are also subject to criticism. Temperature must be measured by an optical pyrometer. Duval (19) admits a possible error of 50° C. due to uncertainty in the calculated emissive power of a dull graphite surface (60). Furthermore, the temperature range of investigation cannot be extended far below 1000° C. without making arbitrary extrapolations of temperature vs. voltage curves. 

In deflagration, the limiting temperature is the adiabatic flame temperature. Figure 11 (41) presents some temperature measurements made with an optical pyrometer on the exit wall of the same ceramic combustion chamber for which pressure loss data were presented in Figure 5. Temperatures w ithin 500° F. of the adiabatic flame temperature were obtained. 

The limiting load for cylindrical pellets 4 mm in size, which worked for a short time under atmospheric pressure and at 10% NH3 in the mixture with air, was near to 10,000 1 mixture (NTP)/cm2 hr. The measurements of the temperature of pellets with an optical pyrometer showed that it is nearly independent of load up to the limiting load. 

It is also possible to obtain excited neutral species by heating the molecules in a furnance. This method was employed to obtain a vibrationally excited N2 beam that was reacted with 0+ ions.127 Since the molecules undergo a large number of collisions with the walls of the furnace before escaping into the beam, a Boltzmann distribution of internal-energy states is established. With such an apparatus, the source temperature is measured by an optical pyrometer and is typically in the range 1000-3000° K. Several reactions of ions with excited neutrals are listed in Table III. 

Fiber-optic thermometers can be applied up to 300°C, but are too fragile for real industrial applications. In turn, optical pyrometers and thermocouples can be used, but pyrometers measure only surface temperatures which in fact can be lower than the interior temperatures in reaction mixtures. Application of thermocouples which in case of microwaves are metallic probes, screened against microwaves, can result in arcing between the thermocouple shield and the cavity walls leading to failures in thermocouple performance. 

All boiler temperatures were measured just prior to and after the collection of the coal samples and their respective fly ashes, since it was physically impractical to collect the samples and measure the temperatures at the same times. In all cases, the temperatures remained essentially constant. An optical pyrometer was used to measure flame temperatures, and water-cooled jacketed thermocouples were used to monitor the boiler temperatures. The wall effects on the temperature measurements were minimized by insertion of the thermocouple into the boiler until temperatures remained constant with distance upon further insertion of the thermocouple into the boiler. 

Optical Pyrometer (Spot Size to Less than 0.8 mm)... 

Ignition properties can be determined by direct measurements. Tig can be measured with fine thermocouples attached to the exposed surface of ignition test specimens, or by using an optical pyrometer. ASTM D 1929 is a bench-scale furnace test method to determine piloted ignition and... 

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