Pyrometers


Pyrometer, optical Pyrometers  [c.831]

The Gzochralski Technique. Pulling from the melt is known as the Czochralski technique. Purified material is held just above the melting point in a cmcible, usually of Pt or Ir, most often powered by radio-frequency induction heating coupled into the wall of the cmcible. The temperature is controlled by a thermocouple or a radiation pyrometer. A rotating seed crystal is touched to the melt surface and is slowly withdrawn as the molten material solidifies onto the seed. Temperature control is used to widen the crystal to the desired diameter. A typical rotation rate is 30 rpm and a typical withdrawal rate, 1—3 cm/h. Very large, eg, kilogram-sized crystals can be grown.  [c.215]

Control Devices. Control devices have advanced from manual control to sophisticated computet-assisted operation. Radiation pyrometers in conjunction with thermocouples monitor furnace temperatures at several locations (see Temperature measurement). Batch tilting is usually automatically controlled. Combustion air and fuel are metered and controlled for optimum efficiency. For regeneration-type units, furnace reversal also operates on a timed program. Data acquisition and digital display of operating parameters are part of a supervisory control system. The grouping of display information at the control center is typical of modem furnaces.  [c.306]

Temperature measurements ranging from 760 to 1760°C are made usiag iron—constantan or chromel—alumel thermocouples and optical or surface pyrometers. Temperature measuriag devices are placed ia multiple locations and protected to allow replacement without iaciaerator shutdown (see  [c.55]

The deterrnination of surface temperature and temperature patterns can be made noninvasively using infrared pyrometers (91) or infrared cameras (92) (see Infrared technology and raman spectroscopy). Such cameras have been bulky and expensive. A practical portable camera has become available for monitoring surface temperatures (93). An appropriately designed window, transparent to infrared radiation but reflecting microwaves, as well as appropriate optics, is needed for this measurement to be carried out during heating (see Temperature measurement).  [c.343]

Material Pyrometer cone equivalent Main crystalline phases Bulk Tme Apparent porosity, %  [c.24]

PCE = pyrometer cone equivalent, as determined by ASTM C24.  [c.28]

PCE = pyrometer cone equivalent.  [c.33]

PCE = pyrometer cone equivalent.  [c.34]

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.  [c.403]

The main elements of a disappearing-filament optical pyrometer ate shown in Figure 7. There is an optical system for viewing the radiating target, a lamp filament, appropriate filters, an eyepiece, and a caUbrated means for varying the lamp current and consequently the brightness of the filament. In the optical path, the filament is visible against the radiating source. The lamp filament current is varied until the image of the glowing filament is of such brilliance that its separate image is indistinguishable from the brilliance of the radiating source. The lamp current is then noted. If a second radiating source also causes the lamp filament to be indistinguishable at that lamp current, the temperature of the second source is said to be the same as that of the first.  [c.403]

The filter and screen of the pyrometer shown ia Figure 9 require specific mention. From equation 21 it is evident that the observed radiation must be limited to a narrow bandwidth. Also, peak intensity does not occur at the same wavelength at different temperatures. The pyrometer is fitted with a filter (usually red) having a sharp cut-off, usually at 620 nm. The human eye is insensitive to fight of wavelength longer than 720 nm. The effective pyrometer wavelength is 655 nm.  [c.404]

It is also necessary to reduce the intensity of the radiation admitted into the pyrometer, because pyrometer lamp filaments should not be subjected to temperatures exceeding 1250°C. The reduction is accomplished by a screen or screens in manually operated secondary pyrometers they are usually neutral-density filters.  [c.404]

Several types of secondary pyrometer are available. In addition to those that measure by varying lamp current, some pyrometers maintain the lamp at constant current but interpose a wedge of graduated neutral density, whose position is a measure of temperature. Also, automatic pyrometers are available in which the eye is replaced by a detector and the measuring element is operated by a servo. In general, the accuracy of the automatic pyrometer is somewhat less than that achieved manually by a skilled operator.  [c.404]

The problem of emissivity from real materials has stimulated the study of pyrometers that measure radiation at two different wavelengths. The principle of the two-color pyrometer is that the energy radiated from a source of one wavelength increases with temperature at a rate different from that radiated at another wavelength. Thus temperature can be deduced from the ratio of the intensities at the two wavelengths, regardless of emissivity. Two-color pyrometers are not widely used.  [c.405]

The temperature in the hottest part of the kiln is closely controlled using automatic equipment and a radiation pyrometer and generally is kept at about 1100—1150°C (see Temperature measurement). Time of passage is about four hours, varying with the kiln mix being used. The rate of oxidation increases with temperature. However, the maximum temperature is limited by the tendency of the calcine to become sticky and form rings or balls in the kiln, by  [c.137]

One limiting form of the Planck equation, approached as XT 0, is the Wien equation [Eqs. (5-113) and (5-114)] with the 1 missing in the denominator. The error is less than 1 percent when XT < (3)(10 ) m K or when T < 4800 K if an optical pyrometer with red screen (A = 0.65 lm) is used.  [c.571]

Measurement of the hotness or coldness of a body or fluid is commonplace in the process industries. Temperature-measuring devices utilize systems with properties that vaiy with temperature in a simple, reproducible manner and thus can be cahbrated against known references (sometimes called secondaiy thermometers). The three dominant measurement devices used in automatic control are thermocouples, resistance thermometers, and pyrometers and are applicable over different temperature regimes.  [c.759]

Pyrometers Planck s distribution law gives the radiated energy flux qb(X, T)dX in the wavelength range X to X -1- dX from a black surface  [c.760]

Disappearing Filament Pyrometers Disappearing filament pyrometers can be classified as spec tral pyrometers. The brightness of a lamp filament is changed by adjusting the lamp current until the filament disappears against the bacKground of the target, at which point the temperature is measured. Since the detector is the human eye, it is difficult to calibrate for on-line measurements.  [c.761]

Ratio Pyrometers The ratio pyrometer is also called the two-color pyrometer. Two different wavelengths are utilized for detecting the radiated signal. If one uses Wien s law for small values of XT, the detected signals from spectral radiant energy flux emitted at the wavelengths and 2 with emissivities and are  [c.761]

Boslough, M.B., and Ahrens, T.J. (1989), A Sensitive Time-Resolved Radiation Pyrometer for Shock-Temperature Measurements above 1500 K, Rev. Sci. Instrum. 60,3711-3716.  [c.111]

Alundum is used for highly refractory bricks (m.p. 2000-2100 C), crucibles, ref ractory cement and muffles also for small laboratory apparatus used at high temperatures (combustion tubes, pyrometer tubes, etc.).  [c.26]

The furnace and thermostatic mortar. For heating the tube packing, a small electric furnace N has been found to be more satisfactory than a row of gas burners. The type used consists of a silica tube (I s cm. in diameter and 25 cm. long) wound with nichrome wire and contained in an asbestos cylinder, the annular space being lagged the ends of the asbestos cylinder being closed by asbestos semi-circles built round the porcelain furnace tube. The furnace is controlled by a Simmerstat that has been calibrated at 680 against a bimetal pyrometer, and the furnace temperature is checked by this method from time to time. The furnace is equipped with a small steel bar attached to the asbestos and is thus mounted on an ordinary laboratory stand the Simmerstat may then be placed immediately underneath it on the baseplate of this stand, or alternatively the furnace may be built on to the top of the Simmerstat box.  [c.470]

The furnace. For heating the tube packing, a small electric furnace E is used, similar to that described in the carbon and hydrogen determination. It is 22 cm. in length and 1 5 cm. in diameter. The furnace is maintained at 680 C., as before, by a calibrated Simmerstat and its temperature is checked from time to time with a bimetal pyrometer.  [c.484]

An electric heating mantle may also be used temperatures up to about 400° C. are readily attained, it can be employed with highly inflammable liquids and bumping is largel eliminated. The construction of a typical electric heating mantle will be apparent from Fig. II, 57, 1, in which it surrounds a single neck flask with a thermometer or sight well. The heating element (nichrome or equivalent resistance wire) is embedded in layers of glass fabric near the exposed surface and is further covered by layers of glass wool insulation. The two hemispherical halves are held together by a Zip fastener or by glass fibre cords. The temperature lag is small since the heating elements are very close to the flask wall. A built-in thermo couple is available in certain types so that the internal temperature can be read with a suitable pyrometer a small thermostat may also be embedded in the heating elements to prevent overheating. Special supports (cradles) for the heating mantles are marketed.  [c.222]

The furnace and thermostatic mortar. For heating the tube packing, a small electric furnace N has been found to be more satisfactory than a row of gas burners. The type used consists of a silica tube (1-5 cm. in diameter and 25 cm. long) wound with nichrome wire and contained in an asbestos cylinder, the annular space being lagged the ends of the asbestos cylinder being closed by asbestos semi-circles built round the porcelain furnace tube. The furnace is controlled by a Simmerstat that has been calibrated at 680° against a bimetal pyrometer, and the furnace temperature is checked by this method from time to time. The furnace is equipped with a small steel bar attached to the asbestos and is thus mounted on an ordinary laboratory stand the Simmerstat may then be placed immediately underneath it on the baseplate of this stand, or alternatively the furnace may be built on to the top of the Simmerstat box.  [c.470]

The furnace. For heating the tube packing, a small electric furnace E is used, similar to that described in the carbon and hydrogen determination. It is 22 cm. in length and 1 5 cm. in diameter. The furnace is maintained at 68o C., as before, by a calibrated Simmerstat and its temperature is checked from time to time with a bimetal pyrometer.  [c.484]

Processings Conditions. Certain variables should be monitored, measured, and recorded to aid in reproducibiUty of the desired balance of properties and appearance. The individual ABS suppHers provide data sheets and brochures specifying the range of conditions that can be used for each product. Relying on machine settings is not adequate. Identical cylinder heater settings on two machines can result in much different melt temperatures. Therefore, melt temperatures should be measured with a fast response hand pyrometer on an air shot recovered under normal screw rpm and back-pressure. Melt temperatures range from 218 to 268°C depending on the grade. Generally, the allowable melt temperature range within a grade is at least 28°C. Excessive melt temperatures cause color shift, poor gloss control, and loss of properties. Similarly, a fiU rate setting of 1 cm/s ram travel will not yield the same mold filling time on two machines of different barrel size. Fill time should be measured and adjusted to meet the requirements of getting a fliU part, and to take advantage of shear thinning without undue shear heating and gas bums. Injection pressure should be adjusted to get a fliU part free of sinks and good definition of gloss or texture. Hydrauhc pressures of less than 13 MPa (1900 psi) usually suffice for most mol ding. Excessive pressure causes flash and can result ia loss of some properties. Mold temperatures for ABS range from 27 to 66°C (60 to 82°C for high heat grades). The final properties of a molded part can be iafluenced as much by the mol ding as by the grade of ABS selected for the appHcation (121). The factors ia approximate descending order of importance are polymer orientation, heat history, free volume, and molded-ia stress. Izod impact strength can vary severalfold as a function of melt temperature and fiU rate because of orientation effects, and the response curve is ABS grade dependent (122). The effect on tensile strength is qualitatively the same, but the magnitude is ia the range of 5 to 10%. Modulus effects are minimal. Orientation distribution ia the part is very seasitive to the flow rate ia the mold therefore, fiU rate and velocity-to-pressure transfer poiat are important variables to control (123). Dart impact is also sensitive to mol ding variables, and orientation and thermal history can also be key factors (124). Heat deflection temperature can be iafluenced by packing pressure (125) because of free volume considerations (126). The orientation on the very surface of the part results from an extensionaHy stretching melt front and can have deleterious effects on electro-plate adhesion and paintabiUty. A phenomenon called the mold-surface-effect, which iavolves grooving the nonappearance half of the mold, can be employed to reduce unwanted surface orientation on the noncorresponding part surface (127—129). Other information regarding the influence of processiag coaditioas oa part quality are givea ia refereaces 130—134.  [c.206]

Some parts fabricated from sheet include transistor mica, suitable for transistor mounting washers interlayer insulator mica, used to insulate transformer cods resistance and potentiometer cards, suitable for winding noninductive resistance cards and in potentiometers vacuum tube mica, generally replaced by transistors natural mica bushings and tubes target and mosaic mica, used in the telecasting industry and in computers and guided missile micas. High quaUty natural mica is used for various other special appHcations, ie, special optical filters, diaphragms for oxygen breathing equipment, washer dials for navigator compasses, microwave windows, and quarterwave plates of optical instmments, pyrometers, neon lasers, and thermal regulators.  [c.291]

Fireclay and High Alumina Brick. ASTM designation C27 covers fireclay and high alumina brick (Table 12). High alumina brick is classified according to alumina content, starting at 50% and continuing up to 99% AI2O2. Manufacturers are allowed 2.5% of the nominal alumina content, except for 85 and 90% (2.0%) and 99% (min 97%). An additional requirement for alumina bricks with AI2O2 content of 50, 60, 70, and 80%, are pyrometer cone equivalents (PCEs) of 34, 35, 36, and 37, respectively.  [c.33]

When a gas adiabatically expands through a no22le into a vacuum, its thermal energy is converted into kinetic energy of mass dow, cooling the gas to effective temperatures of <10 K, and coUapsing any rovibrational stmcture into a few transitions originating from the lowest lying quantum states. Beam work has emphasi2ed basic atomic and molecular stmcture and aggregation, but the methods may eventually be appHed to analysis. Besides I /absorption measurements, absorption can be foUowed in beams by monitoring the beam energy using sensitive pyrometers or other calorimeters. Laboratory detection limits for strongly absorbing species can reach the ppb level.  [c.321]

The austenitic iron—chromium—nickel alloys were developed in Germany around 1910 in a search for materials for use in pyrometer tubes. Further work led to the widely used versatile 18% chromium—8% nickel steels, the socaHed 18—8.  [c.397]

A strip lamp is a convenient means for the caUbration of secondary pyrometers (Fig. 9). The notched portion of the tungsten strip is the target. A pyrometer which has been caUbrated against a radiafing blackbody is sighted on the target, and the strip lamp current is adjusted to radiate at the iatensity of the blackbody, as transferred by the primary pyrometer. The secondary pyrometer is then substituted for the primary, and the current required to raise the lamp filament to the brilliance of the target of the strip lamp is noted.  [c.404]

No object can radiate more energy than can a blackbody at the same temperature, because a blackbody ia equiUbrium with a radiation field at temperature T radiates exacdy as much energy as it absorbs. Any object exhibiting surface reflection must have emissivity of less than 1. Pyrometers are usually caUbrated with respect to blackbodies. This can cause a serious problem ia use. The emissivities of some common materials are fisted ia Table 4.  [c.404]

The Engelhard and Eurecat regeneration processes use rotary calciners rather than moving-bed belt calciners. The catalyst is charged into conical-shaped rotating dmms and is lifted and tumbled by a series of louvers as it is conveyed to the discharge end. A heated, forced air draft flows between the louvers and through the tumbling catalyst bed along the length of the unit. Temperature is measured using trailing thermocouples in contact with the catalyst bed or by pyrometers mounted at the end of the unit.  [c.226]

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).  [c.233]

Red Brass Alloys. In forming red brass alloys, which iaclude leaded red and leaded semired brasses, caution should be exercised to prevent gas absorption by flame impingement or the melting of oily scrap, or metal loss through excessive oxidation of the melt surface. To prevent excessive 2iac volatilization, the melt must be poured as soon as it reaches the proper temperature. The melt should be finally deoxidized and cast at ca 1065—1230°C as measured with a pyrometer. Fluxing is usually not needed if clean material has been melted.  [c.249]

Tin Bronze Alloys. Tin bronze alloys are successfully melted in any type of foundry furnace. Best results are obtained by protecting the melt from either direct flame contact or excessive oxidation. Melting should be carried out in a slightly oxidizing atmosphere. Rapid melting is desired to reduce the opportunity of gas absorption in the melt. Fracture tests exhibit an open grain and discoloration when the melt has been exposed to reducing conditions, contaminants such as Al and Si, or excessive superheating. Oily scrap should be avoided. Pouring temperatures range from 1010 to 1260°C and should be measured with a pyrometer. Pouring should take place at a temperature that gives the best results for a particular gating or risering system. The temperature should be high enough to avoid internal shrinkage that can lead to voids, because gating and risering may not always completely eliminate such internal unsoundness. Dhectional solidification needs to be planned as part of the gating system.  [c.249]

If the target object is a black body and if the pyrometer has a detector that measures the specific wavelength signal from the object, the temperature of the object can be exactly estimated from Eq. (8-92). While it is possible to coustrucl a physical body that closely approxi-  [c.760]

Total Radiation Pyrometers In total radiation pyrometers, the thermal radiation is detec ted over a large range of wavelengths from the objec t at high temperature. The detector is normally a thermopile, which is built by connec ting several thermocouples in series to increase the temperature measurement range. The pyrometer is calibrated for black bodies, so the indicated temperature Tp should be converted for non-black body temperature.  [c.761]

Photoelectric Pyrometers Photoelectric pyrometers belong to the class of band radiation pyrometers. The thermal inertia of thermal radiation detectors does not permit the measurement of rapidly changing temperatures. For example, the smallest time constant of a thermal detector is about 1 msec, while the smallest time constant of a photoelec tric detector can be about 1 or 2 sec. Photoelec tric pyrometers may use photoconductors, photodiodes, photovoltaic cells, or vacuum photocells. Photoconductors are built from glass plates with thin film coatings of 1 [Lm thickness, using PbS, CdS, PbSe or PbTe. When the incident radiation has the same wavelength as the materials are able to absorb, the captured incident photons free photoelectrons, which form an electric current. Photodiodes in germanium or sihcon are operated with a reverse bias voltage applied. Under the influence of the incident radiation their conductivity as well as their reverse saturation current is proportional to the intensity of the radiation within the spectral response band from 0.4 to 1.7 [Lm for Ge and 0.6 to 1.1 [Lm for Si. Because of the above characteristics, the operating range of a photoelectric pyrometer can be either spectral or in a specific band. Photoelec tric pyrometers can be applied for a specific choice of the wavelength.  [c.761]

Accuracy of Pyrometers Most of the temperature estimation methods for pyrometers assume that the objec t is either a grey body or has known emissivity values. The emissivity of the nonblack body depends on the internal state or the surface geometry of the objects. Also, the medium through which the therm radiation passes is not always transparent. These inherent uncertainties of the emissivity values make the accurate estimation of the temperature of the target objects difficult. Proper selection of the pyrometer and accurate emissivity values can provide a high level of accuracy.  [c.761]

Because indirect-heat calciners frequently require close-fitting gas seals, it is customaiy to support aU parts on a selFcontained frame, for sizes up to approximately 2 m in diameter. The furnace can employ elec tric heating elements or oil and/or gas burners as the heat source for the process. The hardware would be zoned down the length of the furnace to match the heat requirements of the process. Process control is normaUy by shell temperature, measured by thermocouples or radiation pyrometers. When a special gas atmosphere must be maintained inside the cyhnder, positive rotaiy gas se s, with one or more pressurized and purged annular chambers, are employed. The diaphragm-type seal ABB Raymond (Bartlett-Snow TM) is suitable for pressures up to 5 cm of water, with no detectable leakage.  [c.1210]


See pages that mention the term Pyrometers : [c.914]    [c.202]    [c.400]    [c.406]    [c.199]    [c.716]    [c.716]   
Gas turbine engineering handbook (2002) -- [ c.0 ]

Plant Engineer's Handbook (2001) -- [ c.0 ]