Two-color pyrometer

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. 

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... 

A two-color pyrometer has been used along with the phase-Doppler anemometer to simultaneously measure the local velocity and size of kerosene droplets and the temperature of burning soot mantle in a swirl burner.[648] The measurements were conducted within the flame brush that develops in the shear layer of a swirl-stabilized, gas-supported kerosene flame with a swirl number of about 0.19 and potential heat releases of 10.6 and 15.5 kW, respectively. The results showed that the maximum burning fraction of the droplets occurs adjacent to the region denoted as gas flame but the value ranges from 20 5 to 40 5% depending on the axial station, and decreases sharply across the shear layer. The flame mantle temperature was found to be independent of droplet diameter, which agrees with previous results in the literature. 

Gillard, P., and Roux, M Study of the Radiation Emitted During the Combustion of Pyrotechnic Charges. Part I Non-Stationary Measurement of the Temperature by Means of a Two-Color Pyrometer, Propellants, Explosives, Pyrotechnics, Vol. 

Ratio Pyrometers The ratio pyrometer is also called the two-color pyrometer. Two different wavelengths are utilized for detecting... 

Figure 8.10 Schematic of Ardocol two color pyrometer. The optical aiming system allows an operator to site the device so that only the target is in view [15).

In the regions below 4000°K., the disappearing-filament optical pyrometer, the two-color pyrometer, or the photoelectric pyrometer can be used to measure International Scale Temperatures. Since optical pyro-metry has been well covered in the literature (F5, Rl), further discussion here would serve no purpose. 

Two-color pyrometers avoid the problem of determining the emissivity of the surface. Those pyrometers make measurements at two different wavelengths and with appropriate computations determine temperature without knowing the emissivity. 

Schematic of the two-color pyrometer instrument used for optical glass surface temperature measurements. (From Flayes, R. R., "Glass Surface Temperature and Incident ITeat Flux Measurements in an Industrial, Regenerative, Natural Gas-Fired Flat-Glass Furnace," MS thesis, Brigham Young University, Department of Mechanical Engineering, 1999.)...

Wien presented a simplified model to describe this phenomenon for low XT products [50]. This relation is known as Wien s Formula (Equation 32.2) and is accurate to within approximately 1% over the XT range covered by the two-color pyrometer used ... 

Cutting Temperature, Fig. 4 Two-color pyrometer with an optical fiber in diamond turning... 

Mahfudz AH, Yamada K, Hosokawa A, Ueda T (2002) Investigation of temperature at tool-chip interface in turning using two-color pyrometer. ASME, J Manuf Sci Eng 124(5) 200-207... 

Ueda T, Sato M, Hosokawa A, Ozawa M (2008) Development of infrared radiation pyrometer with optical fibers two-color pyrometer with non-contact fiber coupler. CIRP Ann 57(l) 69-72... 

Turning with Rotary Toois, Fig. 9 Two-color pyrometer in ADRT... 

The third is infrared radiation pyrometer with an optical fiber (Hosokawa et al. 2010). This method is useful to measure the rotary cutting tool because it makes possible to measure the temperature of very small area which temperature changes very quickly. Tool temperature at the flank face of cutting tool is measured using a fiber-coupled two-color pyrometer in ADRT. The fundamental system of this pyrometer is shown in Fig. 9. Chalcogenide glass fiber-A is embedded in the workpiece, and the incidence face of the fiber is inserted into a small hole... 

During high velocity CG/HW tests, samples were heated inductively to temperatures between 1100°C and 2500°C. Temperature measurements ofthe surface were also obtained by one-color and two-color pyrometry. Use of a two-color pyrometer was again employed to evaluate the spectral emittance ofthe oxidizing surface. Temperature gradients within the sample were measured by monitoring the temperature at the root of internal holes drilled to within 2.5 mm of the surface." ... 

To avoid the uncertainties of temperature measurement associated with the uncertainty of emissivity, a two-color pyrometer is recommended, which analyzes the body radiation properties for two wavelengths. In the two-color or ratio pyrometer the radiation is detected at two separate wavelengths for which emis-sivities of the surface can be considered nearly the same. Thus the ratio of the thermal radiation sensor output calculated for two wavelengths by Wien s law is obtained as... 

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