Extended temperature range for calibration of two-color pyrometers. (News Briefs).Properties of metallic and ceramic coatings produced by the thermal spray process depend strongly on processing conditions. Two-color pyrometry py·rom·e·ter n. Any of various thermometers used for measuring high temperatures. py  ro·met is the most common technique used to determine particle and substrate temperatures, but incorrect calibration procedures can result in significant errors. One error source of is the use of the radiance temperature rather than the absolute temperature to calibrate To adjust or bring into balance. Scanners, CRTs and similar peripherals may require periodic adjustment. Unlike digital devices, the electronic components within these analog devices may change from their original specification. See color calibration and tweak. the pyrometer. The radiance temperature of a test surface is equivalent to the temperature of a perfectly radiating surface (e.g., blackbody blackbodyTheoretical surface that absorbs all radiant energy that falls on it, and radiates electromagnetic energy at all frequencies, from radio waves to gamma rays, with an intensity distribution dependent on its temperature. , [epsilon) = 1) with the same radiant intensity as the test surface at a specified wavelength. Tungsten ribbon lamps, the most readily available temperature standards, are usually supplied with calibrations to radiance temperature since they are normally intended for calibrating single-color pyrometers, where radiance temperature is appropriate. Another error occurs if the deviation of tungsten from gray body behavior (wavelength independent radiance) goes uncorrected. In addition to these errors, extrapolation (mathematics, algorithm) extrapolation - A mathematical procedure which estimates values of a function for certain desired inputs given values for known inputs. If the desired input is outside the range of the known values this is called extrapolation, if it is inside then beyond the range of the NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. calibrated cal·i·brate tr.v. cal·i·brat·ed, cal·i·brat·ing, cal·i·brates 1. To check, adjust, or determine by comparison with a standard (the graduations of a quantitative measuring instrument): tungsten ribbon lamps, will further degrade the accuracy of these temperature measurements. NIST researchers have developed calibration procedures for two-color pyrometers that improve the accuracy of thermal spray particle temperature measurements. The errors associated with the use of radiance temperature rather than true temperature in calibrations were quantified, and the relative accuracy of determining true temperature from literature emissivity Emissivity The ratio of the radiation intensity of a nonblack body to the radiation intensity of a blackbody. This ratio, which is usually designated by the Greek letter ε, is always less than or just equal to one. data versus direct measurement are investigated by comparing both corrections to a blackbody calibration. Errors associated with the deviation of tungsten from gray body behavior were also investigated in this manner. In addition, the calibration range has been extended beyond that which can be achieved with lamp standards to the melting point of tungsten using facilities in the NISTs Subsecond Thermophysics Laboratory. More accurate particle temperature data will lead to an improved ability to predict coating characteristics from spray processing conditions. CONTACT: Steve Ridder, (301) 975-6175; stephen. ridder@nist.gov. |
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