Development of a fast fiber-optic two-color pyrometer for the temperature measurement of surfaces with varying emissivities

A two-color pyrometer has been developed to measure the temperature of surf aces with unknown emissivities during high speed turning processes. Quartz fibers enable measurements at locations with limited optical access. The se nsitivity of the pyrometer has to be high enough to measure temperatures do wn to 300 degreesC of an aluminum alloy with an emissivity as low as 0.2. T he accuracy of the two-color pyrometer has been compared with the accuracy of monochromatic pyrometers for different metallic surfaces. The different arguments for the choice of the two pyrometer wavelengths 1.7 and 2.0 mum a re explained. The influences of the surface emissivities, the digitization, and the noise on the absolute and relative measurement error have been det ermined. Fast amplifiers and data acquisition allow a maximum time resoluti on of a few microseconds and a local resolution of similar to0.5 mm(2). Som e test measurements of an aluminum alloy surface are presented. (C) 2001 Am erican Institute of Physics.