APPARATUS FOR DETERMINING CORRECT PYROMETER READINGS WITH STEAM OR OTHER INTERFERENCE PRESENT

摘要

1387060 Radiation pyrometer USS ENGINEERS & CONSULTANTS Inc 15 March 1972 [25 March 1971] 12158/72 Heading G1A In the determination of the temperature of a surface e.g. hot rolled steel by radiation pyrometry when radiation from the surface is attenuated or scattered away by an interfering substance e.g. steam, spray, dust or smoke, and would cause erroneous measurement, there are provided first and second detectors viewing the same area of the surface, the second detector having a different wavelength response characteristic from that of the first detector and having an error in its output signal caused by the interfering substance in a substantially constant ratio, within the temperature range of interest, to the error in the output signal of the first detector, and the output signals of the two detectors are combined in such a way as to obviate the errors caused by the interfering substance. The detectors may be aligned side by side to view the surface, or more accurately, as in Fig. 1, may be associated with a beam-splitter 10. In Fig. 1, the detectors 16, 20 are a total radiation pyrometer and a silicon cell respectively. The pyrometer 16 has a substantially linear response and its output VR may thus be used directly. The silicon cell output V S has to be linearized at 24 before use, which results in a curve representing, in general three times its previous value i.e. 3V S . It is also found that the error due to the interfering substance with the silicon cell, is one third that for the total radiation cell, so that a true measure of temperature may be obtained by taking VTRUE = (3V S -V R /2). This is carried 2 out with voltage divider 32 and recorder 30. Indicator 34 is provided to indicate e.g. actuate an alarm when the interference is beyond acceptable limits, determined by evaluating the difference between the outputs of pyrometers 16, 20 or as in Fig. 1, of the output of pyrometer 16 and a third (at potentiometer 32) of the output of linearizer 24. It may be necessary to linearize the outputs of both pyrometers.