OCR Text |
Show response was found to be a function of gain, with the response reduced with increasing gain. However, at the first three gain settings, the frequence response was found to be well above the nominal target, being in excess of 4000 Hz. It dropped to 2800 at the fourth setting, and became indetenninate at the fifth. In operation, nevertheless, adequate gain and frequency response for the given experiments was mostly obtained at the lower three of the gain settings. The major components described above are largely conventional, as already noted. What was unique was the addition of a view-depth limiter consisting of a water-cooled target disc held in position by its water cooling tubes using clamps round the main body of the water jacket containing the quartz view rod. This is illustrated in Fig. 4. The target is a water-cooled disc, as shown, set perpendicular to the line of sight of the quartz rod. A single water-supply line strapped to the body of the quartz rod water jacket splits into two near the end of the jacket to supply the end-disc at two points. The water return is then a repeat. The distance of the disc from the tip of the quartz rod is adjustable, but was most commonly set at 5 cm. The viewing volume was, thus, a truncated cone of 5 nun diameter at its base, expanding to about 6 mm at the target. 3 . . Theory. A complete account of the background theory is provided in Ref. 2; following is a necessary summary. The basis for the calculation is detennination of the ratio of the signal intensity at two different wavelengths. The temperature is then calculated from that ratio using a reduced fonn of Wien's Law. For an energy flux emitted from a gray body source at emi.ssivity E, and measured at wavelength A over the wavelength range M, the ratio of energy ·flux intensities, R, measured at two different wavelengths is: [1] where T is the temperature, and C2 is the second We in constant. To allow for the differential response of the equipment at the two different wavelengths, the system is 4 |