OCR Text |
Show through amplifiers to either display and/or to pc storage for analysis. Figure 1 taken from Ref. 2 illustrates the essential layout (with the two separate signals represented for illustration here as separate signals on a recorder). The originating temperature is then calculated from the ratio of the intensities in the radiation signal at the two wavelengths . . ' -The relative (fractional) area of the radiating source can also be calculated. The basis of the probe design is a 6-mm quartz rod contained in a water jacket that is inserted into the particle flame to pick up the radiation signal. The probe is illustrated with dimensions in Fig. 2. The single quartz rod down the center of the jacket was blackened on its outside to aid total internal reflection. With this and related treatment, measurements showed that the viewing volume from the end of the rod into the flame was a cone with a half angle of about 3 degrees. The signal from the quartz rod passed into a optic bundle of about 2500 2-mil glass fibers. The bundle was unravelled about half way along its length, split into two, and strands from each bundle were rewoven into the two separate lines. This procedure was carried out to be sure that the potential for uneven transmission down each split was eliminated as far as possible. The bundles were then bonded at the ends in a clear epoxy cement, clean-cut, and polished for maximum optical transmission. As shown in Fig. 1, the signal in each line then passed through the filters (Corion Co~ Model S-25) at the two' ,selected wavelengths (at 800 and 1000 run with 25 nm bandwidth, and thence to photo detectors (silicon photodiodes) with primary amplification using' OP-07 op ampHfiers, followed by two-stage secondary amplification. The arrangement for a single -channel is shown in Fig. 3. -The switch allows for 5 stages of gain, at 10, .100, 1000, 10,000 and 100,000. The inital amplifier design, for low drift, was found to be generally adequate; however, it was modified for some experiments to increase the frequency response range. Details are to be found in Ref. 4. The initially targeted frequency response was 800 Hz, representing a single particle passing through the viewing volume at a velocity of 5 mls. In testing, the frequency 3 |