| 摘要 |
<p>1493729 Monitoring vapour concentration ATOMIC ENERGY OF CANADA Ltd 16 July 1975 [1 Aug 1974] 29877/75 Heading G1A Apparatus for monitoring the concentration of a vapour with a narrow absorption band in a gas sample relative to its concentration in a reference sample comprises means 21, 23 to pass said samples alternately through a chamber 1, means 7-11 to pass a beam of radiation over a fixed path through it, photo-cell 12 detecting the intensity of the emergent beam, means 13 to give the beam incident on 12 a narrow bandwidth alternately coincident and non-coincident with the absorption band and means giving an indication of the relative vapour concentration. Broad band pass filter 6 is rotated until its spectral slope compensates for that of the other optical components. It may be placed near source 4 instead. Mirrors 7, 8, 9, 10, 11 provide a long optical path. For measuring HDO concentration in excess of the natural, air in duct 20 is pumped by blower 21 through inlet 2 and reference air by blower 23 through inlet 14. Both leave by outlet 3. Modulator 25 causes blowers 21, 23 to operate alternately at 12À5 mHz. Modulator 27 causes torsional oscillator 30 to vary the angle of filter 13, and so its band, at 85 Hz. Amplifier 15 only passes frequencies near 85 Hz. The output of demodulator 28 is proportional to the amplitude of the 85 Hz signal. It is corrected for humidity by signals from sensor 18. Amplifier 16 passes only frequencies below 50 mHz. Demodulator 29 gives a signal proportional to the peak of this waveform and this is smoothed by amplifier 17 to give a signal representing the excess HDO in the sample. The theory is given.</p> |
