| 摘要 |
A concentration measuring device has a polymeric element (12) having volumetric proportions which are sensitive to the presence of the measured gas / vapor, and an optical measuring system. A beam (36) from a light source (24) is focussed on to a movable, light reflecting foil element (20) which extends between the polymeric element (12) and a carrier (16) so that the reflected beam (36') can be detected by a beam-position sensing device (28). The polymeric element may contain a Peltier element to maintain predetermined temperatures and allow measurement of specific gases / vapors in gaseous mixtures. A preferred polymeric element is a sheet of a polysiloxane material, of thickness between 1 micron and 3 mm. Polymeric elements are selected for their swelling characteristics in conjunction with the chemical species required to be measured, e.g. polyvinylmercaptopropylsiloxane is suitable for detection of chlorinated hydrocarbons, ethane, butane, benzene, and toluene. It is preferred that the polymer is cross-linked, particularly if it is to be used at higher pressures. For the optical system the preferred light source is a laser diode , with a segmented photo-diode as a detector.
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