US 5,315,673 A · Optical waveguide vapor sensor

Abstract

An optical waveguide sensor for the detection of acid vapors comprises a chemically sensitive reagent coating of bromothymol blue or thymol blue indicator suspended in a Nafion polymer film. The sensor uses a 562-nm light-emitting diode source and a phototransistor detector. The response to HCl and H.sub.2 S vapors is both rapid and reversible, with an estimated detection limit for H.sub.2 S of less than 15 ppmv (parts per million by volume). The sensor exhibits generalized response to protonic acid vapors, but does not produce an indicator response to CO.sub.2, even at large concentrations (60 volume-%) in the presence of water vapor. The sensor exhibits a systematic interference from water vapor which may be corrected by a differential approach, either using a reference sensor (Nafion without an indicator) or by monitoring the sensor responses at two wavelengths.

Claims20

Dependent claims

A sensor for detecting a selected air constituent comprising:

an optical waveguide having a front end and a rear end;
a light source for transmitting light of a selected wavelength to one end of the waveguide;
and means for measuring the intensity of light emitted from the other end of the waveguide, said waveguide comprising a film of material disposed on a substrate such that multiple internal light reflections occur at the interfaces between the film and the substrate and between the film and air, said material having optical properties that are susceptible to change in the presence of said air constituent, wherein said film comprises a reagent embedded in or forming a part of a polymer, said reagent yielding a substance having characteristic light-transmissive or light-adsorptive properties upon exposure to said air constituent.

Dependencies are inferred from the claim text.

Optical waveguide vapor sensor

Life of this patent

Optical waveguide vapor sensor

Life of this patent

Abstract

Claims20