Optical waveguide vapor sensor
US5315673A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 9, 1992 |
| Grant date | May 24, 1994 |
| Priority date | — |
| Expiry date | Mar 9, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/773
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.