Method and apparatus for spectroscopic measurement of the concentration of a gas
US5173749A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 5, 1991 |
| Grant date | Dec 22, 1992 |
| Priority date | — |
| Expiry date | Mar 5, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2201/0826
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Method and apparatus for spectroscopic measurement of the concentration of a gas in a sample where you detect the intensity of light from a light source (1) passed through the sample (4) and through a reference cell (5) and generates a signal which represents the concentration of the gas. A laser diode (1) constitutes the light source which is locked to the absorption line of the gas at known concentration and pressure contained in a reference cell (5). The laser light with the properly selected wavelength is distributed via optical fibres (2, 3, 6) and/or glass prisms (19, 20) to the reference cell (5) and the sample (4). Non-gas-related transmission variations in the measurement path or in the optics is automatically compensated for by a special laser modulation which generates a time multiplexed reference. The measurement can be performed in a measurement cell incorporating several reflective mirrors (30) to reflect the laser beam several times inside the measurement cell thereby increasing the effective length of the measurement path. The measurement can also be performed using an optical fiber designed so that the surrounding gas or fluid via the evanescent field affects the l…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.