Photoacoustic device and process for multi-gas sensing
US5933245A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 31, 1996 |
| Grant date | Aug 3, 1999 |
| Priority date | — |
| Expiry date | Dec 31, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/1704
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A photoacoustic gas sensing system includes either separate lasers or an arrangement of emitters and filters, to provide infrared energy within at least two distinguishable frequency bandwidths, modulated at two or more associated and different modulating frequencies. The modulated energy signals illuminate a gas cell containing a mixture of gases that experience temperature and pressure fluctuations responsive to the radiant energy. An amplified microphone signal, produced responsive to the pressure fluctuations, is detected at the different modulation frequencies to provide two or more detector signals in digital form. These signals are processed in combination with predetermined constants derived by calibrating the system, to generate two or more concentration values corresponding to the individual gases involved. The system can utilize a photoacoustic cell with walls formed entirely of a polymer that is both gas-permeable and transparent to the infrared radiation. If desired, a temperature sensor and a pressure sensor near the cell provide respective signals based on ambient temperature and ambient pressure. These ambient condition signals are used to provide concentration meas…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.