Measuring and testing – Gas analysis – With compensation detail
Patent
1998-06-01
2000-05-30
Larkin, Daniel S.
Measuring and testing
Gas analysis
With compensation detail
73 2402, 73 3105, 250343, G01N 2161
Patent
active
060678402
ABSTRACT:
A gas sensor (10) is shown having alternately energized infrared radiation sources (14, 16) disposed in a gas chamber (12) at different distances from an infrared detector (18). Both radiation sources are filtered at the absorbing wavelength of a gas to be monitored with one radiation source located proximate to the detector serving as a "virtual reference". The differential absorption between the two radiation sources is used to determine the concentration of a gas being monitored. In a modified sensor (30) one radiation source is seated in a parabolic recess (34a) in a base plate (34) with the radiation focused on one angled end wall (32d) of a dished shaped cover member (32) and reflected over to a second angled end wall (32e) and into the detector with the radiation sources and the detector attached directly to a circuit board (24) mounting the sensor. The recessed cover with opposed angled end walls is also used with another embodiment in which the radiation sources are both located the same distance from the detector, are alternately energized and are filtered with sensing and reference filters, respectively. A modified embodiment (50) has a concave end wall (32e') vertically aligned with the detector and another embodiment (60) has an additional detector (18') along with a semi-reflective, semi-transmitting optical baffle (32k) for use with a gas having a higher absorption level. This embodiment also shows cover member (32") received directly on circuit board (24') with no intermediate base plate.
REFERENCES:
patent: 4412445 (1983-11-01), Spellicy
patent: 4899053 (1990-02-01), Lai
patent: 5163332 (1992-11-01), Wong
patent: 5384640 (1995-01-01), Wong
patent: 5696379 (1997-12-01), Stock
Patent Abstracts of Japan, vol. 011, No. 375 (P-644), Dec. 8, 1987 & JP 62 145143 A (Yokogawa Electric Corp), Jun. 29, 1987.
Ahne Adam J.
Chelvayohan Mahesan
Baumann Russell E.
Larkin Daniel S.
Telecky Jr. Frederick J.
Texas Instruments Incorporated
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