Optically-based chemical detection system

Details Optically-based chemical detection system Optically-based chemical detection system

1994-10-04

1996-08-13

Fields, Carolyn E.

Radiant energy

Invisible radiant energy responsive electric signalling

Infrared responsive

25033912, 250343, 356419, 356436, 356437, G01N 2125, G01N 2131

Patent

active

055458971

ABSTRACT:
An in-situe chemical gas or fluid analyzer for vehicles, industrial, environmental and process control applications. As applied to a vehicle (1) having an internal combustion engine, the analyzer includes: (i) a source of electromagnetic radiation (14, 16); and (ii) a sampling cell (12) which collects emission gases of interest and which is capable of withstanding hostile environments while preserving a "clear" optical path between the sensor sampling cell and the source of radiation. The analyzer further includes: (iii) a solid state sensor (24, 26, 28, 30, 32 ) of monolithic construction which selectively detects electromagnetic radiation that is absorbed or emitted by one or more chemical species of interest, that compensates for temporal and spatial variations in illumination level provided by the source, and that provides an electrical signal output, in either analog or digital format, that is related to the measured concentrations. The sensor includes, in combination, a plurality of highly sensitive electromagnetic radiation detectors (26), spectral filters (24) which may utilize multiple layers of deposited dielectric thin films and/or selectively absorbing layers, and low noise electronics which performs a variety of functions including amplification (28), multiplexing (30), analog to digital (A/D) conversion (33), signal processing (32), and input/output (I/O). In a presently preferred embodiment each radiation detector is a thermopile detector that is integrated upon a common substrate with the support electronics and an associated optical bandpass filter.

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Article entitled "Analytical Approach--IR Long--Path Photometry: A Remote Sensing Tool for Automotive Emissions", by G. Bishop et al., in Analytical Chemistry 1989, 61, 617A.
Publication entitled "Find And Fix The Polluters", by James E. Peterson et al., Chemtech, Jan. 1992, pp. 47-53.

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