Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2000-08-16
2001-11-06
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S343000
Reexamination Certificate
active
06313464
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a portable, infrared gas analyzer capable of measuring multiple gases in a gas sample having one or more infrared absorption gases therein for signalling the concentration of the selected gas or gases in the gas mixture, such as the exhaust gases of gasoline powered engines without resorting to the use of chopping techniques.
Infrared gas analyzers utilizing the infrared absorption principle for determining the quantity of two or more gases in a sample gas to be measured are well known in the art. The infrared absorption principle is based on the fact that the photons are absorbed by an infrared sensitive gas in proportion to the concentration of the gas. The typical prior art infrared gas analyzer relies on the use of a chopper for repeatively and continuously interrupting the infrared beam at a predetermined rate. This prior art technique is resorted to measure the “dark level” or background signal that is present when no infrared beam is applied to the analyzer. Typical prior art patent disclosing these infrared gas analyzers are disclosed in U.S. Pat. Nos. 3,932,754; 4,069,420; 4,420,687, and 4,772,790. Typically these prior art devices employ multiple thermopiles for detecting and signalling the infrared level of the infrared beam applied to the analyzer.
Most of the known prior art infrared analyzers utilized collimated or focused infrared beams in the optical portion and do not permit the infrared beam to reflect off anything but mirrors and as a result require expensive optical systems to control the infrared beams. These prior art systems require splitting the infrared beam by a physical beam splitter or a dichroic beam splitter and the like that must be properly mounted and aligned and produces optical losses due to the beam splitting designs. In addition, these devices require relatively long optical path lengths that may vary from 1-meter to more than 100-meters.
SUMMARY OF THE INVENTION
The present invention comprehends a multiple gas infrared beam analyzers that is portable, compact, and operable with a low power battery pack that is easy to integrate into Host Instruments. The multiple gas analyzer is cost effective and an efficient design that does not incorporate the aforementioned costly features for implementing the aforementioned prior art methods for infrared gas analyzers and measures multiple infrared sensitive gases present in the exhaust gases of a gas powered engine such as carbon monixide, CO, or hydrocarbons, propane or hexane. The hydrocarbons are measured by measuring the hydrocarbon molecular bonds and therefore respond to any gaseous compound containing hydrocarbon bonds in it but the analyzer of the invention is calibrated for carbon monoxide, propane, and hexane. This is intended to measure the unburned hydrocarbons in gasoline but is useful for measuring propane, butane and natural gas fueled combustion engines. The hexane is measured since it is the hydrocarbon which most closely represents gasoline vapor and is an international standard for the gasoline fueled engines. The multiple gas analyzer utilizes thermopile detectors, in a non-chopped configuration to detect decreases in the infrared radiation that are monotonically related to the concentration of the measured gas or gases in the gas mixture applied to the infrared analzer. The infrared optical system is simple, optically efficient and arranged in a unique configuration. The overall path length for the gases to be measured is less than 5-inches. The optical system is operative with non-collimated infrared source and having a folded beam arranged with minimal losses and a space saving arrangement.
From a structural standpoint, the present invention comprises a compact infrared optical system that reflects an infrared beam along internally reflecting, light transmitting pipes over a preselected light path and reflected from mirrors for folding or changing the direction of the infrared beam to confine it within relatively small path to impinge against a plurality of infrared detector-filters for detecting a plurality of gases. The infrared detector-filters are each designed to respond to an individual gas and provide an electrical output signal representative of the concentration of the detected gas in the gas mixture. The detector-filters are advantageously arranged within the infrared analyzer to take advantage of the reflective properties of the detector-filter to cause the reflected beam from one of the detector-filters to be reflected to another detector-filter for responding to a second gas in the gas mixture to provide an electrical output signal representative of the concentration of the second gas of the gas mixture all within a portable, relatively small infrared analyzer.
The infrared analyzer output signals are processed under the control of an analog to digital converter and a microcontroller programmed therefore and provide digital output signals representative of the multiple gas concentrations for transfer to a host processor. The electrical output signals from the infrared detectors are electronically processed including a variable gain amplifier, controlled by a microprocessor command to increase the amplifier gain upon determining that the analyzer has aged and/or been contaminated to provide amplified signals that compensate for the aging. The noise present in the amplified signal is filtered out to provide an analog signal containing the desired gas data, essentially noise free. This analog signal is applied to an analog to digital converter through a run-time offset voltage circuit to improve the resolution of the converter and provide more accurate binary, coded, digital output signals. The digital output signals are processed by a suitably programmed microprocessor for controlling the gain of the amplifier, the application of the offset voltage to the A/D converter during the gas measuring mode only and controls the energization of the infrared source during the calibration of the analyzer for providing the IR dark level value, the zero gas level and the continuous beam measurement mode.
REFERENCES:
patent: 3797942 (1974-03-01), Joly
patent: 4228352 (1980-10-01), Adrian
patent: 4914719 (1990-04-01), Conlon et al.
patent: 5163332 (1992-11-01), Wong
patent: 5222389 (1993-06-01), Wong
patent: 5689114 (1997-11-01), Miyazaki et al.
Da Rin, Esq. Edward J.
Gagliardi Albert
Hannaher Constantine
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