Gas constituent measurement and recording
First Claim
1. A method of measuring the molecular concentration of a constituent in a gas comprising the steps of:
- (a) contacting the gas with a surface of a solid body;
(b) momentarily heating said surface so that said constituent reacts at said surface to alter a property of said surface permanently; and
(c) determining the degree or rate of alteration in said property produced by reaction of said constituent during said momentary heating step, said heating step including the step of momentarily applying heating radiant energy to said surface in a plurality of heating pulses to a plurality of different localized regions of said surface in temporal sequence, said determining step being performed separately for each of said localized regions to thereby provide a plurality of measurements of said molecular concentration, whereby each of said measurements is indicative of said molecular concentration at the time of one of said pulses.
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Accused Products
Abstract
The molecular concentration of a constituent such as oxygen of an anesthetic agent in a gas is measured by contacting the gas with the surface of a solid body, momentarily heating the surface so that the constituent reacts at the surface to alter a property of the surface such as reflectivity, and determining the degree or rate of alteration occasioned by the heating step. The momentary heating operation may be performed by light from a laser focused on to a small localized region. The body surface can include a thin film of a material such as a metal reactive with the gas constituent of interest at elevated temperatures. The preferred methods provide extraordinarily rapid response, and also form a permanent record of each measurement. Where the gas is at substantially constant pressure, the measured molecular concentration can be interpreted as an indication of the proportion of the constituent in the gas. Where the gas is of known composition, the molecular concentration can be interpreted as a measurement of the total gas pressure. Similar techniques are be applied to identify an unknown constituent in a gas or to detect presence of an incorrect constituent, such as an incorrect anesthetic agent in an anesthesia system. Apparatus and recording media are also disclosed.
77 Citations
55 Claims
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1. A method of measuring the molecular concentration of a constituent in a gas comprising the steps of:
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(a) contacting the gas with a surface of a solid body; (b) momentarily heating said surface so that said constituent reacts at said surface to alter a property of said surface permanently; and (c) determining the degree or rate of alteration in said property produced by reaction of said constituent during said momentary heating step, said heating step including the step of momentarily applying heating radiant energy to said surface in a plurality of heating pulses to a plurality of different localized regions of said surface in temporal sequence, said determining step being performed separately for each of said localized regions to thereby provide a plurality of measurements of said molecular concentration, whereby each of said measurements is indicative of said molecular concentration at the time of one of said pulses. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18)
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17. A method of recording the molecular concentration of a constituent in a gas comprising the steps of:
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(a) contacting the gas with a surface of a solid body; and (b) momentarily heating said surface so that said constituent reacts at said surface to alter permanently a property of said surface, the degree of alteration being dependent upon said molecular concentration present at said surface during said momentary heating step, said step of momentarily heating said surface including the step of applying a plurality of pulses of heating radiant energy to a plurality of different localized regions of said surface, said pulses being applied in temporal sequence, whereby the degree of alteration of said property in each of said localized regions is representative of said molecular concentration at the time of one of said pulses. - View Dependent Claims (19, 20, 21)
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22. A method of measuring the molecular concentration of a constituent in a gas comprising the steps of:
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(a) contacting the gas with a surface of a solid body; (b) momentarily heating said surface so that said constituent reacts at said surface to alter a property of said surface; and (c) determining the degree or rate of alteration in said property produced by reaction of said constituent during said momentary heating step, said heating step including the step of momentarily applying heating radiant energy to said surface in a plurality of heating pulses to a plurality of different localized regions of said surface, said determining step being performed separately for each of said localized regions to therby provide a plurality of measurements of said molecular concentration, the determining step for each localized region including the step of measuring the reflectivity or transmissivity of that localized region at or after the end of the heating pulse applied to such localized region. - View Dependent Claims (23, 24)
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25. A method of identifying an unknown constituent in a gas comprising the steps of:
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(a) contacting the gas containing the unknown constituent with a surface of a solid body; (b) momentarily heating said surface to a known extent during said contacting step; (c) measuring the degree of alteration, if any, in a property of said surface caused by reaction of the unknown constituent at said surface during said heating step so as to provide information as to the relationship between extent of heating and degree of alteration in said surface property for the gas containing the unknown constituent; and (d) comparing the information obtained in step (c) with corresponding information for at least one gas containing a known constituent, said heating step including the step of heating a localized region of said surface to an extent sufficient to permanently alter said property of said surface to a substantial degree by applying a pulse of heating radiant energy to said localized region, said comparing step including the step of comparing the extent of heating required to produce said substantial degree of alteration in said property of said surface with the extent of heating required to produce corresponding alteration with gases containing known possible constituents. - View Dependent Claims (26, 27, 28, 29, 30, 31)
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32. Apparatus for recording the molecular concentration of a constituent in a gas comprising:
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(a) means for retaining a solid body; (b) means for contacting a gas containing a constituent with said body; (c) means for momentarily heating a surface of said body so that said constituent reacts at said surface to permanently alter a property of said surface and so that the degree or rate of alteration in said property depends upon the molecular concentration of said constituent at said surface during said momentary heating, said heating means including heating pulse means for applying a series of momentary pulses of heating radiant energy to said surface, and directing each pulse of heating radiant energy to a different localized region of said surface. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39)
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- 40. A medium for recording or determinng the molecular concentration of a constituent in a gas comprising a body having a surface which is substantially nonreactive with a first constituent in a gas at a first temperature, said surface being reactive with said first constituent upon heating to a second temperature higher than said first temperature so that a property of said surface will be permanently altered by reaction with said first constituent upon such heating, said medium further comprising means for engaging the body-retaining means of a gas constituent measurement and/or recording apparatus, said body including a substrate and a first film on said substrate at said surface, said substrate being substantially nonreactive with said constituent, said film being reactive with said constituent at said second temperature but substantially nonreactive with said constituent at said first temperature, the light absorptivity of said film being between about 5% and about 50%, said substrate having a thermal diffusivity of less than about 102 cm 2 /sec, said film including at least one metal and said film being less than about 2,000 Angstroms thick.
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53. A method of measuring the molecular concentration of an anesthetic in a gas comprising the steps of:
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(a) contacting a gas containing an anesthetic selected from the group consisting of enflurane, halothane and isoflurane with a surface of a solid body incorporating at said surface a metal selected from the group consisting of aluminum and the group VIII metals; (b) momentarily heating said surface so that the anesthetic reacts at the surface to form a deposit on the surface during the heating step to thereby lower the reflectivity of said surface; and (c) determining the degree or rate of alteration in the reflectivity of the surface produced by said momentary heating step. - View Dependent Claims (54, 55)
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Specification