Gaseous component identification with polymeric film sensor
First Claim
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1. Electronic gaseous component detecting and measuring apparatus comprising the combination of:
- a first array of electrical conductors disposed over the surface of an electrically insulating substrate member and connected to a first electrical terminal;
a second array of electrical conductors disposed intermediate of said first array conductors on said electrically insulating substrate member and connected to a second electrical terminal;
a chemically reactive gaseous component responsive polymeric thin film membrane member disposed over the surface of said substrate member and the conductors of said first and second arrays, the resistivity of said membrane member being determinative of the electrical conductivity between said first and second electrical terminals;
a source of pulsed electrical energy series coupled with said electrical terminals and generating a pulsed conductivity modulated output signal from said membrane member;
amplifying means series connected with said pulsed electrical energy source and said electrical terminals for enhancing said membrane member conductivity modulated pulsed electrical signal;
Fourier transform means connected with the pulsed output signal of said amplifying means for spectral comparison identification and concentration quantification of unknown gaseous components.
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Abstract
A sensor having an interdigitated gate electrode field effect transistor (IGEFET) coupled to an electron beam evaporated copper phthalocyanine thin film is used to selectively detect parts-per-billion concentration levels of atmosphere contaminants such as nitrogen dioxide (NO2) and diisopropyl methylphosphonate (DIMP). The sensor is excited with a voltage pulse, and its time- and frequency-domain response are examined. The envelopes of the magnitude of the normalized difference frequency spectrums reveal features which unambiguously distinguish the NO2 and DIMP exposures.
63 Citations
27 Claims
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1. Electronic gaseous component detecting and measuring apparatus comprising the combination of:
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a first array of electrical conductors disposed over the surface of an electrically insulating substrate member and connected to a first electrical terminal; a second array of electrical conductors disposed intermediate of said first array conductors on said electrically insulating substrate member and connected to a second electrical terminal; a chemically reactive gaseous component responsive polymeric thin film membrane member disposed over the surface of said substrate member and the conductors of said first and second arrays, the resistivity of said membrane member being determinative of the electrical conductivity between said first and second electrical terminals; a source of pulsed electrical energy series coupled with said electrical terminals and generating a pulsed conductivity modulated output signal from said membrane member; amplifying means series connected with said pulsed electrical energy source and said electrical terminals for enhancing said membrane member conductivity modulated pulsed electrical signal; Fourier transform means connected with the pulsed output signal of said amplifying means for spectral comparison identification and concentration quantification of unknown gaseous components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Apparatus for monitoring gaseous concentrations in a challenge gas comprising the combination of:
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a gaseous sensor member having first and second interposed electrical conductors and an overlying chemically active polymeric thin film membrane member in electrical contact therewith, the instantaneous electrical impedance between said conductors being determined by the conductivity of said thin film membrane member; means for exposing said thin film membrane member to said challenge gas mixture; pulsed excitation voltage source means having a rich harmonic waveform content for energizing said sensor member; waveform analysis means including normalized difference Fourier transformation means for determining the spectral distribution of sensor member conductivity variation imposed modifications of said sourcing means signal in response to unknown challenge gas mixture exposure. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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25. Apparatus for identifying gaseous components comprising the combination of:
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a polymeric thin film chemical reaction modulated electrical resistance detecting element; means for exposing said detecting element to said gaseous components and to a preliminary sequence of purging and conditioning gases; electrical impulse emulating signal excitation means connected with said detecting element for generating a chemical reaction modulated sequence of output signals therefrom; Fourier transformation means for generating the normalized difference Fourier transform spectra of said electrical impulse signals and said chemical reaction modulated output signals; means for comparing said normalized difference Fourier transform spectra with the entries in a library of said normalized difference spectra and for identifying predetermined degrees of spectral match therein. - View Dependent Claims (26, 27)
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Specification