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Gas sensor

  • US 4,474,183 A
  • Filed: 01/03/1984
  • Issued: 10/02/1984
  • Est. Priority Date: 01/17/1983
  • Status: Expired due to Term
First Claim
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1. A gas sensor composed of a hydrogen ion sensitive FET transducer of an oblong gate-insulated field effect transistor structure having the gate part at its front end and the electrode part at the other end, an Ag-AgC1 reference electrode placed adjacent the gate part of the aforementioned transducer, an insulator tube housing the FET transducer and the reference electrode to each of which one end of a lead wire is connected, the FET transducer and the reference electrode being located at an opening part provided in the insulator tube, and the lead wires extended along the tube, with a connector joined to the other end of said lead wire, an electrical insulation resin which is filled at least in the space of the part inside the tube wall housing the lead wire connecting parts, thereby closing the tube, a hydrophilic polymer layer put around the gate part of the FET transducer and the reference electrode, enveloping both of them, said layer containing electrolytes which undergo changes in hydrogen ion concentration, as it absorbs gas, and a gas permeable membrane formed of a colored silicone rubber which gives transmittance less than 10% and the division (P/d) of the gas permeability of nitrogen (P) by the membrane thickness (d) is larger than 2.5×

  • 10-7 [cm3 (STP)/ cm2 ·

    sec·

    cmHg], said membrane coating the whole of the aforementioned hydrophilic polymer layer and the whole of the surface of at least the part of the insulator tube in which the FET transducer is housed.

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