| 摘要 |
Oxygen gas sensor (1) having a first, oxygen receptive semiconductor layer and a second, temperature compensating, oxygen receptive layer, which are both coated with a catalyst (7) to promote substitution, by oxygen , of any carbon dioxide present in the test sample.- DETAILED DESCRIPTION - Oxygen dependent electrical conductivity in semiconductors is a function of oxygen partial pressure and the semiconductor type, as represented by the expression: sigma = sigma 0.(po2)m sigma = conductivity; sigma 0 = sensor constant; - po2 = partial pressure of oxygen; and - m = constant for semiconducting material.- It is also significantly temperature dependent.- An INDEPENDENT CLAIM is included for the measurement method of carbon dioxide using a sensor designed with both oxygen receptive semiconductor layers having essentially linear response at low oxygen concentration, and one of the sensors having a response curve with a minimum inflection point at higher oxygen concentrations.- Preferred Features: The oxygen receptive semiconductor layer (6) is produced from strontium titanate, either as a sputtered, thin layer, or as a thick layer device, promoted with pentavalent tantalum, niobium, or tungsten ions, to provide an electron donor type characteristic with a response which is linear or has only a very slight minimum inflection; the lower, oxygen receptive, semiconductor layer (12) is made of n-promoted strontium titanate by trace addition of iron or chromium ions to provide electron acceptor characteristics; the catalyst coating is aluminum oxide containing trace amounts of platinum, palladium or rhodium; and that an operating temperature of 790-800 deg. C is used for measurements, and is initiated electrically via a central platinum heating structure (16)
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