Specified gas concentration sensor

摘要

A specified gas concentration sensor includes a thin film thermally separated from a substrate, which is provided by a heater, a temperature sensor and an absorbing substance of a specified gas, and temperature change accompanied by heat generation while absorbing the specified gas in an ambient gas being capable of measuring by the temperature sensor. The absorbed specified gas is released from the absorbing substance by heating with the heater, and after stopping heating with the heater, the specified gas concentration in the ambient gas is obtained by utilizing an output of the temperature sensor at a time passing a predetermined time which is a thermal time constant of the thin film or longer at which the specified gas is absent from the heater. An optional heat conductive type sensor having no absorbing substance of the specified gas can broaden the measurable range of the specified gas concentration.

主权项

1. A specified gas concentration sensor which comprises:
a substrate; a thin film thermally separated from the substrate; a heater comprising part of the thin film; a temperature sensor comprising part of the thin film; an absorbing substance of a specified gas comprising part of the thin film, temperature change accompanied by heat generation at a time of absorbing the specified gas in an ambient gas being capable of measuring by the temperature sensor; and a control circuit, wherein the control circuit is configured so that the absorbed specified gas is released from the absorbing substance in a heating cycle by heating with the heater, and in a cooling cycle after stopping heating with the heater, at a time frame in which cooling is substantially finished when the specified gas concentration is 0%, the specified gas once released from the absorbing substance by heating is getting to be absorbed and a temperature rise occurs based on an exothermic reaction at a time of absorbing the specified gas and a thermal time constant τ that tends to become large is utilized, and after stopping heating with the heater, the specified gas concentration in the ambient gas is obtained by utilizing an output of the temperature sensor at a time passing a predetermined time which at least exceeds the thermal time constant τ of the thin film or longer at which the specified gas is not present at the heater, and that will repeat these heating and cooling cycles.