Patent ID: 6859737
Filing Date: 2005-02-22
Classification: G01N

Abstract:
1. A gas detection apparatus using a gas sensor element whose electrical characteristics change in accordance with concentration of a specific gas, comprising: acquisition means for acquiring a sensor output value at predetermined cycle intervals by use of the gas sensor element, the sensor output value increasing with concentration of the specific gas; first calculation means for calculating a present first calculated value at the predetermined cycle intervals during a period in which a low-concentration signal is being generated, the present first calculated value representing a first calculated value at the present time and being calculated by use of a first calculation expression on the basis of a present sensor output value representing a sensor output value at the present time; the first calculation expression including: a reference term including at least one of a tracking term which, while tracking the sensor output value, changes more slowly than does the sensor output value, and an increasing term which gradually increases irrespective of changes in the sensor output value, and an increase-emphasizing term using the present sensor output value and determined in such a manner that the present first calculated value calculated for a time series of sensor output values that are increasing monotonously becomes smaller than a virtual present first calculated value for the time series by use of a virtual first calculation expression obtained through omission of the increase-emphasizing term, and the present first calculated value decreases with the rate of increase in the sensor output values of the time series; and high-concentration-signal generation means for generating a high-concentration signal in place of the low-concentration signal when the present sensor output value and the present first calculated value satisfy a predetermined first relation during the period in which the low-concentration signal is being generated.