GAS DENSITY DETECTION DEVICE AND GAS DENSITY CALCULATION METHOD FOR GAS DENSITY DETECTION DEVICE

摘要

A gas concentration detection apparatus includes a light source (20), a pyroelectric sensor (24), a reflection member (23) that is provided between the light source (20) and the pyroelectric sensor (24) and forms an optical path of infrared radiation, a thermistor (28), and a switcher (32) that selects one of a first band pass filter (34) and a second band pass filter (36) and places the selected filter on the optical path. A first output value obtained when the first band pass filter (34) is selected, a first calibration curve indicating a relationship between a concentration of gas at a criterion temperature and a value obtained by normalizing the first output value with a criterion output value, and a second calibration curve indicating a relationship between a second output value in a criterion concentration and the criterion output value are determined in advance. A calibration factor used to calibrate the second calibration curve is calculated on the basis of the first output value obtained when the second band pass filter (36) is selected. The second calibration curve is calibrated on the basis of the calibration factor. A concentration of the gas is calculated on the basis of the first calibration curve and the calibrated second calibration curve.