GAS CONCENTRATION MEASURING DEVICE AND METHOD OF CALIBRATING SAME

The objective of the present invention is to improve the measuring accuracy of a gas concentration measuring device. A variable value calculating process includes: a step of measuring a propagation time of the propagation of an ultrasound wave through a measurement sector inside a housing 10; a step of obtaining a temperature calculated value on the basis of the measured value of the propagation time and a reference distance for the measurement sector; a step of obtaining a temperature measured value by measuring the temperature inside the housing 10; and a step of obtaining a temperature replacement fluctuation value indicating a difference between the temperature calculated value and the temperature measured value. The variable value calculating process is executed for each of a plurality of temperature conditions under which the temperature of a reference gas inside the housing 10 differs. A temperature compensation table in which the temperature of a gas to be measured is associated with a temperature compensation value relating to the temperature is obtained on the basis of the temperature replacement fluctuation values obtained under each temperature condition.