17. The gas detector according to claim 13, wherein the controller includes means for substantially reducing power applied to the active element while continuing to apply power to the reference element when the controller senses a rise in the concentration of gas being detected above a predetermined...
device under test or a transmitted wave transmitted through the device under test as a scalar value, and a superimposing signal system that superimposes three different vector signals whose relation values are specified in advance on the reflected wave or the transmitted wave of the device under ...