“…The methods of measuring the water content in gases using microwave devices have been developed since the 1940s [ 3 , 4 , 5 , 6 ] due to the advent of required generators, receivers, and circuit solutions [ 7 , 8 , 9 ]. The microwave methods, especially cavity ones, are characterized by sufficiently high sensitivity [ 10 , 11 , 12 ], which allows one to develop sensors for the detection of relatively low moisture content [ 13 ]. Since microwave humidity sensors do not contain moisture-sensitive materials, they make it possible to detect water vapors with no inertia in real time [ 14 ].…”