Abstract: A method of moisture measurement wherein a moisture responsive element is subjected to the measuring environment and its thermal capacitance or resistance temperature coefficient is measured. A system operates by cycling a sensor element between a first temperature and a second temperature and determining the sensor capacitance at each temperature. The sensor capacitance difference, corresponding to its temperature coefficient, is then compared to a previously compiled table of gas humidity or dew point versus capacitance increment values. The differential measurement thus made automatically corrects for systemic error originating in equipment drift, cable capacitance change and various aging and slow hysteresis or sensor capacitance variations.