a high temperature humidity determining device which measures the moisture content of gas streams with temperatures as high as , but not limited to 600 ° f . the device uses a solid state , thin film polymer type relative humidity / temperature sensor and electronic barometer to measure the properties of the gas stream . the unit does not require laboratory quality oxygen , ice water , distilled water or any other cleaning fluids . in order to avoid damage to the sensor , a sample is cooled to below about 300 ° f . prior to sampling . this is done by pumping the sample air through a thermostatically controlled sample conduit , and into a positively pressurized and thermostatically controlled sample chamber . a microprocessor calculates the humidity ratio and dew point of the sample or other moist air properties , and delivers data to a visual process indicator , as well as to any other desired output .