This Small Business Innovation Research Phase I project is expected to produce a remote and in situ ultrasonic dew point sensor that has several advantages over existing optical technology. The advantages include: improved sensitivity and accuracy, compensation for mirror contamination, elimination of frost point transition ambiguities, and lower cost. Cost and performance improvements in dew point instrumentation are particularly important for the study of microscale and mesoscale weather phenomena where a sensitivity of 0.1 K or less is desired. The proposed instrument utilizes a dual surface acoustic wave (SAW) delay line design to measure condensation and temperature simultaneously on a monolithic substrate. This configuration should provide extremely high precision and reliability since SAW sensors can detect mass changes of less than one monolayer of dew and measure temperature to an accuracy of 104 K. The design eliminates the need to indirectly measure dew optically and to attach a temperature sensor to the chilled surface as is done in most commercial dew point sensors. It is also expected that the ability to detect dew formation at levels below those that can be detected optically will result in a compensation method for mirror contamination. In addition, the ability to determine the phase of the dew will allow the elimination of frost point ambiguities.
