Relative Vapor-pressure Measurements Using A Frequency-modulated Tunable Diode-laser, A Tool For Water Activity Determination In Solutions
Two-tone frequency modulation spectroscopy (TTFMS) is applied to the determination of water activity using an 820-nm GaAlAs diode laser. By measuring the relative light absorption of water vapor over a solution and over a pure water reference, the water activity in the solution is determined. Fast, nonintrusive, and selective measurements are demonstrated. The detection limit for measuring a relat