Fiber-Optic Measurement of Liquid Evaporation Dynamics Using Signal Processing

An evaporation rate measurement method based on multiple reflection interference using a simple fiber optic configuration is proposed in this study. The evaporation rate is a major factor in preventing accidents and is used in various industrial, chemical, biotechnological, and biological fields. The evaporation rate sensor measures the interference signal during evaporation of a liquid. The main frequency of an interferogram is linearly proportional to the evaporation rate and can be obtained by applying a fast Fourier transform to the interferogram. In our study, the time-averaged evaporation rates of deionized (DI) water and ethanol were tested. Ethanol evaporated at a rate approximately a factor four faster than that of DI water. In addition, a Hilbert transform was used to retrieve the phase information of the interferogram over time. Our proposed method is a powerful tool for monitoring the evaporation dynamics of a liquid in time. The sensor requires a tiny amount of liquid as a test sample to determine the rate of evaporation and offers high reliability and reproducibility at low cost.