A fiber-optic liquid sensor for simultaneously measuring refractive index, surface tension, contact angle and viscosity

Abstract

A novel fiber-optic liquid sensor was proposed for simultaneously measuring some liquid properties such as concentration, refractive index, surface tension, contact angle and viscosity. Based on the effect of surface tension, tested liquid around fiber probe was pulled upward by the probe. When the balance between the surface tension and gravity was broken, a liquid drop was formed on the end face of the probe. The liquid drop can be regarded as a plane-convex lens, and the light transmission path was affected by the geometrical parameters and refractive index of the drop. The liquid samples (alcohol, water, oil and sucrose) were analyzed using FDLAT. The experimental results indicated that FDLAT can be used for liquid testing and monitoring.