To overcome the limitations/disadvantages of many known liquid film thickness sensing devices (viz. conductivity probes, reflectance based fiber-optics probes, capacitance probes, etc. ), a new liquid film thickness sensor that utilizes fluorescence phenomena and. 1 Departamento de Ingeniería Electrónica, División de Ingenierías Campus Irapuato Salamanca, Universidad de Guanajuato, Carretera Salamanca- Valle de Santiago km 3.