Laser-based measurement of liquid temperature or concentration at a solid–liquid interface

摘要: Abstract This work presents a real-time, non-contact, laser-based thermoreflectance technique to measure changes in temperature or concentration of stationary flowing liquids at transparent solid–liquid interface, e.g., glass window. Variations result change refractive indices the liquid, which, turn, alter reflectivity interface. A 3 mW semiconductor laser diode serves as light source, and silicon photodiode monitors intensity variations reflected beam. The three liquids, water, ethanol, 1-propanol, are measured with very good agreement found between calibrated thermistor. methanol–propanol solution is successfully well. maximum uncertainty 0.6°C for measurement 0.2% measurement, respectively. presented experimental configuration simple, inexpensive reliable. Additionally high spatial temporal resolution possible: beam spot size can be readily reduced ∼20 μm less, ∼1 μs less achieved high-speed data acquisition system. Thus, liquid small-scale devices such microelectro-mechanical-systems (MEMS) microfluidic structures, systems fast variation, rapid solidification mixing, effectively measured.