A Novel Vision-Based Approach for Estimating Viscosity and Concentration of Transparent Liquids

In this letter, we report the development of a viscometer by utilizing a vision-based sensing method. The experimental arrangement includes a cylindrical transparent container with a capillary tube at its bottom and a white cardboard with a vertical black line positioned behind the container. As the liquid sample flows through the capillary tube, the original black line reappears above the meniscus increasing its length, while the refracted line below the meniscus shortens. A camera in association with a Raspberry Pi is used to measure the flow time (FT) from the changing length of a vertical line above the meniscus, which estimates the viscosity from Poiseuille's equation of liquid flow. The system is utilized for viscosity measurements at temperature of 20 °C and 30 °C. Experimental results demonstrate well agreement with standard viscosity values of the test samples. The proposed system offers several merits, including simple in design, low cost, noninvasive operation, automatic flow time measurement, and improved response time facilitated by real-time processing. It is suitable for measuring the viscosity of transparent Newtonian liquids.