Optical Fiber Probe Viscometer based on Hollow Capillary Tube
in: Sensors and Actuators B-Chemical (2019)
An optical fiber probe viscometer was developed using only a single mode fiber, a hollow capillary tube, and a fusion splicer. The sensing structure consists of an air cavity with a small access hole for fluids. The sensor behaves as a two-wave interferometer where the
intensity of the signal is sensible to the position of the air-fluid interface inside the cavity. The intensity variations of the signal over time, at 1550 nm, were monitored during the full process of dipping and removing the sensing head from a fluid solution. Such variations can be converted into detection of fluid displacement inside the cavity. The same study was performed for multiple sucrose solutions with different viscosities, measuring only during the fluid evacuation process. In the first 300 ms of the evacuation process, where the fluid displacement over time can be approximated by linear regime, the slope of the fluid displacement corresponds to the fluid evacuation velocity, which is
related to the fluid viscosity. The reproducibility of the measurements was demonstrated and the influence of temperature is also addressed.