A Novel PCB-Based Sensor for Annular Liquid Film Thickness Measurement in Narrow Rectangular Flow Channels

This article presents a printed circuit board (PCB)-based sensor for measuring the annular flow of liquid film in a narrow rectangular channel. The sensor consists of an array of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 4$ </tex-math></inline-formula> electrode pairs, with each pair comprising a concentric transmitter and receiver electrode. The sinusoidal signal with a frequency of 10 kHz is fed to the transmitter through a wave generator. The voltage generated by the receiver electrode, which is proportional to the thickness, is then used to measure liquid film thickness. The structure and working principles of the sensor are explained in detail, the feasibility of sensing scheme is verified via simulation, and a sensor prototype was fabricated for the final experiment. The experimental results show that the sensor is highly responsive to the liquid film thickness variations in the measurement range of 10–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100~\mu $ </tex-math></inline-formula>m, and an experiment on the liquid film thickness measurement of the sensor in the deformation region was conducted, which proves that the local deformation has a significant effect on the liquid film thickness.