An Inductive Sensing Mechanism for Cantilever-Based Water Flow Measurement

A novel, cost-effective, noninvasive measurement technique for a cantilever-based flow sensor is presented in this article. The sensor comprises a stainless-steel cantilever installed within the pipe. The cantilever deflects as a function of the flow rate, and its bending angle is sensed with the help of flexible planar coils. These coils are attached externally to the insulating water pipe. The proposed deflection sensing mechanism is based on the eddy current principle. In the proposed approach, three sensing coils are used, and changes in the self-inductances of those coils are read using an inductance-to-digital converter (LDC). The bending angle in either direction of the cantilever deflection are obtained from this information. The effectiveness of the sensing mechanism is first confirmed by conducting finite-element analysis (FEA). Later, a prototype sensor is developed and tested in a laboratory-scale arrangement. The change in inductance due to the deflection of the cantilever corresponding to the flow rate is recorded. The FEA and experimental findings exhibit very good consistency, proving that the proposed transduction and readout mechanisms are suitable for the practical realization of a new flow sensor. The prototype sensor showed a full-scale worst case accuracy of 3% for flow rates ranging from 0 to 7 m3/h. The sensing element that does not include any rotary parts. Similarly, no electrical connections are required to the cantilever for measurement. These features may help achieve less maintenance and a longer lifespan for the sensor.