A Capacitive Cantilever-Based Flow Sensor

This paper presents a novel capacitive transduction mechanism for a cantilever-based flow sensor. The sensor has a stainless steel cantilever attached inside the pipe. The cantilever is fitted in such a way that it bends depending on the flow rate and direction of the flow. The proposed sensing mechanism senses the bending angle of the cantilever using specially shaped capacitive electrodes introduced outside the insulating water pipe. The capacitive sensor electrodes are connected to a measurement unit, but no electrical wiring is needed to the cantilever, ensuring a contactless bending angle read-out scheme. This method is new and helps to realize low-cost and easy-to-install flow sensors. The functionality of the sensing mechanism is first verified using finite element analysis (FEA). Later, a suitable sensor was developed in the laboratory and tested on a pipeline test bench. The change in capacitance due to the cantilever deflection with respect to fluid flow is obtained. A prototype sensor has been developed, and its performance for liquid flow measurement is evaluated. A suitable signal measurement circuity that obtains the difference in capacitance corresponding to the bending angle, and hence the water flow, is developed and employed for the experimental studies. The FEA and experimental test results showed that the proposed transduction and read-out mechanisms are suitable for the cantilever-based water flow sensor.