A Time Domain Readout strategy flow sensor

In this paper a novel approach to implement a ferrofluid based flow sensor is presented. The device consists of a glass pipe, with an inner diameter of 5 mm and a length of about 180 mm, filled with de-ionized water and a drop of ferrofluid of 0.01 ml. The sensing methodology exploits the influence of the imposed flow rate on the time elapsed between transitions of the ferrofluid mass between two fixed positions. An array of coils is used to monitor the mass movement and to restore the mass in the null position (the center of the retaining coil). The main novelty of the proposed strategy as respect to solutions available in the literature is the exploitation of a Time Domain Readout (TDR) strategy which shows a high robustness against external influences and is compliant with the concept of frequency output sensors. Other advantages of the sensor are high robustness against mechanical shocks, the intrinsic isolation between the electric part and the liquid medium and the low cost of proposed technology.