Characterization and Design of a Readout Circuit for a Piezoelectric-based Acoustic Disdrometer

Abstract

In 2009, Department of Water Management (DWM) at TU Delft conceptualized the design of a low-cost disdrometer suitable for large scale, remote deployment. But, being a novel idea, its electrical characteristics were not well researched. Also, the system was not sensitive enough to measure the raindrops of diameter less than 0.9mm. Furthermore, it was found that the proposed disdrometer suffers from the edge effect i.e. when a raindrop hits on the edge of the disdrometer; the size of the raindrop is underestimated. All the aforementioned issues have been addressed in this research. The presented work discusses the electrical characteristics of the disdrometer. A readout circuit has been designed to improve the performance of the disdrometer and an innovative technique has been developed to solve the problem of edge effect. The impedance response of the disdrometer has been analyzed and an equivalent electrical model of the proposed disdrometer has been developed and characterized. Furthermore, an elaborative analysis of the edge effect has been presented. Based on this analysis, an innovative technique has been proposed for reducing the edge-effect. This technique uses the envelope of the transducer’s output to determine if the drop hit on edge. Also, a low-power (17.8mA@5V), low-noise (7.8µVrms) readout circuit has been designed. This readout circuit is able to measure the drops of size as low as 0.4mm. Because of the achieved results, this disdrometer is attracting a lot of attention of various groups from industry as well as from academia. A group of researchers from the DWM, TU Delft is looking forward to turn it in to a commercial product.