THE DEVELOPMENT OF A LOW COST PIEZO-BUZZER DISDROMETER

Abstract

For over a century, numerous research studies have been carried out to understand rainfall using techniques ranging from manual gauges, drop counting to satellite based data. The presented work focuses on the development of a low cost disdrometer using a piezo-buzzer as sensing unit to measure and log rain rate, rain drop sizes from 0.5 mm to 5.5 mm in real-time. The developed disdrometer comprises seven sections: the sensing unit, readout circuit unit, microcontroller unit, recording unit, real-time clock, display unit, and power supply unit. The integral part of the developed instrument is the sensing unit which is made up of a piezoelectric disk glued to a conical-shaped stainless steel and a polyvinyl chloride (PVC) to prevent inflow of moisture and short circuit. The readout circuit consists of a 16-bit analog-to-digital converter, an amplifier, and a filter designed to improve the output signal of the disdrometer. It was programmed with C language on the arduino Uno microcontroller using its integrated development environment (IDE). For the calibration of the low cost disdrometer, two methods was employed namely: an experimental calibration setup and field instruments. With the experimental setup, the outputs of the sensing unit were linked to drops of known sizes using burettes and syringes. Calibration of the disdrometer showed a clear relation between the signal energy of a drop and the size of the drop. From measurements, it was observed that the smallest drop measured by the instrument is 0.8 mm, while the biggest drop measured was 5 mm. In order to validate the performance of the developed disdrometer, standard instruments such as the Micro Rain Radar (MRR) and Davis weather instruments were used to determine the level of accuracy and error in the instrument. It was observed that the rain rate and rain drop sizes measured by Micro Rain Radar (MRR) disdrometer were reproduced very well by the developed disdrometer.