An Application of Semiconductor Sensors to Real Time, In-Situ Rain Gauges

This paper presents results in an effort to develop an improved semiconductor rain gauge. A key feature of the rain gauge described herein is the use of piezoelectric ceramic elements to produce real time and direct signals. Another feature of the device is the ability to use the piezoelectric elements as sensors. A methodology is presented for analyzing the feasibility of using a semiconductor device as a key component of the rain gauge. A piezoelectric semiconductor, lead zirconate titanate (PZT) ceramic device, was investigated for the potential application. PZT discs were prepared through a modified sintering method to provide the optimal thickness and diameter for the device, which are key factors in controlling the resonance frequency. The microstructure of the device was determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The device was examined for its optimal resonance frequency using a laser scanning vibrometer in the time domain. The voltages induced by water drops were measured at the optimal resonance frequency with a spectrum analyzer. The voltage fluctuated according to the size of the water drops. This result suggests the PZT device could function as an alternative to the current rain gauges. The experimental results also indicate that even a single rain drop could be measured in real time using the PZT device. Separation of overlapping signals induced by rain drops falling within the relaxation time (10 ms) of the device is a problem that we are now examining, along with practical issues of the remote use of the device with a data logger.