PIEZOELECTRIC VAISALA RAINCAP RAIN SENSOR APPLIED 压电维萨拉雨帽雨量传感器的应用.pptVIP

PIEZOELECTRIC VAISALA RAINCAP? RAIN SENSOR APPLIED TO DROP SIZE DISTRIBUTION MONITORING Atte Salmi, Lasse Elomaa, Panu Kopsala and Emmi Laukkanen Vaisala Oyj, Helsinki, Finland Contents Vaisala RAINCAP? rain sensor DSD measurements in laboratory Disdrometer needs Radar adjustements (DSD) (Z – R relation) Soil erosion (KE flux) agricultury (soil splash erosion, seal formation, soil aggregates brekdown) hydrology (infiltration, evporation, surface runoff) Low-cost disdrometer low purchase price low maintenance costs VAISALA RAINCAP? rain sensor Developed for VAISALA Weather Transmitter Construction of the sensor Robust sensor with negligible maintenance needs ? Simple design without any moving parts Measurement principle The drop impact generates elastic waves to the sensor plate, and further on to the piezoelectric sensor. The resulting mechanical stresses in the piezoelectric material causes a voltage U(t) between the sensor electrodes. The voltage output U(t) from the piezo detector due to a drop impact is proportional to the drop size. Sensor output The instrument divides the measured data into eight drop-size classes and normalizes the drop diameters with a weighted equivalent drop diameter. As an example, all data in the class 1.795-2.244 mm are normalized to 2.0 mm in the number of drops. Therefore, the number of drops in a class can be expressed with a decimal point. Experimental arrangements: Vaisala Rain Laboratory Experimental arrangements: Drop velocity and shape measurements The converted voltage signal, was directly proportional to the area of the laser beam intercepted by the raindrops. Every drop fell through both beams producing two sequential voltage signals. By comparing the resulting signal pairs, we ensured that no acceleration occurred. From the time difference, Δt, between the peak values of the voltage signals, speed of the drop could be calculated. Vertical radius a was calculated from the width of the voltage pulse pro