Design and fabrication of low cost Disdrometer and turbulence sensor

Abstract

Disdrometers detects size and speed of falling rain droplets in a rainfall. They detect droplets either by impact or optical based methods. Optical based ones, use light source and an optical detector. Droplet crossing the light creates shadow on the detector. This change in the intensity and duration of change provides the size and speed of the droplet. Whereas the impact based method utilizes peizo elements to sense the droplet by physical momentum transfer at the time of droplets impact with the sensor. Apart from the technical differences in them, both of these disdrometers fall in the similar cost range. Wind turbulence sensors works on detection of gradients in wind speeds by employing various working principles like thermal anemometer, laser Doppler anemometer, etc. In thermo anemometers, a heating element is maintained at a constant temperature. As the wind flows, it carries some heat energy away from the element. This causes a change in the resistance in the heating element providing further change in voltages across it. Laser Doppler anemometers work on change in wavelength of light scattered by a moving particle which is caught in the wind flow. These techniques are highly accurate in measuring the turbulence in the air but at elevated costs. Aimed at cost efficacy and acceptable performance of the device, a novel concept was implemented in a single device to study its feasibility to work as a disdrometer and a turbulence sensor. It employs the principles of electromagnetic induction and response of a cantilever to impulses. Based on these principles, a device was designed and fabricated to detect rain droplet size and wind turbulence. It was fabricated from readily available materials. The testing of the device in laboratory conditions yielded satisfactory results as compare to the standard commercial instruments.