| Popis: |
The environmental variables influence in the development of plants and animals. One of these variables is the wind, which can be responsible to change the growing of plants and spread diseases. Therefore, the measure of wind speed is necessary to agriculture. Usually, such measuring is done by use of anemometers working with wind cocks which work in only two dimensions, measuring the wind speed and direction by a mechanical system. One disadvantage of this approach is the existence of mobile parts which does not render accurate speed measures, due to air friction and equipment inertia. In this work, an ultrasonic anemometer which measures the direction and speed of the air in three dimensions is presented. Such anemometer use only four piezoelectric sensors arranged in two orthogonal axes non-competitors. So that, joining together the points of each sensor it was get a structure in the form of a regular tetrahedron. The wind speed in three directions can be measured inferring the necessary time (transit time) so that a pulse of ultrasound, sent for one of the sensors, reaches the others three. Moreover, the tetrahedron-shaped structure allows to measure in four different coordinate systems. This adds redundancy to the system so that a better precision in the measures can be achieved. This measurement is performed by a microcontroller and is done to make the system immune to variations of temperature and air humidity. The microcontroller is also responsible for storage of data and later sending them to a microcomputer. |
