APPARATUS FOR MEASURING AND DISPLAYING THE SPEED OF A CRAFT, PARTICULARLY A SAIL-BOARD

摘要

The apparatus comprises on one hand a propeller (1) which is immersed and provided with a permanent magnet and attached to the craft (40) and on the other hand a measurement device installed on the craft. The measurement device comprises a bobbin with a very large member of turns, at least an operational amplifier and a frequency meter to determine the rotational frequency of the magnetic field produced by the magnet of the propeller (1). A tight casing (30) encloses the whole measurement device, as well as its liquid cristal display member and photovoltaic cells for its supply. The apparatus is particularly intended to be removably mounted on a sail-board or a light center-board boat.