This principle of measurement has not succeeded in replacing the mechanical and acoustic principles, described in sections 2.5.1 and 2.5.2, in oceanography. This is mainly due to reasons surrounding accuracy and the uncertainty of measurement. It is, however, widely used in industries that measure flow, as its intrinsic qualities and theory of operation are well known. Measurement of the speed at which water mass moves using this device is based on Faraday’s principle, which states: