Development of Doppler Speed Log

Abstract

A Doppler Speed Log utilizing the Doppler effect of under-water ultrasonic waves has been developed by the authors as an alternative of the existing speed measuring instrument, i. e. pressure log or electro-magnetic log. It has following superior characteristics. (1) To be able to indicate ship's speed against water or ground. (2) To have high accuracy throughout speed range. (3) To have no protrusion from bottom so that it can be used in shallow water or in harbours with floating obstructions. (4) To be low cost compared with Doppler Sonar. It is confirmed that the Doppler Speed Log has sufficient accuracy, reliability etc. after testing on a bulk carrier. In this paper, effect of transducer installation error on accuracy of measurement, frequency of ultraronic weves to be applied, reliability of instrument etc. are discussed.