水中テレメーターに関する実験(日本航海学会第24回講演会)

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タイトル別名
  • Experiment on Underwater Telemeter
  • 水中テレメーターに関する実験
  • スイチュウ テレメーター ニ カンスル ジッケン

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The underwater telemeter to measure the depth on of trawl net board a boat, for which ultrasonic waves are used, is developing in several countries. In Garman type, 30kc megneto-striction type transducers the transmitting surfaces of which are set upward or downward are mounted at the trawl net, the recorder is installed on board a boat, the transmitters and the transducers are joined by a cable, and the depth of the net and the distance between the net and the sea-bottom are measured on board the boat. In American type, about 25kc ultrasonic waves are used as the carrier and the depth of the net and the water temperature are transmitted by FM and AM. They are studied also in our country. The underwater telemeter has many problems, for example, the noises, the wake and the beam of ultrasonic waves. We made the underwater telemeters for which 50kc and 200kc ultrasonic waves are used as carriers and made experiments on them. The results of experiments are as follows. (1) In case of 50kc, the attenuation due to the gathering of bubbles in the wake of the boat is big and S/N ratio was small due to noises of the boat. In case of 200kc, these influnences were hardly found. (2) For the underwater telemeter we can use 200kc ultrasonic waves as a carrier unless the distance is not so long. If we use 200kc, we can make the small transducers. In this case, we should use the lens which makes the beam wide, because the influence due to the shaking of the net is big.

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