Transducer-positioning system scanning around an aquatic for measurements of target strength.

The transducer‐positioning system has been designed in order to measure acoustic target strength (TS) of fragile and unstable in shape aquatic targets such as a squid. It is characteristic that directivity of TS is measured while making a transducer scan a fixed target suspended in the water. This system is loaded in the electric flatcar on the top of a tank. The distance between a transducer and a target is 3.65 m. A transducer moved from −45 to +45 deg in rotation around a target. The minimum unit of set value for a destination is 1 mm. Furthermore, a Laser pointer has been installed so that it becomes easy to observe a point where an axis of ultrasonic beam passes through a target when a target is prepared for suspension. The Laser pointer is set up in exchange for a transducer and is adjustable three‐dimensionally. The situation between a transducer and a target, precision of positioning, and specification required for acoustic measurement system are described in this paper.