G - Physics
01
S
349/25
G01S 15/96 (2006.01)
Patent
CA 1064155
ABSTRACT OF THE DISCLOSURE A fish counter primarily for counting migrating salmon in streams includes a narrow beamwidth side-scanning sonar transducer which is directed to insonify a volume of water in the stream directly above a mechanical structure serving as an artificial bottom. This structure consists of a lightweight, ladder-like frame with transverse support members of arcuate form over which is stretched a thin skin of sheet metal such as aluminum, thereby providing a structure of great stiffness to avoid sagging. The transducer is supplied with transmitting pulses of short duration at regular intervals. After a delay, a receiver is enabled to permit reception of echo signals returning from any fish crossing the artificial bottom. During the period the receiver is enabled, a ring counter separates the return echoes on the basis of the return time from respective sectors of the bottom structure, and these returns are separately counted for each sector to permit each sector to be read out separately or printed out separately. To separate debris from the fish returns, sampling rates are provided such that each fish is sampled five times but only three valid detections are required at the input to the storage registers to insure a count. Other combinations of these numbers may be used. The counts may be accumulated in total, may be printed out on a sector-by-sector basis, or individual sector counts per given time period may be displayed as requested by an operator. To eliminate inordinately high counts from long term debris which may become fastened to the structure, a counter arrangement is provided which receives all the counts on a sector-by-sector basis and responds to an excessively large number in any sector by disabling that part of the ring counter so that no further counts are accumulated for that sector. The disabled sector remains disabled until the passage of a preset time period of, for example, several minutes after which the counter is cleared. If obstruction remains, the ring counter is again disabled. This condition may be indicated on the print-out tape by means of a special character representing debris. -1-
261836
Bridges Robert M.
Menin Albert S.
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