The Bendix Corporation

Albert S Menin

Robert M Bridges

Merrill E Fife

A sonar fish counter, primarily for counting salmon migrating in streams and for providing a separate count of king salmon, includes a narrow beamwidth side-scanning sonar transducer directed to insonify a volume of water in the stream directly above a mechanical beam which serves as an artificial bottom. The transducer transmits pulses of short duration such as 100 microseconds at regular intervals. After a delay following a transmitted pulse, a receiver is enabled to receive echo signals 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 so that the counts may be displayed or printed separately. To deal with unusually high counts which may indicate that long term debris which has fastened to the beam or peak periods of fish migration, a counter arrangement is provided which counts all received echoes on a sector-by-sector basis and responds to a predetermined high count in any sector by either disabling the sector for a period or by providing a special print character which the operator may determine as representing either debris or a high fish count (as during the peak of migration). A discrimination circuit connected to the receiver separates the return pulses which are of unusual length, such as those over 300 microseconds, and supplies them to a separate counting structure since such elongated pulses represent king salmon. The counter and display means may then provide counts of all salmon by sector (across the artificial bottom) plus a separate count of king salmon plus a total. These totals may be recorded and the counter reset at any desired time interval, such as each hour.

Salmon counter with separate king salmon tabulator

A system for counting fish in a body of water uses one or more acoustic focusing liquid lens transducers each of which includes a large number of individual piezoelectric elements arranged in an arc to create a fan-shaped pattern of adjacent beams, each of which has a narrow beam width. An electrical counting circuit includes a clock producing a series of timing pulses supplied to a plurality of binary coded decimal (BCD) actuated switch circuits, one of which initiates sequential operation of transmit pulses from individual transducer elements. Timing of receiver operation is also controlled by said timing pulses after a delay to minimize 'ringing' of the transducer elements from the transmit pulses. Received echo signals are amplified, threshold detected and converted to uniform pulses. A second BCD actuated switch circuit cooperates with a series of range gates also connected to receive said timing pulses to control the distribution of the uniform echo pulses to one of a series of counters each of which receives and counts pulses from a single transducer element. Display means connected to the counters make it possible to read out counts on individual sectors individually or collectively or to print out counts from the counters at specified time intervals. Where a plurality of liquid lens transducers are used, they are connected to the same clock pulses such that they operate in synchronism.

Fish counter with scanning transducer

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.

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Sylmar, CA, United States of America

Albert S Menin