| 摘要 |
<p>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, siuch 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.</p> |
