| 摘要 |
<p>Apparatus for detecting and counting fish in a stream in which three electrodes extend horizontally across the stream and are immersed in the water, the electrodes being connected to form the two arms of an alternating current bridge circuit, the signal output of the bridge being processed to provide a data signal for feeding to a counter or other recording means, the apparatus being arranged so that a fish causes upsetting of the balanced conditions in the bridge, further electrodes connected in an opposite sense providing compensation for wave motion effects on the signal.</p> |
