Automatic sensitivity control system null of fish school detection

摘要

PURPOSE:To adjust sensitivity automatically, by automatically controlling amplification factor in relation to a received signal level and two preset signal levels. CONSTITUTION:When the level of a reflected wave received by an ultrasonic wave transmitter/receiver 11 exceeds a set value of a comparator 17, amplification factor of an amplifier 14 is lowered through an amplification factor control circuit 22. When the level is below the set value of a comparator 18, the amplification factor is lowered. When the level of the reflected wave is between the two set values, the state of the current amplification factor is held. Thus, a control circuit 21 controls the amplification factor of the amplifier 14 to be between the two set values through the circuit 22. This enables automatic adjustment of sensitivity regardless of the level of the received signal when a set level is fixed at a specified value.