| 摘要 |
PURPOSE:To read directly and display the speed of a ship even in case of backward movement of the ship with respect to a Doppler sonar which transmits ultrasonic pulses into water and measures the speed of the ship on a basis of Doppler components included in its reflected waves. CONSTITUTION:In case of backward movement of the ship, the frequency of a receiver 3 is influenced by the Doppler effect in the reduction direction, and the number of pulse trains led to a preset counter 8 is varied from 5,460 to 5,160 when the ship speed is 0-30 knots. Consequently, when the ship is moved backward in a speed of 30 knots, the counted value of the preset counter 8 is 5,160- (4,096-2,732)=3,796 because the counting capacity is 4,096 and 5,160 pulse trains are counted from preset number 2,732. In this case, complement 4,096-3,796=300 to counting capacity 4,096 of the preset counter 8 is displayed to read directly and display a speed of 30 knots of backward movement. Gate circuits 211-216 send the complement value of the preset counter 8 to a latch circuit 12 to read directly and display the ship speed for backward movement. |
