ULTRASONIC DISTANCE MEASUREMENT DEVICE

PURPOSE:To carry out accurate measurement even if long distance is measured and a slight displacement amount is measured. CONSTITUTION:An ultrasonic pulse 6 which synchronizes with a trigger signal 2 is emitted from a wave sending/receiving part 5, and a reflected echo 8 which reflects at a target 7 returns to the wave sending/receiving part 5. A trigger delay part 12 outputs a trigger delay signal 13 which delays in the trigger signal 2. A reflected echo amplification signal 11 for the reflected echo 8 changes into a filter passing signal 15 through an extraction filter part 14, and the extraction filter part 14 becomes into a signal pulse condition at a fixed time after receiving the trigger delay signal 13. A distance signal 23 is obtained from time between the signal receiving timing of the trigger delay signal 13 and the signal receiving timing of the pulse extraction signal 17 which corresponds to the first pulse of the filter passing signal 15. Besides, an off-set distance is obtained from a time difference between the trigger signal 2 and the trigger delay signal 13, and the distance is measured by adding the off-set distance to the distance data of the distance signal 23.