Measurement of air velocity and shape in underground space by ultra sonic

为了了解使用超声波测距仪识别形状的特征，进行了以下实验。实验中使用的超声波频率为40 kHz1。测量了一个大小为1到5厘米的立方体与超声波传感器之间的长度，以了解可以检测到的最小尺寸。超声波传感器检测到的立方体为2厘米。研究了放置在房间角落附近的1米立方体和超声波传感器测量长度的精度。当测量方向与立方体表面接近垂直时，可以相当准确地检测出长度。当测量方向与表面平行时，无法检测到长度。不可能检测到立方体和房间的一面墙之间有一个开口。测量了0~35度不同角度表面反射信号的强度，得到了超声波传感器的基本数据。当角度几乎为0时，强度最高，当角度大于一定程度时，检测不到强度。这可能是实验2中检测不到长度的原因。

The following experiments were executed to know characteristics of the recognition of a shape using an ultra sonic distance meter. The frequency of the ultra sonic used in the experiments was 40 kHz.1. The length between a cube whose size is from one to five centimeters and the ultra sonic sensor was measured to know the minimum size which can be detected. The ultra sonic sensor detected to two centimeters cube.2. The accuracy of the measurement of length was studied between a one meter cube laid near a corner of a room and the ultra sonic sensor. The length could be detected fairly accurately when the direction of the measurement is near perpendicular to the surface of the cube. The length could not be detected when the measurement direction comes to parallel to the surface. It was impossible to detect an opening between the cube and a wall of the room.3. The strength of a signal reflected at a surface in various angle from 0 to 35 degree was measured to get basic date of the ultra sonic sensor. The strength was highest when the angle was almost 0 and was not detected when the angle was larger than some degree. This might be the reason why the length could not be detected in experiment 2.