| 摘要 |
PROBLEM TO BE SOLVED: To know garbage deposits at the ultrasonic wave sensor part provided in a waterway at a distance, and to know garbage depositions on the ultrasonic sensor part of the current velocity installed in a manhole without opening the lid of the manhole. SOLUTION: The ultrasonic-wave Doppler current meter obtains the power spectrum shown by the solid line, by processing a Doppler transition signal through fast Fourier transformation. A mean current velocity is found by using the frequency of a peak A. When the power of the peak A decreases below a specific ratio, it is judged that garbages are deposited. Data on the power spectrum shown in the figure are sent out and confirmed at a distance. |
