| 摘要 |
The apparatus disclosed herein utilizes ultrasound to characterize the flow of fluid material containing suspended particles. Energy scattered by particles in the moving fluid from a brief emitted burst is detected to obtain a return signal and this return signal is compared with a preselected amplitude at a preselected time interval after each burst. Preferably the amplitude threshold is an integrated or filtered value corresponding to the amplitude of the return signal over some earlier time. A binary output signal is generated which continues from each comparison to the next at a level corresponding to the result of the comparison. Accordingly, the output signal includes frequency components representative of Doppler shifts occasioned by the movement of fluid.
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