關鍵詞：超音波、微粒、都卜勒效應 ;ABSTRACT This study establishes a flow velocity and concentration estimation system based on the ultrasonic Doppler principle. Continuous-wave ultrasound was employed for measurements, and the 5 MHz piezoelectric (PZT) transmitter and receiver driver circuits were simulated to analyze the effect of matching inductance on the frequency response. The received signals were captured by an oscilloscope and processed. For flow velocity estimation, the Fast Fourier Transform (FFT) was applied, and further combined with a phase-locked loop (PLL) and the Hilbert–Huang transform (HHT) to perform time-domain flow velocity analysis for comparison and validation. For concentration estimation, the scattering signal energy was analyzed as the concentration indicator in both the frequency and time domains. The experimental setup employed an acrylic chamber with a silicone tube, and a pump was used to regulate the flow rate to simulate various fluid conditions. Experimental results demonstrate that the proposed system can effectively estimate flow velocity and concentration variations within the pipeline, confirming the feasibility of the proposed method for flow velocity and concentration measurement.
