1.Key Laboratory of In Situ Metrology Ministry of Education, China Jiliang University, Hangzhou, Zhejiang 310018, China
2. Zhejiang Institute of Metrology, Key Laboratory of Acoustics and Vibration Precision Measuring Technology for State Market Regulation, Hangzhou, Zhejiang 310063, China
Abstract：The ADCP (acoustic Doppler velocity profiler) can use the method of acoustic response and emission of simulated echoes to carry out flow calibration,but the calibration accuracy and the lower limit of calibration flow velocity are affected by the system clock precision.At present,the ADCP flow calibration system based on this method is difficult to calibrate the small flow velocity of less than 1 m/s.To provides a low-cost,water pool environment implementable broadband ADCP flow calibration system scheme,which is to design a broadband ADCP flow calibration system based on FPGA,collect and process the ADCP transmitted acoustic wave signal,and then transmit the simulated echo signal carrying water flow velocity information to the ADCP.By comparing the simulated velocity value with the actual output value,the flow calibration of the ADCP can be realized.The calibration system uses DDS+PLL (direct digital frequency synthesis and phase-locked frequency synthesis) technology to synthesize high-precision clock signals.The clock signals drive signal acquisition and playback to generate high-precision simulated echo signals.Finally,in a small anechoic water pool,the calibration experiments are carried out for the broadband ADCP with a center frequency of 300 kHz in the small flow velocity range of (0.2~1)m/s.The results show that the measurement uncertainty of this calibration system reaches (0.5% simulated flow velocity + 0.005)m/s,which verifies the reliability of the calibration system.
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2024, Vol. 45 
