超音波都卜勒流速量測系統硬體與泥沙濃度量測系統

Hardware of Ultrasonic Doppler System for Velocity Measurement and Ultrasonic Measurment System for Concentration of Suspended Sediment

張宥駿(You-Jyun Jhang)

指導教授 ： 宋家驥

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.02307

摘要

超音波量測是一種快速、非侵入式、即時的測量技術，且聲波在海水中衰減量較小，有別於光波與電磁波在水中有很大的衰減，在水中難以實現。本篇文章實現了兩種利用超音波達成的量測應用，其中包含了水溶液的濃度量測與利用都普勒效應的特性作水流流速的量測。
其中濃度量測的方法為設置一顆發射與一顆接收換能器，主要是超音波能量會從發射端換能器傳遞至液體中，並被接收端換能器所接收，利用能量在傳遞過程中的衰減量，並搭配實驗中得到的率定曲線，將可以克服不同水溶液中的顆粒粒徑、溫度等因素，即可得到即時的水溶液濃度，而此系統也在實驗中被證實有效量測最高至100,000 ppm高嶺土水溶液濃度；並且我們也利用了曾文水庫的泥漿樣本作實驗，此系統最高可以有效量測至390,000 mg/L的濃度。
另外本文建立一套脈衝超音波都普勒流速量測系統，基於超音波能量散射與都普勒效應為理論基礎，此套系統藉由換能器自發自收回波訊號，量測靜止的水中與拖車的相對流速，並驗證流速的誤差。在硬體上實現了發射端電路供給換能器發射訊號、接收隔離電路用以避免發射與接收訊號互相干擾、二階帶通濾波電路與前置放大，搭配儀器功率放大器、示波器等架構，再來應用分析軟體Matlab作訊號解調、數位濾波、取樣保持與頻譜分析等運算，最後藉由都普勒頻移推得Beam方向流速。此系統總共有五個Beam方向，其中正中間與水面垂直之方向為專門測量深度，另外四個Beam方向測得知流速轉換為三維流速，最後與實驗用定速拖車之速度0.5 m/s、1.1 m/s、1.5 m/s、2.2 m/s、2.5 m/s作比較。

關鍵字

超音波 ； 濃度量測 ； 率定,都卜勒 ； 流速量測

並列摘要

Suspension systems are used extensively in hydrology, biochemistry, and the food industry. The Ultrasonic for concentration measurement has several advantages, such as its non-intrusive, no moving parts. It can penetrate the non-transparent fluid, paring with a complete set of calibration and rating curve in the laboratory. It will be able to overcome all kinds of particle size, temperature, water, the error caused by the bubble fluid. This systems will be extensively used in hydrology, biochemistry, and the food industry in the future. The method for the measurement is to detect the energy attenuation between a transmitter-receiver pair transducer. To increase the accuracy of data analysis, received electric signals are compressed and enveloped as square waves by a logarithmic amplifier AD8310 to avoid the noise effect. The novel signal processing method is evaluated by experimental data in a laboratory environment to provide linear results for kaolin (0 ~ 100,000 ppm) and slurry samples (0 ~ 390,000 ppm) from the Tseng Wen reservoir in Taiwan.
The velocity measurement is an important item in various engineering field. This work establishes a pulsed ultrasonic Doppler system, which is based on scattering and Doppler-effect, consists of power amplifier, transducer , oscilloscope, and digital signal processing software Matlab. And with self-designed circuits, such as transmitter circuit, receive isolation circuit and pre-amplifier second order band-pass filter. This study is conducted using transducer from four directions to output sound beams generated via converse piezoelectric effect, receiving echoes, and obtaining the relative speed of measurement system and water flows by means of signal processing and calculation of Doppler shift.

並列關鍵字

Ultrasonic ； sediment concentration ； rating curve ； Doppler ； Velocity Measurement

參考文獻

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