普萊氏流速儀量測不確定度評估

Abstract

台灣河川具有流域狹小、坡度陡峻、侵蝕及堆積情形嚴重、與洪枯流量懸殊等特徵。使得水資源利用、管理及水利防洪等規劃工作，格外地困難。尤其是有關河川水文資料的觀測、蒐集、調查工作，諸如天然河川洪水位、高洪峰流量推估、河川水深的觀測調查，更因觀測環境難度高、測站位址偏僻或現有觀測儀器功能受限等因素，而使得許多重要水文觀測資料量測與取得之困難。再者，水文基本資料係水資源調配利用、防災預警、各項用水供需計畫研擬及水利工程規劃設計最重要之依據，其精確性與可靠度之重要性自不待言。因此，本研究乃針對目前水利單位最常使用量測河川流速之儀器—普萊氏流速儀(Price current meter)，根據ISO3455之規範進行校正試驗。本試驗共使用五具不同普萊氏流速儀進行試驗，於經濟部水利署水利規劃試驗所所使用之流速儀，其編號分別為Price(a)、Price(b)及Price(c)；而在國立台灣大學工程科學及海洋工程學系船模水槽實驗室所使用之流速儀，其編號則分別為Price(d)及Price(e)。每組儀器皆以八種速度進行校正試驗，並對量測資料進行迴歸分析、器差分析及不確定度分析，其中迴歸分析採最小二次方法迴歸；不確定度分析則採用一階變異估計法。本研究之結論為台車之穩定性與人為操作儀表等兩項因素，是造成本試驗器差及不確定度大小最主要之原因，故流速儀之檢校工作必須在一標準之檢校系統下進行，否則校正之結果反而對實務量測上會造成更大之誤差，進而影響各項水文規劃工作。

Due to the odd characteristics in Taiwan’s river basin including small watershed regions, steep slopes, serious erosion and deposit effects, the usage and management of water resources and flood prevention project has been extremely difficult. Especially about the monitoring, measuring and collecting of hydrological data, such as flood level, peak flow discharge, and flow depth, the difficulty arises with bad environment, far-away hydrologic stations, and restricted measuring equipment. Therefore, hydrological data is the basic and most important information for water resources management, disaster prevention work, water supply project and all sorts of hydraulic construction managements, the accuracy and reliability of these data seems also to be a significant task. This study took the popular flow velocity measuring equipment, Price AA current meter, according to ISO3455, to apply correction tests. In each test, eight different velocity ranges are tested. The regression analysis, measurement equipment error analysis and uncertainty analysis have been carried out. In result, the towing car and manual control is the main source for uncertainty and measurement equipment error. Therefore, current meter correction tests should be conducted by following the standard correction procedure; otherwise the result will make even larger errors and affect all kinds of water resources management work.