化学需氧量(COD)测定仪检定方法及示值误差测量不确定度评定

Verification Method of Chemical Oxygen Demand (COD) Tester And Evaluation of Uncertainty of Measurement Error

文中依据JJG 975-2002《化学需氧量(COD)测定仪》解读仪器检定的关键过程,以化学需氧量(COD)测定仪的示值误差为研究对象建立数学模型,分别评定分光光度法原理、电化学原理仪器的不确定度;分析测量重复性、标准溶液、吸量管体积校准、吸量管中溶液温度与吸量管校准温度差异对合成不确定度的影响,计算各分量灵敏度系数,最终得到仪器示值误差的A类不确定度为2.6%,B类不确定度为0.64mg/L。

The key process of COD instrument verification, specified by the Verification Regulation of JJG 975-2002 Chemical Oxygen Demand (COD) tester, is to be explained in this paper. A mathematical model which takes COD measurement error as the object of study is established to evaluate the uncertainty of COD, based on both spectrophotometric principle and electrochemical principle. The impact of measurement repeatability, standard solution, volume calibration of the pipette, temperature difference between solution and pipette calibration on the synthetic uncertainty is also analyzed, by means of calculating the sensitivity coefficients of each component. The result turns out to be 2.6% for A type uncertainty of the measurement error, and 0.64mg/L for B type.