关于美国ASTM标准E 617砝码参数及相对应的校准天平
WEIGHTS AND BALANCES
砝码和天平
The intent of this section is to bring the requirements for weights into conformity with American National Standard ANSI/ASTM E617, “Laboratory Weights and Precision Mass Standards.” This standard is incorporated by reference and should be consulted for full de.ions and information on the tolerances and construction of weights.1
本节的目的是使对砝码的要求符合美国国家标准ANSI/ASTM E617“实验室砝码和精密质量标准物”。此标准以索引的方式整合在一起，砝码的容许公差和构造应参考完整的说明和资料。1
Pharmacopeial tests and assays require balances that vary in capacity, sensitivity, and reproducibility. Unless otherwise specified, when substances are to be “accuray weighed” for Assay, the weighing to be performed with a weighing device whose measurement uncertainty （random plus systematic error） does not exceed 0.1% of the reading. Measurement uncertainty is satisfactory if three times the standard deviation of not less than ten replicate weighings divided by the amount weighed, does not exceed 0.001. Unless otherwise specified, for titrimetric limits tests, the weighing shall be performed to provide the number of significant figures in the weight of the analyte that corresponds to the number of significant figures in the concentration of the titrant.
The class designations below are in order of increasing tolerances.
以下的类别标号是按照容许公差的升序排列。
Class 1.1 weights are used for calibration of low-capacity, high-sensitivity balances. They are available in various denominations from 1 to 500 mg. The tolerance for any denomination in this class is 5 µg. They are recommended for calibration of balances using optical or electrical methods for accuray weighing quantities below 20 mg.
1.1级砝码是用于校准低负荷、高灵敏度的天平。它们有多种类型，从1 mg到500mg不等。对此级内任何种类砝码的容许公差都是5µg。他们被建议用于校准以视觉或电子方法精密称定20mg重量的天平
Class 1 weights are designated as high-precision standards for calibration. They may be used for weighing accuray quantities below 20 mg. （For weights of 10 g or less, the requirements of class 1 are met by USP XXI class M.）
1级砝码被称为用于校准的标准物。它们可用于称定20mg的重量。（对于10g或更轻的砝码，1级的要求可被美国药典XXI M级满足。）
Class 2 weights are used as working standards for calibration, built-in weights for analytical balances, and laboratory weights for routine analytical work. （The requirements of class 2 are met by USP XXI class S.）2
第2类砝码被用于作为校准的工作标准，分析天平的内置砝码，以及常规分析工作的实验室砝码。（第2类要求可被美国药典21 S级满足。）2
Class 3 and class 4 weights are used with moderate-precision laboratory balances. （Class 3 requirements are met by USP XXI class S-1; class 4 requirements are met by USP XXI class P.） 2
第3类和第4类砝码与中等的实验室天平一起使用。（第3类要求可被美国药典21 S-1级满足；第4类要求可被美国药典21 P级满足。）2
A weight class is chosen so that the tolerance of the weights used does not exceed 0.1% of the amount weighed. Generally, class 2 may be used for quantities greater than 20 mg, class 3 for quantities of greater than 50 mg, and class 4 for quantities of greater than 100 mg. Weights should be calibrated periodically, preferably against an absolute standard weight.
对砝码的类别进行选择，以便所用砝码的容许公差不过称重物重量的0.1%。通常，第2类砝码可用在大于20mg的重量，第3类砝码可用在大于50mg的重量，第4类砝码可用在大于100mg的重量。砝码必须定期进行校准，基于一个标准砝码。
1 Copies of ASTM Standard E 617-81 （Reapproved 1985） may be obtained from the American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103.
1美国ASTM标准E 617-81副本（1985年再次审定）可从美国测试和材料组织中获得，地址：1916 Race Street, Philadelphia, PA 19103。
2 Note that the designations S and P no longer designate weight classes but rather weight grades, that is, design limitation such as range of density of materials, surface area, surface finish, corrosion resistance, and hardness.
2请注意，所用的名称S和P不再指砝码类别，而是指砝码等级，即设计的限度，如材料的密度范围，表面积，表面抛光，耐蚀性，和坚硬度。
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