關(guān)于美國ASTM標(biāo)準(zhǔn)E 617砝碼參數(shù)及相對應(yīng)的校準(zhǔn)天平
WEIGHTS AND BALANCES
砝碼和天平
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
本節(jié)的目的是使對砝碼的要求符合美國國家標(biāo)準(zhǔn)ANSI/ASTM E617“實(shí)驗(yàn)室砝碼和精密質(zhì)量標(biāo)準(zhǔn)物”。此標(biāo)準(zhǔn)以索引的方式整合在一起，砝碼的容許公差和構(gòu)造應(yīng)參考完整的說明和資料。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.
以下的類別標(biāo)號是按照容許公差的升序排列。
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級砝碼是用于校準(zhǔn)低負(fù)荷、高靈敏度的天平。它們有多種類型，從1 mg到500mg不等。對此級內(nèi)任何種類砝碼的容許公差都是5µg。他們被建議用于校準(zhǔn)以視覺或電子方法精密稱定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級砝碼被稱為用于校準(zhǔn)的標(biāo)準(zhǔn)物。它們可用于稱定20mg的重量。（對于10g或更輕的砝碼，1級的要求可被美國藥典XXI M級滿足。）
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類砝碼被用于作為校準(zhǔn)的工作標(biāo)準(zhǔn)，分析天平的內(nèi)置砝碼，以及常規(guī)分析工作的實(shí)驗(yàn)室砝碼。（第2類要求可被美國藥典21 S級滿足。）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類和第4類砝碼與中等的實(shí)驗(yàn)室天平一起使用。（第3類要求可被美國藥典21 S-1級滿足；第4類要求可被美國藥典21 P級滿足。）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.
對砝碼的類別進(jìn)行選擇，以便所用砝碼的容許公差不過稱重物重量的0.1%。通常，第2類砝碼可用在大于20mg的重量，第3類砝碼可用在大于50mg的重量，第4類砝碼可用在大于100mg的重量。砝碼必須定期進(jìn)行校準(zhǔn)，基于一個標(biāo)準(zhǔn)砝碼。
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美國ASTM標(biāo)準(zhǔn)E 617-81副本（1985年再次審定）可從美國測試和材料組織中獲得，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請注意，所用的名稱S和P不再指砝碼類別，而是指砝碼等級，即設(shè)計(jì)的限度，如材料的密度范圍，表面積，表面拋光，耐蝕性，和堅(jiān)硬度。
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