GB/T 351-2019Metallic materials—Resistivity measurement method (English PDF)

GB/T 351-2019 is the English-translated version of 金属材料 电阻率测量方法.

GB/T 351-2019 lays down the method for measuring the resistivity of metallic materials.

Clause 1 states that it specifies the terms and definitions, test equipment, sample, test, test results and calculation, and test records and reports for resistivity measurement, that it is applicable to measuring electrical properties such as volume resistivity, mass resistivity, electrical conductivity and direct-current resistance ratio, and that the method it provides serves both as an arbitration measurement method and as a conventional measurement method under standard conditions over the range 0.01 to 2.0 ohm-square-millimetre per metre.

Its table of contents runs from terms and definitions through test equipment, sample, test, test results and calculation, to test records and reports, with an informative Appendix A giving a schematic diagram of the common conductor clamping tool.

Clause 3 defines resistance per unit length, volume resistivity, direct-current resistance ratio, the Wheatstone bridge as a single-arm bridge using two contacts and generally applied to higher resistances, and the Kelvin bridge as a double-arm bridge using four contacts and generally applied to lower resistances; clause 4 accordingly requires the Kelvin bridge when the sample resistance is below 10 ohm and the Wheatstone bridge when it is 10 ohm or more, and limits the indication error of the thermometer to 0.1 degree Celsius and the smallest division of the micrometer and the vernier caliper to 0.01 mm and 0.1 mm respectively.

Clause 5 requires the sample to be straight, straightened on a soft surface with a wooden or rubber hammer where hand straightening fails, and free of visible cracks or defects longer than 1 mm as well as of grease, rust and other contaminants so that good contact is ensured.

Clause 6 sets the routine test temperature at 20 plus or minus 5 degrees Celsius and covers length measurement, cross-sectional area calculation and the measurement errors of Table 1, while clause 7 fixes 20 degrees Celsius as the standard temperature, requires resistance measured at another temperature to be converted to that standard temperature, and provides the calculation of the direct-current resistance ratio and the rounding off of results according to the relevant product standard or, failing that, to YB/T 081.

Clause 8 states what the test records and the test reports are generally to contain.

It replaces GB/T 351-1995, from which it differs in the modified standard name, the deletion of the definitions of link resistance and lead resistance, the addition of definitions and calculation methods for conductivity, conductivity percent IACS and direct-current resistance ratio, the change from production inspection to routine inspection, tighter temperature control for both routine and arbitration inspection, the addition of the vernier caliper as a length measuring tool, the added rules on numerical rounding off and the new Appendix A. It was issued on 25 March 2019 and has applied since 1 February 2020.

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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.

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