Standards related to:

GB/T 351-2019**GB/T 351-2019: PDF in English (GBT 351-2019) **

GB/T 351-2019

NATIONAL STANDARD OF THE

PEOPLE’S REPUBLIC OF CHINA

ICS 77.040.99

H 21

Replacing GB/T 351-1995

Metallic Materials - Resistivity Measurement Method

ISSUED ON: MARCH 25, 2019

IMPLEMENTED ON: FEBRUARY 01, 2020

Issued by: State Administration for Market Regulation;

Standardization Administration of PRC.

Table of Contents

Foreword ... 3

1 Scope ... 4

2 Normative References ... 4

3 Terms and Definitions ... 4

4 Test Equipment ... 5

5 Sample ... 6

6 Test ... 6

7 Test Results and Calculation ... 10

8 Test Records and Reports ... 13

Appendix A (Informative) Schematic Diagram of the Common Conductor

Clamping Tool ... 15

Metallic Materials - Resistivity Measurement Method

1 Scope

This Standard specifies the terms and definitions, test equipment, sample, test, test

results and calculation, test records and reports for the resistivity measurement of the

metallic materials.

This Standard is applicable to the measurement of the electrical properties such as

volume resistivity, mass resistivity, electrical conductivity and direct-current resistance

ratio, etc.

The method provided in this Standard is an arbitration measurement method and a

conventional measurement method for measuring the resistivity, under the standard

conditions, in a range of 0.01Ω•mm2/m ~ 2.0Ω•mm2/m.

2 Normative References

The following documents are essential to the application of this document. For the

dated documents, only the versions with the dates indicated are applicable to this

document; for the undated documents, only the latest version (including all the

amendments) are applicable to this document.

YB/T 081 Rule for Rounding Off of Numerical Values and Judgement of Testing

Values for Technical Standards of Metallurgy

3 Terms and Definitions

For the purposes of this document, the following terms and definitions apply.

3.1 Resistance per unit length

It indicates, at the temperature of 20°C, the resistance of a conductor per unit length.

3.2 Volume resistivity

It indicates, at the temperature of 20°C, the resistance of conductor per unit length and

per unit cross-sectional area.

3.3 Mass resistivity

when the sample resistance is no less than 10Ω, the Wheatstone bridge shall be used.

Other instruments that conform to the provisions of 4.4 can also be used.

4.2 When clamping the sample by the special tool, the blades on the voltage terminals

shall be sharp and parallel to each other, and perpendicular to the same axis. See

Appendix A for a schematic diagram of common conductor clamping tools.

4.3 Th distance between the voltage terminal and the corresponding current terminal

shall be no less than 1.5 times of the circumference of the cross section of the sample.

4.4 The total error of the bridge measurement system shall not exceed ±0.15%. The

total error includes calibration error of the standard resistance, comparison error

between the sample and the standard resistance, error caused by the contact potential

and the thermoelectrical potential, and the error arising from the sample heating

caused by the measuring the current.

4.5 Thermometer: the indication error shall not exceed 0.1°C.

4.6 Micrometer: the minimum division value shall not exceed 0.01mm.

Vernier caliper: the minimum division value shall not exceed 0.1mm.

4.7 Precision balance: the minimum division value shall not exceed 0.1mg.

5 Sample

5.1 The sample shall be straight. When the sample can’t be straightened by hand,

place it on the surface of a soft material such as wood or rubber, and straightened with

a slight force by a wooden hammer or a rubber hammer.

5.2 The surface of the sample shall be free of visible cracks or defects with a length

greater than 1mm, as well as grease, rust and other contaminants to ensure good

contact.

5.3 In order to ensure the measurement accuracy, the sample shall be, together with

bridge, standard resistance and other measuring equipment, placed under the same

environment for at least 1h.

5.4 The gauge length of the sample shall be no less than 300mm; other dimensions

shall be compatible with the measuring equipment.

6 Test

6.1 Temperature control

π– Pi, take the value of 3.142;

d – arithmetic mean of the sample diameter, in mm.

6.3.2 Weighing method

For sample without the simple cross-section, or if the cross-sectional area error

measured and calculate directly does not meet the requirements of Table 1, the cross-

section area shall be calculated as per Formula (3) by weighing method:

Where:

A – cross-section area of the sample, in mm2;

m – sample mass, in g;

L1 – sample length, in mm;

ds – sample density, in g/mm3.

When the density of the sample is unknown, the density is measured by weighing in

still water. Removing the gas, oil stains absorbed on the surface of the sample, the

mass of the sample in air and still water is weighed by a precisions balance with a

division value of 0.1mg. When weighing in air, the extension of the hanging wire shall

be immersed in the still water to eliminate the influence of the surface tension. The

diameter of the hanging wire shall be as small as possible; when it exceeds 0.05mm,

use the hanging wire with twice diameter to weigh for twice, the mass difference for

the twice measurements shall not exceed ±0.01 [dL / (dS - dL)] % of the apparent mass

of the sample in still water. The temperature of water is the same as the ambient

temperature, meanwhile preventing the effects of the cross-ventilation on the weighing.

The sample density shall be calculated as per the Formula (4):

Where:

dS – sample density, in g/mm3;

mA – apparent mass of the sample measured in the air, in g;

dL – water density during the measurement, in kg/m3;

shall be calculated as per Formula (5):

Where:

R20 – resistance value on the gauge length of the sample at 20°C, in Ω;

Rt – the really-measured resistance value on the gauge length of sample at the test

temperature t, in Ω;

α20 – resistance temperature coefficient of sample at 20°C, in 1/°C; for the black

metallic materials, its value is 0.00455;

t – ambient temperature during the test, in °C.

7.3 Calculation of resistance per unit length

The resistance per unit length is calculated as per the Formula (6):

Where:

RL20 – resistance per unit length of sample at 20°C, in Ω/m;

R20 – resistance of sample at 20°C, in Ω;

L2 – gauge length of sample at 20°C, in m.

7.4 Calculation of volume resistivity

The volume resistivity shall be calculated as per the Formula (7):

ρ20 – volume resistivity of sample at 20°C, in µΩ•m or Ω•mm2/m;

R20 – resistance of sample at 20°C, in Ω;

A20 – cross-section area of sample at 20°C, in mm2;

L2 – gauge length at 20°C, in m.

7.5 Calculation of mass resistivity

7.8 Calculation of direct-current resistance ratio

At the standard temperature of 20°C, the direct-current resistance ratio of the sample

shall be calculated as per Formula (11):

Where

k20 – direct-current resistance ratio of the sample at 20°C;

R1 – standard temperature resistance of sample during the first measurement, in Ω;

R2 – standard temperature resistance of sample during the second measurement, in

Ω.

7.9 Numerical rounding off

The results of the test measurement shall be rounded off according to the requirements

of relevant product standards. If there are no specific provisions of the product

standards, it shall be rounded off according to the provisions of YB/T 081.

8 Test Records and Reports

8.1 The test records generally include the following contents:

a) Sample number;

b) Material types of the sample;

c) Sample length, gauge length;

d) Sample mass;

e) Average cross-section area of the sample; standard deviation of the average

cross-section area under the number of tests and test temperature;

f) Measurement type: arbitration test or routine test;

g) Ambient temperature during the measurement;

h) Equipment type;

i) Under the measured temperature, the sample’s resistance, standard deviation of

arithmetic mean and average resistance;

......

Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.