MIL-STD-202H.pdf - 第248页

MI L - S TD - 202 - 30 4 CO NT E N T S PARAGRAPH PAG E FOREW ORD … ………………………………………………………. ii 1. SCOPE 1 1.1 Purpose …… ………………… …………………. …… .. …………. 1 2. APPLICABLE D O C U M EN T S 1 3. DEFINTIONS 1 4. GENERAL RE Q UI R …

MIL-STD-202-304

FOREWORD

1. This standard is approved for use by all Departments and Agencies of the Department of Defense.

2. This entire standard has been revised. This revision has resulted in many changes to the format, but the most

significant one is the splitting the document into test methods. See MIL-STD-202 for the change summary.

3. Comments, suggestions, or questions on this document should be emailed to std202@dla.mil or addressed to:

Commander, Defense Logistics Agency, DLA Land and Maritime, ATTN: VAT, P.O. Box 3990, Columbus, OH

43218–3990. Since contact information can change, you may want to verify the currency of this address

information using the ASSIST Online database at https://assist.dla.mil.

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MIL-STD-202-304

CONTENTS

PARAGRAPH PAGE

FOREWORD…………………………………………………………. ii

1. SCOPE 1

1.1 Purpose………………………………………….……..…………. 1

2. APPLICABLE DOCUMENTS 1

3. DEFINTIONS 1

4. GENERAL REQUIREMENTS 1

4.1 Procedure…………..…….………………………..….….…..….. 1

4.1.1 Preparation………..…….……….………………..….….…..….. 1

4.1.2 Test temperatures….……….……………………..….….…..….. 1

4.1.3 Measurements……….………………..…………..….….…..….. 1

5. DETAILED REQUIREMENTS 2

5.1 Results……………………………………………..…..…………. 2

5.2 Summary…………………………………………..…..…………. 2

6. NOTES 2

6.1 Supersession data………………………………………………. 2

iii

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MIL-STD-202-304

METHOD 304

RESISTANCE-TEMPERATURE CHARACTERISTIC

1. SCOPE

1.1 Purpose. It is the purpose of this test to determine the percentage change in direct-current (dc) ohmic

resistance from the dc ohmic resistance at the reference temperature, per unit temperature difference between the

test temperature and the reference temperature. The equation (see 5.1) used to calculate this characteristic,

commonly called the "temperature coefficient of resistance", is based on an assumed straight-line relationship

between resistance and temperature over a range of specified test temperatures.

2. APPLICABLE DOCUMENTS

This section not applicable to this standard.

3. DEFINTIONS

This section not applicable to this standard.

4. GENERAL REQUIREMENTS

4.1. Procedure.

4.1.1 Preparation. Test leads used to connect the specimens to the resistance-measuring devices shall be firmly

fastened to the specimens. Precautions shall be taken to minimize errors in resistance measurement due to such

factors as lead resistance, spurious electromotive forces, condensation of moisture, etc., throughout the range of test

temperatures, by utilization of suitable test-lead materials and measurement techniques or by applying appropriate

corrections.

4.1.2 Test temperatures. The reference temperature shall be 25°C or as specified. There shall be two standard

series of test temperatures. The first series shall be 25°, 0°, -15°, and -55°C; the second series shall be 25°, 50°,

75°, 100°, 125°, 200°, 275°, and 350°C. The tolerance on each temperature in both series shall be ±3°C. The lowest

test temperature in the first series, and the highest test temperature in the second series, shall be as specified.

Measurements for each series of temperatures shall be performed in the order shown without interruption.

However, a lapse of time not to exceed 24 hours is permitted between the end of the first series and the start of the

second series.

4.1.3 Measurements. The resistance of each specimen shall be measured 30 to 45 minutes after the chamber

temperature has become stable to within ±0.5°C at a test temperature. However, it will be permissible to measure

the resistance before the end of this period if the resistance has become stable to within ±0.1 percent as determined

by preliminary measurements made at 5 minute intervals after stabilization of the chamber temperature. Unless

otherwise specified, the temperature at the time of measurement shall be measured to an accuracy of ±1 percent of

the temperature difference between the nominal test temperature and the nominal reference temperature +0.5°C.

Resistance measurements shall be made in accordance with MIL-STD-202-303.

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