MIL-STD-202H.pdf - 第32页
MI L - S TD - 202 - 10 5 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-202-105
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.
ii
北测（上海）电子科技有限公司
联系方式：xuyj@beice-sh.com 13917165676
MIL-STD-202-105
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 Apparatus ……………………………………………..…………. 1
4.2. Procedure……..………………..….………………….…………. 2
5. DETAILED REQUIREMENTS 2
5.1 Summary……………..…………………………..………………. 2
6. NOTES 2
6.1 Supersession data………………………………………………. 2
TABLE PAGE
1. Test conditions……………………………………….……………….. 1
iii
北测（上海）电子科技有限公司
联系方式：xuyj@beice-sh.com 13917165676
MIL-STD-202-105
METHOD 105
BAROMETRIC PRESSURE (REDUCED)
1. SCOPE
1.1 Purpose. The barometric pressure test is performed under conditions simulating the low atmospheric pressure
encountered in the nonpressurized portions of aircraft and other vehicles in high altitude flight. This test is intended
primarily to determine the ability of component parts and materials to avoid dielectric-withstanding-voltage failures
due to the lowered insulating strength of air and other insulating materials at reduced pressures. Even when low
pressures do not produce complete electrical breakdown, corona and its undesirable effects, including losses and
ionization, are intensified. Low barometric pressures also serve to decrease the life of electrical contacts, since
intensity of arcing is increased under these circumstances. For this reason, endurance tests of electro-mechanical
component parts are sometimes conducted at reduced pressures. Low-pressure tests are also performed to
determine the ability of seals in component parts to withstand rupture due to the considerable pressure differentials
which may be developed under these conditions. The simulated high altitude conditions of this test can also be
employed to investigate the influence on component parts operating characteristics, of other effects of reduced
pressure, including changes in dielectric constants of materials; reduced mechanical loading on vibrating elements,
such as crystals; and decreased ability of thinner air to transfer heat away from heat-producing components.
2. APPLICABLE DOCUMENTS
This section not applicable to this standard.
3. DEFINTIONS
This section not applicable to this standard.
4. GENERAL REQUIREMENTS
4.1 Apparatus. The apparatus used for the barometric pressure test shall consist of a vacuum pump and a suitable
sealed chamber having means for visual observation of the specimen under test when necessary. A suitable
pressure indicator shall be used to measure the simulated altitude in feet in the sealed chamber.
4.2 Procedure. The specimens shall be mounted in the test chamber as specified and the pressure reduced to the
value indicated in one of the following test conditions, as specified. Previous references to this method do not specify
a test condition; in such cases, test condition B shall be used. While the specimens are maintained at the specified
pressure, and after sufficient time has been allowed for all entrapped air in the chamber to escape, the specimens
shall be subjected to the specified tests.
TABLE 1. Test conditions.
Test
condition
Pressure - Maximum Altitude
Inches of mercury Millimeters of mercury Feet Meters
A
B
C
D
E
F
G
8.88
3.44
1.31
0.315
0.043
17.3
9.436 x10
-8
226.00
87.00
33.00
8.00
1.09
439.00
2.40 x 10
-6
30,000
50,000
70,000
100,000
150,000
15,000
656,000
9,144
15,240
21,336
30,480
45,720
4,572
200,000
1
北测（上海）电子科技有限公司
联系方式：xuyj@beice-sh.com 13917165676