MIL-STD-202H.pdf - 第34页
MI L - S TD - 202 - 10 5 5. DETAIL ED REQUI RE M E N T S 5.1 Summary . The fol l ow i ng det ai l s ar e t o be s p ec i f i ed i n t h e i nd i v i dua l s pec i f i c at i on: a. Method of m o unt i ng ( s ee 4 .2 ). b…
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
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MIL-STD-202-105
5. DETAILED REQUIREMENTS
5.1 Summary. The following details are to be specified in the individual specification:
a. Method of mounting (see 4.2).
b. Test condition letter (see 4.2).
c. Tests during subjection to reduced pressure (see 4.2).
d. Tests after subjection to reduced pressure, if applicable.
e. Exposure time prior to measurements, if applicable.
6. NOTES
(This section contains information of a general or explanatory nature that may be helpful, but is not mandatory.)
6.1 Supersession data. The main body and 38 parts of this revision of MIL-STD-202 replace superseded MIL-STD-
202.
Custodians: Preparing activity:
Army - CR DLA – CC
Navy - EC
Air Force - 85 (Project 59GP-2015-009)
DLA - CC
Review activities:
Army - AR, AT, AV, CR4, MI, SM, TE
Navy - AS, OS, SH
Air Force - 19, 99
NSA - NS
NOTE: The activities listed above were interested in this document as of the date of this document. Since
organizations and responsibilities can change, you should verify the currency of the information above using the
ASSIST Online database at https://assist.dla.mil/
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北测（上海）电子科技有限公司
联系方式：xuyj@beice-sh.com 13917165676
INCH-POUND
MIL-STD-202-106
18 April 2015
SUPERSEDING
MIL-STD-202G
w/CHANGE 2 (IN PART)
28 June 2013
(see 6.1)
DEPARTMENT OF DEFENSE
TEST METHOD STANDARD
METHOD 106, MOISTURE RESISTANCE
AMSC N/A FSC 59GP
北测（上海）电子科技有限公司
联系方式：xuyj@beice-sh.com 13917165676