MIL-STD-202H.pdf - 第40页

MI L - S TD - 202 - 10 6 4.2.3 Numb er of cycle s . S pe c i m en s s hal l b e s u bj e c t e d t o 10 c ont i nu ous c y c l es , ea c h a s s h own on figur e 1. In the event of no more than on e uni nt ent i ona l t …

MIL-STD-202-106

4.2. Procedure.

4.2.1 Mounting. Specimens shall be mounted by their normal mounting means, in their normal mounting position,

but shall be positioned so that they do not contact each other, and so that each specimen receives essentially the

same degree of humidity.

4.2.2 Initial measurements. Prior to step 1 of the first cycle, the specified initial measurements shall be made at

room ambient conditions, or as specified.

NOTES:

1. Allowance of 100 percent RH is intended to avoid problems in reading values close to 100 percent RH, but

actual chamber operation shall be such so as to avoid condensation.

2. Unless otherwise specified, the steady state temperature tolerance is ±2°C at all points within the immediate

vicinity of the specimens and the chamber surfaces.

3. Rate of change of temperature is unspecified; however, specimens shall not be subjected to radiant heat from

chamber-conditioning processes.

4. Circulation of air in the chamber shall be at a minimum cubic rate per minute equivalent to 5 times the volume

of the chamber.

FIGURE 1. Graphical representation of moisture-resistance test.

INITIAL CON-

DITIONING IN A

DRY OVEN 24

HOURS

HUMIDITY

UNCONTROLLED

INITIAL MEASRUEMENTS

AS SPECIFIED IN 4.2.2

END OF FINAL CYCLE

MEASUREMENTS AS

SPECIFIED IN 4.3

VIBRATE IS 15

MINUTES AS

SPECIFIED IN

4.2.4.2

90-100% RH

100% RH

80-100%

+10°C

-2°C

VOLTAGE APPLIED AS SPECIFIED IN 4.2.5

STEPS 7a & 7b (IF APPLICABLE) SHALL BE

PERFORMED A MINIMUM OF 5 OF THE 10

CYCLES. HUMIDITY IS UNCONTROLLED

DURING STEPS 7a & 7b ONLY

STEP 7b

STEP 7a

PRIOR TO FIRST CYCLE

UNLESS OTHERWISE

SPECIFIED

STEP 1 STEP 2

STEP 3

STEP 4

STEP 5

STEP 6 STEP 7

ONE CYCLE 24 HOURS. REPEAT AS SPECIFIED IN 4.2.3

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MIL-STD-202-106

4.2.3 Number of cycles. Specimens shall be subjected to 10 continuous cycles, each as shown on figure 1. In the

event of no more than one unintentional test interruption (power interruption or equipment failure) prior to the

completion of the specified number of cycles (except for the last cycle), the cycle shall be repeated and the test may

continue. Unintentional interruptions occurring during the last cycle require a repeat of the cycle plus an additional

uninterrupted cycle. Any intentional interruption, or any unintentional interruption of greater than 24 hours requires a

complete retest.

4.2.4 Subcycle of step 7. During at least 5 of the 10 cycles, a low temperature subcycle and, if applicable, a

vibration subcycle shall be performed.

4.2.4.1 Step 7a. At least 1 hour but not more than 4 hours after step 7 begins, the specimens shall be either

removed from the humidity chamber, or the temperature of the chamber shall be reduced. Specimens shall then be

conditioned at -10°C ±2°C (14°F ±3.6°F) with humidity not controlled, for 3 hours minimum as indicated on figure 1.

When a separate cold chamber is not used, care should be taken to assure that the specimens are held at

-10°C ±2°C (14°F ±3.6°F) for the full 3 hour period. (If step 7b is not applicable, the specimens shall be returned to

25°C (77°F) at 80 percent relative humidity minimum and kept there until the next cycle begins.)

4.2.4.2 Step 7b (when applicable). Within 15 minutes after completion of step 7a and with humidity not controlled

and temperature at room ambient, specimens shall be vibrated for 15 minutes, using a simple harmonic motion having

an amplitude of 0.03 inch (0.76 mm), (0.06 inch (1.52 mm) maximum total excursion), the frequency being varied

uniformly between the approximate limits of 10 and 55 hertz (Hz). The entire frequency range, from 10 to 55 Hz and

return to 10 Hz, shall be traversed in approximately 1 minute. After step 7b, the specimens shall be returned to 25°C

(77°F) at 80 percent relative humidity minimum and kept there until the next cycle begins.

NOTE: Step 7b is not applicable to parts that include test schedules with vibration requirements (such as method

201 or method 204 of this standard). These parts must routinely be subjected to, and pass, these requirements.

NOTE: Allowance of 100 percent RH is intended to avoid problems in reading values close to 100 percent, but

actual chamber operation shall be such so as to avoid condensation.

4.2.5 Polarization and load. When applicable, polarization voltage shall be 100 volts dc, or as specified. The

loading voltage shall be as specified.

4.3 Final measurements.

4.3.1 At high humidity. Upon completion of step 6 of the final cycle (or step 7 if the subcycle of 4.2.4 is performed

during the tenth cycle), when measurements at high humidity are specified, the specimens shall be maintained at a

temperature of 25°C ±2°C (77°F ±3.6°F), and a RH of 80 percent minimum for a period of 1½ to 3½ hours, after

which the specified measurements shall be made. Due to the difficulty in making measurements under high humidity

conditions, the individual specification shall specify the particular precautions to be followed in making measurements

under such conditions.

(NOTE: Allowance of 100 percent RH is intended to avoid problems in reading values close to 100 percent, but

actual chamber operation shall be such so as to avoid condensation.)

4.3.2 After high humidity. Upon removal from humidity chamber, final measurements shall be made within a

period of 1 to 2 hours after the final cycle. During final measurements, specimens shall not be subjected to any

means of artificial drying.

4.3.3 After drying period. Following step 6 of the final cycle (or step 7 if the subcycle of 4.2.4 is performed during

the tenth cycle), or following measurements at high humidity, if applicable, specimens shall be conditioned for 24

hours at the ambient conditions specified for the initial measurements (see 4.2.2) after which the specified

measurements shall be made. Measurements may be made during the 24 hour conditioning period; however, any

failures which occur shall be considered as failures and shall not be retested later for the purpose of obtaining an

acceptable result.

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MIL-STD-202-106

5. DETAILED REQUIREMENTS

5.1 Summary. The following details are to be specified in the individual specification:

a. Initial measurements and conditions, if other than room ambient (see 4.2.2).

b. When applicable, the polarization voltage if other than 100 volts (see 4.2.5).

c. Loading voltage (see 4.2.5).

d. Final measurements and measurement conditions (see 4.3).

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-2015-010)

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/

北测（上海）电子科技有限公司

联系方式：xuyj@beice-sh.com 13917165676