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MIL-DTL-28827 Switches, Thermostatic, \(Volatile Liquid\), Hermetically Sealed, General Specification ForThis specification covers the general requirements for hermetically sealed volatile liquid thermostatic switches intended primarily for use in equipment requiring rapid temperature response. The operating temperatures and operating temperature ranges of switches covered by this specification are as specified \(see 3.1 and 6.1.2\).

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MIL-DTL-28827C

TABLE III Group A inspection

Requirement

Method

Examination or test

paragraph

Visual and mechanical examination

3.1, 3.3, 3.4

4.7.1

3.25 and 3.26

Calibration

Proof temperature

Proof pressure (when specified)

Seal

Dielectric withstanding voltage

4.7.10

3.14

1/ 100 percent inspection required, in process inspection may be

used to satisfy this requirement.

TABLE IV. Zero defect sampling plan.

Minimum number of

Lot size

switches to be tested

1 - 12

All

13 - 150

151 - 280

281 - 500

501 - 1,200

1,201 - 3,200

3,201 - 10,000

10,001 - 35,000

4.7 Methods of examination and test.

4.7.1 Visual and mechanical examination. Switches shall be examined to verify that the materials,

design, construction, physical dimensions, marking and workmanship are in accordance with the

applicable requirements (see 3.1, 3.3, 3.4, 3.25, and 3.26).

4.7.2 Solderability (applicable to solderable terminals) (see 3.6). Switches shall be tested in

accordance with method 208 of MIL-STD-202. The following details and exceptions shall apply:

a. Number of terminals to be tested � All.

b. Depth of immersion in molten solder � Terminals shall be immersed to the maximum extent

possible.

c. Examination of terminals � Method for evaluation of lugs and tabs shall apply.

d. Dipping machine � Need not be used.

4.7.3 Calibration (see 3.7). The switch sensing element shall be in stalled into a circulating liquid bath

at an initial temperature of at least 10 degrees below the switch actuating temperature. The temperature

shall then be increased until the switch actuates and the actuation point recorded. The temperature of

the liquid bath shall then be decreased until the switch deactuates, and the deactuation point recorded.

This procedure shall be repeated for a total of two times, and the rate of change shall not exceed one

degree per minute within 10 degrees of the switching points. Circulating air ovens shall not be used for

calibration unless the actuation point exceeds 600�F.