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

3.4 Design and construction. Switches covered by this specification shall be of the design,

construction, and physical dimensions specified (see 3.1 and 6.1.2). Switches shall be so constructed as

to ensure proper operation when mounted in any position.

3.4.1 Tamperproof calibration. Unless otherwise specified (see 3.1 and 6.1.2), the switches shall be

sealed in such a manner that any tempering with the calibration after final adjustment by the manufacturer

shall require dismantling of the switch or the breaking of a seal. The seal shall not be easily broken by

manual force or without the use of any device considered a tool, for example, screwdriver, pliers,

soldering iron, and so forth.

3.4.2 Solder terminals. Solder terminals shall be treated to facilitate soldering. The terminal design

shall be such that a mechanical connection can be made prior to soldering. Acceptable solder terminal

designs are turret, hook, pierced, or post type.

3.4.3 Mounting. Mounting shall be as specified (see 3.1 and 6.1.2). Stud mounting shall have threads

in accordance with FED-STD-H28.

3.4.4 Weight. Weight shall be as specified (see 3.1 and 6.1.2).

3.5 Electrical ratings. The electrical ratings shall be as specified (see 3.1 and 6.1.2).

3.6 Solderability (when applicable, see 3.1). When switches are tested as specified in 4.7.2, 95

percent of the total length of fillet, which is between the standard wrap wire and the terminal, shall be

tangent to the surface of the terminal being tested. There shall be no pinholes, voids, and so forth. A

ragged or interrupted line at the point of tangency between the fillet and the terminal under test shall be

considered a defect. After the test, there shall be no evidence of fracture, loosening of parts, or any other

mechanical failure of the switches.

3.7 Calibration. When switches are tested as specified in 4.7.3, the operating points for the opening

and closing temperature shall be within the tolerances specified (see 3.1 and 6.1.2).

3.8 Proof temperature. When switches are tested as specified in 4.7.4, there shall be no evidence of

damage and the operating points shall be within the tolerance specified.

3.9 High temperature exposure. When switches are tested as specified in 4.7.5, the operating points

shall be within the tolerance specified in 4.7.5.

3.10 Low temperature exposure. When switches are tested as specified in 4.7.6, the operating points

shall be within the tolerances specified in 4.7.6.

3.11 Time constant. When switches are tested as specified in 4.7.7, the time required for the switch to

actuate shall be as specified (see 3.1).

3.12 Proof pressure (when specified, see 3.1). When switches are tested as specified in 4.7.8, there

shall be no evidence of leakage or damage, and the operating points shall be within the tolerances

specified (see 3.1).

3.13 Seal (hermetic). When switches are tested as specified in 4.7.9, the leakage rate shall not

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exceed 1 x 10 standard atmosphere cubic centimeters per second (atm cc/sec).

3.14 Dielectric withstanding voltage. Unless otherwise specified (see 3.1 and 6.1.2), when switches

are tested as specified in 4.7.10, there shall be no flashover, arcing, or current flow in excess of 1

milliampere.

3.15 Insulation resistance. When initially measured as specified in 4.7.11, the insulation resistance

between all insulated terminals and enclosures shall be not less than 1000 megaohms.