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

4.7.16.2 Vibration, random.

b. Test condition II, letter E, 1.5 hours.

4.7.17 Shock (see 3.21). Switches shall be tested in accordance with 4.7.17.1 and, in addition, to

4.7.17.2, when specified (see 3.1). The following details and exception shall apply to both methods.

Contact chatter shall be monitored in accordance with method 310 of MIL-STD-202.

Mounting � Switches shall be mounted by their normal mounting means.

Electrical load conditions � The electrical load shall consist of the monitor circuit only.

Temperature conditions � Half of the switches shall be tested in the deactuated position at

10�C below the actuation temperature, and half the switches shall be tested in the actuated

position at 10�C above the deactuation temperature.

e. Measurements during shock � Switch contact stability shall be continuously monitored during

shock. If more than one contact pair is being monitored simultaneously by one chatter

indicator, open contact pairs shall be connected in parallel and closed contact pairs shall be

connected in series during this test. In event of indication of a contact opening greater than

specified, the test shall be modified by applying successive identical blows in the same plane

to monitor contacts, switch by switch, to determine if a switch is defective.

f. Measurements after shock � Switches shall be tested in accordance with calibration (see

g. Examination after test � Switches shall be examined for evidence of broken, deformed,

displaced, or loose parts.

4.7.17.1 Method I, specified pulse.

b. Test condition � C.

c. Allowable contact opening or closure � 250 microseconds maximum.

4.7.17.2 Method II, high impact.

b. Allowable contact opening or closure � 5 milliseconds maximum.

4.7.18 Overload cycling (see 3.22). Each switch shall be tested for overload cycling using the same

voltage, electrical frequency, and the same pair(s) of contacts that will subsequently be used for the

electrical endurance test. The switches shall close and open the overload current of a resistive circuit

equal to 150 percent of the resistive load rating at the particular voltage and electrical frequency. The

cycling rate shall not exceed 6 cycles of operation per minute. Fifty cycles of operation shall be

performed. The duty cycle shall be approximately 50 percent on, 50 percent off.

4.7.19 Endurance (see 3.23). Switches shall be subjected to the specified number of cycles of make-

and-break operations at a cycling rate of 6 cycles per minute maximum at the specified loads (see 3.1

and 6.1.2).

4.7.20 Salt spray (corrosion) (see 3.24). Switches and their mounting hardware and brackets (if

applicable) shall be tested in accordance with method 101 of MIL-STD-202. The following details shall

apply:

a. Test condition � B.

b. Measurements after exposure � Following the drying period, the switches shall meet the

requirements specified in 3.24. Mounting hardware shall be removed at end of the test.