MIL-PRF-24236D
4.6.3.2.2.2 Go-no-go test procedure (for type I switches). Four controlled baths (see 4.6.3.2.2) shall be used. The
following tests may be entered at any step, but tests must be conducted in the sequence shown, with step 1
following step 4.
Step 1
- Stabilize a liquid bath (number 1) at X degrees F minimum. Place switches
in bath and allow to stabilize for five minutes minimum. Monitor the
switches' electrical circuit. At end of this period, switches shall not have
operated.
Step 2
- Stabilize a liquid bath (number 2) at X degrees F maximum. Transfer
switches from bath number 1 to bath number 2 and allow to stabilize for
five minutes minimum. Monitor the switches' electrical circuit. At end of this
period, switches shall have operated.
Step 3
- Stabilize a liquid bath (number 3) at Y degrees F maximum. Transfer
switches from bath number 2 to bath number 3. Allow switches to stabilize
for five minutes minimum. Monitor the switches' electrical circuit. At end of
this period, switches shall not have operated.
Step 4
- Stabilize a liquid bath (number 4) at Y degrees F minimum. Transfer
switches from bath number 3 to bath number 4. Allow switches to stabilize
for five minutes. Monitor the switches' electrical circuit. At end of this
period, switches shall have operated.
4.6.3.2.3 Surface block method. Switches shall be placed on a block and tested by a "go-no-go" method as used
in inspection gages or by recording individual temperatures of each switch.
4.6.3.2.3.1 Individual temperature method. The rate of temperature change shall not exceed 1 degree F per minute
when the temperature is within 5 degrees F of the operating temperature range.
4.6.3.2.3.2 Go-no-go test procedure (for type II switches). Set the temperature of one liquid bath (block or oven) to
a temperature equal to the switch nominal setting MINUS the setting tolerance. Set a second liquid bath (block or
oven) to a temperature equal to the switch nominal setting PLUS the switch tolerance. Place the switch in the first
bath and note the position of the contacts as shown by the indicator light. Transfer the switch to the second bath. The
contacts must operate within one minute. Return the switch to the first bath. The switch contacts must return to their
original position within one minute. NOTE: When calibration block or oven is used, it may be more desirable to
change the block or oven temperature instead of moving the switches. This method may be used provided the
temperature is not changed faster than 1 degree F per minute, and the temperature variation does not exceed the
bath temperatures defined above. The dwell time at maximum and minimum points may be two minutes.
4.6.4 Creepage (applicable to type I switches only, see 3.9). Snap action switches shall be tested through three
complete cycles. Switches shall be heated or cooled as required to cause thermal actuation. Switch opening and
closing functions shall both be checked for creepage. Acceptable instrumentation for this test shall consist of the
following:
Arc duration measurement equipment capable of applying the VDC level as shown below. Arc duration shall be
measured from 90% to 10% voltage and 10% to 90% voltage during switch transition. Arc duration shall be less than
5 milliseconds. The rate of change of temperature of the switch shall be the minimum practicable, consistent with
normal production methods and reliable creepage detection.
500 VDC minimum
300 VDC minimum
300 VDC minimum
450 VDC minimum
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