MIL-PRF-24236D
4.6.3 Calibration (see 3.8). Switches shall be tested as specified in 4.6.3.1 for qualification and as specified in
4.6.3.2 for quality conformance inspection. When disputes arise or different readings are encountered in the
circulated-air method versus the liquid-bath method, the latter shall govern. This does not apply to the surface block
method.
4.6.3.1 Method for qualification inspection. Switches submitted for qualification inspection shall have their
operating points determined by one of the following methods or other suitable method.
(a). Liquid bath method (preferred) - The switch shall be immersed in a well-agitated bath of a suitable
liquid. In order to observe the operation of the contacts, the switch shall be connected to a suitable
indicating circuit. When the temperature is within 5 degrees F of the operating range, the rate of
change shall not exceed 1 degree F per minute. To minimize parallax error in reading temperatures,
the switch shall be run through three cycles; however, each reading shall be within the tolerances
average of the three readings shall be the operating temperature point.
(b). Circulating-air method - Use same procedure as in 4.6.3.1a, except that the switch shall be placed in a
circulating-air chamber. The rate of temperature change shall not exceed 1 degree F per minute.
4.6.3.2 Method for conformance inspection. For conformance inspection, switches shall be tested by one of the
following methods, or other suitable method. Throughout this test, X = upper operating temperature range, and Y =
lower operating temperature range.
4.6.3.2.1 Air-calibration method. The switch shall be placed in a calibration chamber (see 4.6.3.1b). The switch
shall be tested by a "go-no-go" method as used in inspection gages, or by recording individual temperatures of each
switch.
4.6.3.2.1.1 Individual temperature method. The rate of temperature change shall not exceed 1°F per minute when
the temperature is within 5°F of the operating range.
4.6.3.2.1.2 Go-no-go test procedure (for type I switches). 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
- Adjust the temperature of the chamber to X degrees F minimum minus 3 degrees F.
Hold this temperature for three minutes minimum. Adjust the chamber temperature to
X degrees F minimum, and hold this temperature for a minimum of three minutes.
After this period, no switch shall have operated.
Step 2
- Adjust the chamber temperature to X degrees F maximum, and hold this temperature
for six minutes minimum. After this period, all switches shall have operated.
Step 3
- Lower the chamber temperature to Y degrees F maximum plus 3 degrees F and hold
for three minutes minimum. Lower temperature to Y degrees F maximum and hold
this temperature for three minutes minimum. After this period, no switch shall have
operated.
Step 4
- Lower the chamber temperature to Y degrees F minimum and hold this temperature
for six minutes minimum. After this period, all switches shall have operated.
4.6.3.2.2 Liquid calibration method. Switches shall be placed in a well-agitated bath (no stratification of the liquid)
which is capable of holding a given set temperature point of ±.5 degrees F throughout the temperature range of the
test. Switches shall be tested by a "go-no-go" method as used in inspection gages or by recording individual
temperatures of each switch.
4.6.3.2.2.1 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.
12
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business