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|  MIL-S-19819C(OS)
rotation to the center of gravity of the moving parts of the switch
when the moving parts are at rest.
N = revolutions per minute
If the centrifuge does not register rpm directly, but indicates angular
velocity in some arbitrary unit, it will be necessary to obtain a correla-
tion between these units and the rpm.
4.4.4.4.3 Test. Mount the firing switch in the socket on the centrifuge
(4.4.3.4) so that its axis is perpendicular to the plane of rotation with its
base down. Throw the calibration switch into position 2, close the resistor
cutout switch, and start the centrifuge. After attaining an acceleration
of 2 gravity units, increase the acceleration thereafter at a rate not ex-
ceeding 0.1 gravity unit per second. When a pip is observed on the oscil-
loscope screen, note the reading on the centrifuge indicator. Convert this
reading to gravity units in accordance with 4.4.4.4.2, and record this as
the value of instantaneous closure. Slowly increase the acceleration within
the specified rate. When a straight line dc presentation is observed on the
oscilloscope screen, note the reading on the centrifuge indicator. Convert
this reading to gravity units in accordance with 4.4,4.4.2, and record. this
as the value for steady closure. Open the resistor cutout switch and record
the sweep deflection in ohms resistance for the firing switch during steady
closure. If the particular circuit warrants it, short out the firing switch
as close to the socket as is physically possible, and obtain a scope deflec-
tion for the circuit resistance alone, while the centrifuge is still at the
same speed. This resistance shall be subtracted from the value previously
obtained to determine true switch contact resistance in the position tested.
While perpendicularly mounted, test the firing switch for instantaneous and
steady closure acceleration and contact resistance in seven other positions
at 45 plus or minus 1 degree increments of rotation about its axis. The
switch shall meet the requirements of 3.4.4 (Sensitivity) and 3.4.5 (Contact
resistance) in all positions. Check the calibration of the scope deflection
before every test. Then mount the switch so that its axis is parallel to
the plane of rotation and the switch terminals are toward the pivotal axis
of the centrifuge. Conduct one test in this position.
4.4.4.4.4 Dielectric test. Apply the test probes of a megohmmeter
(4.4.3.6) to the terminals of the firing switch when it is in the normally
open condition. The firing switch shall meet the dielectric strength require-
ments of 3.4.6.
4.4.4.4.5 External hydrostatic Pressure test (Type I only). Mount the
firing switch in a hydrostatic test fixture which will expose only that por-
tion of the switch above the O-ring to the test condition. Apply water pres-
sure to the firing switch housing until a pressure of 750 psig is reached.
15
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