MIL-PRF-23419H
4.6.2.1.1 Sampling plan. Unless otherwise specified, 22 sample units each of the maximum and
minimum current ratings shall be selected, from those covered by a single specification sheet, 36 months
after the date of notification of qualification; except for subgroup 3, which shall be selected on a 48-month
basis. The sample units shall be subdivided into subgroups shown in table VI. When production of a
particular type of fuse has been suspended for 36 months or more, sample units shall be selected from
the first lot of the new production presented for acceptance, and after each subsequent 36-month period;
except for subgroup 3, which shall be on a 48-month basis.
4.6.2.1.2 Failures. If one or more sample units fail to pass group C inspection, the sample shall be
considered to have failed.
4.6.2.1.3 Disposition of sample units. Sample units which have been subjected to group C inspection
shall not be delivered on the contract.
4.6.2.1.4 Noncompliance. If a sample fails to pass group C inspection, the manufacturer shall notify
the qualifying activity and the cognizant inspection activity of such failure and take corrective action on the
materials or processes, or both, as warranted, and on all units of product which can be corrected and
which were manufactured under essentially the same conditions with essentially the same materials,
processes, etc., and which are considered subject to the same failure. Acceptance and shipment of the
product shall be discontinued until corrective action, acceptable to the qualifying activity has been taken.
After the corrective action has been taken, group C inspection shall be repeated on additional sample
units (all inspections, or the inspection which the original sample failed, at the option of the qualifying
activity). Group A and group B inspections may be reinstituted; however, final acceptance and shipment
shall be withheld until the group C inspection has shown that the corrective action was successful. In the
event of failure after reinspection, information concerning the failure shall be furnished to the cognizant
inspection activity and the qualifying activity.
4.7 Methods of examination and test.
4.7.1 Visual and mechanical examination. Fuses shall be examined to verify that the materials,
interface, and physical dimensions, marking and workmanship are in accordance with the applicable
4.7.2 Continuity (see 3.6). Continuity of each fuse shall be determined by use of a low voltage
ohmmeter or other suitable method.
4.7.3 Resistance (see 3.7). Resistance shall be measured with a Wheatstone bridge, Kelvin bridge, or
equivalent sensitive instrument or calculated from the voltage drop (see 4.7.3.1). Measurements shall be
taken at room ambient temperature and as close to the fuse element as practicable.
4.7.3.1 Voltage drop (see 3.7.1). Voltage drop shall be measured using a dc voltmeter having a
minimum input impedance of 11 megohms with measurements taken at room ambient temperature and
as close to the fuse element as practicable.
subjected to an ac or dc of 100 percent of rated current and shall be mounted in a fuseholder as specified
(see 3.1).
4.7.4.1 For qualification inspection (group I), the samples shall be apportioned and submitted to the
test at -55°C to -60°C, at +20°C to +35°C (room ambient temperature), and at the maximum rated
temperature for the fuse (see 3.1). The tolerance at the maximum rated temperature shall be -0°C and
+5°C.
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