MIL-PRF-23648F
4.7.2.3 Semiannually. Ten sample units of the highest resistance value shall be inspected
semiannually, with one defective unit allowed.
4.7.3 Disposition of sample units. Sample units which have been subjected to group C inspection shall
not be delivered on the contract or purchase order.
4.7.4 Noncompliance. If a sample fails to pass group C inspection, the supplier shall 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, and processes, and which are considered subject to the same failure. Acceptance of the
product shall be discontinued until corrective action, acceptable to the Government, 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 the original sample failed, at the option of the Government).
Group A and group B inspection may be reinstituted; however, final acceptance shall be withheld until
group C reinspection has shown corrective action was successful. In the event of failure after
reinspection, information concerning the failure and the corrective action taken shall be furnished to the
contracting officer.
4.8 Methods of inspections.
4.8.1 Visual and mechanical inspection. Thermistors shall be inspected to verify that the design,
construction, physical dimensions, marking, and workmanship are in accordance with this specification
(see 3.1).
4.8.2.1 Measurements. All resistance measurements shall be made in a controlled uniform medium
capable of maintaining an accuracy in temperature of:
a. ±0.01°C for beads, beads in rods, and beads in probes.
b. ±0.05°C for all other types.
4.8.2.2 Equipment sensitivity.
a. Resistance: A wheatstone bridge, or equivalent, accuracy to ±0.05 percent or better.
b. Temperature: The time response of the temperature indicator shall be compatible with that of the
thermistor being tested.
4.8.2.3 Test procedure. The test procedure shall be as follows:
a. Mounting: Resistance shall be mounted by normal means in corrosion resistant clips mounted on
0.125 inch (3.17 mm) diameter brass rods.
(1) Beads: Flat noncorrosive clips shall be used. Grip the leads .250 inch ±.0625 inch (6.35 mm
±1.587 mm) from the end of thermistor body.
(2) All other types: Use suitable corrosion resistant clips. Grip the leads 1.0 inch ±.0625 inch
(25.4 mm ±1.587 mm) from the end of the thermistor body.
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