MIL-PRF-14409 Capacitors, Variable \(Piston Type, Tubular Trimmer\), General Specification ForThis specification covers the general requirements for tubular-trimmer, piston-type, variable capacitors intended primarily for use in high-frequency trimming applications where relatively few adjustments are required during the effective life of the equipment.

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MIL-PRF-14409J

4.5.9.1.1.1 Computation of temperature coefficient. The temperature coefficient shall be computed as follows:

(C2 - C1) 106

TC =

(T2 - T1) C1

TC = Temperature coefficient in parts per million per �C.

Where:

C1 = Capacitance at +25�C in pF.

C2 = Capacitance at test temperature in pF.

T1 = +25�C.

T2 = Test temperature in �C.

4.5.9.1.2 Capacitance drift. Capacitance drift shall be the greatest difference between any two of the three

values recorded at +25�C (see table VII).

4.5.9.2 For conformance inspection.

4.5.9.2.1 Temperature coefficient. Capacitance measurements shall be made as specified in 4.5.9.1.1 and table

4.5.9.2.2 Capacitance drift. Capacitance drift shall be computed as specified in 4.5.9.1.2.

4.5.10 Immersion (sealed units only) (see 3.14). Capacitors shall be tested in accordance with method 104 of

MIL-STD-202. The following details shall apply:

a. Test condition: A.

b. Measurements after final cycle: Maximum rated capacitance, insulation resistance, and dielectric

withstanding voltage shall be measured as specified in 4.5.3, 4.5.5, and 4.5.6, respectively.

4.5.11 Salt atmosphere (corrosion).

4.5.11.1 Salt atmosphere (corrosion) (sealed units only) (see 3.14.1). Capacitors shall be tested in accordance

with method 101 of MIL-STD-202. The following details shall apply:

a. Test condition: B.

b. Measurements between 4 and 24 hours after exposure: Insulation resistance, dielectric withstanding

voltage, and driving torque at room ambient temperature shall be measured as specified in 4.5.5, 4.5.6,

and 4.5.8.1.2.1, respectively.

Capacitors shall be examined for evidence of corrosion.

4.5.11.2 Salt atmosphere (corrosion) (unsealed units only) (see 3.14.2). Capacitors shall be tested in accordance

with method 101 of MIL-STD-202. The following details shall apply:

a. Test condition: B

b. Measurement after test not required.

c. Capacitors shall be examined for evidence of corrosion.

4.5.12 Low-temperature storage (see 3.15). Capacitors shall be subjected to storage at -62�C �5�C for a period

of 48 �4 hours. Capacitors shall then be examined for evidence of mechanical damage.