MIL-PRF-19978K
4.7.8 Insulation resistance (see 3.12). Capacitors shall be tested in accordance with method 302, MIL-STD-202.
The following details and exceptions shall apply:
a. Test potential:
(1) Insulating sleeves: When applicable (see 3.1). Test condition B.
(2) Terminal to terminal and terminal to case: A potential equal to the rated dc voltage (see 3.1) or 500 V
dc, whichever is less.
b. Special conditions: The time constant of the measurement circuit with the capacitor connected shall not
exceed 30 seconds.
c. Points of measurement:
(1) Insulating sleeves: The test potential shall be applied between the case and a piece of metal foil placed
around the insulating sleeve; the metal foil shall be of such dimension as to allow at least .125 inch
(3.18 mm) surface exposure of the insulating sleeve on each end (see 3.12.1).
(2) Terminal to terminal: Insulation resistance shall be measured between terminals at the maximum rated
temperature, 3°C, and at +25°C 3°C (see 3.12.2).
(3) Terminals to case: When the case is not a terminal, the measurement shall be made between each
terminal and the case at +25°C ±3°C (see 3.12.3).
d. Electrification time: 2 minutes.
4.7.9 Capacitance (See 3.13.). Capacitors shall be tested in accordance with method 305 of MIL-STD-202. The
following details shall apply:
a. Test frequency: 1,000 Hertz (Hz) 100 Hz for capacitors whose nominal capacitance does not exceed 1 F
and whose dc voltage rating does not exceed 3,000 volts. For capacitors not within these limits,
measurements shall be made at a frequency of 100 Hz 6 Hz or corrected thereto.
b. Limit of accuracy: Shall be within 0.l percent.
4.7.10 Dissipation factor (see 3.14). The dissipation factor shall be measured with an ac voltage not greater than
20 percent of the dc voltage rating, at a frequency of 1,000 100 Hz, for capacitors whose nominal capacitance does
not exceed 1 F and whose dc voltage rating does not exceed 3,000 volts. For capacitors not within these limits,
measurements shall be made at a frequency of 100 Hz 6 Hz or corrected thereto. Measurement accuracy shall be
one of the following:
a. For dial reading: 2 percent of dial reading or .001, whichever is greater.
b. For digital readout: .001 percent 2 percent of reading.
4.7.11.1 Low frequency. Capacitors shall be tested in accordance with method 201 of MIL-STD-202. The
following details and exceptions shall apply:
a. Tests and measurements prior to vibration: Not applicable.
b. Method of mounting: Securely fastened by normal mounting means, except that capacitors without
mounting retainers in sizes 1.562 inch (39.67 mm) long or .670 inch (17.02 mm) in diameter or larger shall
be mounted by a supplemental means other than the wire leads. Wire-Lead capacitors shall be secured .5
inch .125 inch (12.7 mm 3.18 mm) from the case. The extraneous leads beyond the .5 inch (12.7 mm)
securing point may be removed or supplemental support may be added.
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