MIL-DTL-13276C
NATIONAL CONFERENCE OF STANDARDS LABS (NCSL)
NCSL Z540.3
- General Requirements for Calibration of Measuring and Test
Equipment
(Copies of these documents are available online at https://www.ncsli.org or from NCSL
International 2995 Wilderness Place, Suite 107 Boulder, Colorado 80301-5404.)
2.4 Order of precedence. Unless otherwise noted herein or in the contract, in the event of a conflict
between the text of this document and the references cited herein, the text of this document takes
precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a
specific exemption has been obtained.
3. REQUIREMENTS
3.1 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or
environmentally preferable materials should be used to the maximum extent possible provided that the
material meets or exceeds the operational and maintenance requirements, and promotes economically
advantageous life cycle costs.
3.2 Materials. The material for the wire shall be as specified herein.
3.3 Strands. Each strand of wire W-28 shall consist of a silicon bronze alloy wire with a diameter of
0.032 inch, 0.001 inch (20 AWG).
3.4 Conductor construction. Wire W-28 shall be constructed of 7 strands of wire as specified in 3.3,
concentrically stranded with a left-hand lay to form a tight cylindrical conductor. The length of lay shall be
between 7.5 and 15 inches.
3.5 Conductor joints. Factory joints in conductors shall be avoided, and in no case shall they exceed
two joints per strand per length of wire, with joints spaced not less than 50 feet apart. All joints shall be
butt brazed using silver alloy solder and a nonacid flux; and shall be finished smoothly in a workmanlike
manner. No twist joints shall be used. The tensile strength of a section of each strand, which includes a
joint, shall not be less than 90 percent of the tensile strength of an adjacent section of the strand of equal
length without a joint.
3.6 Breaking strength. Wire W-28 shall have a breaking strength of not less than 600 pounds (see
4.6).
3.7 Elongation. The elongation shall be not less than 0.80 percent of the zero length of stranded
conductor. The elongation shall be determined by measurements made between the jaws of the testing
machine. The zero length shall be the distance between the jaws when a load equal to 60 lbs. is applied.
The zero length shall be as near 60 inches as practicable. The final length shall be the distance between
the jaws at the time of rupture (see 4.6).
3.8 DC resistance. The dc resistance of wire W-28 shall not exceed 10.5 ohms per 1000 feet at or
corrected to 68F (see 4.7).
3.9 Workmanship. Strands and complete wire W-28 shall be manufactured and finished in a careful
and workmanlike manner in accordance with the good design and sound practice.
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