UR.

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MIL-DTL-5794C

4.6.14 Blast test for microphone unit M-51/UR (see 3.5.9).

4.6.14.1 Blast test for microphone unit M-51/UR. The microphone unit shall be subjected to 30 rounds

of blast at a peak pressure of 9.5 pounds per square inch, by using one of the following methods:

a. The microphone unit shall be mounted so that the pressure produced by ammunition explosion

strikes the face of the microphone unit under test. A transducer capable of operating under a

peak pressure of twelve pounds per square inch or more and of a known calibration shall be

placed in the same relative position as the microphone under test. The voltage produced by this

transducer shall be fed into a fast response oscilloscope, with an oscilloscope camera available.

Photographs of the pressure produced on the transducer by the ammunition explosion shall be

recorded at the 1st, 10th, 20th, and 30th round to show instant pressure.

b. The microphone unit shall be elevated at least 6 feet above the ground and located at least 12

feet, for a 5 inch 25 caliber gun, or 14 feet, for a 5 inch 38 caliber gun, from the gun muzzle in the

plane through the muzzle perpendicular to the gun axis. The front edge of the microphone unit

shall be positioned so that its axis will be coincident with that of the gun muzzle.

4.6.14.2 Blast test for microphone unit M-51/UR. After the above conditioning, the microphone unit

shall meet the requirements of 3.5.9.

4.6.15 Impact test (see 3.6.6).

4.6.15.1 Impact test (Microphone Unit M-6A/UR). The microphone unit shall be subjected to the

following combination of tests, which shall be repeated 3 (three) times:

a. Five cycles of exposure to moisture resistance tests, as specified in 4.6.7.

b. Exposure to the temperature cycling test as specified herein, except that the temperatures shall

be maintained for 2-hour periods, as specified in 4.6.9.

c. Impact test shall consist of 10 (ten) random drops. The drops shall be from a 6-foot height to a

concrete floor, covered with 0.125 (1/8) or 0.1875 (3/16) inch thick asphalt tile thoroughly

cemented to the concrete floor, using a 4 (four) inches minimum thickness of cement.

4.6.15.2 Impact test (Microphone, Carbon M-51/UR). The microphone shall be subjected to 20

random drops from a 6-foot height to a covered concrete floor. The covering shall consist of 0.125 (1/8)

or 0.1875 (3/16) inch thick asphalt tile thoroughly cemented to the concrete floor, using a 4 (four) inches

minimum thickness of cement.

4.6.16 Anti-packing (see 3.5.7). The microphone unit shall be tested for surges, overload-current, and

extended operation using the circuit on figure 3. The microphone unit shall not be conditioned prior to

making the response measurements required to determine degradation in performance.

5. PACKAGING

5.1 Packaging. For acquisition purposes, the packaging requirements shall be as specified in the

contract or order (see 6.2). When packaging of materiel is to be performed by DoD or in-house contractor

personnel, these personnel need to contact the responsible packaging activity to ascertain packaging

requirements. Packaging requirements are maintained by the Inventory Control Point's packaging

activities within the Military Service or Defense Agency, or within the military service's system commands.

Packaging data retrieval is available from the managing Military Department's or Defense Agency's

automated packaging files, CD-ROM products, or by contacting the responsible packaging activity.