A-A-52036B
3.4 Level indicators.
3.4.1 Coarse level indicator. The coarse leveling indicators shall be clearly visible when the instrument is set up, horizontal, and parallel to the line of sight. The level indicator sensitivity shall be by instrument type as follows:
a. Type I 10 ±2 minutes of arc per 2 mm division. b. Type II 7 to 15 minutes of arc per 2 mm division.
3.4.2 Telescope (precise) level indicator. The type I telescope level indicator shall have a sensitivity of 8 to 10 seconds of arc, per 2 mm movement. Level indicator readings shall be clearly discernible in temperatures of -25° to +120°F.
3.5 Mounting. The instrument shall be mounted on a tribrach with a baseplate and leveling screws. Leveling screws shall operate without binding, backlash, or end play in temperatures of
-25° to +120°F. For interface with existing instruments, the tribrach shall have at its center a means of accepting an instrument mounting screw with .625 (5/8)-11 UNC-2B thread in accordance with ASME B1.1. When leveled, the instrument shall smoothly and easily rotate through a full horizontal circle without binding or end play.
3.6 Horizontal circle. When provided, the horizontal circle shall have index marks graduated in one-degree intervals, labeled at 10-degree intervals, in a clockwise direction. Angle readings to the nearest 10 minutes shall be visible through a supplied magnifying viewer sufficient to estimate the reading to the nearest minute. The circle shall have a fine adjustment capability for precise positioning of the vertical cross hair in the horizontal circle plane.
3.7 Tripod. The level shall be provided with a wide frame tripod having collapsible legs. A means to secure the legs when collapsed in transport configuration shall be provided. The overall length of the tripod, with legs secured but fully extended, shall not be less than 168 cm (66 inches). A head or adapter ring to interface with the tribrach mounting threads shall be supplied. A thread protective cap to be used when the instrument is not mounted on the tripod shall be supplied. A means of secure storage for the cap, when not in use, shall be provided on the tripod. The tripod material shall be of sufficient strength to rigidly support the instrument and rugged enough to withstand large changes in temperature or humidity. Leg ends shall be configured for penetration of hard natural surfaces with the application of force.
3.8 Accessories. The instrument shall be provided with the following accessories. a. Lens cleaning brush
b. Screwdriver for instrument adjustment as required
c. Adjusting pin for reticle adjustment as required d. Objective lens dust cap
e. Eyepiece lens cover
f. Objective eyepiece sunshade
g. Waterproof cover for the instrument (level)
3.9 Carrying case. A carrying case for the instrument and accessories shall be provided. The case material shall be sufficiently rugged to withstand normal handling and usage. The case liner shall form fit the instrument and shall be securely attached to the case. The level shall be
secured in the case. The case shall be provided with locking latches. Each case shall contain
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