MIL-DTL-3971F
3.4.2 Finish. Aluminum, when utilized on exposed portions of the meter, shall be anodized.
Visible parts of the meter, as viewed when mounted, shall be finished with a durable non-
reflecting black. A black finish on the case is optional.
3.4.3 Window. The window shall be clear, uncolored, and free of bubbles, scratches, or other
imperfections which may interfere with the reading of the meter and shall show no evidence of
damage when tested in accordance with 3.5.4.
3.4.4 Grounding. Cases shall not be externally grounded.
3.4.5 Elapsed time indicator. The elapsed time indicator shall be a drum register type having
a total range of 10,000 or 100,000 hours, as specified in 1.2.
3.4.6 Running indicator.
3.4.6.1 Type I. A running indicator shall be clearly visible. The indicator shall, within 30
seconds after the meter is energized, be evidence that the meter is operating.
3.4.6.2 Type II. A running indicator is optional. If a running indicator is used, it shall be as
specified in 3.4.6.1.
3.4.7 Terminals. Meters shall be provided with terminals for connecting electrical wires to
the meter. Terminals for soldered connections shall be hot-tin dipped or solder coated to
facilitate soldering. Screw terminals shall be #8-32. Blade terminals shall be 0.25 inch (6.3 mm)
nominal width.
3.4.7.1 Terminal polarity. Type I meters, which are polarity sensitive, shall have the positive
terminal identified as such by marking on that portion of the case adjacent to that terminal.
3.4.7.2 Terminal location. The terminals (two) shall be located on the back of the case and
positioned in a manner that will not interfere with mounting of the meter.
3.4.8 Mounting hardware. Machine screws, nuts and either split-ring lock-washers or
internal tooth lock washers shall be furnished with each meter. The machine screws shall be
fully threaded and 0.5 inch (12.7 mm) in length. The hardware shall have a non-reflecting black
finish.
3.4.9 Coils. The coils shall be properly insulated from the case and other ground parts.
3.4.10 Insulation resistance. The insulation resistance between the terminals and the case
shall exceed 100 megohms.
3.4.11 Electromagnetic compatibility (mechanical designs only). Grade A meters shall
conform to the electromagnetic compatibility requirements for class IIC as specified in
MIL-STD-461.
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