![img](MIL-DTL-1603400008im.jpg)
MIL-DTL-16034B
3.6.4.1.1 Selector switches. Range selector switches, when provided on multiple-range portable-type meters,
shall be suitably indexed and marked so that the correct scale can be easily selected. Switches shall be designed to
eliminate danger of electric shock to the operator. The switch shall have a life of 10,000 continuous no-load
operations without impairing the operation of the meter sufficiently to cause it to exceed the rated accuracy (see
3.6.4.2 Switchboard meters. Terminal studs shall be firmly anchored to the base of the meter in such a manner as
to prevent turning or movement sufficient to cause damage to internal construction. Each terminal stud shall be
furnished with the necessary nuts or screws, and washers.
3.6.4.2.1 Polarity. On all DC switchboard meters the left-hand terminal (looking at the rear of the meter in the
normal mounting position) shall be the positive terminal (see 3.26.1.2).
3.6.4.2.2 Bonding. All permanent-magnet, moving-coil meters shall have the magnetic system and dial
electrically connected to one terminal. Insulated cases having metallic bezel rings shall have this ring connected to the
same terminal by means of a brush contact so that the mechanism can be readily withdrawn.
3.6.4.2.3 Connection diagrams. Meters having more than one circuit shall have a print showing the wiring
diagram of connections with or without transformers, resistances, and reactances for three-phase, three-wire systems
and two-phase, four-wire systems, together with instructions attached permanently or sufficiently secured to prevent
loss during shipment.
3.6.5 Self-contained limitations. Unless otherwise specified (see 3.1), meters shall be self-contained for the
following ranges:
Portable ammeters, AC and DC
80 amperes or less
Portable voltmeters, AC and DC
800 volts or less
Switchboard ammeters, 60-cycle AC, and DC
50 amperes or less
Switchboard ammeters, 400- and 800-cycle AC
no ranges
Switchboard voltmeters, DC
800 volts or less
Switchboard voltmeters, AC
600 volts or less
3.6.6 Mounting switchboard meters. Switchboard meters shall be mounted by means of mounting bolts or studs.
The necessary mounting bolts (screws), nuts, and lock washers shall be supplied with each meter.
3.6.6.1 Four-and-one-half-inch meters. The 4½-inch meters shall mount on a panel drilled in accordance with the
specified panel-drilling plan (see 3.1).
3.6.6.2 Six-inch meters. The 6-inch meters shall mount on a panel drilled in accordance with the specified panel-
drilling plan (see 3.1), or shall be furnished with a suitable adapter to permit mounting without drilling additional
holes.
3.7 External accessories. External shunts, shunt leads, resistors, and transformers shall be furnished when
specified (see 6.2). External resistors used with DC meters shall conform to MIL-PRF-29; other external accessories
shall conform to MIL-I-1361.
3.7.1 Calibration Potentiometer Single Meter Sensing. Meters shall be equipped with an internal or external
mounted calibration potentiometer (or trim pot) to compensate the meter for up to 5 ohms of line lead resistance. The
potentiometer shall be adjusted from 0 to 5 ohms, 10 turn and adjustable from the exterior of the meter.
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