TM5-6675-296-14
Section II. OPERATION UNDER UNUSUAL CONDITIONS
should be removed from storage in sufficient time
before use to allow the temperature of the metal to
(-18C))
approach that of the outside air.
With proper precautions and servicing, the
theodolite can be used in extreme cold. Its use is
2-7. Operation in Dusty or Sandy Areas
limited only by the endurance of operating per-
Special care must be given instruments which
sonnel and conditions affecting visibility. The
are being used in dusty or sandy areas, since both
theodolite should be kept out-of-doors or in
dust and sand are highly abrasive. If dust and
unheated buildings for short periods of non-use.
sand are allowed to remain on threaded or sliding
Extreme temperature changes will induce internal
surfaces, moving parts of the theodolite will soon
stresses affecting accuracy and lenses, and prisms
bind and the instrument will become inaccurate or
may become fogged. Theodolites to be used under
inoperable. The theodolite should be brushed
conditions of extreme cold should be cleansed, and
frequently and carefully wiped clean. Be extremely
all lubricants should be removed before the in-
careful not to scratch lens and prism surfaces
s t r u m e n t s are used. Snowfall, winds, and
during cleaning operations. Always protect the
refraction of light are some of the conditions en-
instrument from blowing dust and sand. Place a
countered at low temperatures. Winterization
protective cover over theodolite when it is not in
eyepiece and control knob covers are provided for
use.
protection against contact with bare metal sur-
2-8. Operation Under Rainy or Humid Conditions
faces. During operation in extreme cold, avoid
In humid areas, a slight lowering of the tem-
breathing on telescope/microscope lenses and
perature will cause condensation of moisture and
theodolite mirrors.
fogging of lenses and prisms. Internal fogging can
CAUTION
usually be removed by placing theodolite in a
Avoid subjecting the theodolite to sudden
warm, dry place. Corrosion caused by high
changes in temperature.
humidity can be partially eliminated by using
2-6. Operation in Extreme Heat
warm, dry storage areas and desiccants. After use,
Operation of the theodolite in extreme heat and
dry instrument thoroughly with a soft, lint-free
under direct rays of the sun can cause internal
cloth.
stresses and distortion in the instrument and
2-9. Operation in Salt Water Areas
produce poor sightings because of heat waves. If
possible, the theodolite and instrument man should
Salt is highly corrosive to metals. When
be protected from direct sunlight by an umbrella or
operating the theodolite in salt water areas, wipe
other suitable means. Under these conditions,
the instrument frequently with a soft, clean cloth.
shorter sightings will decrease the amount of
If the theodolite is exposed to direct salt spray, it
sighting errors. Taking sightings during early
should be cleaned thoroughly and should be
morning and late evening will also minimize error
returned to an instrument shop for overhauling as
soon as possible. Cleaning intervals should be
instrument man will reduce eyestrain and fatigue.
shortened considerably for theodolites subjected to
If the theodolite is kept in a cool storage place, it
salt air exposure.
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