ARMY TM 5-6675-308-34
MARINE CORPS TM 08837A-34/2
cate instrument, and care must be taken not to drop it
a. The theodolite must be kept in correct adjust-
or bump it against any object. If the instrument gets
ment if accurate results are to be obtained.
wet, it must be dried before it is returned to the
There are five tests and adjustments of the theod-
carrying case. As soon as possible, the instrument
olite that should be made periodically. These
should be placed in a dry room or tent. It should be
tests should be performed in the sequence in
removed from the carrying case so that it may dry
which they are discussed in paragraphs 5-15
completely. If left in the closed carrying case, it will
through 5-19, When a test indicates that an
absorb the humidity in the air if there is an increase in
adjustment is necessary, this adjustment should
temperature. Should the temperature drop afterwards,
be made and the instrument tested for accuracy
the moisture will condense on the interior of the instru-
before the next test is performed.
ment, A man on foot may carry the instrument,
b. The five tests and adjustments of the theodolite
mounted on the tripod, with the tripod under one arm
are made with the instrument mounted on its
and a hand supporting the theodolite itself. All motions
tripod and accurately leveled. For these tests and
should be clamped with the telescope in the vertical
adjustments, the instrument should be set up in
position. When the theodolite is carried over rough
the shade on firm ground with the head of the
terrain, the instrument should be transported in its
tripod as nearly level as possible. The theodolite
carrying case. When transported in a vehicle, the theod-
should also be protected from the wind.
olite should be in the dome-shaped carrying case, and
the case should be in the padded box. For short dis-
tances, the carrying case may be held in an upright
position on the lap of the instrument operator.
a. Purpose. The purpose of the plate level adjust-
ment is to make the vertical axis of the theodo-
lite truly vertical when the bubble of the plate
kept clean and dry. During use, as necessary, and after
level is centered in its vial.
use, the instrument should be cleaned as follows:
b.
Test. To test the adjustment of the plate level,
place the axis of the plate level parallel to two
Painted surfaces should be wiped with a clean
a.
of the three leveling screws. With these two
cloth.
leveling screws, center the bubble of the plate
b. The lenses should be cleaned only with a cam-
level. Rotate the instrument 1,600 mils and again
el's-hair brush and lens tissue. The lens should be
center the bubble, using the third leveling screw.
cleaned first with the brush to remove any dust
Repeat these steps until the bubble remains
or other abrasive material and then with the lens
centered in both positions. Carefully center the
tissue. Any smudge spots remaining after the lens
bubble in the first position and then rotate the
tissue is used can be removed by slightly moist-
instrument 3,200 mils. If the bubble does not
remain centered, adjustment is required; the dis-
ening the spot and again cleaning with the lens
tissue. Care should be taken not to scratch the
crepancy noted in the position of the bubble is
the apparent error, or twice the actual error, of
lens or remove the coating. The coating reduces
the plate level.
glare for the observer.
c. Adjustment. To adjust the plate level, remove
c. All metal parts of the tripod should be cleaned
one-half of the apparent error (the actual error)
with a cloth moistened with an approved clean-
by turning the capstan adjusting screw located
ing solvent and wiped dry. The wooden parts
below the collimation level illuminator. The
should be cleaned with a soft cloth moistened
adjusting pin is used to turn the capstan adjust-
with water and then dried thoroughly. The
ing screw. Repeat the test to detect any error
leather strap should be cleaned with a suitable
remaining in the adjustment of the plate level
leather cleaner.
and adjust, if necessary.
explained in paragraphs 5-15 through 5-20) and repair
of the theodolite must be performed by qualified instru-
a. Purpose.
of the optical plumb ad-
ment repair personnel. Theodolites in need of adjust-
justment is to make the vertical axis of the
ment or repair should be turned in to the engineer unit
theodolite pass through the station mark when
responsible for providing maintenance service. TM
the theodolite is properly leveled and the station
5-6675-286-12 and/or TM 08837A-12/1 outlines the
mark is centered in the reticle of the optical
plumb.
categories of maintenance.
5-11
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