instrument becomes wet, you should remove it from its
carrying case and dry it thoroughly at room temperature
once you get home. NEVER leave a wet instrument
stored in the carrying case.
NEVER rub the lenses of a telescope with your
fingers or with a rough cloth. Clean chamois leather or
a lint-free soft cloth is suitable for this purpose.
Occasionally, you may clean the lenses with a soft cloth
that is dampened with a mixture of equal parts of water
and alcohol.
You should always remove mud and dirt from
tripods, range poles, leveling rods, and so forth,
immediately after each use. This is very important,
especially when the surveying gear is made of a material
that is susceptible to rust action or decay.
When lubricating instruments, you must use the
right lubricant that is recommended for the climatic
condition in your area; for instance, it is recommended
that graphite be used to lubricate the moving parts of a
transit when the transit is to be used in sub-zero
temperatures; however, in warmer climates you should
use alight film of oil (preferably watch oil).
Consult the manufacturer’s manual or your senior
EA whenever you are in doubt before doing anything to
an instrument.
INSTRUMENT ADJUSTMENTS AND
REPAIRS
Making minor adjustments and minor repairs to
surveying instruments are among the responsibilities of
EA personnel. Minor adjustments and minor repairs are
those that can generally be done in the field using simple
tools. Major adjustments and major repairs are those
generally done in the factory. If the defect in the
instrument cannot be corrected by minor adjustment or
minor repair, do not attempt to disassemble it; instead,
make necessary arrangements for sending the
instrument to the manufacturer. Most surveying
instruments are precision instruments for which major
adjustments and recalibration require special skills and
tools that can be provided only by the instrument
company or its subsidiaries.
INSTRUMENT ADJUSTMENTS
As stated previously, adjustment, as used in this
chapter, means the process of bringing the various parts
of an instrument into proper relationship with one
another. The ability to make these adjustments is an
important qualification of any surveyor. To make proper
adjustments, the surveyor should have the following
knowledge:
1. They must be familiar with the principles upon
which the adjustments are based.
2. they must know the methods or tests used to
determine if an instrument is out of adjustment.
3. They must know the procedure for making
adjustments and the correct sequence by which
adjustments must be made.
4. They must be able to tell what effect the
adjustment of one part will have on other parts of the
instrument.
5. They must understand the effect of each
adjustment upon the instrument when it is actually used
for measurement.
Generally, instrument adjustments involve the level
tubes, the telescope, and the reticle; for example, if one
or both of the plate-level bubbles of an engineer’s transit
are centered when the plate is, in fact, not level, the
instrument is out of adjustment. An optical instrument
equipped with vertical and horizontal cross hairs is out
of adjustment if the point of intersection between the
cross hairs does not coincide with the optical axis. If the
reflected bubble on a Locke or Abney level is centered
when the optical axis is other than horizontal, the
instrument is out of adjustment.
The process of adjustment chiefly involves the steps
that are necessary to bring a bubble to center when it
should be at center or to bring a cross-hair point of
intersection into coincidence with the optical axis.
Instrument manufacturers publish handbooks
containing recommended adjustment procedures. These
are usually small pamphlets, obtainable free of charge.
The following discussion is intended to give you an
idea of general instrument adjustment procedures. For
adjusting your particular instruments, however, you
should follow the appropriate manufacturer’s
instructions.
General Adjustment Procedures
Instruments should be carefully checked
periodically to determine whether or not they need
adjustment. There is an adage that an instrument should
be checked frequently but adjusted rarely. The basis for
this adage is the fact that modern quality instruments get
out of adjustment much less frequently than is generally
believed; consequently, a need for adjustment is
frequently caused by a previous improper adjustment
that was not really required but resulted from errors in
checking.
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