Basic Operation; Reading The Staff - Topcon DL-501 Instruction Manual

10.BASIC OPERATION

10.1

Reading the Staff

Simply focus on the RAB* code for an automatic reading of the staff. The following explains how to
read the RAB code of the staff.
*RAB code (RAndom Bi-directional code) is a coded staff used with certain digital levels.

• Set up the staff in an area free of obstacles.
• Avoid placing the staff next to mirror-like surfaces. The effect of strong light could make
measurements impossible.
• Support the staff so that it is perpendicular, checking the circular bubble scope on the staff. If the
staff is tilting, height and distance measurements will be incorrect.
• If the surface is catching the light, turn it just enough to stop the reflection.
• Make sure shadows are not cast on the staff as this could make measurement impossible.
• When holding the staff during measurement, make sure your hand does not cover the RAB code.
• If dark locations make measurement difficult, shine a flashlight on the staff. Stand at a distance so
that the beam shines evenly over the length of the staff.
• If waterdrops or dirt adhere to the barcode, measurement may be impossible. Wipe the staff clean
with a soft cloth.
• Clean the staff if grit or dirt gets stuck between the sections. If the staff is dirty, measurements will
not be very accurate.
• Avoid scratching or soiling the barcode surface as this could make measurement impossible. Store
and carry the staff inside its case.
• If the BIS/BGS series staff is used for leveling, and the height difference and temperature difference
are much larger than normal, temperature variations may cause the staff to expand or contract and
cause differences in relative height measurements. DL reads in measurements up to 0.01mm and
minor deviations in the accuracy of the staff will adversely affect accuracy. To obtain high accuracy
measurements, it is important to perform temperature corrections for the staff. See  below.

• Formula for correcting expansion and contraction of the staff due to temperature changes.
Δ
C={C0+(T-T0)x
Δ
C: Staff correction value
C0: Scale factor
T: Measured temperature during observation (average
temperature during measurement of known site,
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α Δ
}x h