12 LTL-XL Retroreflectometer DELTA
Important guide lines for the correct use of the LTL-XL
Positioning of the instrument on the road marking
Select an area of the pavement marking that is level when taking readings. The measurement
field is marked with a yellow sticker on one side of the base cover. The measurement field is
approximately 50 mm / 1.97 inch wide and 185 mm / 7.28 inch long. Ensure that the pave-
ment marking to be measured before taking measurements is free of debris. Make sure that
the instrument is stable positioned.
Reason: The LTL-XL has three support pads, each with a small footprint, two smaller in the
front and one larger at the back. An uneven marking or a small piece of gravel trapped below
one of the pads will move the measurement field and affect the reading.
Taking the measurement
Press the green OK button to take a single or double reading as selected. Do not put pressure
on the handle when taking a measurement.
Reason: Pressure on the handle can tilt the instrument slightly and affect the measurement
geometry and thus influence the reading.
Number of measurements.
For accurate readings, do not take just one reading of a road marking. Three readings will
give a more accurate result than one reading. Five readings will give an even more accurate
result than three readings, etc. Take the readings in adjacent areas of the marking. Let the in-
strument calculate the average of the readings (fixed or moving average options).
Reason: A road marking’s retroreflectivity varies from area to area. It is not unusual to see
variations of 5% - 20% when the instrument is moved even less than 10 mm / ½” in either
direction.
Protective display shield.
For the protection of the display and longevity of the instruments keep the display shield
closed when the instrument is not used. For further information please see section 2.
Remember:
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