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CHECKING & CALIBRATION
THIS CHAPTER IS VERY IMPORTANT. Here are instructions to check the GradeLight
calibration. Remember that the laser is a precision instrument and that it is important that it
be calibrated and in proper condition. The accuracy of work is completely the responsibility
of the user. The instrument should be checked before beginning each job, and especially
after the instrument has taken a sharp jolt or been dropped, or when temperature changes
greater than 50° F (28° C) have occurred.
Checking Level Accuracy
Select a reasonable level area. Set up the GradeLight on a stable surface. The cross axis
vial should be centered and the legs adjusted so the unit is level.
It will be easier to adjust the laser to strike stake B in Figure 1 by using the single centerline
leg in the front (beam end) or by using the trivet with height adjustable rod.
After the unit has self-leveled, set the grade at 0/000%.
1. Establish two benchmarks:
Figure 1: Drive two stakes (A & B) in line with
the laser beam, but low enough for the beam
to pass over both stakes. Stake A should be
about 1 foot (0.3 m) from the unit, and stake B
about 100 feet (30 m) away.
2. Check the instrument:
Figure 2: Place a short 2 X 4 or something similar
on stake A, and mark where the center of the
beam strikes. Call the mark A1.
Place the same 2 X 4 on stake B and again mark
where the center of the beam strikes. Call this
mark B.
3. Move the laser to the far side of stake B
(Figure 3) so the beam will cross over both
stakes as before, but in reverse order.
a. Be sure the height of the unit is set to that
when the 2 X 4 is placed on stake B, the
beam will strike at mark B.
b. Now place the 2 X 4 on stake A. Make a
second mark (A2) where the center of the
beam strikes.
At 100 feet, the marks should be no more than
1/8 inch apart (at 30 m, no more than 3 mm
apart). This is within the stated accuracy of
±1/16 inch at 100 feet.
If the marks are close enough, the beam is
accurately projecting level. If they are not close
enough, take it to an authorized AGL service
center for calibration, or adjust the unit using the
following procedure.
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