CHECKING & CALIBRATION
THIS CHAPTER IS VERY IMPORTANT. Here are a few simple instructions to check your
GradeLight for calibration. Remember that the laser is a precision instrument and that it is
important that you keep it calibrated and in proper condition. The accuracy of your work
is completely your responsibility and you should check your instrument before beginning
each job, and especially after the instrument has taken a sharp jolt or been dropped, or
when temperature changes greater than 50 degrees F (28 degrees C) have occurred.
Checking Level Accuracy
Select a reasonably 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 if you use the single centerline
leg in the front (beam side) or if you use a 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’ (.3m) from the unit, and stake B
about 100’ (30m) away.
2. Check the instrument:
A. Figure 2: Place a short 2x4 or something
similar on stake A, and mark where the center
of the beam strikes. Call this mark A1.
B. Place the same 2x4 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 so
that when the 2x4 is placed on stake B,
the beam will strike at mark B.
B. Now place the 2x4 on stake A. Make a
second mark (A2) where the center of
the beam strikes.
At 100 ft., the marks should be no more than
1/8” apart (at 30m, no more than 3 mm apart).
This is within the stated accuracy of ± 1/16”
at 100 ft.
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.
21
Stake
A
Fig. 1
100’
Stake
B
Stake
A
A1
B
Fig. 2
Stake
B
Stake
A
A2
A1
B
Fig. 3
Stake
B
