Angle measurement
As shown in Fig. 5, sight point A and rotate the horizontal circle until the reference mark is on “0”.
Rotate the level and sight point B; the reference mark will indicate the angle between A and B.
CALIBRATION
Your Automatic Level has been factory calibrated; however, you should occasionally check your
level for errors caused by shipment or rough handling.
Compensator lock button
Check the compensator for proper operation before use or anytime the operation of the instrument
is in question. Push and release the compensator lock button to shake the compensator. The
compensator should return to the exact horizontal position sighted before the lock button
was pressed.
Circular bubble vial
Center the vial bubble using the leveling screws, then rotate the instrument 180°. The bubble
should remain centered (Fig. 6). If the bubble moves out of center, the vial needs adjustment (Fig.7).
Turn the leveling screws to bring the bubble halfway to center (Fig. 8). Using the Allen wrench, turn
the two vial adjustment screws to center the bubble (Fig. 9).
Repeat the above procedure until the bubble remains centered when the level is rotated 180°.
Line-Of-Sight
The line-of-sight needs to be horizontal within 3 mm of level to be accurate.
Set up and level the instrument on a tripod midway between two leveling rods set approximately
30m to 50m apart. Sight rods A and B; the height readings are a1 and b1 (Fig. 10). The value “H” is
equal to (a1 – b1). Move the instrument to within 6 feet (2m) of rod A and re-level. Again sight rods
A and B; these height readings are a2 and b2 (Fig. 11).
If a1 – b1 = a2 – b2 = H, the line-of-sight is horizontal. If not, the level should be adjusted as follows.
Because the instrument is set halfway between A and B, any error in the line-of-sight causes both
readings to be erroneous by the same amount. Error “e” cancels out, so the value a1 – b1 = H is
correct. Therefore, a2 – H = b3, the adjusting value.
To adjust, unscrew the eyepiece cover. Turn the adjusting screw with the adjusting pin (Fig. 12)
until the horizontal cross hair gives the reading b3, on rod B. Repeat the above Procedure until
{(a1-b1) – (a2-b2)} </= 3 mm.
AL8 AutoLevel • 5
After doing any job using any instrument, it is advised that you check your work. To check your
work, set up the instrument in a different location from the place where you originally set up
(approx. 16 m) and reshoot a few of your original targets. The new readings should agree with the
first readings.
If the new readings do not agree, you should have the instrument checked by a David White
Authorized Repair Center, or try the
Line-of-sight adjustment.
USING THE INSTRUMENT
Setting up the instrument and centering the bubble
1.
Set up the tripod and attach the level using the tripod mounting screw.
2.
Adjust the tripod legs until the tripod head is roughly level. Center the bubble within the vial
by turning the leveling screws as shown in Fig. 2.
2a – Turn screws A and B to move the bubble to the right side.
2b – Turn screw C to center the bubble.
Focusing the instrument
1.
Focus the cross hairs (Fig. 3) by pointing the telescope towards a bright background or
holding a white sheet of paper in front of the objective lens, then turning the eyepiece until
the cross hairs are sharp and black.
2.
Focus the telescope by locating a target, such as a leveling rod, using the optical peep sight.
Looking through the eyepiece, use the focusing knob to bring the target into sharp focus.
Center the vertical hair within the target using the horizontal drive knobs on either side of
the instrument.
Reading measurements using a leveling rod
Height reading
Read the rod where it is intersected by the horizontal hair. For example, the height reading in Fig. 4
(Fig. 4/a) is 2.0 ft (1,195 m).
Distance measurement
Read the rod where it is intersected by the upper and lower stadia hairs; in Fig. 4 (Fig. 4/a) these
readings are at 1.9 ft and 2.1 ft (1,352 m and 1,038 m). The stadia ratio is 1:100; therefore, the
distance from the instrument to the rod is: (2.1 - 1.9) x 100 = 20 feet - Fig. 4/a (1,352 – 1,038) x 100 = 31,41m.
4 • AL8 AutoLevel
