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GDF121 Leica Tribrach without Optical Plummet For Total Stations
Model: GDF121
Specifications:
Torsional Stiffness: <1"
Weight: 780g
Features:
Introduction:
The accuracy with which a tribrach returns to its starting position
once the instrument has stopped, is called torsional rigidity or
hysteresis. This hysteresis is the relative movement between the
top plate and the base plate of a tribrach that occurs through the
rotation of a TPS instrument. The hysteresis has direct influence
on the angular accuracy of the instrument – and that speaks for the
original. To optimize the hysteresis as Leica Geosystems has done
is complex and calls for the highest precision: a movement of the
top plate to the base plate of 0.3µm corresponds to an angle error
of 1". Especially motorized instruments with their high
acceleration and brake power require tribrachs with very high
torsional rigidity.
The foot screws are maintenance free and have a larger diameter.
This allows for fine adjustments, even when wearing work gloves
under difficult environmental conditions.
Tribrach Adjusting
Optical Plummet Adjustment Using: Tribrach Adjusting Cylinder or
Tribrach Adjuster
EQUIPMENT NEEDED: Tribrach Adjusting Cylinder or Tribrach Adjuster, Tripod or
instrument stand, 2 tribrachs, target
1. Place the tribrach on the tripod. Put the adjuster in the
tribrach. Place the tribrach to be adjusted on top of the adjuster
so that it is upsidedown looking at the target on the ceiling. The
distance between the tribrach and target should be between 4 and 5
feet.
2. Using the leveling screws of the bottom tribrach, point the
crosshair of the tribrach being tested to coincide with the target.
3. Rotate the tribrach being tested 180 degrees on the adjuster.
Crosshairs will stay on the target of an adjusted tribrach.
4. After 180 degree turn if the crosshair does not stay on the
target, half the error should be corrected with the adjusting
screws provided by the manufacturer of the tribrach. The remainder
should be corrected with the leveling screws of the bottom
tribrach.
5. Repeat steps 2, 3 & 4 until the crosshair stays on target at
all positions.
Tribrach Circular Vial Adjustment Using: Tribrach Adjuster
EQUIPMENT NEEDED: Tripod or instrument stand, Tribrach Adjuster and adjusting pins.
1. Place the tribrach on the tripod and fasten to the tripod.
2. Place the adjuster in the tribrach and level the tribrach using
the vial on the adaptor. Ignore the circular vial on the tribrach.
3. To level the Adjuster: Point one end of the adaptor vial to any
leveling screw and using that screw bring the vial to center.
4. Now turn the adjuster 90 degrees so that each end of the vial is
as close as possible to the other two leveling screws. Using these
two leveling screws, center the vial.
5. Turn the vial 90 degrees back to the original leveling screw and
level again if necessary.
6. Repeat 1,2 & 3 until the vial remains centered at both
positions.
7. To test the adjustment of the adjuster vial at any centered
position, rotate the #2002 180 degrees. The vial should stay
centered within one graduation. If not, take half the error back to
the center with the vial mounting screw that is on the high side.
8. If the circular vial on the tribrach is not centered, use the adjusting screws and bring to center.