Survey Instrument Motorized Total Station Tribrach GDF121

Product Specification

GDF121 Leica Tribrach without Optical Plummet For Total Stations

Model: GDF121

Specifications:

Torsional Stiffness: <1"

Weight: 780g

Features:

1. High Accuracy
2. Maintenance Free
3. Individually Tested
4. Suitable for all high angular accuracy requirements.
5. Torsional stiffness <1"
6. Weight: 760g

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.