Ball Prism System
Precision Ball prism
The stainless steel ball prism is a precisely manufactured steel ball with a triple prism mounted very precisely in the center of the ball.
Outer ball - Ø1.5“ (38,1 mm), Prism constant: K= -16,9 (Leica = +17,5) mm
The triple prism with its centrally symmetrical point (= visible prism center) is ideally located in the center of the steel ball. If the prism is inaccurately aligned with the total station, only the smallest inaccuracies will occur.
Accuracies The diameters of the balls are manufactured with an accuracy of ± 0.05 mm. Other geometries, such as the position of the prism center to the ball center, height offsets and centering fits, have an accuracy of ± 0.1 to ± 0.2 mm.
Centering base with integrated magnet
On the cylindrical ball base with cone-shaped upper part, the ball prism comes to rest in a force-centred position and can be aligned in all directions over a 180° range. The steel ball is kept reliable in the base by an integrated permanent magnet. The point indicated by the visible prism center is always exactly on the center axis of the base and has a distance (height offset HO) of 30.8 mm from its underside.
This ensures the highest accuracy for repeated measurements.
Four notches
• for staking out points. After determining the correct position, the four notches are marked. After removing the base and connecting the respective diametrical markings with ruler and pen, the target point is staked out quickly and precisely. The thickness of the pen can be selected according to the accuracy requirements.
• for measuring points. For this purpose, a cross line must be drawn over the point to be able to be measured. The centering base is then positioned using the notches and the position of the ball prism is determined. If the base is used on horizontal surfaces, an exact height is also obtained. For this, the height offset of 30.8 mm in the Z coordinate must be taken into account.
Centering plate for Centering Base with integrated magnet
For a variety of monitoring tasks or control point surveying it is not necessary to permanently equip each point with a prism. If the observation points are easily accessible, it‘s often enough to attach centering plates before doing the measurement.
Only during the measurement itself is the ball prism (together with the magnetic base) inserted into the centering plate and aligned and force-centered.
Instead of the centering plate, the base can also be attached directly to the object point. This can achieve a further increase in accuracy. With a centering plate, exact repeated measurements can be carried out at the same point - over many years. Particularly with a large number of points to be checked, it is much cheaper to attach centering plates to the object. Depending on the surface, they are screwed on or glued on (non-destructively).
Ball base with integrated magnet and thread connections
• The distance of the ball center from the base underside to the center of the prism is always exactly 50 ± 0,1 mm (without thread)
• All bases are shipped including cover plate for protection against dirt
Centering Pin
Instead of or in addition to the 4 notches, a centering pin can also be used to stake out or measure the points.
• Stakeout of points. After correct positioning, the ball is removed. Use the pin to mark the point to be staked out with a light hammer blow, if necessary.
• Measuring of points. Using the centering pin, the base can be placed at a point that is already marked on the object (e.g. cross, grain).
Accessories
Ball prism Ø 1.5“, K = -16,9 (Leica = +17,5) mm, stainless steel (ID 1445.S)
Base for ball prism Centering Base (Product ID 1458.A)
Centering plate for base, to use with adhesive or to screw onto object (Product ID 6009)
Centering pin Ø 5 x 100 mm, stainless steel, hardened tip (Product ID 1458.ZS)
Base for ball prism, inner thread 1/4" (Product ID 1466.14)
Base for ball prism, inner thread M8 (Product ID 1466.08)
Base for ball prism, inner thread 5/8" (Product ID 1466.58)
Base for ball prism, inner thread 1/4" x 8 mm (Product ID 1466.14a)
Base for ball prism, inner thread M8 x 8 mm (Product ID 1466.08a)
Base for ball prism, inner thread 5/8" x 11 mm (Product ID 1466.58a)
Note
When placing an order, please include the product IDs for accessories needed to create a ball prism system.