HAMAR LASER L-708, Operation Manual

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8
Model A-512 2-Axis Self-Centering Target
Hamar Laser has developed the world's first self-
centering target (A-512) that uses no moving
parts. It takes just seconds to position the target
in the bore for an accurate measurement down to
.0005 in. (0.0127 mm). The target is designed so
that the PSD, ( position sensing detector ) a piece
of silicon that detects the center of energy of the
laser beam, is centered axially between the four
feet of the adapter, two of which are offset
axially from the other two. This puts the PSD on
the pivot point of the adapter and allows the
angle of incidence to the laser beam to vary by
up to 45 degrees. The A-512 takes advantage of
this property by making the adapter slightly
larger than the bore. To insert the target into the
bore, attach the insertion handle (see Mounting
the Laser/Adapter and Inserting the Target on
Page 19).
The A-512 Target unit is comprised of a target cell, a bore adapter, and an insertion handle (see Figure
5). The target is inserted into the bore to sense the position of the laser beam. Laser beam position data is
displayed on a readout. As the bore is adjusted, the readouts display data in real time.
The A-512 target and adapter (in self-centering mode) are inserted into the reference bore. A
measurement is taken with the target in both the NORMal and INverted positions (see Appendix A – The
NORMIN Method beginning on Page 23). The two readings are averaged and the result is the starting
measurement for the laser. At each subsequent measuring point, two sets of readings (NORMal and
Inverted) are taken and averaged. Subtract the result from the reference measurement to obtain the
diameter change.
The target cell is a position-sensitive photo cell surrounded by a stainless steel housing. When light
contacts the photo cell, the continuous flow of current across the cell is altered. The location of the
contact is recorded as a change in voltage, which the digital readout or computer interface displays as an
offset from the target center. The effective cell sensitivity range is ± .100 in. (2.5 mm), and changes in the
x and y axis positions of the target can be displayed on a digital readout to within .0005 in. (0.0127 mm)
over 50 ft. (15 m).
The target cell has a milled keyway designed to slipfit onto a location pin in the bore adapter for self-
centering mode. Four matched and offset (90°) stainless steel legs serve to center the adapter in the bore.
Adapters are available in many different sizes for use in specialized bores.
Figure 5 –
A-512Target with A-514A Small Bore Self-Centering Bore
Adapter