TABLE OF CONTENTS The laser, when employed in the manner of commercial alignment fixtures, is a radial displacement-measuring device, as are dial indicators and electronic gages. The dial indicator, however, is a direct mechanical indicator of a mechanical parameter. The electronic gages have an energy conversion of mechanical to electrical; hence, calibration becomes more important. The laser deals with three physical phenomena light, mechanical, and electrical energies, and the measurement process becomes much more abstract. Calibration of the measurement system is critical to have any confidence at all, and, as will be explained later, some do not have much confidence in the laser. Lasers measure misalignment indirectly, through three levels of abstraction: various energy conversions, the reverse-indicator method, and computerization. Figure 18.1 shows a laser-alignment system set up across a coupling.
The laser-alignment systems have brought a high degree of automation to the measurement and calculation portions of the task. They were first introduced in 1985, when computer technology was mature, and the computer was integrated into the basic process. The measuring devices using a laser are relatively new, but the method is the same old reverse-indicator. In fact, all laser-alignment systems use only the reverse-indicator method and are incapable of doing face-and-rim or other variant methods. Therein lies their weakness: lasers are limited to common alignment tasks using one method only. Virtually all plants that have purchased laser-alignment instruments have found it necessary to keep their dial-indicator systems...
