Rim and Face
A rim-and-face system comes complete with two dials that are placed on each of the shafts. One dial is affixed with a rim and an indicator and another indicator is attached to the rod. Readings determine the position of the face relative to the rim as the shaft rotates and discrepancies are alleviated by applying pressure to the shaft.
This system uses a similar dials system, but the readings are calibrated with neutral values that would be set by an aligned shaft. Readings are taken after the dials are rotated 0, 90, 180, 270 and 360 degrees and discrepancies from the neutral values are fixed by applying pressure in a corresponding direction of the shaft.
Many machines are now computerized and have sensors that send information regarding the shaft to a processor that reads the information and determines any misalignment. A continuous automatic system provides constant data and can provide regular adjustments.
Laser systems are the most accurate and provide the most precise readings regarding shaft alignment. A laser is bounced off the shafts' rotors and reflected to a sensor connected to a dial, which reads the reflected laser light, giving measurements that indicate their alignment. The connection is then adjusted in the same fashion as other alignment methods.