摘要 |
A method and apparatus is provided for determining workpiece drift from its nominal or intended position. The apparatus includes two proportionate sensors 19, each of which gives an output reading that depends upon how much of the sensor beam 24 is blocked by an edge of the workpiece 30. A computer can calculate positional drift based upon these readings. Also disclosed is a method for aligning proportionate sensors 19 to be parallel to one another. |