| 摘要 |
<p>A sensor assembly (24) is traversed (28) continually across the material (4) and produces a signal at each edge of the material. The signals are then processed in a computer (8) to give an immediate value of the width of the material. The sensor assembly (24) comprises a light source and detector with a reflector placed behind the material (4). Preferred Features: The traversing path extends beyond the material width to produce a uniform velocity in the measuring section. The traverse drive includes an incremental transducer and the traverse speed is calibrated by fixed markers in the path, such as additional reflectors, magnets or proximity sensors. The sensor has a polarizing filter and a focussing arrangement to restrict the beam, e.g. a slit or cylindrical lens.</p> |
