Traditional timeof-flight sensors use a photodiode to detect laser signals bouncing off an object to detect the distance between the sensor and the object.
But such sensors are expensive, large, and not well suited for industrial environments. The efector pmd laser sensor from ifm effector inc., Exton, Pa. (ifmefector.com), however, combines the detector and electronics on a single chip called the photonic-mixer device. This makes the 42 42-mm device smaller and less expensive. The sensor uses a visible red Class II laser and features extraneous light suppression, which lets it be used as a background suppression sensor. Dual switch points let operators monitor an object's position in continuous processes, such as web monitoring. It can also be programmed to output two signals that activate at preset distances or to output an analog signal that indicates the diameter of a roll being measured. A four-digit display shows distance to within a few millimeters.