Sorting through proximity and distance sensor technology choices
Available teach-ins enable designers to adapt these sensors to specific application requirements. In addition, integrated functions like speed settings, standard and precision measurement modes, and foreground and background suppression mean a single sensor can be used in an array of applications. The sensor series includes four variants, which differ in their operating distances and mounting options.
All objects between the sensor and the sensing distance (set to the background) are detected. To ensure reliable sensing, the background needs to be relatively bright and should not vary in height. When objects are on a reflective surface like a white or light- colored conveyor belt, foreground suppression can improve detection. Rather than detecting light reflecting from the object, the sensor detects the object by the absence of the light reflected by the conveyor belt. Retro-reflective In a retro-reflective sensor, the emitted light hits a reflector, and the reflected light is evaluated by the sensor. Errors can be minimized by using polarizing filters. Stretch films and plastic wrappings that are transparent can interfere with these sensors. Reducing sensor sensitivity can help overcome those challenges. In addition, the replacement of standard IR light emitters with lasers can enable longer sensing ranges and higher resolution. Retro-reflective sensor performance can be improved using a lower- than-normal switching hysteresis. In these designs, even minimal light attenuation between the sensor and reflector, for example, caused by glass bottles, can be reliably detected. SICK also offers a
monitoring system called AutoAdapt that continuously regulates and adapts the switching threshold in response to the gradual buildup of contamination that could lead to failure of the sensing system. Through-beam In contrast with retro-reflective sensors, through-beam sensors use two active devices: a sender and a receiver. Through-beam sensing enables longer sensing ranges. The replacement of IR emitters with laser diodes can further enhance sensing distance while maintaining high resolution and precise sensing.
Background suppression
Photoelectric proximity sensors with background suppression (BGS) use triangulation between the sending and the receiving elements. Signals from objects behind the set sensing range are suppressed. In addition, SICK’s BGS technology ignores highly reflective objects in the background and can handle difficult ambient lighting conditions. Background suppression is especially useful when the target object and the background (like a conveyor belt) have similar reflectivity or if the background reflectivity is variable and can cause interference with detection. Foreground suppression Photoelectric proximity sensors with foreground suppression (FGS) can detect objects at a defined distance.
Fiber-optic
Fiber-optic sensors are a variation on through-beam designs. In a fiber-optic photoelectric sensor, the sender and receiver are copackaged in a single housing. Separate fiber optic cables are used by the sender and receiver. These sensors are especially suited for use in high-temperature applications and in hazardous and harsh environments. Photoelectric sensor arrays The RAY26 Reflex Array family of photoelectric sensors like the model 1221950 enable reliable object detection of flat objects as
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