Many industries use foil wrappers to package products. For quality control, it is a good idea to have a system capable of automatically detecting when the contents of those wrappers are missing. Some companies use human beings to manually pick and choose wrappers, which is tedious, and not very efficient. There is a solution that really works; infrared photoelectric sensors.
Position one set of infrared photoelectric sensors in a through-beam configuration, so that the foil wrapper will move between the sensors at a given point. Adjust the sensitivity of the infrared photoelectric sensors so that they will detect the foil wrapper whether it is full or empty. The sensors should be at their most sensitive setting for this. The output from this set of sensors will report to the PLC to let it know when a foil wrapper is present.
Position the second set of infrared photoelectric sensors beside the first set, also in a through-beam configuration and facing the same direction. Be sure that the sensors are set to different frequencies to avoid cross-talk between the two sets. This set of sensors should be adjusted to its least sensitive setting. In other words, crank the gain setting to the max. Assuming that the photoelectric sensors being used are industrial grade, they should be able to see through an empty wrapper easily, but not one containing product. This set should also report to the PLC.
Now, you have two infrared beams of light striking the foil wrapper as it passed. One is used as a reference to let the PLC know when a foil wrapper is present. The second set of sensors lets the PLC know when a foil wrapper is missing its expected contents. This system is very reliable and is in use at a number of companies worldwide.
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