Presence Check of Nonwoven Fabric on the Bottom of Coffee Capsules with Contrast Sensors
In order for hot water in coffee machines to be pressed evenly through the coffee capsules and thus ensure a uniform taste, the capsules must each have a white, wafer-thin nonwoven fabric at the bottom and at the top opening. Contrast sensors are installed above the multi-lane conveyor belt to check the presence of the lower nonwoven fabric before the filling process. The sensors look vertically from above at the lowest point of the capsules and detect the fine contrast between the capsule base and nonwoven fabric.
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Contrast sensors with switching or analog output measure the brightness of objects. Sensors with switching output compare the brightness level with a reference value in order to detect contrast marking, for example. Sensors with analog output provide the measured brightness as a proportional voltage signal in order to monitor brightness curves, for example.