An American beverage producer conducts a final, pre-shipment check on all cases of bottles after the corrugated cardboard case has been sealed. Product integrity is verified by detecting bottle caps through layers of cardboard at the top of each sealed case.


  • Cost effective solution
  • Non contact / non-marring of packaging
  • Eliminates shipment of damaged or soiled product
  • Long performance history


  • Long operating distance (3x standard value)
  • Easy mounting and adjustment
  • Secure distance between moving object and sensor
  • High switching frequency
  • Excellent sensing stability, even with small and thin targets


The packaging of bottles into a corrugated cardboard case with hot glued flaps requires verification of placement and verification of bottles to confirm quality and quantity. A flawed bottle may have broken on impact with the bottom of the case, presenting a risk of contamination to machinery and subsequent packages. Bottles may be wrongly positioned or absent. A cap may be missing. Not having the ability to visually inspect the closed package demands an alternative approach.

A missed placement or shattered bottle is an indication for pack rejection that can be identified by the absence of a bottle cap in a specified position. In a relatively high speed packaging process, the challenge is therefore to detect caps through multiple layers of corrugated cardboard material of varying thickness and density, while interfacing with the controller that makes the logical decision to accept the package or reject and divert.


Basic range inductive sensors from the Extra Distance family (series 500), with operating distances 3x the standard sensing range, meet this challenge. A sensor bridge is built over the travel path of the cardboard cases. For each lane of bottles in a case, one 30 mm diameter inductive sensor is mounted on the bridge. The 30 mm non-embeddable sensor is chosen as it most closely equates to the size of the bottle cap and yields the greatest sensing distance for the available target area.

The extended sensing distance is sufficient to allow for minor variations in the height of the case as it passes under the sensor bridge. This not only ensures reliable sensing, but also keeps the sensor at a safe distance from any impact, avoiding consequent downtime. Some caution needs to be observed in mounting and spacing of the sensors so as to avoid the possibility of mutual interference (cross talk).