Analog inductive sensors check presence of cans in cardboard box


A Japanese manufacturer of canned products uses inductive sensors with analog outputs in the packaging department to check that closed cartons have the required number of cans inside. The sensor’s analog output enables it to process different can sizes and materials in a final pre-shipment quality check for a range of product types.

Customer Values

  • A single solution to check different can types
  • Reliable quality of deliveries
  • Direct interface to a controller (0 – 10 VDC or 4 – 20 mA)
  • Long service life
  • Simple installation
  • Non-visual solution

Specific Product Advantages

  • Analog output with direct interface to controller (0 – 10 VDC or 4 – 20 mA)
  • Long sensing distances compared to market standard
  • Excellent temperature stability
  • Very good repeating accuracy
  • Sensing range up to 40 mm
  • Resolution in µm range
  • Current and voltage outputs in same device
  • Several switch points with a single device

Customer Application

Canned products are fragile, easily crushed or pierced. They are protected during delivery by being tightly packed into sturdy cardboard boxes. However, this packaging process may itself damage the cans if a fault occurs and, once the box is closed, there is no longer any possibility of a final visual check.

To eliminate product faults that may have occurred during upstream processes, the customer seeks a means of verifying product quality inside the box. The solution chosen must be able to deal with all canned products in the manufacturer’s delivery range, comprising cans in different sizes and materials. This is not possible with an ordinary on-off switching sensor output. The verification process must also be integrated into a fast-moving automated packaging and pre-shipment line, accepting or rejecting each carton instantly.

Customer Solution

Analog inductive sensors from the 509 Series are ideal for this application. Their Condist® oscillator technology ensures excellent environmental stability – especially to temperature – and so allows operating distances up to 3 times the standard (in this case 40 mm). The extra distance enables them to obtain a good signal not only through multiple layers of cardboard, but also from different conductive metals at varying distances, depending on can type.

The customer has mounted inductive analog sensors on two conveyor lines. By mounting them both above and below the passing lanes of cans, the double layer of cans in each carton can be checked through the box. Size M30 was chosen to yield the greatest sensing distance for the project parameters.

The continuous output from these sensors is connected directly to a PLC with a high-speed analog input card. Resolution is in the µm range and repeat accuracy is very good. The solution is durable, adaptable, reliable and simple to install.