Ten green bottles

For a sensor manufacturer, the specific requirements can be translated into terms such as surface finish, compatibility with foodstuffs, effective sealing, resistance to temperature and corrosion, and general functional safety.

Guidelines for the objective inspection of characteristics are published by independent institutions such as the EHEDG (European Hygienic Engineering & Design Group). These institutions are also responsible for monitoring the conformity of products with these specifications and issuing the relevant certificates of compliance. This activity is supplemented by ECOLAB tests, where compatibility with cleaning and sterilization products are the key concern.

The 1.4404 grade stainless steel is roto-finished to achieve a surface roughness of Ra <0.8. This fulfills the requirement that no microbiological contamination should occur even if the sensor comes in contact with the product during the process, so that the highest hygiene standards can be met.

In beverage filling systems, incoming and outgoing bottles must be continuously counted regardless of the material and type of liquid. At the outlets of PET bottle blowing machines and bottle washing machines, individual bottles are detected in order to ensure material flow.

The benefits of ultrasonic sensors are readily apparent. Regardless of colour and surface, an object can be detected with millimetre precision. Dust and dirt do not have a detrimental effect on the measurement result. The high-frequency vibration of the ultrasonic transducer surface simply shakes off any dirt.

An ultrasonic transducer, which is essentially the combination of piezoceramics and an acoustic adaptation layer, is stimulated in transmission mode by a high-frequency burst packet or single current pulse. The transducer then operates as a microphone. The received acoustic pulse creates a millivolt-level signal at the piezo that is then converted to a distance value by the microcontroller. In this operating mode, the strength of the received signal has no bearing on the measurement.

Individual detection of conveyed bottles is normally too fast for sensing by standard ultrasonic sensors. The bottles pass the sensor too quickly and the gaps between the bottles are often too small. For this reason, ultrasonic thru-beam sensors are used for bottle counting.

Detecting and counting the bottles at several points in the machine ensures the continuous monitoring of material flow. The entry and exit of bottles in the filling system is optimised and missing bottles in the chain are reliably detected. The use of hot steam and chemicals for machine cleaning requires ultrasonic thru-beam sensors with a high degree of chemical resistance. The IP degree of protection should be at least IP68/69K.

In the Pepperl+Fuchs range, the UBEC300-18GM40-series is particularly suitable. In machine areas not affected by cleaning cycles, it is possible to use standard ultrasonic thru-beam sensors such as the UBE1000-18GM40-series.

Because the ultrasonic sensors recognise even the most difficult materials, transparent glass or plastic bottles are reliably detected.