Central processes in the IIoT environment involve the generation, transportation and processing of information. All information is based on intelligent sensors: They collect status information directly on site in machines and systems in real time in order to create a virtual image of the physical world. They also collect a large amount of secondary data. In addition to the pure switching signal via IO-Link, smart optical sensors also provide valuable information on the sensor status or the current ambient conditions.

Balluff, for example, has an 'all-rounder' that works with red light and allows a choice between different sensor modes: Background suppression, energetic diffuse sensor, retro-reflective sensor or through-beam sensor. These sensor principles are the most commonly used in optoelectronic sensors worldwide. This provides additional flexibility in production, as the sensor principles can be switched at any time, even during operation. This means that completely different objects can be reliably detected under changing operating conditions. Storage is also simplified as the sensor combines four sensor principles in one device.
Replacing sensors is also straightforward with components of this type, as the parameter sets can be updated and uploaded at any time via IO-Link. Intelligent sensors work together with IO-Link and use central data storage to save users the hassle of manual adjustment on site. The functions can be configured via IO-Link so that a remote teach-in can be triggered via the controller.

The 'BOS 21M ADCAP' multisensor offers a choice of four sensor modes: background suppression, energetic diffuse sensor, retro-reflective sensor or through-beam sensor.

© Balluff

The additional data generated by intelligent sensors can be used to implement smart maintenance concepts and thus significantly increase system availability. For example, an operating hours counter is often integrated as an important tool for predictive maintenance. Thanks to additional smart diagnostic information, increasing soiling, sensor misalignment, setting errors or other irregularities can be reliably detected at an early stage.

Diagnostic aid for light remission

Four sensor modes and an extensive portfolio of functions combined in just one sensor.

© Balluff

In many applications, the light emission values are helpful - for example, when the ambient conditions inevitably lead to increased sensor contamination. If these values are made available as raw data via IO-Link, they enable trend analyses, for example, in order to optimize maintenance intervals and adapt them to actual requirements.

The production of car tires provides an illustrative example: if the transport of the tires, which are still hot after vulcanization, comes to a standstill due to a dirty sensor, the tires slip on top of each other, resulting in expensive rejects. At the same time, production comes to a standstill until the conveyor belt is cleared. In the worst case, promised delivery quantities cannot be met. Sensors such as the 'BOS 21M ADCAP' from Balluff, which offer a corresponding diagnostic option, therefore quickly pay for themselves in such a case: thanks to the light emission values, the system operator knows the degree of contamination of each sensor and can arrange for cleaning before production comes to a standstill.

In the same way, the light emission value makes it possible to continuously monitor the quality of the sensor signal. Time and again, vibration or other external influences cause the mechanical alignment in the systems to creep out of alignment. In the long term, this leads to a reduction in signal quality and therefore also in the reliability and precision of object detection. Until now, there was no way of detecting and evaluating this gradual deterioration. Although sensors with a preset threshold value report when the amount of light received becomes too low, they do not offer the possibility of deriving a trend from the raw data and carrying out a quantitative and qualitative evaluation of detection reliability.

Monitoring the transmission LED

Stefan Hornung is a portfolio manager at Balluff in Neuhausen.

© Balluff

The power of the emitting LED can also be directly monitored optically. For this purpose, there is a monitor diode inside the opto-sensor that continuously records the amount of light emitted by the emitting LED, unaffected by external influences. The resulting intelligent evaluation of the transmission power can be queried as a percentage, but is also displayed clearly and concisely by a three-stage 'traffic light'. This prevents malfunctions and thus also reduces machine downtimes. Critical operating states can be counteracted in good time due to the inevitable ageing of the LED.

Similarly, the internal sensor temperature and the supply voltage are monitored as so-called 'stress levels'. Both parameters allow solid conclusions to be drawn about the load status of the sensor and therefore also about the risk of failure. As the detection signals are already pre-processed in the sensor, the intelligent sensor also helps to reduce the load on the higher-level control system and simultaneously reduce data traffic on the fieldbus.