Mr. Elter, the proximity switch has a long history at Pepperl+Fuchs. What was the decisive factor for the latest development?

Johann Elter: We have a long history in this technology, and this history means that we had a large number of products at different technical levels - some outdated, some up-to-date. Due to the lack of uniformity, this inventory was difficult to maintain - a reason for us to consolidate the whole thing, combine it sensibly and at the same time increase customer benefits. To do this, we looked at which technologies were dead ends and which were promising. We combined the promising ones and at the same time developed the technology further - in line with the customer requirements of recent decades, such as an extended temperature range or high switching frequencies.

Can you give a few specific examples?

Elter: Above all, we want to serve customers who are pursuing unusual solutions with our sensors. For example, the sensors can now be operated directly at 5 V, which is completely new compared to the previous products. This was triggered by a company that we supply with sensors for their 3D printers. Here, the sensors have to be operated at 5 V. Such requests come up again and again.

Proximity switch for reliable detection of highly dynamic objects.

© Pepperl+Fuchs

Another important feature of the new portfolio is that the product family has consistently high switching frequencies. These always play a role when highly dynamic objects need to be detected - in conveyor technology, for example. It is also advantageous for speed detection if the sensor has a high switching frequency.

Another important feature is the temperature range: some customers use the sensors on forklift trucks that drive in and out of a cold store. Here it is -25 °C inside, while the blazing sun shines outside. Corrosion resistance is also important in such applications: outdoor use means high stress for sensors as they weather very easily, so a robust coating is essential here. We have therefore chosen a white bronze housing coating for these cases. When it comes to chemical loads, such as those caused by cleaning agents, we still offer our well-known plastics.

What other technical innovations are market-driven?

Elter : Our previous projects were sometimes difficult to adapt to customer requirements. One of our goals was therefore to achieve greater flexibility - among other things, by being able to generate variants very quickly. The automated configuration with a large number of possible variants helps us here: Previously, we had to modify each variant individually and create the corresponding structures, had to ensure that the relevant verification documents were available for each component, et cetera. An enormous amount of work! Furthermore, there was no uniform technical standard.

The new generation of inductive cylindrical standard sensors.

© Pepperl+Fuchs

Our completely new portfolio complies with the latest versions of the relevant standards and is state of the art. We have also improved the performance of the sensors. In addition to the electronic features I mentioned, there are also purely mechanical factors where we have set ourselves higher quality targets that even exceed the standard.

To what extent has the quality of the mechanics improved?

Elter : In terms of mechanics, we now have a uniform design with the aforementioned white bronze coating instead of the previous nickel coating, which offers us significant advantages both in terms of sensors and corrosion protection. In addition, our standard sensors now already meet IP68, and sensors with IP69 are available for higher requirements.

The Pepperl+Fuchs green end cap on the cable sensors with a clearly separated, transparent LED window is externally and directly recognizable for customers. The size and brightness have been significantly improved so that the LED is clearly visible from all sides.

What other features are characteristic of the new portfolio?

Elter: Instead of the usual printing, we have robust laser marking on the housings. The previous sensors were mainly printed on the front surface, which is often difficult to access in customer applications and therefore difficult to read.

Another point is the different length variants in the portfolio, which allow us to quickly generate customer-specific sensor lengths. We can quickly generate different length variants in 5 mm increments as we have developed extremely compact electronics. The entire production concept is very flexible.
One aspect that should not be underestimated is that the shorter response and development times have eliminated a previous competitive disadvantage, especially with our Asian customers! In principle, customer inquiries are always about speed. But while Europeans are patient and used to waiting, Asians expect a solution on their desk within two weeks. That's why our sales representatives in China, for example, always have to explicitly point out when they show the customer a sample that it's just a sample and not a ready-to-use series product that will soon be available. It is difficult to explain that all our testing and certification measures are responsible for the delays. Thanks to our new processes, customer variants can now be produced and delivered much faster. Apart from exotic products - which would be feasible for us - we can produce all housing lengths from 30 to 70 mm. The typical Pepperl+Fuchs lengths were always the classic 50 mm, like the competition. Then came the short 40 mm housings, and that was it. We have significantly expanded the portfolio upwards and downwards.

Where do you see the future of inductive proximity switches, also in the context of Industry 4.0?

Elter: We are currently developing a generation of sensors that will serve Industry 4.0 - a solution based on the same mechanical concept with IO-Link. However, the inductive sensor in its current form will by no means die out, as demand is still very high and is in fact currently tending towards classic sensor technology. Not every customer wants to deal with digital communication or has the need to integrate digitalized applications into their production. Quite a few of our users are electrical system installers, for example, who want to screw on the sensors and set the switching point by screwing them in or out.

Johann Elter is Team Leader Development for Customer Applications & Lifecycle in the Innovation Unit Electromagnetic Sensors at Pepperl+Fuchs in Mannheim.

© Johann Elter

Furthermore, the sensors must signal reliably: One of our customers manufactures wind turbines and wanted to measure the wear on its pitch bearing in the generator using an analog signal. We offered to supply the signal digitally via an IO-Link interface. However, the customer preferred to receive the raw signal and evaluate it using his own algorithms. Intelligent sensors are not required here, as the intelligence is in the controller.

The steps we have taken so far - new coating, new materials, better visibility of the LED - show the way. There probably won't be a major revolution in this design - ultimately we are dealing with a cylindrical sensor with a threaded sleeve. But it will continue on the path we are on now - as an evolution.