WMF – Germans associate these three letters with quality and elegance of cutlery, cooking utensils, kitchen tools, cutting tools and table and home accessories. Hardly anyone knows that the "Württembergischen Metallwarenfabrik AG", founded in 1853 in Geislingen an der Steige, launched a high-quality coffee machine for the catering industry back in 1927. The coffee makers are still developed and produced in Geislingen to this day. "Our fully automatic coffee machines can be found worldwide in high class hotels as well as on cruise liners, in offices, cafés and bistros", says Ralf Weber, the buyer responsible for sensors.

Sensors for maximum coffee enjoyment
Modern WMF machines are full of electronics to ensure guaranteed maximum coffee enjoyment. "For example, we have to determine the temperatures in the hot water and steam boilers within seconds so that the machine can accordingly reheat quickly and the required degree value can be maintained", explained Ralf Weber. "This is only possible with reliable temperature sensors." Here the buyer believes nothing can top the SONTEC technology. "We initially purchased SONTEC sensors through a system distributor", he recalls. "As they then changed the manufacturer the quality of the sensors supplied nose-dived."
Following market research WMF switched to the original sensor manufacturer. Since then SONTEC has been one of the A-list suppliers of the Swabian firm. For many WMF machines the sensor specialist in Lennestadt produces tailormade solutions made up of sensor, cable, connector and fixing – like WMF, Made in Germany. "In our collaboration with SONTEC we value the company's development expertise and flexibility", says Ralf Weber. For example, SONTEC replaced an NTC temperature sensor, which previously consisted of three expensive rotational parts, with one sensor with deep-drawn sleeve. "This is also tapered at its tip and has a special heat transfer paste to optimise the response of the sensor." In this way a WMF machine can control its temperatures even more quickly.
On schedule delivery and a complaints rate of almost zero are also important to the buyer. No wonder then that the SONTEC orders increase continuously. Whereas the Sauerland company delivered around 23,000 sensors to Geislingen in 2013, last year the number rose to over 62,000, divided between nine different types. SONTEC sensors can also be found in the new WMF espresso machine. For example, an NTC immersion sensor in the autosteam lance, to measure the temperatures of milk and foam quickly and reliably.

The family business VIESSMANN is considered a technological trendsetter in the heating sector and for decades has already been producing heating systems for oil and gas that are particularly low in harmful substances and energy efficient, as well as solar plants, wood combustion systems and heat pumps. Today the corporate group has around 11,500 employees worldwide, the group turnover currently amounts to 2.2 billion euros. The company has always recognised the principle of sustainability - one of six company policies which act as a sort of constitution at VIESSMANN. 

One of the company policies with the title “top quality” additionally describes the in-house expectation for processes and products. As an employee in the Research and Development department,
Klaus-Dieter Arnold has to therefore fulfil high standards when working with solar plants with flat and vacuum pipe collectors: “Since it can reach up to 270°C at midday in high summer on the roof in a solar plant, all installed components should be able to safely withstand 300°C.”

A big challenge for the materials used, for example for the temperature sensors. These inform the in-house control technology which temperatures are currently “coming from the roof” and can be brought into the heat accumulator. “However, if the accumulator is heated up, the heat from the roof can no longer be discharged, and it can reach very high temperatures in the plant,” as Klaus-Dieter Arnold knows. 

The best sensors can withstand 300°C 

For years VIESSMANN have backed the competence of the manufacturer from Sauerland, SONTEC, in high quality special sensors. It was soon clear to the company’s experts that, with the company’s high demands, 300°C could not be achieved with the materials usually used for sensors and wiring. Even for the production of these high-performance sensors new paths had to be taken.

“In the company we began to have long series of tests with various wires,” remembers head of the company Patrick Sonntag. “Moreover our developers and production team searched for the best solution to reliably assemble the NTC sensor to safely connect the wire with the sensor element.” Instead of crimping, SONTEC decided on a welding process that is admittedly expensive but ultimately emerged as the optimum method. “This way proved itself to be the right one,” R&D team member Arnold was glad to report. This was because, according to him, the SONTEC solution did not show any weaknesses even during the tough VIESSMANN tests.

“In over 100 countries worldwide, consumers have a high regard for our company’s products”, says Uwe Dralle, Head of Process Automation at the Hochwald site in Hungen. The raw milk is delivered from eight German federal states between Schleswig-Holstein and Bavaria and from areas close to the border in the Lorraine region of France, in Luxemburg and the Netherlands. It is then processed by Hochwald into a wide range of dairy products. Hochwald, with its subsidiary in the Netherlands and sales and distribution organisations for Belgium and Dubai, also has an international presence. “At the Hungen plant alone, well over a million litres of milk are processed every day into a variety of products which the end customer can then purchase under familiar brand names in supermarkets.” Controlled processes, he explains, constitute for the company the basis for continual optimisation and improvement in the customers’ interest and in the interest of the commercial development of the company. 

Conductivity sensor for good-value-for-money phase and product monitoring

The new conductivity sensor CPS-7 is undergoing test runs at Hochwald; this sensor was designed to detect product changes and for phase separation in plants in the food and pharma industries. It uses the conductive measurement principle in measuring ranges from 1 μS to 15,000 μS/cm, with response times below 0.5 s. Consequently, the CPS-7 performs extremely accurate and reliable measurements even with highly viscous or lumpy media which, depending on the sector, may be present in the plants. It works at 24 VDC and on the output side makes 4…20 mA or PNP signals available.

Owing to its compact design, the sensor can even be used in small pipe diameters of DN25 thanks to a hygienic G1/2”-process connection. Its stainless steel and PEEK casing has no influence on the product quality of the liquids flowing through it. For the CPS-7, the process connections customary in the industry, namely Tri-Clamp, Varivent, ‘milk pipeline fitting’ etc. are available. The sensor is introduced into the product pipeline using a hygienic welding sleeve. The measuring point is constructed exclusively with FDA-approved materials such as PEEK and VA; the process connection is EHEDG-compliant. Also new is the model ICS-8 which, thanks to optimised flow geometry and very rapid response times are ideally suited to phase separation, product detection and measurement of the media concentration in CIP plants.

The sensor offers excellent precision even at low conductivity values or very low flow rates. Its range of measurement lies between 0 and 999 mS/cm.