Quick processing of carrots and onions thanks to reliable measured values

The shortest path from the field to the store shelf leads past automated packaging processes. The compact radar level sensor VEGAPULS C11 plays a decisive role in this at the German agricultural company Gemüseland Schlereth.

The Gemüseland Schlereth farm in Unterpleichfeld, Germany, keeps a close eye on every step from harvest to supermarket shelf. Thanks to its own packaging system and logistics, the vegetables can be delivered fresh from the field to retailers. A mission not without its challenges. Martin Schlereth runs the family business together with his brother: "We have to observe more and more legal requirements. At the same time, we are feeling climate change. Higher temperatures, a greater chance of extreme weather and longer periods of drought are already a reality for us farmers." 

High degree of automation

But customers just want beautiful, tasty carrots. The brothers therefore opted for a high level of automation. In addition to high throughput, this allows them to achieve consistent quality. When it comes to level measurement, VEGA sensors can be found in various places in the sorting, filling and packaging plants. At the center is the compact radar level sensor VEGAPULS C11. Electrical engineer Joachim Hammer is responsible for its automation. When it came time to renew the root sorting and distribution plant in 2019, he asked VEGA's field service to design the facility. There are no off-the-shelf systems in this industry; each facility is built from scratch. And the time frame was tight. "A carrot doesn't care when the processing line is ready. When it is ripe, it has to be harvested. Normally an installation like this takes months; this system was ready within a week," Hammer said.

Level measurements basis for automation

To ensure that the entire system runs smoothly and the individual graders and scales operate without interruption, the plant has numerous conveyors and changeovers with bunkers in between. Everything is controlled by a PLC. "Initially, we tried to measure the level optically. But dust accumulation kept causing problems," Hammer says. Rapid level changes, difficult surfaces, tight space and short distances to the medium also posed a challenge. But level measurement is just crucial to achieve a high level of automation. The problem was solved with multiple VEGAPULS C 11 installed at 1 to 2 m intervals above the chutes, belts and hoppers. "The hermetically sealed VEGAPULS C 11 is very robust, which comes in very handy given the moist clay soil here in the area. It sticks to the vegetables. And then it also delivers reliable and more accurate values," Hammer summarizes the plus points. 

Reliable measurement, quick connection

Not only do radar sensors operate independently of temperature fluctuations, vacuum and high pressure, they are also insensitive to contaminants. The new VEGAPULS series additionally measures at 80 GHz and therefore has very good signal focusing to better separate measurement and interference signals. Another plus: compactness. "You build a system like this the way you need it. So in tight places, we were only too happy that the sensor is so compact," Hammer admits. The small size comes from the new radar microchip, which is distinguished by a very small size and low energy-
need. Both the sensors and measuring amplifiers can be conveniently set up via bluetooth on the smartphone or tablet. Based on the positive experiences, the plant for onion processing and packaging was also tackled. Although slightly smaller than the carrot line - only six VEGAPULS C 11 were needed - onions create a lot of dust in the plant. The sensors must therefore be insensitive to fouling.

Always the right support

Although the VEGAPULS C 11 is very interesting in terms of price, this argument alone was not decisive for Hammer. "I find it much more important to have a direct contact person who also visits the site from time to time. As a rule, level measurement is only a small part of the overall installation. I can't know every sensor in detail, so it's good if the manufacturer is there quickly when you have questions." An argument Schlereth confirms, "The communication through our electrical engineer was good. The same was true of the quick and helpful advice on the various possible applications." Schlereth is sure that when facilities need to be modernized or new construction is required, the company will contact VEGA first and foremost when questions about sensors arise.