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Sensor Solutions for Harsh Environments
Srinivas Rajkumar Grundfos Direct Sensors TM is a result of a huge effort within applied physics and material science at Grundfos since 1992. In 2005, the first Grundfos Direct Sensors™ products based on the proprietary coating, SiliCoat® were launched in world markets.

In 2008, Grundfos Sensor A/s was extracted from Grundfos New Business activities and a separate business unit was established to facilitate the continued aggressive growth rates of the business unit. These coated sensors are called Direct Sensors TM as the protection enables the sensor to measure the process media directly, without any intermittent layers of oils or gels, which gives a fast temperature, pressure or flow response. The direct contact (wet or wet-wet) with the media secures a very sensitive sensor with a fast response on flow, pressure and temperature with excellent repeatability.

Innovation is the Essence
It all started with an internal requirement at Grundfos for a suitable sensor way back in 2003. Tina Romedahl, development engineer at Grundfos, clearly remembers the reaction when telling the then deputy of the Department of Micro-technology at the Technical University of Denmark about an idea she and some of her colleagues had: to invent a protective material only 1µm (1/1000 mm) thick, which would make it possible to build a pressure sensor that was small enough to be built into small pumps and cheap enough to become a special offer. That was in the early 1990s, and the deputy had obviously forgotten that the Grundfos Company had been founded on the notion that if a product or spare part could not be purchased, you would develop and manufacture it yourself. In 1990, Grundfos had launched a small, highly sophisticated frequency converter, but if it was to be used as a control unit it needed something to control from, e.g. pressure or temperature, and a pressure sensor needed to be equally small, sophisticated and cheap. The problem was that the pressure sensors of that time were large, clumsy and very expensive. Hence the wish for a micro-sensor which formed the basis of what we see today at Grundfos Sensors.

Tina Romedahl consulted with two authorities within this field: Karsten Dyrbye had written a Ph.D. dissertation about metal glass, and following his Ph.D. degree, Gert Friis Eriksen had worked with silicon. Those 2 materials were the core materials of the development project. Silicon, which is the actual sensor, must under no circumstances come into contact with water. At that time large metal housings, steel or rubber membranes and oil were therefore used to protect the sensor and the sensor was expensive because of the material encasing it. Silicon is available in large quantities and suitable for the mass-production of inexpensive sensors. If it were possible to identify an inert material that could be placed on top of the small silicon chip, like a film, you would have an inexpensive micro-sensor.

The Real Challenge
How do you prove that a microthin protective film which will be completely resistant to media for a minimum of 10 years? “From time to time things looked hopeless,” says Gert Friis Eriksen. “But our courage never failed us, also because we had the support of the top management all the way through.” Although the silicon chip was developed within a few years, it attracted very little attention in Denmark. Nobody at the technical university seriously believed that it was possible to create a film that was thin enough to protect the chip. The requirements to the tightness of such a film are so extreme that it was difficult to envisage how the desired result could be obtained. One experiment followed the other. For a long time, progress was limited, and for several years the three engineers were the only ones who believed that they would succeed. Small victories along the way kept their spirits high, like for example when they had tested an O-ring used to seal the protected and unprotected parts of the sensor and found out that the material properties did not alter.

Simple but True!
"Things looked really bright then," says Gert Friis Eriksen. When the rumour spread that they were using O-rings, many people shook their heads in wonder. One of the lecturers at the Department of Micro-technology expressed in words what everybody was thinking:”What you do is so simple that it cannot be true!” But the Grundfos engineers continued their steady work, as they knew that they were going in the right direction. "We had never aimed at anything fancy," says Gert Friis Eriksen. ”On the contrary, we wished to make it as simple as possible using as many well-known technologies as possible.” And O-rings were wellknown to Grundfos – although the company had never before used an O-ring measuring less than ˝ cm in diameter. Once the first sensor covered with the metal glass film had been produced and proved to work, the victory was celebrated with champagne and cake. The laughing deputy had long fallen silent. At that time Grundfos had patented the film protection, had acquired clean room facilities in the Danish town of Farum, and were busy assembling production equipment for the sensor production. The silicon chip is manufactured and the film applied at Farum, before the chip is sent to Bjerringbro, where it is built into various sensor models. The sensor fulfils 4 different tasks: it measures differential pressure, flow, relative pressure and temperature. Tina Romedahl, who heads Grundfos’ development of industrial pumps, no longer works with sensors. But her heart beats warmly when thinking back on the years when the idea of the micro-sensor took shape. She keeps a model of the sensor as a souvenir reminding her of a fruitful working relationship developing a unique product. No looking back for Grundfos Sensors from thereon, with current work force of around 70 people working on this innovative platform, we at Grundfos are committed towards bringing a cost effective sensor solutions to the Industry. Grundfos has invested over 100 million Euros in material sciences to live up to the commitment. With the use of MEMS (Micro-electro Mechanical Systems) silicon sensor technology and developing a patented amorphous coating, Grundfos Direct Sensors TM has introduced a unique, new intelligent and robust range of sensors to measure Pressure, Differential Pressure, Flow and Temperature.