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Customised sensor delivers a competitive advantage

Customised sensor delivers a competitive advantage

The number and variety of standard sensors appears enormous, and yet factors such as measurement methods, size, performance and interfaces mean that many compromises often have to be made in specific applications. Swiss HVAC valve and actuator specialist Belimo Automation has chosen an alternative that requires no compromises, commissioning a customised sensor solution.

So what prompted the company to commission the development of this application-specific sensor solution? “Having our own sensor frees us from the dependencies and compromises associated with the integration of standard sensors,” explains Andreas Marty, head of product management at Belimo Automation. “Standard sensors might seem cost-effective at first glance, but they present considerable risks – especially for specialists such as Belimo.

“If a major buyer requests changes, for example, manufacturers often respond by modifying specifications and models. This forces us to invest a great deal of time and money in modifying our applications, or we pay for sensor features that we do not need. The situation is similar when it comes to availability. Operating our own sensor production facilities tailored precisely to our needs and requirements not only gives us plenty of freedom but also secures competitive advantages

for us.”

Most people never see Belimo products, and yet they play a crucial role in guaranteeing energy-efficient operation as well as adequate ventilation and air-conditioning in modern buildings. Belimo supplies damper manufacturers with the necessary volumetric flow controllers. Belimo’s core product in the single-room range is the VAV-Compact D3, a neatly packaged electronic unit that combines measurement, regulation and control functions.

The VAVCompact D3 is mounted from the outside on a special air damper. Pressure differences are measured by a differential pressure sensor in the duct segment (a constriction or flow element). The device uses the pressure difference to calculate the current volumetric flow rate, compares it with the target value and uses the motor to reposition the damper blade. Information is transmitted to fan controllers, maintenance systems and monitoring systems via digital interfaces connected to various bus systems.

“This application places very specific requirements on the sensor,” says Marty. “The most important factor is that the unit is installed in the building, amid the labyrinthine network of ventilation ducts. This requires a sensor solution that is extremely stable over long periods, fully calibrated and suitable for all installation positions. Stability over long periods is important for the accurate, long-term reproducibility of measurements as well as resistance to dirt. It is also essential that the sensor and electronics form a compact module that can be easily installed in our housings without taking up too much space.”

For a solution, Belimo turned to First Sensor. The customised First Sensor solution is a flow-based MEMS pressure sensor that connects to the ventilation duct with two robust pressure hoses. The flow channel in the sensor is extremely narrow. As a result, the small quantity of air flowing through protects the sensor unit from contamination. The calorimetric measurement principle employed by the sensor involves a heating element that creates a temperature profile in the medium which is displaced by the air flow. This results in temperature differences at upstream and downstream thermopiles, which are measured in the form of electrical voltage and serve as a means of calculating pressure differences at the sensor.

The electronic assembly with which the sensor is installed features a microprocessor for linearisation and temperature compensation for the signal/pressure curve, including purpose-built electronics and firmware. The entire assembly is produced and calibrated at the First Sensor factory.

“Unlike simple engineering service providers, we also handle series production and services relating to quality assurance,” explains Arne Wollmann, sales manager at First Sensor. “One benefit here is that it allows business models that enable customers to defer some of the development costs to series production later on. In this way, First Sensor takes responsibility and assumes some of the technical and commercial risks of its customers. A second benefit is that because First Sensor offers development and production under one roof, it ensures that quality and design-for-manufacturability aspects are incorporated in initial and ongoing development and that costs can be reduced in series production.”

Marty concludes: “The result of this collaboration is a highly flexible solution that is perfect for us.”

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