Grundfos: Direct Sensors – the sense organs of the pump

grundfos DirectYou can only change what is accessible by measurement – whoever wants to control a process flow of a pump needs reliable current data on the one hand, and on the other, possible intelligent linking and interpretation of this data: Sensors deliver data, microchips have stored software to interpret this and actuators implement the commands. To also offer technical benchmarks, the pump manufacturer Grundfos maintains well-equipped own research and development departments, finance and personnel dealing with motors, frequency converters, sensors, microchips and their programming.

The ‘Direct Sensor’ development is a micro-mechanical semiconductor sensor (MEMS, Micro-Electro-Mechanical System), which is produced in its own wafer fabrication facility of purity grade 10.

The 2-in-1 sensors detect the flow rate, the pressure or the differential pressure and at the same time generate a temperature signal. What is so interesting: Through the simultaneous measurement of the temperature, their influence on the pressure measurement can be corrected directly. The measurement signals are calibrated and processed by means of a microprocessor, which are then available as an analogue or digital signal for a control or a SPS.

For industrial usage Grundfos has developed the IDS series (Industrial Direct Sensors). These sensors (VFI flow sensors, RPI/RPI+T pressure sensors and DPI/DPI+T differential pressure sensors) are particularly distinguished by these properties:

  • Robust design in stainless steel for industrial use
  • Advanced specification regarding temperature range, pressure resistance and protection type
  • Industry signals 4-20 mA or 0-10 V standard power supply 13-30 VDC
  • Extended measuring ranges for flow, pressure and differential pressure.

The area of application of the VFI flow sensors (Vortex Flowsensor Industry) was extended in DN 100, for example, with ranges up to 240 m³/h.

The special innovation is the ‘direct’ measurement on a silicon chip. Unlike conventional sensors, which are either elaborately encapsulated or exposed unprotected to the medium, a non-porous surface coating of amorphous metal glass provides a permanent protection of the sensor chip (‘Silicoat technology’). This new technology makes a very compact design possible by waiving the encapsulation, which also results in an excellent price/ performance ratio. The almost direct contact with the medium also ensures fast response time, accurate measurement, high bandwidth and high repeat accuracy.

Conclusion: The five senses (sight, hearing, smell, taste, touch) have in pump technology an equivalence as it were: Flow, pressure, differential pressure, temperature and humidity are important parameters that can be detected by means of suitable sensors for the design and safe operation of a pump.

Because you can only rely on technology which you can permanently monitor. The same applies to pumps: The constant monitoring of the actual state of pumps helps the operator to detect unauthorised operating conditions – this reduces wear and damage and extends service life. Last, but not least a controlled operation saves electrical energy; in the sense of the energy revolution this is an important point.

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