[IT]

Melt Pressure
Transducer and transmitters

Gefran patented:

IMPACT sensor technology

IMPACT is the acronym for Innovative Melt Pressure ACcurate Transducer, an innovative technology for measuring the pressure of high-temperature fluids.

Topics


Pressure measure at high temperature presents some typical challenges that must be overcame by the technology.

The traditional technologies for high temperature pressure measurements are based on a transfer by a fluid of the measured pressure from the process at high temperature to a measurement point at room temperature.

In the traditional technology the main aspects are:
  • The sensing element designed to have predefined deformation in specific area where a foil strain gauge is bonded to convert the mechanical stress into an electric signal
  • The contact diaphragm designed to transfer the pressure of the media to the filling fluid
  • The fluid that must have very low compressibility factor and very high boiling point
The limits are:
  • The contact diaphragm has to be thin to transfer pressure --> low resistence to abrasion.
  • The fluid could be a contaminant of the industrial process.
The IMPACT technology goes beyond the limits of the traditional one because:
  • It is based on a primary element resistant to high temperature.
  • It has a very thick diaphragm facing the process.
  • It has no fluid inside.
  • It has limited effect of the high temperature on the pressure measurement.
  • Compensates all the effect due to the temperature process and obtain a “clean” pressure signal.
These targets have been reached by:
  • Design and manufacturing of a pressure die obtained by SOI (max working temperature 350°C).
  • Use a 5mm push rod to transfer the pressure from the process to the die --> convert a pressure measurement into a deflection measurement to increase the thickness of the contact diaphragm.
  • Use different material with different thermal expansion coefficient to compensate the effect of the temperature.
Together with the main benefits listed before the IMPACT technology guarantee:
  • Long term stability, measured as the variation of the output signal at zero pressure applied per year.
  • Reliability, since the sensor are often used in safety and breaking related loops.
  • Accuracy of the measured value.
The long term stability relies on both mechanical and electronic stability.

About the mechanical aspects, much care should be put on the reliability of the raw material itself and, of course, on the compensation of the drifts related to high temperature.
On the other hand, the electronic topics are mainly related to the compensation of the electrical signal coming from the primary sensing element.

To assure a good reliability much care should be put on the degradation process enhanced by temperature following the Arrhenius law.
Reliability is strictly linked also to the resistance to harsh environment, in particular to media with wearing and corrosion effects.

Having reliable sensor is also desirable both to decrease the machine stop for testing or changing the sensor and to avoid operations that could be long lasting or dangerous for the operators.
The accuracy is based on the conditioning of every dummy signal induced by temperature or by electromagnetic field.
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FAQ
What is the operative principle of Impact sensors?

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