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Pressure Transmitter Technology

A pressure transmitter can be divided into two functional components:

  1. A sensor element that converts the pressure to an electronic signal.
  2. The transmitter electronics that amplify, convert, and apply signal conditioning such as linearization to the raw sensor signal.

The sensor element measures the pressure using strain gauge measuring technology. A thin sensor membrane alters its shape with changes in pressure, which can be measured with a Wheatstone bridge on the membrane. A Wheatstone bridge is an electronic circuit whose properties change proportionally to the altering shape of the sensor membrane, and this electronic change can be measured with extreme accuracy. Thus, the signal output from the sensor is proportional to the changes in pressure.

The sensor elements in Trafag’s pressure transmitters are mainly based on two different technologies: thin-film on steel and thick-film on ceramic. Piezoresistive sensors are also common in the market but are only used by Trafag in special cases.

Thinfilmonsteel(2)

Thin-film on Steel Sensors

A thin-film electronic circuit is sputtered onto a metal membrane, the membrane is only a few microns thick and acts as the strain gauge.

A pressure transmitter with thin-film on steel sensor has a completely welded design, thus only two parts are in contact with the media: the sensor and the pressure connection. Our pressure transmitters feature a stainless-steel sensor (1.4542/AISI 630) with excellent mechanical strength and corrosion resistance. The pressure connection and transmitter housing are available in different materials. The design is reliable and leak-proof, with no internal O-rings used.

Thin-film on steel sensors are robust, with excellent long-term stability and overpressure ratings. Thus, the pressure transmitter will not change its signal characteristics over time due to mechanical fatigue.

The Advantages with Thin-film on Steel Sensors:

  • Excellent long-term stability
  • Withstands high media temperature
  • Welded design, no internal o-rings
  • High overpressure (up to 5x nominal) and pressure ranges up to 3500 bar.
Thickfilmonceramic(2)

Thick-film on Ceramic Sensor

In this type av sensor, a thick-film electronic circuit is printed onto a ceramic membrane. The measuring principle of a ceramic sensor is similar to that of as a steel sensor; the printed circuit act as a strain gauge.

Ceramic sensors are an alternative to steel sensors for applications where steel sensors are not compatible, such as highly corrosive or chemical media. Since ceramic sensors cannot be welded, an internal O-ring is used to seal the sensor and pressure connection. The choice of material for the pressure connection and O-ring is adapted to the application requirements for chemical combatibility.

The Advantages of Ceramic Sensors:

  • Chemical compatibility and corrosion resistance
  • Ideal for low pressures and absolute measurement
ASIC

Electronics and ASIC

The pressure transmitters from Trafag are well known for their high performance and reliability. The sensor element is an important part, but the pressure transmitter electronics are just as important. Trafag has developed an ASIC (Application Specific Integrated Circuit) specifically for their pressure transmitters to ensure high-quality signal conditioning and low noise.

  • The ASIC supports all sensor technologies (thin-film on steel, thick-film on ceramic and piezoresistive)
  • A wide operating temperature of -40 to 125°C
  • Multi-parameter signal conditioning with advanced 3D mapping, such as temperature compensation

Explore Further

Explore our different pressure transmitter and learn more in our article how you can tell the difference between sensors, transducers and transmitters.

Please contact us if you have any questions or thoughts.

Our Pressure Transmitters
Sensors, Transducers and Transmitters – What is the Difference?

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