Functionality and technology of pressure sensors

Pressure sensors deliver precise and reliable pressure measurements across a wide range of industrial applications. In this article, PIF caught up with German sensor aficionados Baumer to find out more about their various types of pressure sensor devices, including their standout features, benefits and typical applications.

Applications of pressure measurements

There are four main applications of pressure measurements that we measure:

• Absolute Pressure – is the measurement of pressure with respect to vacuum.
• Relative Pressure – is the measurement of pressure with respect to atmospheric pressure.
• Compound Pressure – is the measurement of both negative and positive pressures.
• Differential Pressure – is the measurement of the difference between two pressures.

Types of pressure sensor technology

To carry out these pressure measurements, there are essentially two main measurement principles: piezo-resistive pressure measurement and resistive pressure measurement. Baumer offers several types of pressure sensor technology based on these measurement principles.

Piezo-resistive silicon semiconductor sensors

Baumer’s silicon semiconductor sensors employ a sensitive silicon chip to measure the signal produced by changes in the resistance of the semiconductor’s materials arising from the variable mobility of the electrons in the crystalline structure.

Transmitters that use piezo-resistive silicon technology are noted for their high accuracy and long-term stability. Fully welded housings mean they are durable and can also be used in potentially explosive ATEX areas. They are also suitable for small measuring ranges, particularly for hydrostatic level measurements.

Resistive ceramic thick-film and metal thin-film sensors

The ceramic measuring cells used in Baumer’s ceramic thick-film sensors offer good long-term stability and corrosion resistance, while the stainless steel base bodies of their metal thin-film sensors promise excellent resistance to pressure peaks and bursting pressure.

Both types of sensor feature four resistors that are interconnected to create a Wheatstone bridge. These resistors are exposed to the highest strain in the middle of the diaphragm and the greatest compression at their edges. The measuring membrane is simultaneously the separating membrane from the medium.

Hygienic pressure sensors

Hot steam is widely employed to sterilise equipment and small devices like sensors are often sterilised in suitable chambers called autoclaves. Large-scale installations will more often than not feed hot steam through the system as part of a process known as sterilisation in place (SIP).

With that in mind, sensors must therefore be robust enough to withstand the demands of steam sterilisation and washdown applications. That requires a design that can comfortably survive the inherent temperatures and pressures for any given length of time (134 °C at more than 3 bar for 30 minutes, for example).

Baumer’s range of hygienic pressure sensors is ideally suited to controlling sterilisation processes. Their sensors deliver accurate pressure monitoring even when faced with rapid fluctuations in temperature, making it easier to control the process in a reliable, repeatable and safe manner.

For more information, visit Baumer.