Pressure sensor design

Pressure sensors play a crucial role in numerous industrial applications by precisely detecting the pressure of liquids or gases. Their ability to convert pressure values into measurable signals is essential for controlling, regulating and monitoring various processes.

Components of pressure sensors

The basic structure of pressure sensors comprises several essential components that interlock to enable precise pressure measurement. Each of these components fulfills specific functions that are crucial for converting the physical pressure into a usable electrical signal.

The following section takes a closer look at the central components of a pressure sensor, from the elements that directly measure the pressure to the interfaces that enable communication with other systems. The main components include the measuring element, the pressure connection, the signal converter, the signal processing & calibration, the output signal & the interface as well as various protective and additional components. Each of these components can be realized in different designs and technologies, depending on the specific application and the requirements of the pressure sensor.

Measuring diaphragm and sensor element

The measuring diaphragm and the sensor element form the heart of every pressure sensor. The measuring diaphragm is in direct contact with the medium to be measured and deforms minimally but measurably when the pressure changes. This deformation is transferred to the sensor element behind it, which converts the mechanical impulse into an electrical signal. This signal is proportional to the applied pressure and serves as the basis for further processing. Depending on the sensor type, the diaphragm and sensor element are made of different materials and technologies that are designed for precise detection of pressure changes. The mode of operation can be divided into three steps:

  • Firstly, pressure detection through diaphragm deformation
  • Secondly, the physical conversion into a measurable variable – for example by changing resistance, capacitance, inductance or piezo effects.
  • Thirdly, the signal transmission to the downstream measuring or control unit.

Pressure connection

The pressure connection is an essential interface in a pressure sensor. Its main task is to ensure that the pressure to be measured reliably enters the sensor housing and can act on the measuring element. The pressure connection therefore makes the actual pressure measurement possible.

The core functions of the pressure connection include pressure transmission, which ensures that the medium (e.g. air, water, oil, gas) reaches the sensor to record the current pressure value. Furthermore, tightness and protection are of crucial importance in order to prevent leaks and protect the sensor from damage caused by the medium. The materials and seals of the connection are specially adapted to the respective applications. To ensure a secure connection to the system, there are various thread types (e.g. G1/4, NPT, M20x1.5) or flange connections that are used depending on the application.

Another important aspect is pressure distribution and stability, as the connection ensures even pressure distribution on the measuring diaphragm or sensor element in order to achieve precise measurement results. The pressure connection also provides protection against environmental influences by protecting the sensor from external influences such as dirt, moisture or aggressive chemicals.

Signal converter

The signal converter plays a decisive role in the design of a pressure sensor by taking on the task of converting the physical signal (pressure) generated by the measuring element into an electrical signal, which can then be further processed or displayed. The main function is to convert the pressure signal into a proportional electrical quantity such as

  • Tension,
  • Current,
  • Resistance or
  • Frequency.

It can also be used for filtering and noise suppression in order to minimize interference or fluctuations in the signal. Another important aspect is the linearization of some sensors whose characteristics are not linear. In such cases, the signal converter adjusts the output signal in order to establish a linear relationship between the pressure and the electrical output signal. Finally, the output signal is often standardized in standardized formats such as 4-20 mA or 0-10 V or in digital interfaces such as I²C or SPI to facilitate integration into various industrial systems. Depending on the requirements of the industrial application, analog or digital signal converters are used.

Signal processing & calibration

Signal processing in a pressure sensor has the central task of processing the raw signal coming from the sensor element in such a way that an accurate, stable and evaluable measured value is produced. This process comprises several key steps. Firstly, the signal is converted and amplified, as the original signal is often very weak and needs to be boosted. Another important aspect is temperature compensation, as pressure sensors are sensitive to temperature. Here, temperature fluctuations are detected by an additional sensor and errors are corrected electronically using algorithms.

If the signal is to be further processed digitally, an analog-to-digital conversion (ADC) is carried out. To further increase measurement accuracy, filtering and noise suppression are used to avoid high-frequency noise or interference.

Calibration is another crucial step in order to compensate for manufacturing tolerances of the pressure sensor and to correct errors such as offset drift or hysteresis. Finally, the processed signal is provided in a predefined format.

Output signal & interface

The output signal and the interface of a pressure sensor define how the measured pressure values are transmitted to downstream systems for further processing. The output signal itself provides the measured pressure value in the form of an electrical signal. This signal is used to supply controllers, displays or other measuring systems with the necessary information. Depending on the application, the output signal can be analog or digital:

  • Analog output signals include 0-10 V, a voltage output that can be more susceptible to interference and better suited for short distances, and 4-20 mA, a current output that is less susceptible to interference and ideal for longer cable runs.
  • Digital output signals use various communication protocols such as I²C and SPI, which are often used to connect to microcontrollers or embedded systems. Protocols such as Modbus and CAN bus are used for industrial fieldbus systems for data transmission.

Protection & additional components

Protective and additional components play an important role in the design of a pressure sensor in order to ensure functionality, durability and measurement accuracy under various operating conditions. Protective components are used to protect the sensor from potential damage caused by mechanical, electrical or thermal influences. Mechanical protection includes, for example, a protective membrane that protects the measuring element from direct contact with the measured medium and thus prevents contamination or chemical reactions.

The housing and seals ensure a robust and often water- or corrosion-resistant design. Shock and vibration protection can also be integrated to absorb shocks that could otherwise lead to measurement deviations or damage. In the area of electrical protection, components such as overvoltage protection, which prevents damage caused by sudden voltage peaks, EMC protection (electromagnetic compatibility) to reduce interference from external fields and reverse polarity protection to protect against incorrect electrical connections are important. Thermal protection includes temperature compensation, which corrects measurement deviations due to temperature fluctuations, as well as overheating protection to protect against excessive temperatures in the sensor. In addition to these protective functions, additional components can extend the performance and functionality of the pressure sensor.

What are the critical components of a pressure sensor?

Of the various components of a pressure sensor, some are particularly critical to its function and performance. These critical components can be divided into mechanical and electrical components.

1. mechanical components:

  • Measuring diaphragm (measuring cell): This is the heart of the sensor, as it directly detects the pressure to be measured and converts it into an electrical variable.
  • Housing: The housing protects the internal components from external influences such as mechanical stress, moisture and chemicals. The materials used include stainless steel, aluminum and plastic.
  • Seals: They ensure a pressure-resistant seal between the sensor and the process medium and thus prevent leaks.

2. electrical components:

  • Bridge circuit (Wheatstone bridge): This circuit is often used in piezoresistive pressure sensors to convert changes in resistance into a measurable voltage.
  • Temperature compensation: As pressure sensors are temperature-sensitive, it is essential to correct measurement deviations due to temperature fluctuations. This can be done using thermal sensors or special algorithms.
  • Signal amplifier: The signals generated by the sensor element are often very weak and must be amplified to reduce noise and external interference and to enable accurate further processing.

These components are crucial to the reliability and accuracy of a pressure sensor. A failure or malfunction of one of these critical components can affect the entire measurement.

Is every pressure sensor constructed in the same way?

No. There is a wide range of pressure sensor technologies and designs that vary depending on the application, measuring task and specific requirements.

Although the basic components such as measuring element, pressure connection, signal converter, signal processing and output signal are present in most pressure sensors, their design, technology and materials can vary greatly.

For example, different measuring elements use different physical principles for pressure measurement (piezoresistive, capacitive, piezoelectric, etc.) and are made of various materials that are optimized for the respective pressure range and measuring medium. Depending on the application, the pressure connection can also have different thread types, designs (e.g. open diaphragm for viscous media) or materials.

Request application-specific pressure sensors

At DDM Sensors, we offer the opportunity to develop application-specific pressure sensors. This underlines our commitment to offering customized solutions that are precisely tailored to the individual needs and requirements of a wide range of applications. Our experts will be happy to advise you on your individual application.

Andreas Happ: Vertrieb und Marketing DDM Sensors | Sales and Marketing