A pressure sensor converts change of mechanical pressure in gases or liquids into electrical signals. The most common types of pressure sensors are based on the piezoresistive, capacitive or piezoelectric principle.
How does a pressure sensor work?
A pressure sensor measures pressure using the deformation caused at a membrane under the pressure. With different sensor technologies, the deformation is converted into electrical signals for processing and transmission to external devices for monitoring and control of pressure-related processes. Pressure measurement is one of the most important and most common technologies for machine and system monitoring and control in process technology.
Design and types of pressure sensors
A pressure sensor includes several main components. A pressure sensor consists of a measuring diaphragm deforming at changing pressure, an opening for pressure intake, various sensor elements (e.g. piezoelectric, capacitive or piezoresistive), a signal processing unit for signal amplification and processing, a protective housing as well as electrical and mechanical connections for connectivity to external devices. These components interact to provide precise pressure measurement results in various applications.
Basically, there are different pressure sensor types based on different measuring principles:
1. Resistive pressure sensors measure pressure by change in the electrical resistance resulting from mechanical stress imposed on a material.
2. Piezoelectric pressure sensors generate electrical voltage through charge displacement in piezoelectric material under pressure.
3. Capacitive pressure sensors detect changing capacitance in a capacitor caused by membrane deformation.
4. Inductive pressure sensors measure pressure by changing coil inductance at moving a magnetic core or membrane.
5. Pressure sensors with Hall element use the Hall effect to measure pressure changes.
MEMS pressure sensors use micro-mechanical structures on a silicon chip to measure pressure.
Principles for pressure measurement
Absolute pressure
Absolute pressure means the pressure in relation to a complete vacuum and is therefore always positive. It is measured in units such as Pascal (Pa), Bar or Psi (abs). Measurements are with sensors using a vacuum as a reference. Frequently used are MEMS sensors, capacitive sensors and piezoresistive sensors, which measure pressure by deformation of a membrane or change in electrical properties.
Typical areas of application:
Monitoring or controlling physical processes by the absolute pressure, such as steam pressure in sterilizers or autoclaves
CIP/SIP cleaning
Vacuum pumps
Relative pressure
Relative pressure is measured in relation to the prevailing air pressure and can assume positive or negative values. It is specified in units such as Pascal (Pa), Bar or Psi (gauge). Relative pressure sensors require regular calibration and operate on different technologies. Piezoelectric and capacitive sensors to convert change in pressure into electrical signals. These sensors often provide ventilation holes for referencing.
Typical areas of application:
Hydrostatic level measurement in vented tanks
Holding force by vacuum during workpiece handling
Pressure measurement in hydraulic or pneumatic systems
Differential pressure
Differential pressure means the pressure difference between two points in the system and can assume positive or negative values. It is measured in units such as Pascal (Pa), Bar or Psi and uses various sensor technologies such as capacitive and piezoelectric pressure sensors. Differential pressure sensors are less sensitive to ambient conditions and require regular calibration. Differential pressure can also be measured with two individual sensors that deliver two signals to the control unit for calculating the differential pressure.
Typical areas of application:
Fill level measurement in closed containers
Flow rate measurement in fluids
Detecting clogged filters
