Pressure Sensors Explained: 7 Essential Types and Industrial Uses
Pressure sensors are devices that detect the pressure exerted by a gas or liquid and convert it into an electrical signal or another measurable output. Depending on their design, they measure pressure relative to atmospheric pressure, a perfect vacuum or another pressure point. Common technologies include piezoresistive, capacitive and strain-gauge sensing. Industrial applications include hydraulic systems, HVAC equipment, process automation, water management, pneumatic machinery and fluid monitoring. Selecting the right device depends on pressure range, accuracy, media compatibility, operating temperature, electrical output and installation requirements.
What Is a Pressure Sensor?
A pressure sensor is a measurement device that detects the force exerted by a fluid or gas over a surface and converts that pressure into a signal that can be interpreted by a monitoring or control system.
Pressure is generally expressed as force per unit area. In the International System of Units (SI), the standard unit is the pascal (Pa). Industrial instruments commonly use kilopascals (kPa), megapascals (MPa), bar, millibar or pounds per square inch (psi).
For example, a manufacturing plant may use a pressure sensor to monitor hydraulic pressure in a machine. When pressure rises or falls outside the expected operating range, the control system can alert an operator or adjust the process.
Although the terms are sometimes used interchangeably, pressure sensors can differ significantly in their measurement reference, sensing technology, electrical output and intended operating environment.
How Do Pressure Sensors Work?
Most pressure sensors use a sensing element that responds mechanically to applied pressure. The device converts that physical response into an electrical signal that a display, controller, data acquisition system or programmable logic controller (PLC) can interpret.
The exact process depends on the sensor design, but the basic sequence is similar.
Step 1: Pressure reaches the sensing element
Gas or liquid pressure acts on a diaphragm or another pressure-sensitive component. The diaphragm is designed to respond to pressure within the device's specified operating range.
Step 2: The sensing element responds
The applied pressure causes a small, measurable change in the sensing element. Depending on the technology, this may involve resistance, capacitance, strain or another physical property.
Step 3: The change is converted into a signal
The sensor's internal circuitry converts the physical change into an electrical response. Some devices produce a low-level millivolt signal, while others provide a conditioned voltage or current output.
Step 4: The system interprets the measurement
The output is processed by a compatible indicator, controller or monitoring system. The resulting pressure reading can be used for process control, alarms, performance monitoring or data logging.
Main Types of Pressure Sensors: Gauge, Absolute and Differential
Pressure sensors are commonly classified according to the pressure reference they use. Understanding this distinction is one of the most important steps in selecting the right device.
1. Gauge pressure sensors
Gauge pressure sensors measure pressure relative to the surrounding atmospheric pressure.
For example, a tyre pressure gauge typically reports pressure above atmospheric pressure rather than total pressure measured from a perfect vacuum.
Gauge pressure is often written as barg, kPa(g) or psig, depending on the unit convention.
Common applications include:
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Hydraulic machinery
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Compressed air systems
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Water pumps and pipelines
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Industrial process equipment
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General-purpose pressure monitoring
Gauge pressure is a suitable choice when the application needs to know how much pressure exists above the surrounding atmospheric pressure.
2. Absolute pressure sensors
Absolute pressure sensors measure pressure relative to a perfect vacuum. Their readings include atmospheric pressure when measuring a system exposed to the atmosphere.
Absolute pressure is important in applications where atmospheric changes must not alter the measurement reference.
Common applications include:
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Vacuum systems
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Barometric pressure measurement
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Scientific instruments
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Certain gas processing systems
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Applications involving pressure calculations based on absolute values
For example, vacuum equipment may require absolute pressure measurement because gauge pressure alone does not always provide the reference needed for process calculations.
3. Differential pressure sensors
Differential pressure sensors measure the difference between two pressure points. They typically have two pressure ports, often labelled high pressure and low pressure.
The output represents the difference between the two applied pressures, rather than either pressure independently.
Common applications include:
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Filter blockage monitoring
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HVAC air pressure measurement
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Flow measurement across a restriction
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Tank level measurement in suitable installations
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Pressure drop monitoring in industrial processes
For instance, a filter monitoring system can measure the pressure before and after a filter. As the filter accumulates contaminants, the pressure difference may increase, indicating that inspection or replacement is required.
Gauge vs absolute vs differential pressure
| Feature |
Gauge |
Absolute |
Differential |
| Measurement reference |
Atmospheric pressure |
Perfect vacuum |
Second pressure point |
| Measures |
Pressure above or below atmosphere |
Total pressure from vacuum reference |
Difference between two pressures |
| Typical applications |
Hydraulics and pumps |
Vacuum and barometric systems |
Filters, HVAC and flow monitoring |
| Key selection factor |
Atmospheric reference is appropriate |
Absolute reference is required |
Two-point pressure comparison is needed |
Pressure Sensor Technologies: Piezoresistive, Capacitive and Strain-Gauge
Pressure sensors also differ in the physical principle they use to detect pressure. No single technology is universally best; the right choice depends on measurement requirements, operating conditions and total system design.
Piezoresistive pressure sensors
Piezoresistive sensors use a material whose electrical resistance changes when mechanical stress is applied. Pressure causes deformation in a sensing structure, producing a resistance change that can be measured electrically.
These sensors are widely used in industrial and embedded pressure measurement. Their suitability depends on the design, pressure range, temperature characteristics and signal conditioning.
Typical applications include hydraulic pressure monitoring, industrial equipment and electronic pressure measurement modules.
Capacitive pressure sensors
Capacitive pressure sensors detect a change in electrical capacitance. Pressure may cause a diaphragm to move relative to another conductive surface, changing the capacitance between them.
This technology can be useful where sensitivity to small pressure changes is important. However, performance varies with the sensor design and operating conditions.
Potential applications include low-pressure measurement, HVAC monitoring and specialised process instrumentation.
Strain-gauge pressure sensors
Strain-gauge pressure sensors use gauges attached to, or integrated with, a pressure-sensitive structure. When the structure deforms under pressure, the strain gauges experience a change in electrical resistance.
The resistance changes can be measured using a suitable circuit, often a Wheatstone bridge, and converted into a pressure-related signal.
Strain-gauge principles are also used in load cells, where mechanical force is converted into an electrical output. However, a load cell measures force or weight, while a pressure sensor is designed to measure pressure.
Applications include industrial process monitoring, hydraulic equipment and pressure testing systems.
Comparing sensing technologies
| Technology |
Operating principle |
Potential advantages |
Considerations |
| Piezoresistive |
Resistance changes under stress |
Compact designs and broad application range |
Temperature effects and conditioning |
| Capacitive |
Capacitance changes with diaphragm movement |
Can provide high sensitivity in suitable designs |
Construction, environment and electronics |
| Strain-gauge |
Resistance changes with mechanical strain |
Established measurement principle and useful signal conditioning options |
Bridge circuitry, mounting and temperature compensation |
Technology alone does not determine measurement quality. Review the complete device specification and verify that the sensor meets the application's required performance.
Common Industrial Applications
Pressure sensors support measurement, automation and maintenance across a wide range of industries.
Manufacturing and industrial automation
Manufacturing equipment uses pressure sensors to monitor pneumatic actuators, hydraulic circuits, lubrication systems and production processes. Reliable readings help operators detect abnormal conditions and maintain consistent operation.
HVAC and building management
Heating, ventilation and air-conditioning systems use pressure measurement to monitor air ducts, filters, fans and fluid circuits. Differential pressure devices are especially useful when monitoring pressure changes across filters or other components.
Water and wastewater management
Pressure sensors can monitor pumps, water distribution networks, treatment equipment and pipelines. They help identify pressure fluctuations and support automated control strategies.
Automotive and transport
Pressure measurement is used in suitable automotive and transport systems, including fluid circuits, engine-related applications and tyre pressure monitoring. The required device depends on the measured medium, operating temperature, vibration and pressure range.
Oil, gas and process industries
Pressure instrumentation supports monitoring in pipelines, vessels, processing equipment and other industrial systems. Applications may require specialised materials, hazardous-area approvals or additional protection, depending on the operating environment.
Food, beverage and pharmaceutical processing
Pressure sensors may be used to monitor tanks, pumps, pipelines and processing equipment. Hygienic design, cleanability, material compatibility and applicable regulatory requirements are important selection factors in these environments.
Research and laboratory equipment
Laboratory instruments can require precise pressure measurement for vacuum systems, test rigs, gas handling and experimental processes. The appropriate accuracy, range and reference depend on the test method.
Key Pressure Sensor Specifications to Understand
Before purchasing a pressure sensor, review the technical specifications and compare them against the actual operating conditions.
Pressure range
The pressure range defines the minimum and maximum pressure the device is designed to measure. Select a range that accommodates normal operation and expected pressure variations without sacrificing required measurement resolution.
Accuracy
Accuracy describes how closely the measurement agrees with the reference value under stated conditions. Manufacturers may express it as a percentage of full scale, a percentage of the reading or another specified tolerance.
Always check the manufacturer's definition because different accuracy statements are not necessarily directly comparable.
Output signal
Common outputs include millivolt signals, voltage outputs and current loops such as 4–20 mA. Digital communication options are also available on some devices.
Confirm that the output is compatible with the receiving PLC, indicator, data logger or control system.
Operating temperature
Temperature can influence sensor performance, materials and electronics. Check both the compensated temperature range, where specified performance is maintained, and the allowable operating temperature range.
Wetted materials and media compatibility
Wetted materials are the components that contact the measured gas or liquid. These materials must be compatible with the process medium to reduce the risk of corrosion, contamination, leakage or premature failure.
Pressure connection and installation
Check the required thread type, port configuration, sealing method, mounting orientation and available installation space. A mechanically incompatible connection can create installation and reliability problems.
Overpressure and pressure spikes
Industrial systems can experience short pressure surges above normal operating conditions. Check the specified overpressure limit and burst pressure where relevant. These terms are different, and neither should be treated as a recommended continuous operating pressure.
Ingress protection and approvals
Environmental protection ratings, hazardous-area approvals and industry-specific certifications may be essential depending on where the sensor will operate. Verify the exact rating and approval for the selected model rather than assuming all devices in a product family have the same features.
Frequently Asked Questions About Pressure Sensors
What does a pressure sensor measure?
A pressure sensor measures the pressure exerted by a gas or liquid. Depending on its design, it may measure gauge pressure, absolute pressure or the difference between two pressure points.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to atmospheric pressure, while absolute pressure is measured relative to a perfect vacuum. The correct type depends on the measurement reference required by the application.
What is a pressure transmitter?
A pressure transmitter typically converts a pressure measurement into a conditioned, standardised signal that can be transmitted to a PLC, controller or monitoring system. Common industrial outputs include 4–20 mA.
Where are pressure sensors used?
Pressure sensors are used in manufacturing, HVAC, water management, automotive systems, oil and gas processing, food production, laboratories and many other applications requiring pressure monitoring or control.
Conclusion
Pressure sensors help industrial teams monitor equipment, control processes and identify abnormal operating conditions. Selecting the correct device begins with understanding the measurement reference, sensing technology, pressure range and installation environment.
Gauge sensors suit applications that reference atmospheric pressure, absolute sensors support measurements referenced to a vacuum, and differential sensors measure the difference between two pressure points. Beyond these categories, specifications such as accuracy, temperature range, output signal and media compatibility are essential to a reliable installation.
