Pressure Sensor Technology Comparative Guide

Introduction

In modern engineering and industrial processes, the accurate measurement and control of pressure is vital for ensuring operational efficiency and safety. Pressure sensors play a crucial role in converting mechanical pressure into electrical signals, enabling systems to monitor and respond to pressure variations. The selection of the appropriate pressure sensor technology is essential, as each technology has distinct characteristics that suit specific applications and operating environments.

This guide provides a comparative analysis of various pressure sensor technologies, including bonded foil strain gauge, ceramic diaphragm thick film strain gauge, ceramic diaphragm variable capacitance, thin film strain gauge, and silicon sensors. By understanding the working principles, advantages, and limitations of each technology, engineers and technicians can make informed decisions when selecting pressure sensors for their specific needs.

Usage Requirements Rating Table

This table compares different sensing technologies for pressure measurement based on various criteria. It looks at factors like material, media compatibility, and pressure range suitability, and assigns ratings from bad to excellent for each combination. A final comparison rating summarizes the overall performance of each technology.

Sensing technology	Si-Chip	Si-Isolated	Thick-Film	Var-Cap	Thin-Film	BFSG
Sensing diaphragm material	Excellent	Excellent	Fair	Fair	Good	Good
Media compatibility	Bad	Good	Excellent	Excellent	Good	Good
Oil fill leak risk	Excellent	Bad	Excellent	Excellent	Excellent	Excellent
Pressure containment	Poor	Good	Fair	Fair	Excellent	Excellent
Small size	Excellent	Good	Fair	Poor	Good	Fair
Corrosion resistance	Bad	Good	Excellent	Excellent	Fair	Fair
Abrasion resistance	Bad	Bad	Excellent	Excellent	Fair	Fair
High pressure spikes	Bad	Poor	Fair	Poor	Good	Good
Overpressure rating	Good	Excellent	Fair	Good	Poor	Poor
Very low pressure < 100mb	Good	Poor	Bad	Good	Bad	Bad
Low pressure 100…1000mb	Good	Good	Poor	Good	Bad	Bad
Medium pressure 1…100bar	Fair	Excellent	Excellent	Fair	Good	Fair
High pressure 100…1000bar	Bad	Good	Fair	Bad	Excellent	Good
Very high pressure > 1000bar	Bad	Bad	Bad	Bad	Good	Excellent
Absolute pressure ranges	Fair	Excellent	Good	Good	Bad	Bad
Accuracy	Excellent	Good	Poor	Fair	Good	Fair
Output Sensitivity	Excellent	Excellent	Fair	Excellent	Good	Fair
Frequency response	Excellent	Good	Fair	Poor	Good	Fair
Comparison rating (90 max)	56	63	59	61	62	57

Application Technology Selector Tool

This tool will assist you in selecting the most suitable pressure sensor technology for your application requirements.

Get technology rating for your application

Pressure Sensor Technologies Comparison

Each pressure technology described in terms of its working principles, advantages, limitations, and ideal applications.

Silicon

Silicon pressure sensors utilise a thin silicon diaphragm with implanted semiconductor strain gauges. Pressure-induced diaphragm deflection changes the strain gauges’ resistance, which is measured and converted to a pressure reading.

Key Advantages

High Accuracy and Sensitivity: Silicon sensors offer exceptional accuracy and sensitivity, making them suitable for demanding applications.
Fast Response Time: The low mass and high natural frequency of silicon diaphragms enable rapid response to pressure changes.
Excellent Repeatability and Stability: The monolithic construction and integrated strain gauges ensure consistent and reliable performance over time.
Wide Operating Temperature Range: Silicon sensors can operate across a broad temperature range.
High Overpressure Tolerance: The elasticity of silicon allows for a high overpressure rating, protecting the sensor from damage.

Key Limitations

Susceptibility to Shock Pressures: Sudden pressure spikes can damage the silicon diaphragm, limiting their use in certain hydraulic or pneumatic systems.
High Vacuum Limitations: Oil-filled silicon sensors can experience calibration shifts or performance issues in high vacuum conditions.

Ideal Applications

Industrial Automation: High accuracy, stability, and fast response make them ideal for precise control and monitoring in industrial processes.
Medical Devices: Small size, biocompatibility, and high accuracy are suitable for medical applications like blood pressure monitoring.
Automotive: Used in tire pressure monitoring, engine control, and brake systems due to their durability and wide operating temperature range.
Aerospace: Lightweight, compact, and able to withstand harsh environments.

Ceramic Diaphragm Thick Film Strain Gauge

Ceramic based thick film strain gauge pressure sensor module with integral signal conditioning PCB.

This sensor utilises a ceramic diaphragm with thick-film strain gauges printed onto its surface. The diaphragm’s deflection under pressure causes resistance changes in the strain gauges, which are measured and converted to a pressure reading.

Key Advantages

Cost-Effectiveness: Simple design and manufacturing process lead to lower costs.
Chemical Resistance: Ceramic’s inert nature makes it suitable for harsh chemical environments.
Abrasion Resistance: The hardness of ceramic provides excellent protection against abrasive media.
Compact & Hygienic: No oil-filled seals or complex internal components, resulting in a compact and easy-to-clean sensor.

Key Limitations

Lower Accuracy: Compared to other technologies, accuracy can be slightly lower.
Lower Signal-to-Noise Ratio: Can be a consideration in applications requiring high precision.
Limited Pressure Ranges: Typically not suitable for extremely high or low pressures.
Vulnerability to Surface Damage: While abrasion-resistant, the diaphragm can be damaged by sharp impacts.
Elastomer Seals: The use of elastomer seals can limit their use in high-temperature applications.

Ideal Applications

Chemical Processing: Chemical resistance makes them ideal for harsh chemical environments.
OEM Design: Compact size and affordability make them suitable for integration into various equipment.
Industrial Printers: Corrosion resistance is beneficial in the demanding environment of industrial printers.
Water & Wastewater Treatment: Resilience to harsh conditions is useful in these applications.

Ceramic Diaphragm Variable Capacitance

Ceramic based variable capacitance pressure sensor module with integral signal conditioning PCB.

This sensor employs a ceramic diaphragm and a fixed electrode, forming a capacitor. Pressure-induced diaphragm deflection changes the capacitance, which is measured and converted to a pressure reading.

Key Advantages

High Precision & Sensitivity: Can detect minute pressure changes, ideal for precise measurements and control.
Excellent Long-Term Stability: Capacitance remains stable over time, ensuring consistent accuracy.
Corrosion Resistance: Ceramic diaphragms are resistant to various corrosive media.
Wide Temperature Range: Can operate reliably across a broad temperature range.
Good Overload Protection: Can withstand high overpressure without damage.
Low Power Consumption: Requires less power than some other sensor types, suitable for battery-powered devices.
Versatility: Can be used for both absolute and gauge pressure measurements.

Key Limitations

Cost: Can be more expensive due to complex manufacturing and materials.
Fragility: Ceramic diaphragms can be susceptible to mechanical shock or vibration.
Limited Pressure Range: Measurable pressure range might be limited compared to other technologies.
Complexity: Measurement principle and signal conditioning can be more complex.
Hysteresis: May exhibit some hysteresis, affecting output depending on pressure change direction.

Ideal Applications

Chemical Process Monitoring: High accuracy, corrosion resistance, and wide temperature range are ideal for harsh chemical environments.
Environmental Monitoring: Resilience and accuracy are useful in monitoring contaminated water or industrial wastewater.
Research & Development: Precise measurements, corrosion resistance, and wide temperature range are valuable in laboratory settings.

Thin Film Strain Gauge

Thin-film pressure sensors utilise a piezoresistive effect to measure pressure. A thin film sensing element deposited on a flexible diaphragm changes resistance under pressure-induced strain, which is measured and converted to a pressure reading.

Key Advantages

Miniaturisation: Thin-film technology allows for incredibly small and compact sensor designs.
High Sensitivity: Piezoresistive materials exhibit significant resistance changes under strain, enabling precise measurements.
Wide Pressure Range: Can measure a broad range of pressures, from low to high.
Excellent Durability: Robust construction and materials withstand harsh environments and mechanical stress.
High-Temperature Operation: Can operate at elevated temperatures due to the absence of organic adhesives and the use of high-temperature resistant alloys.
Specialised Gas Measurement: Suitable for measuring gases like hydrogen, oxygen, or helium due to its all-welded construction and thicker diaphragm, preventing gas permeation and contamination.

Key Limitations

Lower Output Sensitivity: Compared to semiconductor strain gauge technologies, the output sensitivity might be lower.
Limited Absolute Pressure Ranges: Designing for very low absolute pressures can be complex due to the need for a stable vacuum reference.
Less Repeatability at Low Pressures: Performance at very low pressures might be less repeatable and more susceptible to temperature variations.
Fewer Options for Differential Pressure: Integrating an additional diaphragm for differential pressure measurement can be challenging.

Ideal Applications

Motorsport: Miniature size, high-temperature operation, and resistance to shock and vibration are crucial in motorsport applications.
Hydraulics: High-pressure tolerance and compact size are beneficial in hydraulic systems, especially in mobile equipment.
Research & Development: Small size, accuracy, and durability make them suitable for testing prototypes and collecting precise pressure data.
Aerospace: Lightweight, compact, and able to withstand harsh environments, making them suitable for aerospace applications.
Industrial Applications: Can be used in various industrial settings where high accuracy, durability, and wide pressure ranges are required.

Bonded Foil Strain Gauge

The bonded foil strain gauge pressure sensor employs a thin metal foil (often Constantan) bonded to a stainless-steel diaphragm. Pressure-induced diaphragm deflection strains the foil, changing its electrical resistance, which is measured and converted to a pressure reading.

Key Advantages

Robustness: Handles high-pressure ranges and dynamic pressure changes well, suitable for demanding applications like hydraulics.
Cost-Effectiveness: Mature manufacturing process and readily available materials contribute to lower costs.
Reliability: Simple design with minimal moving parts translates to fewer failure points and a longer lifespan.
High Shock & Vibration Tolerance: The strong bond between the foil and diaphragm, along with the materials’ mechanical properties, enables it to withstand harsh conditions.

Key Limitations

Accuracy & Repeatability: Can be lower than other technologies due to hysteresis, creep, and temperature effects on the bonding adhesive and diaphragm material.
Manufacturing Time: Photo-etching and manual processes can lead to longer lead times compared to newer technologies.
Output Sensitivity: Generally lower than piezoresistive or capacitive sensors due to the lower gauge factor of metal foil strain gauges.
Overpressure Rating: Limited by the elastic limit of the metal diaphragm.
Calibration Drift: Can experience calibration shifts over time due to fatigue in the diaphragm and adhesive.

Ideal Applications

Hydraulics & Pneumatics: The robustness and high-pressure tolerance make them suitable for hydraulic and pneumatic systems.
Industrial Applications: Cost-effectiveness and reliability are advantageous in various industrial settings where high accuracy may not be critical.
High-Pressure Environments: Can handle high static and dynamic pressures, making them suitable for demanding applications.

Conclusion

In conclusion, selecting the right pressure sensor technology is pivotal in achieving accurate and reliable pressure measurements in various applications. Each technology discussed in this guide offers unique advantages and considerations that should be carefully weighed against the specific requirements of your project.

Bonded foil strain gauge sensors stand out for their robustness and cost-effectiveness, making them suitable for demanding industrial environments and high-pressure applications. Ceramic diaphragm thick-film strain gauge sensors offer a budget-friendly solution with excellent chemical and abrasion resistance, ideal for harsh chemical processing and OEM integration.

Ceramic diaphragm variable capacitance sensors excel in high-precision applications, delivering exceptional long-term stability and corrosion resistance, particularly valuable in chemical process monitoring. Thin-film strain gauge sensors boast miniaturisation, high sensitivity, and durability, catering to applications like motorsport, hydraulics, and aerospace, where space constraints and harsh conditions are prevalent. Lastly, silicon sensors deliver superior accuracy, fast response, and a wide operating temperature range, making them the preferred choice for industrial automation, medical devices, and automotive systems.

Remember, the ideal pressure sensor technology hinges on the specific demands of your application, considering factors like pressure range, accuracy requirements, environmental conditions, and cost constraints. For further assistance in sensor selection or to explore detailed specifications and application notes, we encourage you to delve into the comprehensive content pages dedicated to each technology via the buttons below.

Silicon Thick-Film Var-Cap Ceramic Thin-Film BFSG