Before we discuss the pressure sensor types, let’s take a look back at history.

As early as the mid-1600s, people became deeply intrigued by the invisible force of pressure. The very first attempts to capture and measure it relied on simple glass tubes filled with liquids like mercury or water. By observing how much the fluid column rose or fell inside these tubes, experimenters could literally see the push and pull exerted by atmospheric pressure or other forces. These early barometers were the foundation, turning an unseen phenomenon into something visible and quantifiable.

Fast forward to today, we’ve moved far beyond tracking fluid levels in glass. We now harness the remarkable ways pressure alters materials – changing their shape, resistance, or even generating tiny electrical signals.

This deep understanding allows us to build incredibly sophisticated pressure sensors. Thanks to these miniature marvels, often etched onto silicon chips smaller than a fingernail, measuring pressure fluctuations has become an effortless feat of astounding precision and accuracy.

This invisible technology quietly ensures our car tires are safe, our weather forecasts are reliable, our medical devices function, and countless everyday systems operate smoothly. From watching mercury move in a tube to reading digital signals in an instant, our grasp of pressure has transformed the modern world

What is a pressure sensor?

Think about the invisible push of air around us, the squeeze of fluids in pipes, or the force deep underwater. A pressure sensor is our modern way of catching that invisible force and turning it into something we can see, measure, and use. It’s the clever successor to those early glass tubes where people watched liquid levels rise and fall.

Instead of relying on a moving column of mercury or water, today’s pressure sensors work their magic by sensing how pressure physically affects special materials inside them. When pressure pushes on these materials – whether it’s air, gas, liquid, or even a solid touch – it causes tiny, precise changes. It might bend a microscopic diaphragm ever so slightly, alter the electrical resistance of a wire, or make a crystal produce a tiny voltage.

These whisper-quiet reactions are then transformed into clear electrical signals. Sophisticated electronics instantly read these signals, translating the push of the invisible force into precise numbers we can understand on a screen or use to control a system. From keeping your car tires safe and your weather app accurate, to ensuring medical equipment delivers the right dose or your espresso machine brews perfectly, these unseen sentinels are constantly measuring the push and pull of our world, making the invisible, visible.

How pressure sensors work

No matter which Pressure Sensor Types, they work by detecting physical changes caused by pressure differences, then turning those changes into electric signals teams can use. This process gives real-time insights into equipment health. Here’s how it happens step by step:

Pressure physically changes a sensor component

When pressure pushes against a sensor (like in a pipe or tank), it causes a tiny physical deformation. Most types of pressure sensors use a strain gauge – a sensitive component that stretches or compresses under pressure. This bending or flexing is the first key reaction the sensor measures.

The physical change becomes an electrical signal

The strain gauge converts the physical deformation directly into an electrical signal. As it bends, its electrical resistance changes. This change in resistance creates a small voltage signal. The strength of this signal increases or decreases precisely based on how much pressure is applied.

The signal is sent as usable pressure data

This electrical signal now represents the actual pressure (in PSI, kPa, bar, etc.). The sensor sends this signal immediately to a PLC (Programmable Logic Controller). The PLC acts as the central brain of machinery or processes, collecting real-time data from sensors across the equipment or production line.

The PLC takes action based on the reading

With pressure data live in the PLC, it automatically responds if readings go outside set limits.

• High pressure: The PLC might trigger an alarm, shut down a pump, or open a relief valve to prevent equipment damage or rupture.

 

• Low pressure: It could signal a leak (e.g., in air lines or hydraulic systems), start a backup pump, or halt a process to avoid quality issues. This gives operators instant visibility and control over system conditions

Pressure Sensor Types: 8 kinds of pressure sensors

Pressure sensors are classified based on their distinct mechanisms for detecting and measuring pressure changes, utilizing various physical principles to sense mechanical stress. Some of the most common Pressure Sensor Types are listed below:

Piezoresistive (Most Common)

Piezoresistive sensors utilize materials whose electrical resistance changes when mechanically stressed. Pressure applied to the sensor deforms a diaphragm embedded with piezoresistive elements. This deformation alters the resistance, which is measured as a change in voltage across a circuit. This voltage change is then converted to a corresponding pressure reading. Their high output signal, robustness, and relative simplicity make them the most widely used pressure sensor type.

Capacitive

Capacitive sensors measure pressure based on changes in electrical capacitance. They consist of two conductive plates separated by a small gap, often with one plate being a flexible diaphragm. Applied pressure deflects the diaphragm, altering the distance between the plates and thus changing the capacitance. This capacitance change is detected electronically and converted into a pressure measurement. They offer good sensitivity, stability, and low power consumption, suitable for low-pressure ranges and harsh environments.

Piezoelectric

Piezoelectric sensors generate an electrical charge when subjected to physical force, utilizing the piezoelectric effect. Pressure applied to a piezoelectric crystal material creates a proportional charge across the crystal. This charge is measured and converted into a voltage signal representing the pressure. These sensors excel at measuring dynamic, rapidly changing pressures due to their high-frequency response and are often compact, but typically measure only changing pressure, not static pressure.

Optical

Optical sensors measure pressure by detecting changes in light properties. Pressure typically alters the position, shape, or refractive index of an optical element (like a diaphragm or fiber Bragg grating) within the sensor. This change modulates light intensity, phase, wavelength, or polarization traveling through the system. The modulated light signal is then analyzed to determine the applied pressure. They are highly immune to electromagnetic interference and suitable for remote sensing or hazardous environments.

Electromagnetic

Electromagnetic sensors measure pressure by detecting the movement of a ferromagnetic core within a coil. Pressure moves a diaphragm connected to the core. This displacement changes the inductance of the coil or the reluctance of a magnetic circuit. The resulting change in the coil’s electrical characteristics (inductance, impedance) is measured and converted to a pressure reading. They are robust and can handle high pressures but may be sensitive to external magnetic fields.

Strain Gauge

Strain gauge sensors rely on the principle that a material’s electrical resistance changes as it deforms under force. A spring element (like a diaphragm) deforms when pressure is applied. Strain gauges bonded to this element experience the same deformation, causing a proportional change in their electrical resistance. This resistance change, detected as a voltage shift in a Wheatstone bridge circuit, is calibrated to display the pressure. They are versatile, widely available, and excellent for long-term monitoring.

Resonant

Resonant sensors measure pressure by detecting shifts in the natural resonant frequency of a vibrating element. Pressure changes typically strain a diaphragm or beam designed to resonate at a specific frequency. This strain alters the element’s stiffness or mass, causing its resonant frequency to shift. The sensor electronics track this frequency change, which is directly correlated to the applied pressure. They offer very high accuracy, stability, and digital output capability.

Thermal

Thermal sensors measure pressure, especially gas pressure, by detecting changes in heat transfer properties. They contain a heated element. As gas pressure changes, the rate at which heat is conducted away from the element by the surrounding gas molecules also changes. This alters the element’s temperature and thus its electrical resistance (if a thermistor) or the power needed to maintain a constant temperature. This change is measured and correlated to pressure, common in vacuum and low-pressure applications.

8 Pressure Sensor Types: Features & Compassion

Key Pressure Sensor Applications

“The diverse Pressure Sensor Types available today unlocks numerous applications across your facility. This versatility means nearly any critical asset can benefit from pressure monitoring. Below we have listed  some of the most common and impactful uses for reference.

Automotive systems

Pressure sensors are fundamental to vehicle safety and performance. They continuously monitor critical parameters like tire inflation pressure and engine oil pressure. Precise sensing ensures optimal engine operation, fuel efficiency, and alerts drivers to potential tire failures.

Medical devices

Patient care relies heavily on accurate pressure measurement. Sensors are vital components in non-invasive blood pressure monitors and respiratory equipment like ventilators and anesthesia machines. They deliver the precise pressure readings essential for patient diagnostics and life-sustaining therapies.

Industrial process control

Maintaining consistent production quality demands rigorous pressure monitoring. Sensors are embedded throughout manufacturing lines to regulate fluid flows, chemical reactions, and system pressures in real-time. This ensures processes operate within strict parameters for both product standards and operational safety.

Weather and environmental monitoring

Atmospheric pressure measurement remains crucial for weather forecasting. Beyond predicting storms, sensors are integral to environmental systems, tracking pollution levels, monitoring emissions control devices, and optimizing the performance of wind turbines and related management systems.

Aerospace and aviation

Flight safety is critically dependent on pressure sensing. Sensors monitor cabin pressure for passenger comfort and safety, measure altitude via static air pressure, and ensure the integrity of critical hydraulic and fuel systems operating under extreme flight conditions.

HVAC systems

Efficient building climate control hinges on pressure measurement. Sensors optimize airflow in ducts, monitor filter status to maintain air quality, regulate refrigerant pressures, and ensure balanced system operation – all contributing to significant energy conservation.

Hydraulic and pneumatic equipment

These high-power systems operate under significant stress, often reaching pressures of 3000 psi or more in hydraulics. Sensors constantly detect pressure anomalies, identify leaks, monitor pump health, and prevent catastrophic system failures by ensuring pressures stay within safe operating limits.

Oil and gas industry

Operations in this sector face extreme conditions, from pipeline pressures (often 200-1500 psi for gas transmission) to deep well drilling. Pressure sensors are essential for pipeline integrity monitoring, wellhead control, refining process efficiency, and ensuring safety compliance across all extraction and distribution phases.

Conclusion

Modern Pressure Sensor Types show the sophisticated successors to those early barometers, transforming the invisible push and pull of forces—whether gas, liquid, or solid—into precise, actionable data. They achieve this by exploiting how pressure induces minuscule physical changes in specialized materials: bending diaphragms, altering electrical resistance, generating charges, or shifting resonant frequencies.

This core principle—detecting physical deformation and converting it into an electrical signal—enables astonishing accuracy and reliability. The diversity of sensing mechanisms, from piezoresistive and capacitive to piezoelectric and optical, allows tailoring sensors to specific pressures, environments, and applications. Integrated with control systems like PLCs, these signals provide real-time insights, triggering automated responses to maintain safety and efficiency.

Crucially, pressure sensors have become ubiquitous, silent sentinels underpinning modern life. They ensure automotive safety and performance, enable life-saving medical diagnostics and treatments, guarantee industrial process control, deliver accurate weather forecasts, maintain aircraft cabin pressure, optimize HVAC efficiency, manage powerful hydraulic systems, and secure operations in the demanding oil and gas sector.

From historical curiosity to fundamental technology, pressure sensors have evolved into indispensable tools, continuously making the invisible forces shaping our world visible, measurable, and manageable.

FAQ

When discuss the topic of “how to choose ceramic pressure sensor” for your application, the choice between a monolithic design and a flush diaphragm configuration can have a significant impact on the sensor’s performance, durability, and suitability for your specific needs.

Both types of ceramic pressure sensors offer unique advantages, and understanding the key differences can help you make an informed decision that aligns with your requirements.

In this post, we will explore the critical factors to consider when choosing between monolithic ceramic pressure sensor and flush diaphragm ceramic pressure sensor, providing you with a framework to make the most appropriate selection for your application.

Construction structure & sensing element

Monolithic

In a monolithic ceramic pressure sensor, the sensing elements are directly fabricated onto the ceramic diaphragm.

The key aspects are:

• The sensor has a single, monolithic ceramic structure.
• The sensing element is a thin, ceramic diaphragm, typically made of alumina (Al2O3) or zirconia (ZrO2).
• The ceramic diaphragm typically ranges from 50 to 500 micrometers (μm) in thickness.
• Piezo resistors or strain gauges are directly deposited onto the surface of the ceramic diaphragm using thick-film or thin-film techniques.
• The sensing elements are integrated onto the diaphragm but are not part of the diaphragm itself.

This construction provides a robust and integrated design, where the sensing elements are directly coupled to the deformation of the ceramic diaphragm when pressure is applied.

ESS501 Monolithic Type

Flush Diaphragm

In a flush diaphragm ceramic pressure sensor, the sensing elements are integrated directly into the ceramic diaphragm itself, creating a seamless interface with the sensor’s housing or surface.

The key aspects are:

• The sensing element is a thin, ceramic diaphragm, typically made of alumina (Al2O3) or zirconia (ZrO2).
• The sensor has a ceramic diaphragm, typically ranging from 50 to 500 micrometers (μm) in thickness, that is flush with the sensor’s housing or surface.
• The pressure-sensing elements, such as piezo resistors or capacitive sensors, are embedded within the ceramic diaphragm itself.
• This integrated design creates a smooth, uninterrupted surface, where the sensing elements are part of the diaphragm.

The flush diaphragm design is advantageous in applications where clogging or buildup of media needs to be avoided, as the seamless interface facilitates easy cleaning and maintenance of the sensor.

ESS502 Flush Diaphragm Type

Pressure and range requirements

Another important consideration is the pressure and temperature range requirements.

Both monolithic and flush diaphragm ceramic pressure sensors can cover a wide range of pressure measurements, typically from as low as 0-7 psi (0-50 kPa) up to as high as 0-10,000 psi (0-69 MPa). However, flush diaphragm sensors tend to have a slightly higher pressure range capability compared to monolithic sensors, due to their robust and integrated construction.

Monolithic

1. Pressure Range:
   • Monolithic ceramic pressure sensors are available for a wide range of pressure measurements, typically from as low as 0-7psi (0-6.9 kPa) up to 0-5,000 psi (0-34.5 MPa).
   • The specific pressure range for a monolithic sensor is largely determined by the thickness and design of the ceramic diaphragm.
2. Diaphragm Thickness:
   • The ceramic diaphragm in a monolithic sensor typically ranges from 50 to 500 micrometers (μm) in thickness.
   • Thinner diaphragms, around 50-100 μm, are used for lower pressure ranges, while thicker diaphragms, around 300-500 μm, are used for higher pressure ranges.
   • The diaphragm thickness is a critical factor in determining the sensor’s pressure range and sensitivity.
3. Sensitivity:
   • Thinner diaphragms in monolithic sensors generally exhibit higher sensitivity, as they can undergo greater deformation under the applied pressure.
   • This increased sensitivity allows monolithic sensors to accurately measure lower pressure ranges, down to 0-7psi (0-50 kPa).

Flush Diaphragm

1. Pressure Range:
   • Flush diaphragm ceramic pressure sensors can cover an even wider pressure range, typically from 0-7 psi (0-50 kPa) up to 0-10,000 psi (0-69 MPa).
   • The flush diaphragm design, combined with the inherent strength of the ceramic material, enables these sensors to withstand higher pressure levels.
2. Diaphragm Thickness:
   • The ceramic diaphragm in a flush diaphragm sensor also typically ranges from 50 to 500 micrometers (μm) in thickness.
   • However, the flush diaphragm design allows for slightly thinner diaphragms, as the sensor’s housing and construction provide additional support and protection.
3. Sensitivity:
   • Similar to monolithic sensors, thinner diaphragms in flush diaphragm sensors tend to exhibit higher sensitivity, enabling accurate measurements at lower pressure ranges.
   • The flush configuration and integrated design of the sensing elements within the diaphragm also contribute to the sensor’s sensitivity.

When it comes to temperature, both sensor types can operate over a wide range, often from -40°C to 125°C or higher, depending on the specific design and materials used.

That said, the flush diaphragm configuration may offer slightly better temperature resistance and stability, as the integrated design provides enhanced thermal management properties.

Pressure type

When measuring sealed gauge or absolute pressure, it is generally better to choose a flush diaphragm ceramic pressure sensor over a monolithic type.

Monolithic

• For sealed gauge or absolute pressure measurements, monolithic ceramic sensors would require a sealed and evacuated reference chamber within the sensor housing.
• Maintaining a high-quality vacuum reference can be more complex and potentially prone to degradation over time, which can affect the accuracy and long-term stability of the absolute pressure measurements.

Flush Diaphragm

• Flush diaphragm ceramic sensors can integrate the absolute or sealed pressure sensing elements directly into the ceramic diaphragm.
• This integrated design allows for a more robust and reliable absolute pressure measurement, as the sensing elements are an integral part of the diaphragm, minimizing the potential for leaks or instability in the reference vacuum.
• The flush configuration also provides a more compact and streamlined sensor design, which can be advantageous in applications with limited space.

In both sealed gauge and absolute pressure measurements, the integrated design and flush configuration of the flush diaphragm ceramic pressure sensors can offer several advantages over the monolithic type:

1. Improved Stability and Reliability: The integrated sensing elements and robust diaphragm design of flush diaphragm sensors can provide better long-term stability and reliability for sealed or absolute pressure measurements.
2. Compact and Space-Saving: The flush diaphragm design allows for a more compact and space-efficient sensor, which can be beneficial in applications with limited available space.
3. Enhanced Media Compatibility: The flush diaphragm configuration can also offer better resistance to media-induced issues, such as clogging or buildup, making it more suitable for applications involving harsh or contaminated process fluids.

Media compatibility

Media compatibility is another crucial factor to consider.

It is fact that both types are ceramic based solutions and share the most same characteristic when handle most material however, flush diaphragm ceramic pressure sensors are generally more resistant to clogging, buildup, and corrosion due to their seamless, flush interface with the process media. This makes them particularly well-suited for applications involving harsh or abrasive fluids.

Monolithic sensors, while still suitable for many industrial applications, may be more susceptible to media-induced issues, as the sensing elements are fabricated onto the diaphragm surface rather than being integrated into it.

Dimension and cost requirements

In addition to the application requirements and media compatibility, the size and form factor of the sensor can also play a role in the selection process.

Flush diaphragm ceramic pressure sensors can often offer a more compact and space-saving design compared to monolithic sensors. This is because the flush interface allows for a smaller overall sensor footprint, as the sensing elements are integrated directly into the diaphragm (instead of onto).

Click to Download Datasheet: ESS502 Flush Diaphragm Ceramic Sensor Cell

Monolithic sensors, on the other hand, may have a slightly larger form factor due to the separate construction of the diaphragm and sensing elements.

Click to Download Datasheet: ESS501 Monolithic Ceramic Sensor Cell

Finally, cost and availability should also be considered. Monolithic ceramic pressure sensors are generally more widely available and may have a lower cost, especially for lower-end applications. Flush diaphragm sensors, due to their specialized manufacturing process and design complexity, can be more expensive.

However, the enhanced performance and suitability for certain applications may justify the higher cost for specific use cases.

Application and Cost

Application Considerations

Monolithic ceramic pressure sensors are well-suited for general industrial applications where a robust, integrated design is preferred. These sensors feature a single, unified ceramic structure with the sensing elements directly fabricated onto the diaphragm, providing excellent mechanical stability and resistance to harsh environments.

Monolithic sensors are commonly used in applications such as pneumatic systems, hydraulic equipment, and general process control.

On the other hand, flush diaphragm ceramic pressure sensors are better suited for applications where the sensor needs to interface with a process fluid or media, such as in the food processing, pharmaceutical, or chemical industries.

The flush diaphragm design creates a seamless, uninterrupted surface that facilitates easy cleaning and prevents clogging or buildup of the media, making it the preferred choice for these types of applications. Flush diaphragm sensors are commonly used in applications involving corrosive liquids, slurries, or other aggressive media where a clean and easily maintainable sensor interface is required.

Cost Considerations:

Monolithic ceramic pressure sensors are generally more widely available and may have a lower cost compared to flush diaphragm sensors, especially for lower-end applications. The simpler and more integrated construction of monolithic sensors can contribute to their relatively lower manufacturing costs, making them a more cost-effective option for applications where the higher degree of integration and robustness is sufficient, without the need for the specialized flush diaphragm design.

Conversely, flush diaphragm ceramic pressure sensors may be more expensive due to the specialized manufacturing process and design complexity required to achieve the seamless, flush interface. The additional steps and materials involved in the production of flush diaphragm sensors can result in a higher overall cost compared to monolithic sensors.

However, the enhanced performance and suitability for specific applications, such as those involving harsh media or strict hygiene requirements, may justify the higher cost for certain use cases.

Take example

Let’s consider a practical example.

Imagine you are working on a food processing application that requires monitoring the pressure of a corrosive cleaning solution. In this case, a flush diaphragm ceramic pressure sensor would be the more appropriate choice. The seamless, flush interface of the sensor’s ceramic diaphragm would prevent any buildup or clogging of the cleaning solution, ensuring reliable and consistent pressure measurements.

Additionally, the enhanced media compatibility of the flush diaphragm design would provide superior resistance to the corrosive nature of the solution, extending the sensor’s lifespan and reducing the need for frequent maintenance or replacement.

On the other hand, if you are working on a general industrial application, such as monitoring the air pressure in a pneumatic system, a monolithic ceramic pressure sensor may be the more suitable option.

The robust, integrated construction of the monolithic sensor would provide the necessary durability and resistance to withstand the harsh industrial environment, while the lower cost and wider availability of these sensors could be advantageous for your application.

Take away

For your quick reference and help guide the selection, here are some take away we concluded when choosing between a monolithic ceramic pressure sensor and a flush diaphragm ceramic pressure sensor.

Application requirements:

• Monolithic sensors may be more suitable for general industrial applications where a robust, integrated design is preferred.
• Flush diaphragm sensors are better suited for applications where the sensor needs to interface with a process fluid or media, such as in food processing, pharmaceutical, or chemical industries, where a flush and easily cleanable surface is essential.

Pressure range:

• Both monolithic and flush diaphragm sensors can cover a wide range of pressure measurements, typically from 0-7 psi (0-50 kPa) up to 0-10,000 psi (0-69 MPa).
• However, flush diaphragm sensors tend to have a slightly higher pressure range capability compared to monolithic sensors, due to their robust construction.

Temperature range:

• Both sensor types can operate over a wide temperature range, typically from -40°C to 125°C or higher, depending on the specific design and materials used.
• However, the flush diaphragm design may offer slightly better temperature resistance and stability due to the integrated construction.
•  

Media compatibility:

• Flush diaphragm sensors are generally more resistant to clogging, buildup, and corrosion due to the seamless, flush interface with the process media.
• Monolithic sensors may be more susceptible to media-induced issues, but can still be suitable for many industrial applications.

Size and form factor:

• Flush diaphragm sensors can offer a more compact and space-saving design, as the flush interface allows for a smaller overall sensor footprint.
• Monolithic sensors may have a slightly larger form factor due to the separate construction of the diaphragm and sensing elements.

Cost and availability:

• Monolithic ceramic pressure sensors are generally more widely available and may have a lower cost compared to flush diaphragm sensors, especially for lower-end applications.
• Flush diaphragm sensors may be more expensive due to the specialized manufacturing process and design complexity.

Wrap up

In summary, when choosing between a monolithic ceramic pressure sensor and a flush diaphragm ceramic pressure sensor, consider the specific application requirements, pressure and temperature ranges, media compatibility, size constraints, and cost factors to determine the most suitable option. Consult with experienced engineers or manufacturers to ensure the selected sensor meets the necessary performance and reliability requirements for your application.

Datasheet Download

• Download Datasheet: ESS502 Flush Diaphragm Ceramic Sensor Cell
• Download Datasheet: ESS501 Monolithic Ceramic Sensor Cell

Introduction

Ceramic piezo resistive pressure sensor is one of the most popular models that adopt the sensing technology of ceramic piezo resistive, which have excellent piezo-resistive sensing features like high stability, good accuracy and temperature features, what is more, ceramic piezo resistive pressure sensor also have remarkable ability to work under corrosive situation where silicon piezo-resistive sensing is not very suitable.

The demand for more robust, stable, and versatile pressure sensors led to the development of ceramic piezo resistive pressure sensors. These sensors employ a ceramic diaphragm combined with a Wheatstone bridge, screen-printed with conducting layers. Ceramic piezo resistive pressure sensors offer several advantages, such as:

• – High accuracy levels
• – Long-term stability
• – Wide pressure range
• – Resistance to corrosion and abrasion
• – Versatility in various applications

As a result of their unique benefits, ceramic piezo resistive pressure sensors have become an attractive choice for both engineers and manufacturers.

The Design and Composition

Ceramic piezo resistive pressure sensors bring together the unique characteristics of ceramic materials and advanced thick film technology, creating a highly reliable and stable pressure sensing solution. Here, we will explore the design and composition of these sensors, focusing on the materials used, the importance of the ceramic substrate, and the screen-printed resistive circuitry and electrodes.

Materials used in the Construction

Ceramic piezo resistive pressure sensors employ a combination of materials that work together to ensure durability, precision, and stability in various environments. The primary materials used are:

Ceramic substrate: Alumina (Al2O3) or zirconia (ZrO2) are the most common ceramic materials for the substrate. They provide excellent mechanical and thermal characteristics, contributing to the sensor’s resistance to pressure, temperature, and corrosion.

Thick film materials: A combination of conductive and resistive paste materials, usually comprising metal alloys or metal oxide mixtures, are used to create the sensing elements and their conducting paths.

Protective coating: An additional layer of glass or polymer material may be applied to shield the sensing elements from mechanical damage and corrosive effects.

The Role of Ceramic Substrate

Stability and Strength: The Foundation for Resilience
When it comes to pressure sensing, stability and strength are paramount. Ceramic materials, with their excellent mechanical properties, provide the robust and durable foundation that ceramic thick-film pressure sensors require. 

Chemical Resistance: Thriving in Harsh Conditions
In many industrial and process control applications, the pressure sensors are exposed to a wide range of corrosive gases, liquids, and chemicals. Ceramic substrates shine in this regard, offering exceptional resistance to these harsh elements.

Thermal Stability: Maintaining Precision Across Extremes
Temperature fluctuations can wreak havoc on pressure sensing systems, but ceramic substrates are engineered to withstand these challenges. With their low thermal expansion coefficients, ceramic materials can accommodate wide temperature ranges with minimal impact on the sensor’s performance. 

Compatibility: Forging a Reliable Bond
The integration of thick-film pressure sensing elements onto the substrate is a critical step in the sensor’s fabrication. Ceramic materials exhibit excellent compatibility with the thick-film materials, facilitating a stable and reliable bond between the two. This compatibility helps to ensure the sensing elements remain firmly in place, maintaining the sensor’s integrity and performance over its lifetime.

Screen-printed Resistive Circuitry and Electrodes

The Wheatstone Bridge: The Heart of Pressure Sensing
At the core of a ceramic thick-film pressure sensor is the resistive circuitry, typically designed as a Wheatstone bridge. This ingenious configuration consists of four resistive elements that are strategically deposited onto the ceramic substrate using the screen-printing process.

As pressure is applied to the sensor’s diaphragm, these resistive elements change their resistance in a predictable and measurable way, enabling the accurate detection and monitoring of the applied pressure.

Reliable Conductive Pathways: Ensuring Robust Electrical Connectivity
In addition to the Wheatstone bridge, the screen-printing process also allows for the creation of consistent and reliable conducting paths on the ceramic substrate. These conductive traces play a crucial role in transmitting the electrical signals from the sensing elements to the external connectors or circuitry, ensuring the seamless flow of data and enabling precise pressure measurements.

Stable and Robust Electrodes: The Backbone of Electrical Integration
Complementing the resistive circuitry and conductive paths, the screen-printing process is also used to deposit metal electrodes onto the ceramic substrate. These electrodes, typically made from materials such as silver, gold, or platinum, provide stable and reliable electrical connections between the sensing components and the external interface.

Precision and Repeatability: The Hallmarks of Screen-Printing
The beauty of the screen-printing process lies in its ability to create these critical sensor elements with remarkable precision and repeatability. By carefully controlling the deposition of the conductive and resistive materials, engineers can ensure consistent and reliable patterns, ensuring the sensor’s performance remains stable and predictable over its lifetime.

Unlocking the Full Potential of Ceramic Thick-Film Pressure Sensors
The screen-printing process is a testament to the engineering prowess that goes into the fabrication of ceramic thick-film pressure sensors. By leveraging this advanced manufacturing technique, engineers can unlock the true potential of these remarkable devices, delivering unparalleled precision, reliability, and performance in a wide range of industrial, automotive, and process control applications.

Applications of Ceramic piezo resistive Pressure Sensors

Ceramic piezo resistive pressure sensors have firmly established themselves as essential components in the pursuit of enhanced efficiency, safety, and performance across a wide range of critical applications.

Check below table for details of application that used ceramic piezo resistive pressure sensor

Not suitable cases

While ceramic thick-film pressure sensors excel in static or slowly varying pressure applications, they may not be the optimal choice for dynamic pressure measurement scenarios that require an exceptionally fast response time. In applications where the pressure changes rapidly, such as in high-speed automotive or aerospace systems, sensors with a quicker reaction time and higher bandwidth may be more suitable.

Although ceramic thick-film pressure sensors are known for their thermal stability, there are certain applications that operate in temperature ranges beyond the typical limits of these sensors (-40℃-125℃). In environments with extreme temperatures, either extremely high or cryogenic, specialized pressure sensing solutions designed for such conditions may be necessary to ensure reliable and accurate pressure monitoring.

In some applications, the materials used in the construction of ceramic thick-film pressure sensors may not be compatible with the specific chemicals, solvents, or media present in the operating environment.

In such cases, engineers may need to explore pressure sensing technologies that utilize alternative materials better suited to the given application’s requirements.

ESS5 series ceramic pressure sensor

Comparison among different piezo-resistive sensing

What is silicon piezo resistive sensing

The underlying principle of silicon piezo-resistive pressure sensing is the piezo-resistive effect, where the electrical resistance of certain materials, in this case, silicon, changes when subjected to mechanical stress or pressure. By leveraging this phenomenon, silicon piezo-resistive pressure sensors can accurately detect and measure pressure variations.

The key components of a silicon piezo-resistive pressure sensor are:

Silicon Substrate:

• The sensing element is fabricated on a silicon substrate, which serves as the foundation for the sensor.
• Silicon is chosen due to its excellent mechanical properties, enabling it to withstand the applied pressure without deformation.

Piezo-Resistors:

• Piezo-resistors are carefully diffused into the silicon substrate, precisely positioned to detect the pressure-induced changes.
• These piezo-resistors are typically made of doped silicon, which exhibits a strong piezo-resistive effect.
• The resistance of the piezo-resistors varies linearly with the applied pressure, allowing for accurate pressure measurement.

Wheatstone Bridge Configuration:

• The piezo-resistors are arranged in a Wheatstone bridge circuit, which is a fundamental electrical configuration used to measure small changes in resistance.
• This configuration enables the sensor to detect the pressure-induced resistance changes and convert them into an electrical output signal, typically a voltage or current.

How silicon piezo resistive working

As mentioned above, the working principle of silicon piezo-resistive pressure sensors is based on the piezo-resistive effect, which is the fundamental phenomenon that enables these sensors to detect and measure pressure changes.

Pressure Application

• When an external pressure is applied to the sensor, the silicon substrate experiences mechanical deformation, which in turn causes the piezo-resistors to undergo a change in their electrical resistance.
• The magnitude of the resistance change is directly proportional to the applied pressure, following a linear relationship.

Wheatstone Bridge Configuration:

• The piezo-resistors are connected in a Wheatstone bridge circuit, which is a well-established electrical arrangement used to measure small changes in resistance.
• In the Wheatstone bridge, the piezo-resistors are connected in such a way that two of them experience an increase in resistance, while the other two experience a decrease in resistance, when pressure is applied.
• This differential resistance change creates an electrical imbalance in the Wheatstone bridge, which can be measured as a voltage or current output.

Signal Conditioning and Amplification:

• The small voltage or current output from the Wheatstone bridge is then processed by signal conditioning circuitry, which typically includes amplifiers, filters, and analog-to-digital converters (ADCs).
• The signal conditioning stage amplifies the sensor output, filters out any unwanted noise, and converts the analog signal into a digital format for further processing and analysis.

Silicon piezo resistive Example: diffused silicon pressure sensor

The diffused silicon pressure sensor is a device that fabricated under the principle of Silicon piezo resistive sensing, in case of diffused silicon pressure sensor, the externally applied pressure is transferred to a sensitive chip through a stainless steel diaphragm and internally sealed silicon oil (the sensitive chip does not directly contact the tested medium).

This causes the diaphragm to produce a micro-displacement proportional to the medium pressure, causing a change in the sensor’s resistance value. This change is detected by an electronic circuit and converted into a standard measurement signal corresponding to this pressure.

With its high sensitivity output, good dynamic response, high measurement accuracy, good stability, and easy miniaturization, it is sensitive to temperature. However, it is the preferred choice for mid-range sensors that can measure pressures greater than 7kPa, but less than 1000bar normally.

How diffused silicon pressure sensor fabricated?

The fabrication of diffused silicon pressure sensors involves a series of well-established semiconductor manufacturing processes, which leverages the semiconductor manufacturing techniques, enables the production of high-quality, reliable, and cost-effective silicon piezo-resistive pressure sensors.

Let’s delve into step by step as following,

1. Silicon Wafer Preparation
2. Thermal Oxidation
3. Photolithography
4. Dopant Diffusion
5. Interconnect Formation
6. Packaging and Passivation

The precision and control achieved during above fabrication steps are crucial in delivering the exceptional performance characteristics that make these sensors so widely used in various industries.

Pros and cons

Firstly, let’s delve into the key strengths that have made silicon piezo-resistive pressure sensors a go-to solution for so many applications.

Pros 1: Unparalleled Sensitivity and Precision

One of the standout features of these sensors is their exceptional sensitivity, with typical values ranging from 0.1 to 10 mV/V/kPa. This remarkable responsiveness allows them to detect and measure even the slightest pressure changes, making them invaluable in applications that demand the utmost precision, such as industrial process control, medical equipment, and high-performance automotive systems.

Pros 2: Remarkable Accuracy and Linearity

Accuracy is another area where silicon piezo-resistive pressure sensors truly shine. With errors typically less than 0.1% of the full-scale output, these sensors deliver unparalleled precision, ensuring reliable and consistent pressure measurements. Moreover, the highly linear pressure-to-output relationship simplifies the calibration and signal processing requirements, further enhancing the overall performance.

Pros 3: Lightning-Fast Response Times

In today’s fast-paced world, speed is of the essence. Silicon piezo-resistive pressure sensors rise to the challenge, boasting response times in the microsecond range. This lightning-fast performance enables real-time pressure monitoring and control, making them indispensable in applications that require rapid, high-precision pressure management.

Pros 4： Exceptional Temperature Stability and Durability

Engineered to withstand the rigors of demanding environments, silicon piezo-resistive pressure sensors are designed to maintain their performance across a wide temperature range, typically from -40°C to 125°C or beyond. Coupled with their inherent reliability and resistance to factors like vibration, shock, and corrosion, these sensors ensure consistent and dependable pressure measurement, even in the most challenging conditions.

While the advantages of silicon piezo-resistive pressure sensors are truly impressive, it’s important to acknowledge the potential drawbacks that engineers must consider when selecting the appropriate technology for their applications.

Cons 1: Sensitivity to Mechanical Stress and Strain

As these sensors rely on the piezo-resistive effect, they are inherently sensitive to mechanical stress and strain, which can impact their output. Careful design and packaging are required to minimize the influence of external mechanical forces on the sensor performance.

Cons 2: Temperature Dependence and Compensation

While modern silicon piezo-resistive pressure sensors have improved temperature stability, there is still some residual temperature dependence in their output. This necessitates the implementation of temperature compensation circuitry or algorithms to maintain accurate pressure measurements across a wide temperature range.

cons 3: Susceptibility to Moisture and Environmental Factors

Silicon-based sensors can be vulnerable to moisture and other environmental factors, which can potentially degrade their performance or even lead to sensor failure. Robust packaging and sealing techniques are essential to protect the sensor from these environmental influences.

Cons 4: Manufacturing Complexity and Cost

The fabrication of silicon piezo-resistive pressure sensors involves a multi-step semiconductor manufacturing process, which can be more complex and costly compared to some alternative pressure sensing technologies. This complexity can impact the overall cost and scalability of sensor production.

Cases that silicon piezo resistive is not suitable

Case 1: Dynamic, vibration or shock

One of the primary drawbacks of silicon piezo-resistive pressure sensors is their inherent sensitivity to mechanical stress and strain. This sensitivity, which is a core aspect of their operating principle, can become a double-edged sword in certain applications. For instance, in environments with high levels of dynamic, vibration or shock, the sensor output may be susceptible to interference from these external mechanical forces, leading to inaccuracies and potential failures.

In such cases, alternative pressure sensing technologies (piezo-electrical sensing) that are less sensitive to mechanical disturbances may be more appropriate.

Case 2: Rapid temperature fluctuations

While modern silicon piezo-resistive pressure sensors have made significant strides in improving temperature stability, there is still some residual temperature dependence in their output. In applications where the operating temperature range is particularly wide or where rapid temperature fluctuations are common, the need for sophisticated temperature compensation circuitry or algorithms can add complexity and cost to the overall system design.

For these scenarios, pressure sensors with inherently better temperature stability or self-compensation capabilities may be a more suitable choice.

Case 3: Some corrosive projects

Silicon-based pressure sensors, like many electronic devices, can be susceptible to the detrimental effects of environmental factors such as moisture, corrosive substances, and extreme atmospheric conditions. In applications where the sensor is exposed to harsh environments (for example ocean water) or where it must operate in the presence of these environmental stressors, the need for robust packaging and sealing becomes paramount.

Failure to adequately protect the sensor can lead to performance degradation, premature failure, and unreliable pressure measurements. In such cases, the use of specialized enclosures or the selection of pressure sensors designed for rugged environments may be necessary.

For example, in some corrosive seawater monitor system, it is better to use titanium alloy housing, ceramic capacitive sensing type level/ pressure transmitter, check details of: EST341 ceramic capacitive sensing transmitter

Case 4: Affordable budget cap

The fabrication of silicon piezo-resistive pressure sensors involves a multi-step semiconductor manufacturing process, which can be more complex and costly compared to some alternative pressure sensing technologies. In applications where cost is a critical factor or where the production volumes are relatively low, the higher manufacturing complexity of silicon sensors may make them less economically viable. In such scenarios, engineers may need to explore more cost-effective pressure sensing solutions (like ceramic piezo-resistive sensing instead) that still meet the necessary performance requirements.

Case 5: Other cases that more than the limitation

Let’s take an example of ESS319, one of the most popular models of silicon piezo resistive pressure sensor made by Eastsensor, the minimal measurable pressure is 7kpa, and max is 1000bar, any pressure if range less than 7kpa, or bigger than 1000bar (check EST380 for 2200bar), then silicon piezo resistive solution will be no the best one.

The most workable operation temperature for silicon piezo resistive is -40℃ to 85℃, any working temperature lower or higher than that, it is better to look for other solution, check the details in our blog: how to handle in extreme and harsh environments

The widely accepted accuracy for silicon piezo resistive sensing is 0.1% -0.5%/FS, if the project need higher accuracy, for example, 0.075 or 0.05%/FS, you may need to refer to EST4300M industry pressure solution.

Comparison among different piezo-resistive sensing

Piezoresistive Sensing

Piezoresistive sensing is kind of technique that used to measure force, pressure, or mechanical stress by exploiting the piezoresistive effect, which is the change in electrical resistance of a material when it is subjected to mechanical deformation or strain.

The piezoresistive effect is the change in electrical resistivity of a material when it is subjected to mechanical stress or strain. This effect is observed in certain materials, such as semiconductors (e.g., silicon, germanium) and some metals and semiconductor ceramics. The change in resistivity is proportional to the applied stress or strain, allowing the measurement of force, pressure, or mechanical deformation by monitoring the change in electrical resistance.

The principle behind piezoresistive sensing is based on the fact that when a material is subjected to mechanical stress or strain, its atomic structure and electronic band structure are altered, leading to a change in its electrical resistivity. This change in resistivity is typically linear and proportional to the applied stress or strain within a certain range.

Piezoresistive sensor

In a piezoresistive sensor, a piezoresistive material is integrated into a sensing element, often in the form of a thin film or a bulk material with a specific geometry. When a force or pressure is applied to the sensing element, it deforms, causing a change in the resistance of the piezoresistive material. This change in resistance can be measured and converted into an electrical signal output that is proportional to the applied force or pressure.

Piezoresistive sensors are widely used in various applications, including:

1. Pressure sensors: Used to measure pressure in various fields, such as automotive, industrial, and medical applications.
2. Force sensors: Used to measure forces in load cells, strain gauges, and tactile sensors.
3. Accelerometers: Used to measure acceleration and vibration in applications like inertial navigation, shock detection, and motion sensing.
4. Tactile sensors: Used in robotics and haptic interfaces to detect touch, pressure distribution, and surface texture.

In now days, the piezoresistive effect is often combined with other sensing principles, such as capacitive or piezoelectric sensing, to create more advanced and versatile sensor systems.

Click to check: 5 Pressure Sensor Working Principles You Need to Know

How Piezoresistive Pressure Sensors Work

Piezoresistive pressure sensors are a type of sensor that work through the piezoresistive effect, which is the change in resistance of a material when mechanical strain is applied. This effect is usually obtained with semiconductor materials such as silicon or germanium.

The basic structure of a piezoresistive pressure sensor includes a diaphragm and a resistor, or piezoresistor. When pressure is applied to the diaphragm, it deforms or flexes, causing a strain that changes the resistance of the piezoresistor.

Steps breakdown

Here’s a step-by-step breakdown of how piezoresistive pressure sensors work:

1. The sensor is exposed to a pressure input (such as air or liquid pressure). The pressure is typically applied to a thin silicon or metal diaphragm where the piezoresistors are located.
2. The applied pressure causes the diaphragm to deform or flex. The amount of deformation is proportional to the amount of applied pressure.
3. The deformation of the diaphragm causes a change in the strain experienced by the piezoresistors.
4. This strain changes the electrical resistance of the piezoresistors. Typically, the change in resistance is proportional to the applied pressure, allowing for a measurement of the pressure.
5. The change in resistance is then measured by an electrical circuit. This is typically done through a Wheatstone bridge configuration, an electrical circuit setup used to measure the resistance.
6. The change in resistance is then converted into an electrical signal (voltage or current) that can be read, processed, and interpreted by a readout or control device.

An example

Imagine you have a small, thin square of silicon, which is a semiconductor material. This square is called a piezoresistive sensing element. It’s designed to change its electrical resistance when it’s deformed or squeezed.

Now, let’s say we want to measure the pressure of a gas or liquid. We take this piezoresistive sensing element and carefully mount it on a thin, flexible metal diaphragm. This diaphragm acts like a drumhead – it can bulge or deflect when pressure is applied to it.

When there’s no pressure, the diaphragm and the piezoresistive sensing element are flat and unstressed. In this state, the sensing element has a specific resistance value, let’s say 1000 ohms.

But when we apply pressure to the diaphragm, it starts to bulge or deflect. This deformation causes the piezoresistive sensing element to be squeezed or stretched, changing its resistance value. The higher the pressure, the more the resistance changes.

For example, in a typical piezoresistive pressure sensor designed for automotive applications, the sensing element might have a resistance change of about 0.2 ohms for every 1 psi (pound per square inch) of pressure applied. So, if the pressure is 100 psi, the resistance would change from 1000 ohms to around 1020 ohms.

We can measure this resistance change using a simple electrical circuit and convert it into a 4-20mA current or 0-5v voltage or I2C digital signal that represents the pressure value.

Now, let’s talk about some specific technical specifications:

• Sensing Element Material: Silicon is commonly used for its excellent piezoresistive properties and compatibility with integrated circuit fabrication processes.
• Diaphragm Material: Stainless steel, silicon, or other materials with good mechanical properties and compatibility with the sensing element.
• Pressure Range: Piezoresistive sensors can be designed for various pressure ranges, from millibar (mbar) levels for low-pressure applications to thousands of psi for high-pressure applications.
• Sensitivity: Typically expressed as the resistance change per unit of pressure, e.g., 0.2 ohms/psi.
• Linearity: Most piezoresistive sensors have good linearity (linear resistance change with pressure) over a wide range, often better than 0.5% of full-scale output.
• Temperature Compensation: Integrated circuits or software algorithms are used to compensate for temperature effects on the sensing element and electronics.

The most common types of piezoresistive sensing

Silicon Piezo-Resistive (Diffused) | The Epitome of Sensitivity and Speed

Silicon piezo-resistive pressure sensors harness the power of the piezo-resistive effect, where the electrical resistance of certain materials changes in response to mechanical stress or pressure. These sensors feature a silicon-based sensing element, with piezo-resistors carefully diffused into the substrate. By arranging these piezo-resistors in a Wheatstone bridge configuration, these sensors can precisely detect and measure the pressure-induced resistance changes. What sets silicon piezo-resistive sensors apart is their exceptional sensitivity, remarkable accuracy, and lightning-fast response times, often reaching the microsecond range. These capabilities make them indispensable in a wide array of applications, from industrial process control and medical equipment to automotive systems.

Ceramic Piezo-Resistive (Thick-Film) Pressure Sensors: Rugged and Versatile

Ceramic piezo-resistive pressure sensors offer a unique approach to pressure measurement. Instead of relying on silicon, these sensors utilize a ceramic-based sensing element, typically a mixture of oxides, with a thick-film piezo-resistive layer deposited on top. This design allows for the creation of pressure sensors with an impressive range, from low pressures in the millibar range to high pressures in the hundreds of bars.

Ceramic piezo-resistive sensors are renowned for their exceptional robustness, exceptional temperature stability, and remarkable resistance to harsh environmental conditions. These attributes make them invaluable in industrial automation, process control, and automotive applications where durability and reliability are paramount.

Thin-Film Piezo-Resistive (Sputtering) Pressure Sensors: Miniaturized Precision

Thin film piezo resistive innovative devices leverage the sputtering deposition process to create a highly sensitive and compact sensing element, often just a few microns thick.

This thin-film approach allows for the fabrication of miniaturized pressure sensors with remarkable sensitivity and fast response times, making them ideal for integration into micro-electromechanical systems (MEMS) and other compact, high-performance applications.

From medical diagnostics and industrial process control to consumer electronics, thin-film piezo-resistive pressure sensors are redefining the possibilities of pressure measurement.

Comparison among different piezo-resistive sensing

What is Thin Film Pressure Sensor?

A thin-film pressure sensor is a type of pressure sensing device that utilizes a thin-film sensing element deposited on a substrate material. The sensing element is typically a thin layer of material, such as polysilicon, silicon nitride, or metal alloys, with a thickness ranging from a few nanometers to a few micrometers.

The basic structure of a thin-film pressure sensor consists of the following components:

Substrate: The substrate material serves as the base for the sensor’s construction. Common substrates used include silicon, glass, or ceramic materials.

Thin-film sensing element: This is the core component responsible for pressure sensing. The sensing element is deposited on the substrate using techniques like sputtering, chemical vapor deposition (CVD), or other thin-film deposition methods.

Diaphragm: A thin, flexible diaphragm is created on the substrate, often through micromachining or etching processes. The thin-film sensing element is strategically placed on or near the diaphragm.

The diaphragm structure is often bonded to a backing material or a second substrate to create a sealed cavity or reference pressure chamber.

The sensing principle

The operating principle of a thin-film pressure sensor is based on the piezoresistive effect, where the electrical resistance of the thin-film sensing element changes in response to the mechanical strain or deformation caused by applied pressure.

When pressure is applied to the diaphragm, it deflects, causing the thin-film sensing element to experience strain, which in turn changes its electrical resistance.

This change in resistance is detected and converted into an electrical signal using appropriate signal conditioning circuitry, allowing the measurement of pressure.

The thin-film sensing element is often configured in a Wheatstone bridge or other resistive circuit arrangement to enhance sensitivity and provide temperature compensation.

The thin-film sensing element is often configured in a Wheatstone bridge arrangement, with two active resistors (sensing pressure) and two reference resistors (not subjected to pressure). This configuration allows for temperature compensation, increased sensitivity, and common-mode noise rejection.

The change in resistance of the active resistors due to the applied pressure creates an imbalance in the Wheatstone bridge, resulting in a measurable voltage difference across the bridge’s output terminals.

The output voltage from the Wheatstone bridge is typically small and requires amplification and signal conditioning. This is achieved using instrumentation amplifiers, analog-to-digital converters (ADCs), or dedicated signal conditioning circuits.

The conditioned output signal is then processed, often by a microcontroller or digital signal processor, to calculate the corresponding pressure value. This calculation is based on the calibration data and the known relationship between the output signal and the applied pressure.

Thin-film pressure sensors can be designed and optimized for different pressure ranges, sensitivities, and environmental conditions by adjusting factors such as the diaphragm size, thickness, and material properties, as well as the dimensions and configurations of the thin-film sensing element.

Additionally, these sensors can be integrated with microelectronic circuits and signal conditioning components on the same substrate, enabling the development of compact, highly integrated pressure sensing solutions for various applications, including automotive, industrial, medical, and consumer electronics.

Highlight feature

High accuracy and precision: ±0.1%-±0.25%

One of the most significant advantages of thin-film pressure sensors is their ability to achieve high accuracy and precision in pressure measurements.

High-quality thin-film sensors can typically achieve an accuracy of ±0.25% to ±0.5% of the full-scale output (FSO) or better like±0.1%.

For example, a common automotive manifold absolute pressure (MAP) sensor with a 0-5 bar range and ±0.25% FSO accuracy would have an error of ±12.5 mbar across the entire pressure range.

Wide pressure range: 0.001bar(1mbar)~2000bar

Thin-film pressure sensors can be designed to measure pressures ranging from a few millibars (mbar) to hundreds of bars, making them suitable for a wide range of applications.

For instance, some thin-film sensors can measure low pressures as low as 1 mbar, materials like sputtered or implanted polysilicon are commonly used due to their high sensitivity and good performance；

For high pressures, up to 2000 bar or even higher in specialized applications, materials like silicon carbide (SiC) or specific metal alloys (e.g., platinum, nickel-chromium) may be preferred due to their high strength and stability under extreme conditions.

The sensing element design and layout can be optimized for different pressure ranges, with larger sensing resistors for low pressures and smaller resistors for high pressures.

However, after assembly process, when such sensor has been produced pressure transmitter or transducer, in order to keep full balance and ensure long term stability, the minimal measurable range will increase to 4bar about.

On the other hand, the technics of packaging and sealing also take important effect to achieve wide pressure range.

Hermetic packaging techniques, such as welding or brazing, are essential to ensure a leak-tight enclosure and prevent moisture ingress or contaminants from affecting the sensor’s performance.

For high pressures, specialized pressure ports and fittings made of high-strength materials like stainless steel or Inconel may be required to withstand the extreme pressures without leakage or deformation.

It’s important to note that achieving such a wide pressure range often results in larger sensor sizes, higher manufacturing costs, and increased complexity. Additionally, rigorous testing and qualification processes, including pressure cycling tests, burst pressure tests, and long-term stability evaluations, are essential to ensure the reliability and performance of these specialized thin-film pressure sensors.

Temperature compensation: -20℃~120℃；  -20℃~150℃/200℃

The main techniques to design a thin film pressure sensor that endures high temperatures is: Choose tough materials. Design it to handle thermal expansion. Pack it up in a material that can take the heat. Use wiring that won’t melt. Add circuits that adjust the readings when it gets hot. And don’t forget to use a temperature-resistant adhesive.

It’s important to note that designing thin-film pressure sensors for high-temperature operation often involves trade-offs in terms of sensor size, cost, and complexity. Extensive testing and qualification processes, including temperature cycling tests and long-term stability evaluations, are crucial to ensure the reliability and performance of these specialized sensors.

High burst pressure performance: 3X-10X

By carefully selecting materials, optimizing diaphragm designs, implementing robust packaging techniques, and incorporating overload protection mechanisms, it is possible to develop thin-film pressure sensors with high burst pressure capabilities, ranging from 3X to even 10X the maximum rated pressure, while maintaining the desired accuracy and performance characteristics.

How to design High Temperature thin film pressure sensor

Designing thin-film pressure sensors to withstand high working temperatures up to 150°C (302°F) requires a careful selection of materials, specialized fabrication techniques, and effective temperature compensation strategies.

Substrate Material Selection

It’s true that most silicon substrates have a temperature limit of around 125°C, beyond which their properties can degrade. For some high-temperature applications up to 150°C or higher, suitable substrate materials include aluminum nitride (AlN) and silicon carbide (SiC).

AlN has a high thermal conductivity (180-200 W/m·K) and a compatible coefficient of thermal expansion (CTE) with silicon, making it a good choice for temperatures up to 300°C.

SiC has an even higher thermal conductivity (270-370 W/m·K) and can withstand temperatures up to 600°C, making it suitable for extreme high-temperature environments.

Diaphragm Material Selection

The diaphragm material should have a compatible CTE with the substrate to minimize thermally induced stress and deformation. For temperatures up to 150°C, materials like silicon nitride (Si3N4), polysilicon, or silicon carbide (SiC) can be used for the diaphragm.

Si3N4 has good mechanical properties and can withstand temperatures up to 850°C. Polysilicon exhibits good piezoresistive properties and can operate up to 300°C.

SiC has excellent mechanical strength and can withstand temperatures up to 600°C.

Thin-Film Sensing Element

It is important that the thin-film sensing element should maintain its piezoresistive properties and stability at high temperatures.

In practice, sputtered or implanted polysilicon is a common choice for temperatures up to 300°C.

Silicon carbide (SiC) thin films can be used for temperatures up to 600°C due to their exceptional stability and piezoresistive properties.

Metal alloy thin films, such as platinum (Pt) or nickel-chromium (NiCr), can also be used for high-temperature applications, but they may require additional temperature compensation techniques.

Temperature Compensation

Implementing effective temperature compensation is crucial to maintain accuracy over a wide temperature range.

Basically, the Wheatstone bridge configuration, with two active and two reference resistors, can provide basic temperature compensation by canceling out resistance changes due to temperature.

Advanced compensation techniques involve integrating on-chip temperature sensors, such as resistive temperature detectors (RTDs) or diodes, and implementing compensation algorithms in the signal conditioning circuitry or digital signal processing.

Good compensation algorithms can account for non-linear temperature effects and variations in material properties, ensuring accurate pressure measurements across the entire temperature range.

Packaging and Sealing

Hermetic packaging techniques, such as welding or brazing, are essential to prevent moisture ingress and ensure a leak-tight enclosure.

Materials used for packaging should have compatible CTEs with the sensor components to minimize stress and deformation at high temperatures. Glass-to-metal sealing or ceramic packaging may be employed for high-temperature applications.

Signal Conditioning and Interfacing

High-temperature signal conditioning circuits and interfacing components are required to ensure proper operation and accuracy at elevated temperatures.

Specialized high-temperature operational amplifiers, analog-to-digital converters (ADCs), and microcontrollers can be used to process and digitize the sensor output signals.

Digital signal processing techniques can further enhance accuracy, stability, and temperature compensation capabilities.

How to design High Accuracy thin film pressure sensor

To achieve high accuracy like 0.1% or 0.25% , the designers always need to focus on several key aspects of the sensor design and manufacturing process.

First, the diaphragm, which is the primary component responsible for translating the applied pressure into mechanical deflection, needs to be designed with utmost precision. The diaphragm thickness and geometry play a crucial role in determining the sensor’s sensitivity and linearity.

Typically, materials like silicon, silicon nitride, or single-crystal silicon carbide are used for high-accuracy diaphragms. The thickness can range from a few micrometers to tens of micrometers, depending on the pressure range and desired sensitivity.

Additionally, specialized diaphragm geometries, such as corrugated or bossed designs, can improve linearity and reduce stress concentrations, which can affect accuracy.

Next, the thin-film sensing element, which converts the diaphragm’s deflection into an electrical signal, must exhibit excellent piezoresistive properties, stability, and minimal hysteresis (the tendency to exhibit different output values for the same input, depending on the direction of change).

Sputtered or implanted polysilicon is a common choice due to its high sensitivity and good linearity. Silicon carbide thin films can also be used, especially in high-temperature applications, as they offer exceptional stability and linearity.

Effective temperature compensation is crucial for maintaining high accuracy over a wide temperature range. This involves integrating on-chip temperature sensors, such as resistive temperature detectors or diodes, and implementing advanced compensation algorithms in the signal conditioning circuitry or digital signal processing.

These algorithms can account for non-linear temperature effects, variations in material properties, and offset and span errors, ensuring accurate pressure measurements across the entire temperature range.

High-resolution analog-to-digital converters (ADCs) with low noise and high linearity are essential for achieving high accuracy.

Specialized instrumentation amplifiers with low offset and drift can be used to amplify the sensor’s output signals with minimal error.

Digital signal processing techniques, such as linearization algorithms, filtering, and advanced calibration methods, can further enhance accuracy and compensate for non-linearities and errors.

Rigorous calibration and trimming processes are necessary to achieve high accuracy specifications. Laser trimming techniques can be used to precisely adjust the resistor values in the sensing element or bridge circuit, minimizing offset and span errors.

Automated calibration systems and mathematical models can be employed to characterize and compensate for non-linearities, hysteresis, and other error sources.

Finally, hermetic packaging techniques, such as welding or brazing, are essential to prevent moisture ingress and ensure long-term stability. Packaging materials and designs should minimize stress concentrations and thermal gradients that can introduce errors or non-linearities.

Environmental protection measures, such as shielding and filtering, may also be necessary to minimize electromagnetic interference (EMI) and other external factors that can affect accuracy.

By carefully considering and optimizing these various aspects of the sensor design, manufacturing, and calibration processes, it is possible to achieve thin-film pressure sensors with high accuracy levels, such as 0.1% or 0.25% of the full-scale output.

Click to check more details about Pressure Sensor Accuracy

Other Piezo-Resistive Pressure Sensors

On top of above discussed Thin-film pressure sensor which using piezo-resistive principle, with four resistors are placed on a diaphragm in a Wheatstone bridge pattern to track the diaphragm’s deformation under pressure.

There are also other types of piezoresistive pressure sensor, like the following:

Ceramic Thick-Film Pressure Sensor

Thick-film sensors use the same setup as thin-film sensors by grouping four resistors into a Wheatstone bridge. But instead of attaching them to the base, thick-film sensors print the resistors onto a base such as ceramic using special technology, and then they heat it to a high temperature. They also detect change in resistance due to the diaphragm’s deformation, caused by stretching and compressing the material.

Diffused Silicone Piezo-resistive Pressure Sensor

Unlike the first two types, diffused silicone, actually act as kind of semi-conductor to uses a silicon measuring diaphragm with special diffused structures. They take advantage of the piezoresistive effect, which involves changing electrical resistance in the silicon due to stretching and compressing, thereby affecting electron mobility under mechanical stress.