Pressure sensors are important devices in various industrial applications, and their performance heavily depends on the core technology used. The pressure sensing element, or the core, is the heart of these devices and determines their accuracy, stability, and suitability for specific use cases.
In this article, we will explore the most widely used types of pressure sensors, including sputtered thin film pressure sensors, piezoresistive silicon pressure sensors, strain gauge pressure sensors, ceramic thick film pressure sensors, and ceramic capacitive pressure sensors. We’ll compare their working principles, advantages, limitations, and ideal applications.
1. Sputtered Thin Film Pressure Sensor
Working Principle
Sputtered thin film technology involves depositing a thin layer of metal or metal alloy onto a substrate, usually a ceramic or silicon base. The thin film is patterned into resistive elements, which change resistance when subjected to pressure. These sensors are typically used in high-performance applications due to their high stability and accuracy.
Advantages
High Long-term Stability and Accuracy: Sputtered thin film sensors provide exceptional long-term stability and high precision.
Wide Pressure Range: They can handle a wide range of pressures, from low to very high.
Temperature Compensation: They are less affected by temperature changes compared to piezoresistive sensors.
Strong Overload Capability: they can withstand conditions that exceed its rated limits without suffering damage or significant performance degradation, suitable for applications where fluctuations in pressure, temperature, or other operating conditions can occur unexpectedly.
Limitations
Higher Cost: Due to the complex manufacturing process, these sensors tend to be more expensive.
Applications
Sputtering thin film sensors are widely used in aerospace, industrial automation, high-pressure systems, hydraulic systems, and heavy equipment.
2.Piezoresistive Silicon Pressure Sensor
Working Principle
Piezoresistive pressure sensors work based on the principle that the resistance of certain semiconductor materials (typically silicon) changes when subjected to mechanical strain. A silicon diaphragm is typically used, and when pressure is applied, the diaphragm deforms. This deformation causes a change in the resistance of the material, which is then measured and converted into a pressure reading.
Advantages
High Sensitivity and Accuracy: Silicon-based pressure sensors are known for their excellent sensitivity and precise measurements. And the stability is also good.
Small Size: The technology allows for compact designs, ideal for applications where space is limited.
Cost-Effective: Piezoresistive sensors are relatively inexpensive to produce.
Limitations
Temperature Sensitivity: These sensors can be sensitive to temperature fluctuations, which may require additional compensation.
Limited Pressure Range: They are typically used for medium pressure applications and may not perform well under extreme conditions.
Applications
Piezoresistive silicon sensors are commonly used in automotive, me-dical devices, and HVAC systems, where high accuracy and compactness are critical.
3. Strain Gauge Pressure Sensor
Working Principle
Strain gauge pressure sensors operate by using a strain gauge, which is a resistor that changes resistance when stretched or compressed. The strain gauge is typically bonded to a diaphragm, which deforms under pressure. The change in resistance of the strain gauge is then measured to determine the applied pressure.
Advantages
High Accuracy: Strain gauges are known for their high accuracy and reliability.
Wide Application Range: They are versatile and can be used for various pressure ranges, from low to very high pressures.
Low cost: this technology is quite mature and it offers quite economic sense.
Limitations
Temperature Effects: Strain gauges can be affected by temperature changes, which may require compensation.
Complex Calibration: Strain gauge-based systems require precise calibration to ensure accuracy.
Applications
Strain gauge sensors are used in applications requiring high accuracy, such as in aircraft, me-dical instruments, and industrial machinery.
4. Ceramic Thick Film Pressure Sensors
Working Principle
Ceramic thick film sensors are based on a ceramic substrate that is coated with a resistive film. This film is applied using a thick-film process, where a conductive material is deposited onto the ceramic. The sensor's resistance changes when pressure is applied, which is then converted into a readable electrical signal.
Advantages
High Durability: Ceramic pressure sensors are resistant to harsh environments, high temperatures, and aggressive chemicals. It is strongly corrosion resistant.
Wide Pressure Range: They are well-suited for both low and high-pressure and temperature applications.
Cost-Effective: They are cheaper to produce than thin-film sensors.
Limitations
Lower Accuracy: Compared to thin film and piezoresistive sensors, ceramic thick film sensors typically have lower accuracy.
Applications
Ceramic thick film sensors are commonly used in automotive systems, me-dical equipment, hydraulic systems and refrigeration systems.
5. Ceramic Capacitive Pressure Sensors
Working Principle
Ceramic capacitive pressure sensors utilize a diaphragm that forms part of a capacitor. When pressure is applied, the diaphragm moves, changing the distance between the capacitor plates and thus altering the capacitance. This change in capacitance is measured and converted into pressure data.
Advantages
High Accuracy and Stability: These sensors are highly accurate and stable over time, even in fluctuating environmental conditions.
High Sensitivity: Ceramic capacitive sensors offer excellent sensitivity, especially at low pressure ranges.
Low Power Consumption: These sensors require less power than other types.
Limitations
Sensitivity to Mechanical Shock: They can be sensitive to mechanical shock and vibration, which can affect their performance.
Applications
Ceramic capacitive pressure sensors are used in high-precision applications, including me-dical devices, automotive sensors, and industrial pressure monitoring systems.
6. How to Choose the Right Pressure Sensors?
Since there are so many types of pressure transmitters on the market, then how we choose the right one? Generally, it depends on factors as below.
Pressure Range
Select a sensor that matches the pressure range of your application. Make sure the sensor can handle the maximum and minimum pressures you expect to measure.
Type of Pressure
The pressure is divided into gauge, absolute, and differential pressure. Gauge pressure sensors measure relative pressure to atmospheric pressure. Absolute pressure sensors measure pressure relative to a perfect vacuum. Differential pressure sensors measure the difference between two pressures. Choose based on your application needs.
Environmental Conditions
Ensure the sensors can operate within the required temperature limits, and environments. Choose the proper materials for different environments.
Accuracy
Ensure the sensor provides the accuracy needed. Higher accuracy is essential for critical applications.
Output Signal
Different sensors offer different signals, for example, analog output (e.g., 4-20mA, 0-10V, 0.5-4.5V), and digital output (e.g., RS485, Modbus).
Power Supply
Choose a sensor with a power supply that matches your system's requirements. For example, DC Supply, battery power or sonar power.
Durability and Lifespan
Consider the sensor’s IP rating, explosion-proof performance. Sensors designed for harsh environments typically last longer and require less maintenance.
Cost
Except the product cost, consider the maintenance and calibration costs over time too.
7. Conclusion
Choosing the right pressure sensor involves assessing several key factors and the sensing technology. Whether piezoresistive, capacitive, sputtering film or ceramic, should match your specific application requirement.
