Pressure Sensors Guide: Categories, Material Selection, and Key Performance Features

Pressure sensors are categorized primarily based on the type of pressure measurement they perform:

• Absolute Pressure Sensors: Measure pressure relative to a perfect vacuum (zero reference). They always provide positive values and are used in applications like altitude measurement, barometric pressure sensing, and vacuum systems.
• Gauge Pressure Sensors: Measure pressure relative to atmospheric pressure. These sensors have one side vented to atmosphere and give readings above or below ambient pressure, commonly used in hydraulic or pneumatic systems.
• Differential Pressure Sensors: Measure the difference in pressure between two points. Typical uses include fluid flow measurement, filter condition monitoring, and valve leak detection.

Another way to classify sensors is by their sensing technology, including piezoresistive, capacitive, piezoelectric, inductive, and optical sensors, each suited for different applications and environments.

Choosing appropriate materials for pressure sensors is crucial as materials impact durability, corrosion resistance, accuracy, and environmental compatibility.

• Sensing Element Materials:
  • Silicon: Widely used due to high sensitivity and stability but sensitive to temperature changes.
  • Stainless Steel: Excellent for harsh, corrosive environments with good strength but less sensitive than silicon.
  • Ceramic: Chemically resistant and stable but brittle, suited for harsh environments with moderate pressure ranges.
  • Metal Foil Strain Gauges: Durable with good stability, albeit less sensitive than silicon.
• PCB Materials:
  • FR-4: Common, cost-effective, with good mechanical and electrical properties.
  • Polyimide: Suitable for high temperatures with excellent flexibility.
  • PTFE (Teflon) and Rogers Laminates: Ideal for high-frequency applications but expensive.

Additional components such as O-rings, cables, wiring insulation, and housing materials also need selection based on their chemical compatibility and mechanical stress resistance to ensure sensor longevity and accuracy in specific media.

Selecting the right pressure sensor entails considering important performance specifications:

• Pressure Range and Rated Pressure: Defines the sensor's operating limits from minimum to maximum pressure to avoid damage.
• Accuracy and Linearity: Indicates how closely the sensor’s output matches the actual pressure and the consistency of output across the measurement range.
• Temperature Compensation and Stability: Since materials and electronics are temperature-sensitive, compensation ensures reliable readings across varying temperatures.
• Response Time: Important for dynamic applications requiring rapid pressure changes measurement.
• Sensitivity and Resolution: Determines how small a change in pressure the sensor can detect.
• Durability and Media Compatibility: Assess sensor resistance to mechanical stress, vibration, and exposure to fluids or gases in harsh environments.

For harsh environments, pressure sensors with stable long-term performance, high sensitivity, wide pressure range, and compatibility with corrosive or aggressive media are preferred. Advanced models integrate sealed designs and employ materials such as stainless steel and ceramics with features like lifetime drift below 0.5% and operation at temperatures from –40 °C to 150 °C.