Core working principle
Pressure sensors detect changes in medium pressure and convert it into measurable electrical signals. The common principles can be divided into three categories:
Piezoresistive: Utilizing the piezoresistive effect of semiconductor materials, the resistance value changes when the pressure changes, and the voltage signal is output through a Wheatstone bridge. For example, MEMS piezoresistive sensors integrate piezoresistive elements onto silicon membranes through micro machining technology, which has high sensitivity and is suitable for low-pressure measurements (such as 0-1MPa).
Piezoelectric: Based on the positive piezoelectric effect of piezoelectric materials, pressure causes the material to generate an electric charge, and the amount of charge is proportional to the pressure. For example, quartz crystal or PVDF piezoelectric sensors are commonly used for dynamic pressure measurement (such as vibration, shock), but they need to be used in conjunction with charge amplifiers and cannot measure static pressure.
Capacitive: The capacitance value varies with pressure by changing the distance between the capacitor plates or the dielectric constant. For example, ceramic capacitive sensors use ceramic membranes and fixed electrodes to form capacitors, which have good stability and are suitable for medium to high voltage scenarios (such as 1-60MPa).
Key performance parameters
Range: Select according to the application scenario (such as 0-100kPa for air pressure measurement and 0-100MPa for hydraulic systems).
Accuracy: including linearity, hysteresis, repeatability, and comprehensive error is usually expressed as a percentage of full scale (such as ± 0.5% FS).
Output signal: Analog output (such as 4-20mA, 0-5V) has strong anti-interference ability, while digital output (such as I ² C, RS485) is easy to integrate.
Medium compatibility: The chemical compatibility between the sensor and the measuring medium needs to be considered (such as using stainless steel or ceramic materials for corrosive liquids).
Selection Guide
Low voltage scenarios (such as medical equipment, HVAC): Choose piezoresistive MEMS sensors with small size and low cost.
Dynamic pressure (such as engine testing, explosion shock): Choose piezoelectric sensors with fast response speed (microsecond level).
Medium to high voltage industrial scenarios (such as hydraulic systems, petrochemicals): Choose ceramic capacitors or diffused silicon sensors that are resistant to high voltage and have high stability.
Harsh environment (such as high temperature, strong corrosion): Choose ceramic or stainless steel packaging, with a protection level of IP67 or above.
Example: To measure the water level in a water tank (pressure range 0-0.1MPa), a pressure resistance sensor (range 0-0.2MPa, output 4-20mA) can be selected; If monitoring the detonation pressure (transient high pressure) of a car engine, a piezoelectric sensor (range 0-50MPa, response time<1 μ s) is required.