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Pressure sensor working principle

2026.03.20

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     The core objective of a pressure sensor is to convert physical pressure—whether from gas, liquid, or mechanical force—into a measurable electrical signal. This "conversion" process typically occurs in two steps:
     1. The sensing element detects the pressure and produces a slight deformation (strain or displacement).
     2. The transducer element converts this deformation into a change in electrical properties, such as resistance, capacitance, or voltage.

     Based on the different technologies used in these two steps, the main working principles of pressure sensors can be broadly categorized as follows:

1. Piezoresistive pressure sensor

This is the most widely used and technically mature type of pressure sensor.

  • Core Principle:
           The Piezoresistive Effect – When semiconductor or metallic materials are subjected to mechanical stress, their electrical resistivity undergoes a significant change.
  • Work process：
           1. Typically, on a silicon wafer, four equivalent resistors are fabricated through diffusion or ion implantation processes and connected to form a Wheatstone bridge.
           2. When pressure acts on the silicon diaphragm, the diaphragm undergoes a slight bending deformation.
           3. This deformation causes two resistors in the bridge to experience tensile stress (increasing resistance), while the other two experience compressive stress (decreasing resistance).
           4. The originally balanced bridge becomes unbalanced, outputting a voltage signal proportional to the pressure.
  • Advantages: High precision, excellent frequency response, compact size, and high cost-effectiveness.
  • Disadvantages: It is greatly affected by temperature and requires temperature compensation.
  • Main Applications: Automotive (Tire Pressure Monitoring, Intake Manifold Pressure), Medical Equipment (Blood Pressure Monitors), Industrial Process Control, etc.
2. Capacitive pressure sensor

  • Core Principle: 
           Utilizes pressure to induce changes in the distance or area between the capacitor plates, thereby altering the capacitance.

  • Working process:
  1. There is a parallel plate capacitor inside the sensor, with one plate fixed and the other being a flexible diaphragm.
  2. Pressure acts on the diaphragm, causing it to deform, thereby changing the distance between the two plates.
  3. According to the parallel plate capacitor formula C=εA/d (where C is the capacitance, ε is the dielectric constant, A is the area, and d is the distance), a change in distance d will lead to a change in capacitance C.
  4. The measuring circuit detects this capacitance change and converts it into a voltage or frequency signal.
  • Advantages: 
            Low power consumption, temperature-insensitive, high sensitivity, suitable for measuring low pressure.  
  • Disadvantages:
            Poor linearity, output signal is susceptible to parasitic capacitance effects.  
  • Main applications:
           Differential pressure transmitters, micro-differential pressure measurement (e.g., HVAC systems), barometric altimeters, etc.
3. Piezoelectric pressure sensor

  • Core Principle: Piezoelectric Effect – When certain specific materials (such as quartz, piezoelectric ceramics) are subjected to mechanical stress, electric charges are generated on their surface.
  •  Working Process:
          1. The piezoelectric crystal acts as the sensing element and deforms when subjected to pressure.
          2. The deformation causes a relative displacement of the positive and negative charge centers within the crystal, generating equal amounts of positive and negative charges (i.e., a voltage) on its two surfaces.
          3. This charge or voltage signal is measured via electrodes.

  • Key Features: It can only measure dynamic pressure or fluctuating pressure, and cannot measure stable static pressure, as the generated electric charge will slowly leak over time.  
  •  Advantages: Extremely high frequency response, compact size, robust and durable.  
  •  Disadvantages: Unsuitable for static pressure measurement; the output signal requires a specialized amplifier (charge amplifier).  
  • Main Applications: Knock detection in engine cylinders, blast wave measurement, acoustic microphones, vibration measurement.