Pressure sensors are typically composed of a sensitive element, a transduction component, and a subsequent signal processing unit. Among various types, strain gauges are widely used to measure pressure. The working principle of strain gauges is based on the Wheatstone bridge circuit. When the resistances in the four arms of the bridge satisfy the condition R1R3 = R2R4, the bridge is balanced, and the output voltage is zero. However, when the resistance changes due to applied pressure, the bridge becomes unbalanced, producing a measurable voltage output. This configuration can be implemented as a single-arm, double-arm, or full-bridge circuit, with the output voltage showing a linear relationship with the change in resistance.
Below are the principles and applications of five commonly used pressure sensors:
**1. Principle and Application of Ceramic Pressure Sensors**
Ceramic pressure sensors are known for their corrosion resistance and direct contact capability with most media. The sensor uses a ceramic diaphragm that deforms slightly under pressure, which is then converted into an electrical signal via a thick-film resistor printed on the back of the diaphragm. These resistors form a Wheatstone bridge, and due to the piezoresistive effect, the bridge generates a voltage signal proportional to the applied pressure. The output is typically calibrated to 2.0, 3.0, or 3.3 mV/V, making it compatible with strain gauge sensors. With laser calibration, these sensors offer high temperature and long-term stability. They also include built-in temperature compensation and operate reliably over a wide temperature range, from -40°C to 135°C. Their excellent insulation properties, strong output signals, and high precision make ceramic sensors a cost-effective and high-performance choice in many industries.
**2. Principle and Application of Strain Gauge Pressure Sensors**
Strain gauge pressure sensors are among the most widely used in industrial applications. These sensors rely on the deformation of a strain gauge, which converts mechanical strain into an electrical signal. There are two main types: metal and semiconductor strain gauges. When force is applied to the base material, the strain gauge deforms, changing its resistance. This change is measured through a Wheatstone bridge circuit, amplified, and then processed by an ADC before being sent to a CPU for display or control. The resistance change is directly related to the strain, allowing precise pressure measurement. These sensors are known for their high accuracy, good linearity, and affordability.
**3. Principle and Application of Diffused Silicon Pressure Sensors**
Diffused silicon pressure sensors use a thin diaphragm made of silicon that deforms under pressure. This deformation causes a change in the resistance of the doped silicon, which is detected by an electronic circuit and converted into a standard output signal. These sensors are widely used in environments where high accuracy and reliability are required, such as in industrial automation and process control systems.
**4. Principle and Application of Sapphire Pressure Sensors**
Sapphire pressure sensors utilize a sapphire crystal as the sensing element, offering superior durability and stability. Sapphire is highly resistant to wear, corrosion, and thermal stress, making it ideal for extreme conditions. The sensor incorporates a strain-sensitive bridge circuit on a sapphire sheet, which is connected to a titanium alloy diaphragm. When pressure is applied, the diaphragm deforms, causing a change in the bridge output. This change is proportional to the pressure and is converted into an electrical signal for further processing. These sensors are known for their high accuracy, minimal temperature drift, and long service life.
**5. Principle and Application of Piezoelectric Pressure Sensors**
Piezoelectric pressure sensors work based on the piezoelectric effect, where certain materials generate an electric charge in response to mechanical stress. Common materials include quartz, potassium sodium tartrate, and artificial crystals like PZT. These sensors are ideal for dynamic pressure measurements, as they cannot be used for static measurements due to charge leakage. They are widely used in vibration and shock monitoring, engine combustion pressure measurement, and military applications such as measuring bullet pressure and muzzle blast waves. Their compact size, high sensitivity, and durability make them suitable for a variety of demanding environments.
In summary, pressure sensors play a crucial role in industrial automation, environmental monitoring, and scientific research. Each type has its own advantages and is chosen based on the specific application requirements. Whether it's ceramic, strain gauge, diffused silicon, sapphire, or piezoelectric, each technology continues to evolve, providing more accurate and reliable solutions for modern engineering challenges.
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**Tag:** Pressure sensor, Piezoelectric sensor, Strain gauge, Piezoelectric effect, Principle and application
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