Pressure transmitters are one of the most common sensor types used in industrial automation control. Piezoresistive type, capacitive type and monocrystalline silicon resonant type are three main types, each with its own unique working principle, advantages and disadvantages and application scenarios
Piezoresistive pressure transmitter
Working principle
Piezoresistive pressure transmitters use the piezoresistive effect of monocrystalline or polysilicon to convert mechanical deformation caused by pressure into electrical signals:
1. The pressure acts on the sensing diaphragm, and the diaphragm becomes elastic deformation.
2. The piezoresistive element (resistor) on the diaphragm changes its resistance value due to force.
3. The resistance change is converted into a voltage signal through the Wheatstone bridge, and the output electrical signal is proportional to the pressure.
Advantages:
1. High precision.
2. Simple structure and low cost.
3. Fast response speed, suitable for dynamic pressure measurement.
Disadvantages:
1. It is sensitive to temperature and needs temperature compensation.
2. Susceptible to mechanical vibration.
3. General long-term stability, large drift.
Application scenario
• Pressure measurement of liquids, gases and vapors.
• Extensive engineering applications, such as water treatment equipment, automotive oil pressure, refrigeration systems, etc.
Capacitive pressure transmitter
Working principle
Capacitive pressure transmitter uses pressure to cause capacitance change principle:
1. The pressure acts on the metal or non-metal diaphragm, causing elastic deformation of the diaphragm.
2. The diaphragm and the fixed electrode form a variable capacitor, and the pressure change causes the capacitance value to change.
3. The capacitance change is converted into an electrical signal, and the output signal is proportional to the pressure.
Advantages:
1. High sensitivity, especially suitable for small pressure measurement.
2. Low temperature effect, good long-term stability.
3. Suitable for high and low pressure measurement.
Disadvantages:
1. Sensitive to impurities, moisture and other environments, requiring special treatment.
2. The signal processing is complex and the cost is relatively high.
3. The response speed is slightly slower than piezoresistive type.
Application scenario
• Precision scenarios, such as medical air pressure, food processing equipment.
• High temperature, high pressure, highly corrosive conditions, such as chemical and petroleum industries.
Monocrystalline silicon resonant pressure transmitter
Working principle
Monocrystalline silicon resonant pressure transmitter uses the principle of resonant frequency change in monocrystalline silicon:
1. Micro resonators are processed on the monocrystalline silicon diaphragm.
2. The pressure causes the deformation of the diaphragm, resulting in the stress change of the resonator.
3. Stress change changes the vibrational frequency of the resonator.
4. After measuring the resonant frequency change, calculate the pressure value through the algorithm.
Advantages:
1. High precision
2. Good long-term stability, small drift, suitable for long-term measurement.
3. Strong anti-interference ability, insensitive to electromagnetic and environmental interference.
4. Suitable for high temperature, high pressure and harsh environment.
Disadvantages:
1. High manufacturing cost and high price.
2. The response speed is slightly slow, suitable for static or quasi-dynamic measurement.
3. Complex design and calibration.
Application scenario
Applications that require high accuracy and reliability, such as oil and gas pipelines, aerospace pressure measurement.
• Metrology and research equipment.
