A pressure sensor is a device that can sense pressure and convert the pressure signal into an electrical signal, which can then be output as a corresponding pressure value through a backend display instrument.
Working Principle: Pressure sensors can be categorized based on different working principles, including:
Piezoresistive Pressure Sensor: It measures pressure using the piezoresistive effect. There are four resistors on the sensor chip, and when pressure acts on the sensor diaphragm, the deformation causes the resistance values of the four resistors to vary, forming a Wheatstone bridge. The pressure change is then converted to a signal change through a signal processing circuit.
Piezoelectric Pressure Sensor: It utilizes the piezoelectric effect. When pressure acts on the diaphragm, the internal material forms an electric charge proportional to the pressure. The sensitive element generally contains materials such as quartz, lead zirconate titanate (PZT), or piezoelectric polymers (e.g., PVDF).
Capacitive Pressure Sensor: This type of sensor uses changes in capacitance to monitor pressure changes. Capacitors serve as the sensitive elements. When pressure acts on the sensor diaphragm, the capacitance between the film and the fixed electrode changes, and an electrical signal related to the voltage is derived through the measurement circuit.
Resonant Pressure Sensor: It converts pressure signals into electrical signals using a resonant element. It is mainly divided into vibrating string type, vibrating cylinder type, diaphragm type, and quartz crystal resonant type.
Types of Pressure Measurement
Gauge Pressure (Relative Pressure): Measures pressure relative to atmospheric pressure. It can be positive (higher than atmospheric pressure) or negative (vacuum applications). Common applications include tire pressure monitoring and industrial process control.
Absolute Pressure: Measured relative to a perfect vacuum (zero pressure). Absolute pressure sensors are used in barometric pressure monitoring, altimeters, and vacuum systems.
Differential Pressure: Measures the difference between two pressure points. This is used in applications such as flow measurement across filters, HVAC systems, and liquid level monitoring in tanks.
Sealed Gauge Pressure: The sealed gauge pressure is a sensor that encapsulates the local atmospheric pressure of the production location. Therefore, if the product is used in other places, errors will occur.
Selection Criteria
Measurement Range: Selecting the correct pressure range is essential to avoid sensor damage and ensure accuracy. A common rule of thumb is to select a sensor with a measurement range that covers at least 80% of the expected maximum pressure.
Output Signal Type: Pressure sensors provide various output signals, including analog outputs (current output like 4-20mA for long-distance transmission and high-noise environments, and voltage output like 0-5V, 0-10V for faster response times) and digital outputs (such as RS485 for multi-sensor networks, and I2C and SPI for embedded systems and IoT applications).
Compatibility with the Measurement Medium: Different pressure sensors are designed to work with specific types of media. For corrosive media (e.g., acids, alkaline solutions), choose sensors made from stainless steel (316L), Hastelloy, or ceramic. For high-temperature applications, ensure the sensor can withstand the operating temperature without degradation.
Accuracy and Calibration: The accuracy of a pressure sensor is defined by its accuracy class, which determines the measurement error as a percentage of full-scale output (FSO). Common accuracy levels include 0.1% FSO for high precision in laboratory settings, 0.25% FSO for industrial applications requiring moderate precision, and 0.5% FSO for general-purpose applications.
Environmental and Installation Factors: Consider the operational environment, such as temperature, vibration and shock, electrical interference, and ingress protection (IP rating). For example, in high-noise environments, opt for current output sensors (4-20mA) or shielded cables.
Electrical and Mechanical Connections: Depending on the application, different electrical connections (e.g., cable connections for sealed and outdoor environments, M12 or DIN connectors for easy installation and maintenance) and mechanical connections (e.g., threaded connections for industrial applications, flange or welded connections for high-pressure or sanitary applications) may be required.
Applications
Industrial Automation: Pressure sensors monitor the pressure of pipelines and equipment, reducing safety accidents caused by overpressure or underpressure. They feedback pressure data through the backend system, enabling timely notifications for abnormal pressure situations.
Automotive Industry: Pressure sensors are widely used in engine systems, brake systems, turbocharger systems, and tire pressure monitoring systems.
Medical Care: They monitor patients' physiological parameters or changes in medical equipment, such as in ventilators, blood pressure monitors, infusion pumps, analgesic pumps, and endoscopes.
Environmental Monitoring: Pressure sensors can predict weather changes, assess floods and droughts, monitor waste gas and sewage discharge, and analyze the marine environment.
Aerospace: Pressure sensors monitor combustion chamber pressure, fuel hydraulic pressure, and lubricating oil pressure, optimizing combustion efficiency and preventing risks. They also play a vital role in atmospheric data systems, life support systems, and rocket recovery systems.
Water Conservancy Projects: Pressure sensors sense the pressure changes of water bodies and the operation of water conservancy equipment in real-time, providing data for water resource management and flood prevention.
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