Understanding Pressure Sensors

Pressure sensors are devices that detect pressure and play a crucial role in both civilian and industrial applications. This guide will provide an overview of pressure sensors, including their definitions, working principles, types of pressure, and applications.

What is a Pressure Sensor?

A pressure sensor is an instrument that senses pressure signals and converts them into useful electrical signals according to specific rules. It typically consists of a pressure-sensitive element and a signal processing circuit. Pressure sensors can be categorized based on the type of pressure they measure, including:

• Gauge Pressure Sensors
• Differential Pressure Sensors
• Absolute Pressure Sensors

Pressure sensors are widely used in various industrial automation environments, such as:

• Water resources and hydropower
• Railway transportation
• Intelligent buildings
• Production control
• Aerospace and military applications
• Petrochemical industries
• Electric power generation
• Marine applications
• Machine tools and pipelines

How Does a Pressure Sensor Work?

Pressure sensors convert external pressure into electrical signals. Their working principle involves changes in internal sensitive components (such as piezoresistive, capacitive, or inductive elements) when subjected to external pressure. This results in changes in resistance, capacitance, or inductance, generating a corresponding electrical signal output.

Types of Pressure Sensors

1. Piezoresistive Pressure Sensor

   • Utilizes the piezoresistive effect to measure pressure. When external pressure is applied, the shape of the internal components changes, altering the resistance. By measuring this resistance change, the external pressure can be determined.

2. Capacitive Pressure Sensor

   • Measures pressure through changes in capacitance. Typically consists of two metal electrodes and a variable medium. When pressure is applied, the capacitance changes, allowing for pressure measurement.

3. Piezoelectric Pressure Sensor

   • Uses the piezoelectric effect, where certain crystals produce charge separation under mechanical stress. This sensor comprises piezoelectric crystals and electrodes; when pressure is applied, the charge change can be measured to determine pressure.

In summary, pressure sensors work by monitoring changes in sensitive components due to external pressure, converting these changes into electrical signals for pressure measurement.

Types of Pressure Measured

Pressure sensors can measure four main types of pressure:

• Absolute Pressure: Measured relative to a perfect vacuum (zero gas molecules).

• Gauge Pressure: Measured relative to atmospheric pressure. A positive value indicates pressure above atmospheric levels, while a negative value indicates pressure below it.

• Sealed Gauge Pressure: Measures pressure within a closed system relative to external atmospheric pressure. It can also be positive or negative based on the internal pressure compared to the outside atmosphere.

• Differential Pressure: The difference between two pressure values (p1 and p2).

Applications of Pressure Sensors

Pressure sensors are extensively used in daily life and industrial production, including:

• Industrial Automation: Monitoring and controlling liquid and gas pressures in industrial equipment to ensure stability and safety during production.

• Automotive Industry: Monitoring pressure changes in engines, braking systems, and tires to enhance performance and safety.

• Medical Care: Monitoring physiological pressures such as blood pressure and respiratory rates to assist in diagnoses and treatment monitoring.

• Environmental Monitoring: Measuring atmospheric pressure, ocean depth, and underground levels.

• Aerospace: Tracking air pressure changes in aircraft and rockets to ensure flight safety and performance stability.

• Water Conservancy Projects: Monitoring water pressure and levels to manage resources and control flooding.