A pressure transmitter is an instrument that converts pressure signals into transmittable standard electrical signals. It has wide applications in industrial production, automation control, aerospace, and medical fields. The following is a detailed introduction:
Working Principle
The core component of a pressure transmitter is the pressure sensor. When pressure is applied to the sensor, the sensor will produce a corresponding strain or displacement. This physical change is then converted into an electrical signal by a conversion element. Common pressure sensors include capacitive, piezoresistive, and piezoelectric types.
* **Capacitive Pressure Sensor:** This type utilizes the principle that the capacitance between two plates changes with pressure. When pressure is applied to a movable plate, the distance between the plates changes, resulting in a change in capacitance. The pressure is determined by measuring this change in capacitance.
* **Piezoresistive Pressure Sensor:** This type is based on the piezoresistive effect, where the resistance of a semiconductor material changes under pressure. When pressure is applied to the sensor's sensitive element, its internal resistance changes, causing a change in the electrical signal, which is then used to measure the pressure.
• Piezoelectric pressure sensor: Certain crystalline materials generate an electric charge when subjected to pressure, the amount of which is proportional to the applied pressure. The magnitude of the pressure is reflected by measuring the generated charge.
Structural Components
• Pressure sensor: In direct contact with the medium being measured, it senses the pressure and converts it into a corresponding physical quantity change; it is the core component of the pressure transmitter.
• Conversion circuit: Amplifies, processes, and converts the weak electrical signal generated by the pressure sensor into a standard electrical signal output, such as a 4-20mA DC current signal or a 0-5V DC voltage signal, for transmission and subsequent display and control.
• Housing and connectors: Protect the internal electronic components from external environmental influences, while providing a connection interface with the measured object to ensure accurate pressure transmission to the pressure sensor.
Classification
* By Pressure Measurement Type:
* **Absolute Pressure Transmitter:** Measures absolute pressure, i.e., pressure relative to absolute vacuum. Commonly used in applications requiring precise absolute pressure measurement, such as aerospace and vacuum coating.
* **Gateway Pressure Transmitter:** Measures pressure relative to atmospheric pressure, i.e., gauge pressure = absolute pressure - atmospheric pressure. Widely used in industrial production, such as pipeline pressure measurement and hydraulic system pressure monitoring.
* **Differential Pressure Transmitter:** Used to measure the difference between two pressures, typically used to measure parameters such as fluid flow rate and liquid level. For example, fluid flow rate can be calculated by measuring the pressure difference before and after a throttling device.
* By Output Signal Type:
* **Analog Output Pressure Transmitter:** Outputs an analog signal, such as a 4-20mA current signal or a 0-10V voltage signal. The analog signal has a linear relationship with the measured pressure, facilitating connection to traditional analog control systems.
Digital Output Pressure Transmitters: Output digital signals, such as HART, PROFIBUS-PA, and Modbus protocols. They offer advantages such as strong anti-interference capabilities, long transmission distances, and bidirectional communication, facilitating easy integration with modern digital control systems.
Features
• High Precision: Accurately measures pressure signals, typically achieving ±0.1% FS (full scale) or even higher, meeting the needs of various high-precision measurement applications.
• Good Stability: Exhibits excellent long-term stability, maintaining measurement accuracy and performance during extended use, reducing measurement errors caused by environmental factors and time variations.
• High Reliability: Utilizes high-quality materials and advanced manufacturing processes, possessing strong anti-interference capabilities and protective performance, enabling reliable operation in harsh industrial environments such as high temperature, high pressure, humidity, and corrosive media.
• Wide Measurement Range: Offers products with various measurement ranges to meet different application requirements, from micro-pressure measurement to ultra-high pressure measurement.
Applications
* **Industrial Process Control:** Used in chemical, petroleum, metallurgical, and power industries to monitor and control pressure within pipelines and containers, ensuring the safe and stable operation of production processes. For example, in the distillation towers of oil refineries, pressure transmitters monitor the pressure inside the tower in real time to adjust the feed and discharge rates, ensuring product quality.
* **Liquid Level Measurement:** Indirectly measures the liquid level by measuring the pressure at the bottom of the liquid. Widely used in water towers, oil storage tanks, and other liquid level monitoring applications, enabling remote monitoring and control of liquid levels. This facilitates timely understanding of liquid level changes and prevents overflows or excessively low levels.
* **Flow Measurement:** Used in conjunction with throttling devices (such as orifice plates and nozzles), calculates the fluid flow rate by measuring the pressure difference before and after the throttling device. Widely used in industrial pipelines for flow measurement of various fluids (such as liquids, gases, and steam)
• Aerospace: Used to measure parameters such as intake air pressure, fuel pressure, and hydraulic system pressure in aircraft engines, providing crucial pressure data support for safe flight and ensuring the normal operation of engines and other systems.
• Healthcare: In medical equipment such as blood pressure monitors and ventilators, pressure transmitters are used to accurately measure and control pressure parameters, providing accurate pressure data for disease diagnosis and treatment, ensuring patient safety and treatment effectiveness.