Pressure transmitters are devices used to measure pressure and convert it into an electrical signal for transmission to control systems, data acquisition systems, or other monitoring devices. There are several types of pressure transmitters, each utilizing different sensing technologies and working principles. Here are some common types:

1. Strain Gauge Pressure Transmitters:

   • Working Principle: These transmitters use strain gauges bonded to a flexible diaphragm or a metal element. When pressure is applied, the diaphragm deflects, causing strain in the gauges, which changes their resistance. This change in resistance is measured and converted into an electrical signal proportional to the applied pressure.
   • Applications: They are widely used in industrial applications requiring high accuracy and stability, such as process control and monitoring in manufacturing, oil and gas, and aerospace industries.

2. Capacitive Pressure Transmitters:

   • Working Principle: Capacitive pressure transmitters measure pressure changes by detecting changes in capacitance between two conductive plates separated by a flexible diaphragm. As pressure changes, the distance between the plates changes, altering the capacitance. This change in capacitance is measured and converted into an electrical signal proportional to the applied pressure.
   • Applications: They are suitable for measuring a wide range of pressures, including low-pressure applications, and are often used in industries such as HVAC, automotive, and medical devices.

3. Piezoresistive Pressure Transmitters:

   • Working Principle: Piezoresistive pressure transmitters utilize the piezoresistive effect, where certain materials change their resistance in response to applied mechanical stress. These transmitters typically consist of a diaphragm with piezoresistive elements integrated into it. When pressure is applied, the resistance of the piezoresistive elements changes, and this change is measured and converted into an electrical signal.
   • Applications: They are widely used in automotive, aerospace, and industrial applications where high accuracy, fast response time, and robustness are required.

4. Differential Pressure Transmitters:

   • Working Principle: Differential pressure transmitters measure the difference in pressure between two points in a system. They typically consist of two pressure sensing elements connected to a differential pressure sensor. The transmitter measures the pressure difference between the two sensing elements and converts it into an electrical signal.
   • Applications: They are commonly used in HVAC, fluid flow measurement, level measurement, and filtration systems.

5. Absolute Pressure Transmitters:

   • Working Principle: Absolute pressure transmitters measure pressure relative to a perfect vacuum. They typically contain a sealed reference chamber connected to the pressure sensing element. The pressure in the reference chamber is maintained at a known vacuum level, allowing the transmitter to measure absolute pressure.
   • Applications: They are used in applications such as altitude measurement, barometric pressure measurement, and vacuum processes.

6. Digital Pressure Transmitters:

   • Working Principle: Digital pressure transmitters utilize digital signal processing technology to measure and transmit pressure data. They may incorporate various sensing technologies such as strain gauge, capacitive, or piezoresistive sensors, but the output signal is digitized for communication with digital control systems.
   • Applications: They are suitable for applications requiring high accuracy, fast response time, and digital communication capabilities, such as industrial automation, process control, and data acquisition systems.

These are some common types of pressure transmitters and their working principles. The selection of the appropriate type depends on factors such as the application requirements, pressure range, accuracy, environmental conditions, and compatibility with existing systems.