A pressure level transmitter operates by measuring the pressure exerted by the liquid column above the sensor to determine the liquid’s level. These transmitters convert the pressure measurement into an electrical signal, which can be read and processed by a control system. The device typically utilizes piezoresistive sensors, which respond to pressure changes with high sensitivity and accuracy.
Detailed Explanation
Basic principle
Pressure level transmitters function based on the hydrostatic pressure principle. The hydrostatic pressure (PPP) at a given depth in a liquid is determined by the formula:
P=ρghP
Where:
ρ = density of the liquid
g = gravitational acceleration
h = height of the liquid column above the sensor.
By measuring this pressure, the transmitter calculates the height (hhh) of the liquid, representing the level in the tank or vessel.
Key components and operation
Pressure sensor
Most pressure level transmitters use piezoresistive sensors. These sensors detect pressure changes caused by the liquid column and convert the mechanical force into a measurable electrical signal.
Example
The “PT600” series uses a piezoresistive sensor filled with silicon oil to transfer pressure from the diaphragm to the sensing element, ensuring accuracy and temperature stability.
Diaphragm and capillary system: The diaphragm isolates the process fluid from the sensor. Any pressure exerted on the diaphragm is transmitted through the capillary filled with silicon oil to the sensing element.
Electronics and compensation: Modern pressure transmitters include microelectronics for signal processing, temperature compensation, and communication. These electronics ensure that the output is accurate even under fluctuating environmental conditions.
Output signal: The transmitter typically outputs a 4–20 mA signal, which is proportional to the measured pressure. Advanced models support communication protocols like HART, MODBUS, or PROFIBUS, allowing remote configuration and monitoring.
Applications
Pressure level transmitters are commonly used in:
Water and wastewater treatment plants
Food and beverage industries
Chemical processing
Oil and gas industries
Storage tanks and silos
PT600 Pressure Transmitter
The “PT600” transmitter by Pondus Instruments exemplifies a versatile device for level measurement. It features:
Piezo-resistive sensing technology for high precision.
An innovative autozero function for recalibration without complex procedures.
Compatibility with MODBUS and HART for seamless integration into control systems.
Conclusion
Pressure level transmitters are reliable instruments for accurately measuring liquid levels across various industries. Their ability to integrate with digital systems and withstand demanding environments makes them indispensable in modern process control.
For more detailed specifications or to find a suitable transmitter for your application, feel free to contact Pondus Instruments.
