A submersible level transmitter is an instrument used to measure liquid level height. Based on the hydrostatic pressure principle, it converts the liquid level height into an electrical output signal by immersing the sensor into the measured liquid, thereby achieving accurate measurement and monitoring of the liquid level. A detailed introduction is provided below.
Working Principle：
The working principle of the submersible level transmitter is based on the relationship between hydrostatic pressure and liquid level height. According to the formula
P=ρgh (where Pis the hydrostatic pressure, ρ is the liquid density, g is the acceleration due to gravity, and h is the liquid level height), the pressure acting on the sensor is proportional to the liquid level height when the sensor is immersed in the liquid.
The sensor converts the detected pressure into an electrical signal, which is then processed by the internal circuit of the transmitter and converted into standard output signals, such as 4-20mA current signal, 0-5V or 0-10V voltage signal. These signals can be directly received by control systems or display instruments, thus realizing the measurement and display of liquid level.
Structural Composition：
· Sensor Probe
This is the part that directly contacts the measured liquid. It is usually made of corrosion-resistant materials such s stainless steel or ceramic. It contains pressure-sensitive elements inside, such as piezoresistive, capacitive, or piezoelectric sensors, which convert liquid pressure into electricaal signals.
· Ventilated Cable
It is used to connect the sensor probe and the transmitter body, with an air vent tube and signal wires inside.
The air vent tube transmits the atmospheric pressure on the liquid surface to the reference side of the sensor to compensate for the influence of atmospheric pressure on measurement. The signal wires transmit the electrical signals generated by the sensor to the transmitter for processing.
· Transmitter Body
It includes signal amplification, processing, conversion circuits, and a power supply module. It amplifies, filters, and linearizes the weak electrical signals from the sensor, and converts them into standard output signals, while providing stable power for the sensor.
Some transmitters also feature temperature compensation to improve measurement accuracy.
Features
• Easy installation: Simply immerse the sensor probe into the liquid to be measured and connect the transmitter to a display instrument or control system via cable. No complicated installation or commissioning is required. Suitable for liquid level measurement in vessels of various shapes and structures.
• High accuracy: Adopts high-precision pressure sensors and advanced signal processing technology to achieve high measurement accuracy, typically ranging from ±0.2% FS to ±0.5% FS, meeting most liquid level measurement requirements in industrial and civil applications.
• Excellent stability: Features good temperature stability and long-term stability, maintaining accurate measurement under different ambient temperatures. Small measurement drift during long-term operation reduces the frequency of regular calibration and maintenance.
• Strong adaptability: Capable of measuring the level of various liquids, including water, oil, acids, alkalis, and other corrosive and non-corrosive media. It can also adapt to harsh working conditions such as high temperature, high pressure, and high humidity.
• Standard output signal: Usually provides a standard 4–20 mA current signal or other standard analog signals, facilitating easy interfacing with automated control systems, PLC, DCS, and other equipment to enable remote monitoring and automatic control of liquid level.
Applications
• Industrial field: Widely used for level measurement and control in storage tanks, reactors, water basins, etc., in petroleum, chemical, pharmaceutical, food and beverage, paper making, power and other industrial processes. Provides accurate level data for automated production control and ensures safe and stable operation.
• Water treatment industry: Used for level monitoring in water tanks and towers of water supply plants and sewage treatment plants, as well as level control in industrial circulating water systems, helping to achieve rational use and conservation of water resources while ensuring the normal operation of water treatment equipment.
• Construction & municipal engineering: Plays an important role in level monitoring of water tanks and fire pools in high-rise buildings, as well as level measurement in pump stations and inspection wells of urban water supply and drainage systems, helping to ensure water supply safety and normal operation of urban drainage systems.
• Agricultural irrigation: Can be used for level monitoring in irrigation ponds and dams, helping farmers rationally control irrigation water, improve water use efficiency, and realize precision irrigation.
