What is Submersible Pressure Transmitter?

A submersible pressure transmitter is basically a type of pressure instrument employed for the accurate measurement of the level of substances in tanks, wells, shafts and bore holes among others.

It permits the placing of the sensor right into the liquid; another position is near the base for measuring hydrostatic pressure which is equal to the level of liquid above it.

Installation is straightforward: As for the sensor component it is placed directly in the liquid, and the transmitter may be fixed to a safe area by using flange or bracket. It is endowed with a vented cable that helps fight fluctuations in air pressure so as to provide accurate measurement values. This cable length can however be made to be custom to certain range depending on the requirement of the particular application.

Upon incorporation of the unit, the transmitter gives accurate distance measurements from the sensor to the liquid. The liquid level information is finally output to an external environment by again translating the current 4-MA signal output proportional to the liquid level to a temperature compensated and linearity correction factor.

These devices are also referred to as static pressure level transmitter, submersible level sensor, and submersible water level meter. Stainless steel construction is used to provide durability, flange installation is used for easier installation and they come with displays and calibration localized to the area. Also, they have a model specifically designed for ATEX explosion zone, so the devices can be used in dangerous area.

Where Submersible measurement is preferred?

In circumstances where it is impossible to mount level sensors on the side of the chamber, submersible measurement is carried out. Here are some specific scenarios where submersible probes are ideal:Here are some specific scenarios where submersible probes are ideal:

Deep Wells and Boreholes:

In these applications, it is sometimes not possible to have sensors on the side of the depth and narrowness of the structure. Level indicators can be directly placed in the water thus making it possible to get accurate levels of water.

Open Bodies of Water:

If used in monitoring water level in lakes, rivers or reservoirs submersible probes are required since the latter can be plugged at the depth of the reading to be taken.

Tanks Without Side Access:

Sometimes it is possible not to find any appropriate place on the sides of the tanks or containers to install a sensor. Whereas probes which are submersible can be installed by simply lowering them from the top.

Hazardous Environments:

ATEX explosion-proof submersible probes are useful for applications where the regular instruments cannot be applied due to explosive atmospheres.

Wastewater and Slurry Tanks:

For tanks containing fluids with solids or other materials, submersible probes are ideal for levels’ measurement and are not influenced by the nature of the contained substances.

How does a Submersible Pressure Transducer Work?

Thus, the principle of operation of a submersible pressure transducer is based on the piezoresistive effect whereby pressure is translated to an electrical signal. The mechanism of this device is a flexible diaphragm with a strain gauge attached to it. A compression of the diaphragm results to a change of the resistance of the strain gauge and the electronics of the transducer converts into electrical signal.

The housing of a submersible pressure transmitter is also made in a way that does not let environment factors such as corrosion and pressure affect the performance of the transmitter. This protective casing also has a cable that connects the transducer to a data acquisition system or control unit.

Besides, a submersible pressure transducer is convenient to use as it provides accurate and reproducible measurements even in extreme conditions.

How is a Submersible Pressure Sensor/ Level Probe Constructed?

A submersible pressure sensor or a level probe is carefully designed to suit the type and nature of liquid it would be submerged in. Here’s a breakdown of its components and construction:Here’s a breakdown of its components and construction:

Sensor or Measuring Cell

This is the key part in the design of which the main function is the determination of the hydrostatic pressure at the desired point. That touches the pressure which is exerted by the column of the liquid above this point.

Electronics

Similar to a conventional pressure sensor, the electronics in a submersible pressure sensor convert the pressure signal from the measuring cell into a precise, scaled industrial signal. This conversion process is designed for high accuracy.

Case

This is enclosed in a solid casing that will prevent if from being affected by environmental factors as well as chemical degradation. The nature of the case is determined through the medium measured in order to avoid cases that causes corrosion of the material chosen.

Cable Inlet and Connection Cable 

The cable used for connection has other uses as well. Apart from this, it forms a part of the circuit used for venting and measures the hydrostatic pressure means the pressure built at a certain level up in relation to the ambient pressure. The cable must be sealed in such a manner that the liquid cannot penetrate inside it; it should also be constructed out of materials that cannot be corroded by the liquid.

Venting Capillary

This feature helps to balance the pressure inside the sensor to the atmospheric pressure so that accurate pressure measurement can be achieved.

Overvoltage Protection

One of the key advantages of a submersible pressure sensor is its integrated overvoltage protection, which shields the sensor from electrical surges, such as those caused by nearby lightning strikes.

Working Principle of Submersible Liquid Level Transmitter

The submersible liquid level transmitter functions on the principle that the static pressure experienced by the sensor is directly proportional to the height of the liquid above it. When the transmitter is submerged to a certain depth in the liquid, the pressure exerted on the sensor’s face can be calculated using the formula:

Where:

• P = Pressure applied on the sensor
• ρ = Density of the liquid
• g = Acceleration due to gravity
• H = Depth of the transmitter in the liquid
• Po = Atmospheric pressure at the liquid’s surface

The liquid pressure is applied to the positive pressure cavity of the sensor through a gas-conductive stainless steel membrane. Meanwhile, the atmospheric pressure Po​​ is connected to the negative pressure cavity to compensate for the atmospheric pressure at the back of the sensor. This setup ensures that the pressure measured by the submersible sensor is only ρ⋅g⋅H, representing the liquid column’s height.

By measuring the pressure P, the transducer can accurately determine the depth of the liquid, making it a powerful tool for level measurement in various applications.

What’s the use of submersible pressure transducers in water?

Submersible pressure transducers are versatile devices used in various water-related applications to provide accurate and reliable measurements. Here are some of their key uses:

1. Water Level Measurement: These transducers are ideal for measuring water levels in natural bodies of water like rivers, lakes, and channels. They provide precise readings of water pressure at different depths, enabling the calculation of water levels.
2. Tank Level Monitoring: In both industrial and agricultural settings, submersible pressure transducers are used to monitor the levels of liquids in tanks, such as water, fuel, or chemicals. This helps in effective resource management and prevents spills or leaks.
3. Groundwater Monitoring: These devices are crucial for monitoring groundwater levels in aquifers and measuring water pressure in wells. The data collected can be used to assess groundwater availability and sustainability.
4. Environmental Monitoring: Submersible pressure transducers play a role in environmental monitoring by measuring water quality indicators like dissolved oxygen levels. They also track changes in water pressure due to variations in temperature or salinity, helping to detect environmental changes and potential pollution sources.
5. Oceanography: In oceanographic research, these transducers are used to measure seawater pressure at various depths. This data is valuable for studying ocean currents, tides, and waves, as well as monitoring changes in ocean temperature and salinity.

 Advantages of Submersible Transmitters

Submersible transmitters offer several advantages that make them highly effective for various liquid level measurement applications:

1. Direct Liquid Level Sensing: Submersible transmitters can measure liquid levels directly without being affected by foam or the deposition of the process medium, ensuring accurate readings.
2. Precision Measurement: They provide high-precision measurements, making them ideal for applications where accuracy is critical.
3. Good Stability: These sensors offer excellent stability, maintaining consistent performance over time.
4. Flexible Installation and Easy to Use: Submersible transmitters are designed for easy installation and use in a wide range of environments, allowing for flexible deployment in various applications.
5. Small Size and Lightweight: Their compact and lightweight design makes them easy to handle and install, even in confined spaces.
6. Anti-Vibration Construction: The sensors are built to withstand vibrations, ensuring reliable performance even in dynamic environments.
7. Easy Submersible Installation: Their design allows for straightforward submersion into liquids, simplifying the installation process.
8. Advanced Microprocessor Technology: The sensors leverage cutting-edge microprocessor technology, enhancing their accuracy and efficiency in processing measurement data.

Click here for Mastering Level Measurement Technologies: A Comprehensive Guide