Submersible pressure sensors, also known as level probes or submersible pressure transmitters, are pressure sensors with a specific design. They are responsible for hydrostatic level measurement in tanks, wells, shafts and boreholes and guarantee unsurpassed leak tightness as well as media resistance. Submersible pressure sensors for general applications are used in rivers and lakes as well as tank and storage systems, assist in the control of sewage lifting and pumping stations and are used to monitor clarifiers, settling tanks and rainwater retention basins. Submersible pressure sensors for demanding applications are additionally used in deep well and groundwater monitoring and battery-operated level measurement systems as well as in overfill and dry-running monitoring.
The submersible pressure sensor, also called a level probe or submersible pressure transmitter, is immersed in the liquid to be detected and lowered to near the bottom. The submersible pressure sensor should be installed at the lowest measuring location, suspended above the bottom. There, the submersible pressure transmitter measures the hydrostatic pressure, which enables a direct conclusion regarding the current level.
The submersible pressure sensor consists of the sensor or measuring cell, the electronics, the case, the cable inlet and the connection cable itself. In addition to the signal line, the connection cable also includes a venting capillary in order to be able to measure the hydrostatic pressure relative to the ambient pressure. The sensor is used for measuring the hydrostatic pressure at the measuring point. Even in the toughest applications, such as in wastewater treatment plants and septic tanks, the submersible pressure sensor guarantees the greatest process reliability. The electronics of a submersible pressure sensor are similar to those of a conventional pressure sensor. The pressure signal from the measuring cell is converted, with high accuracy, into a scaled industrial signal. The advantage of a submersible pressure sensor over a conventional pressure sensor is the integrated overvoltage protection, which is designed to protect the pressure sensor from the effects of a nearby lightning strike. The case material must always be selected to suit the medium to be measured in order to avoid chemical degradation processes and corrosion. The connection of the cable to the case requires an optimal, hermetically sealed design and must be specially developed for many applications. The cable material must also be selected to suit the application and the aggressiveness of the liquid to be measured in order to guarantee maximum media resistance and to prevent the liquid from entering the cable.
Hydrostatics is the science of fluids not in motion. A hydrostatic level sensor is a form of level probe that is used especially for level monitoring by measuring the hydrostatic pressure in a virtually static liquid at a pre-determined level of submersion. So hydrostatic pressure, also called gravitational pressure, is the pressure that occurs within a fluid at rest due to the influence of the gravitational force. A fluid is a liquid or a gas.
In hydrostatic level measurement, a liquid generates a weight force that changes corresponding to the filling height due to its specific gravity and the prevailing force of gravity. This weight force, increasing proportionally with the filling height, is called the liquid column. When measuring the level with a submersible pressure sensor, the hydrostatic pressure is thus measured as the height-dependent weight force of the liquid column acting on it. The rule of thumb for the measurement is 1 m water column corresponds to about 100 mbar. Hydrostatic level measurement is used in tanks, wells, shafts and boreholes.
In hydrostatic level measurement, the measuring cell of the submersible pressure sensor detects the smallest changes in hydrostatic pressure, which increases or decreases depending on the filling height. The output signal is generated from the integrated electronics through the applied pressure being converted into an electrical signal.
A hydrostatic level sensor is a submersible pressure transmitter that has a pressure diaphragm where the inner side of the diaphragm is vented to atmospheric pressure through a vent tube in the cable and the outer side is in contact with the liquid and measuring the static pressure of the liquid column above the transmitter. This static pressure is basically caused by the weight of the fluid on top of the transmitter and is used to calculate the level of the liquid. The hydrostatic level sensor is a specialised sensor for level monitoring, most commonly used in the water and waste water industry and for all common oils and fuels. Its simple use and reliable and accurate measurement technology make it one of the most commonly used level sensors by far.