Hydrostatic level sensors provide continuous measurement of liquids in tanks and vessels by measuring the pressure. These level sensors are used for level measurement of water, oil and chemicals in industrial applications and processes.
Hydrostatics is a science that deals with the properties of vacuum, liquid and vapor.
This discipline relies on the action of the pressure exerted by the fluid at its surface to determine the heights or volumes involved.
The principle of hydrostatics was developed in the 16th century by an Italian mathematician named Evangelista Torricelli (1608-1647). It is one of the fundamental bases in hydraulics.
Hydrostatic level sensors measure the hydrostatic pressure which is proportional to the measured liquid height.
Consisting of a pressure measuring cell, the stainless steel or other material diaphragm of the sensor reacts to changes in level.
The force exerted by the diaphragm is converted by the level sensor into an analog electrical output signal.
The relationship between the height h of the liquid and the hydrostatic pressure P in a liquid at rest and at atmospheric pressure, can be written as follows:
The pressure measured by the transmitter is proportional to the liquid column.
For example, for a water level measurement in a tank, the pressure varies by 100 mbar per meter of water column. For a tank height of 12 meters, the level probe measures a pressure on the sensor membrane of 1.2 bar relative.
Hydrostatic level measurement involves determining the height of a liquid using the hydrostatic pressure exerted by the liquid on its surface.
The higher the liquid level, the higher the measured pressure applied to the membrane. There are two different methods of measuring hydrostatic level.
Un capteur de pression manométrique assure la mesure de pression statique à une position basse du réservoir. Cette pression est ensuite convertie en hauteur en utilisant l'équation du niveau hydrostatique.
In closed tanks, a second measurement is required to measure the pressure of the gas atmosphere (air or gas above the liquid being measured). A differential pressure transmitter measures the differential pressure at two different points in the tank where the tank is subjected to a pressure different from the atmospheric pressure. The measuring cell calculates the pressure difference between these two points to determine the liquid level.
For an accurate hydrostatic level measurement, the specific weight of the product in the tank or vessel as well as gravity must be taken into account. Hydrostatic pressure transducers are preferred for use where the density of the liquid is constant.
Common industrial applications of hydrostatic pressure transducer level measurement are as follows:
These pressure sensors are used in processes in the chemical and petrochemical industries (chemicals), the food industry (water, beverages, milk), the water industry (water and wastewater), the environment and the shipbuilding industry (sea water).
Hydrostatic level probes use proven measurement technology, as they offer many advantages, including:
To choose a hydrostatic pressure sensor, it is important to know the following parameters:
The choice of the level sensor will depend on these components.
The scale of the sensor's measuring cell, the materials of construction such as stainless steel, hastelloy C, monel must be adapted to guarantee a reliable and accurate measurement display over time.