VEGABAR, VEGAWELL, VEGADIF: Hydrostatic level measurement

Hydrostatic pressure refers to the mass of a stationary liquid at a given point of measurement.  As level increases inside a tank, the hydrostatic pressure increases proportionally. Thus, the higher the hydrostatic pressure measurement, the higher the liquid level measurement. 
Making this measurement requires installing a pressure transmitter on a tank so the instrument’s measuring cell is submersed in liquid. The transmitter measures hydrostatic pressure and converts it to a level measurement reading based on the equation below.
Height (Level) = Hydrostatic pressure/(Liquid density * Specific gravity)

 

What are the advantages of hydrostatic level transmitters? 

Hydrostatics have been in use in the process control industry for a long, long time. They are field-proven and familiar to users in many industries. Hydrostatic level instruments provide a reliable, accurate liquid level measurement even through adverse conditions in a tank such as foam, agitation, and obstructions. Users do not have to consider dielectric constant, and the instruments are easy to calibrate. 

While hydrostatic level measurement is a process automation mainstay, the sophistication of the sensors is constantly increasing. Users are now empowered to choose the best measurement cell material for their process. For example, VEGA offers dry ceramic measuring cells for abrasion resistance and durability as well as metallic measuring cells allow for reliable measurement of many different liquids.

Calculating hydrostatic level accurately means having known specific gravity and density measurements for the product inside the tank or vessel. Because of the importance of these two values, hydrostatic transmitters are used in applications where specific gravity and temperature (because it changes liquid density) are consistent and predictable. Hydrostatic transmitters are often found in open or vented tanks in industrial plants or in reservoirs and open channels in water and wastewater treatment applications. A closed tank would require a second pressure measurement of the gas pressure above the liquid.