Hydrostatic Level Measurement

Hydrostatic Level Measurement

Hydrostatic Level measurement determines continuous liquid level by measuring the hydrostatic pressure exerted by the liquid column at a reference point and converting that pressure into level using the liquid density and gravitational constant. Implementations include submersible probes, flush-mounted transmitters, and differential pressure arrangements for pressurized or closed vessels. It is a pressure-based approach optimized for liquid services.

Hydrostatic methods are appreciated for predictable behavior in turbulent, foaming, or aerated liquids where surface-based echo technologies can struggle. The sensor “sees” head pressure rather than the surface condition, so agitation and splashing have limited effect when installed appropriately. The technology is also practical for sumps, basins, and wells, and it can be extended with tank linearization to provide volume output for inventory and batching.

Accuracy depends on stable density; temperature changes, concentration shifts, or entrained gas can introduce error if density compensation is not considered. In closed tanks, vapor-space pressure must be measured or canceled (via differential pressure or a second reference measurement) to avoid offset errors. For corrosive, viscous, or hot services, diaphragm seals, capillaries, and material selection are critical, and sensor placement must consider sedimentation, plugging, and cleaning access.

Typical applications include wastewater wet wells, lift stations, clarifiers, open basins, chemical day tanks, neutralization and dosing systems, and process vessels with mixers where surface conditions are poor. Submersible designs are common for wells and reservoirs, while differential pressure configurations support pressurized vessels and separators. The method is also used where a simple, rugged continuous signal is required and periodic recalibration is acceptable.

Integration is typically via 4–20 mA and industrial digital protocols, with diagnostics for sensor health and wiring integrity. Good practice includes defining density assumptions (or providing compensation), ensuring proper venting for gauge references, and selecting sealing materials suitable for the medium. Calibration can be performed against known fill heights, and redundant installations support higher availability and safety-related duties.

Miller Mechanical Specialties, an exclusive authorized representative of sales and service for Endress+Hauser.