Displacer level transmitter – operating principle

A diver is a traditional liquid level transmitter which detect liquid level using electrical or pneumatic technology. It is mounted in a vessel called a diver chamber, mounted on top of the tank or in a side measuring chamber. It consist displacer element which is suspended from a hanger with a torque tube thus producing a proportional output signal. The displacer length is determined by the operating range.

Advantages and disadvantages of liquid level measurement with a displacer level transmitter

Displacement type level transmitters – advantages

The displacer level transmitter, due to its robust design, finds its use in applications where high pressure and temperature conditions prevail, as well as with corrosive liquids.

Another advantage is its simple operating principle based on Archimedes' law. Moreover, due to its widespread occurrence, this device is well known to maintenance services.

Displacer level instrument – disadvantages

However, often the benefits of these advantages outweigh the troubles caused by the nuisance disadvantages of the displacer level transmitter, such as:

• non-resistance to changes in process fluid density

• tendency to stick

• sensitivity of the measurement to vibrations of the measuring installation

• susceptibility to overgrowth of core and torsion springs (mechanical suspension system)

• relatively long measuring response time

Float switch – how to eliminate displacement type level instruments defects

Float switch – principle of operation

The float switch operates, like a plunger transducer, on the basis of Archimedes' buoyancy law.

In JUMO NESOS devices, a float with an integrated magnet uses its magnetic field to switch one or more reed contacts at increasing or decreasing levels. Alarms, pumps, signal lamps, valves and horns are usually switched using a contact protection relay.

Divers and float switches therefore share the advantage of a simple and easy-to-understand operating principle. Furthermore, they are not burdened with many of the disadvantages of plunger transmitters.

Advantages of float switches

The float switches of the JUMO series offer advantages such as:

• accurate measurement in process liquid regardless of foam formation, conductivity/conductivity or pressure ratio

• applicability over a wide temperature range from -52 to 240°C

• cost-effective installation and assembly

• maintenance-free

• very good price/quality ratio

• high switching point accuracy of ±2 mm.

• switching operation is contactless, wear-free and does not require auxiliary energy

Certifications and approvals of JUMO NESOS float switches

In addition, we have versions of float switches with approvals for use in shipbuilding and/or hazardous areas, as well as a certificate of conformity to the Pressure Equipment Directive (PED).