Density and concentration

Density measurement is a parameter associated with the quality of a product, the concentration of a mixture, type of product, amount of solids, content ratio, contamination of a fluid, phase detection, dosage, saturation, among other characteristics of a fluid that is necessary to know in industrial processes.

Endress + Hauser has designed different measurement principles for density depending on the application, the process conditions and the required precision:

Vibronic measurement principle (tuning fork)

A piezoelectric drive excites the Liquiphant's tuning fork to its resonant frequency. If the density of the liquid medium changes, the resonance frequency of the tuning fork also changes. The density of the medium has a direct impact on the resonance frequency of the tuning fork.

By storing specific properties of the medium and mathematical relationships in the system, the exact concentration of the medium can be calculated, for example.


Liquiphant FTLXX + FML621 Density Computer

Density / concentration measurement system using tuning fork and density computer with up to 4 channels, compensated by temperature and pressure (optional) for applications in tanks or pipes.


  • Density measurement of liquids in pipes or tanks in all industries
  • Detection or differentiation of fluids (phase detection)
  • Process conditions: temperature 0… 80 °C and maximum pressure 25 bar
  • Calculation of concentration in a liquid in units of ° Brix, ° Baumé, ° API etc
  • Approved in sanitary processes, corrosive fluids or explosive atmospheres
  • Scalable multichannel system for up to 4 measurement points

Surface acoustic wave measurement principle

A piezoelectric transducer stimulates these high-frequency sound waves, which propagate along the metal wall of the measurement device. A second piezoelectric transducer acts as a receiver. When sound waves come into contact with the liquid, the waves scatter through the liquid at a Rayleigh angle (ΘR). This angle depends on the relationship between the speed of sound of surface waves and the speed of sound of the liquid.

During this process, the measuring device also determines the acoustic impedance and acoustic density of the liquid, in addition to the speed of sound. Another sensor also measures the temperature. Combining all these characteristic values and applying through a software, it is possible to determine the density / concentration of substances in a liquid mixture.


Teqwave T

Portable density / concentration measuring device for temporary analysis of liquids on site.

Teqwave I

Density / concentration measuring device for continuous and accurate analysis of liquids in vessels.

Teqwave F

Density / concentration measuring device for continuous and accurate analysis of liquids in pipes.


  • Measurement of Density / Concentration of liquids in pipes or tanks in a fixed or portable way
  • Process conditions: temperature 0… 100 °C and maximum pressure 16 bar
  • Detection of failure in filtering systems
  • Monitoring of chemical processes, for example. particles in fluids
  • Measurement of concentration in fluids, for example. glycol
  • Monitoring of fluid contamination, e.g., leak detection in heat exchangers

Coriolis measurement principle

The Coriolis principle within a Coriolis flow sensor (which, according to its design, may have one or two internal measurement tubes). Fluid flows through measuring tubes that are constantly excited to oscillate at their resonant frequency. Any change in the density of the fluid produces a corresponding change in the resonance frequency of the entire vibratory system (measuring tube and fluid).

The resonant frequency, therefore, is a function of the density of the fluid: the higher the density, the lower the resonant frequency. In this way, by measuring the frequency of the system we can determine the density of the fluid.


Promass Proline Family

Through the different models of Coriolis flowmeters, in addition to measuring the mass flow and temperature, the ability to measure the density of liquids directly in the pipeline is added. Models are available for different process conditions and approved for use in all process industries.


  • In line measurement of Density / Concentration of liquids in pipes from up to 1/24” to 16” in any industry
  • Multivariable density, temperature and mass flow transmitter that allows concentration monitoring and dosing at the same time
  • Process conditions: temperature from -200 to 350 °C and pressure up to 400 bar
  • Calculation of concentration in liquid in units of ° Brix, ° Baumé, ° Alcohol, etc
  • Approved for use in custody transfer systems

Radiometric principle

The radiometric principle is based on the fact that isotopes, contained within a source container, emit Gamma radiation that is damped when it penetrates a material (the medium). A detector mounted on the opposite side of a pipe containing this flowing medium converts the radiation it receives into an electrical signal.

The measurement effect as such is derived from the absorption of radiation by the medium. Gammapilot M uses the received (attenuated) radiation to calculate the density and also the concentration of the measured substance.


Gammapilot FMG50

The compact two-wire transmitter for level detection, level measurement, interface and density.

Gammapilot FMG60

Compact 4-wire transmitter for level detection, continuous level measurement, and density and interface measurement.

Gamma modulator FHG65

Effective removal of background radiation and external radiation on the Gammapilot FMG60.

Radioactive source container FQG60

Radioactive source container with manual opening and closing of the beam.

Radioactive source container FQG61 / 62

Lightweight radioactive source container with bracket for manual or pneumatic activation / deactivation.


  • Measurement of Density / Concentration of liquids in pipes, bypass or tanks without interrupting the process, mainly in the primary industry, mining, chemical and oil & gas
  • No restrictions with process conditions: applicable extreme temperature conditions, high pressures or strong abrasion
  • Measurement of solid concentration in mineral abrasive pulps and mining water
  • Determination of product density in closed reactors at high pressure
  • Measurement of solids concentration in drilling sludge
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