Physical and Chemical Sensors

Continuous online measurement of water quality parameters

In situ sensors offer real-time detection of alterations in water

Water polluted by discharges impacts directly on the health of humans, as well as having secondary socio-economic consequences on populations.

ADASA achieves rapid detection of pollutants by monitoring physical-chemical parameters that indicate water quality and protect the environmental state of natural water sources. We have extensive experience in handling potentiometric, polarographic and optical technologies.

Tracking sensors also optimise processes in wastewater treatment plants, aquaculture facilities and any sectors where water plays a significant role.

Image of an aquaTest-Mo

Potentiometric sensors measure the potential difference between two sensors (indicating sensor and reference sensor) immersed in a solution. The indicator sensor provides the potential that is generated as a function of the concentration of specific ions. In contrast, the reference sensor has a known, stable potential, independent of the ions present in the solution. Potentiometric sensors are widely used for the measurement of pH, ORP and conductivity.

Polarographic sensors, used to measure dissolved oxygen, have a gas-permeable membrane that separates them from water. The oxygen that passes through the membrane reduces, creating a current proportional to the oxygen concentration that the sensor can measure. These sensors are inexpensive but require frequent maintenance. They need a constant flow of water as they consume the oxygen that diffuses through the membrane.

Optical sensors measure different properties of light, depending on the parameter to be determined:

  • Dissolved oxygen: based on fluorescence extinction measurement. The sensor membrane contains a luminescent compound that, when excited with blue LED light, emits red light. The more dissolved oxygen in the sample, the more this red fluorescence is quenched. The intensity and lifetime of the luminescence are inversely proportional to the oxygen concentration.
  • Turbidity: optical sensors can measure the refraction of light two ways. Firstly, light emitted by the LED is scattered proportionally by the turbidity of the sample. Secondly, by attenuation and absorption - the light emitted by the LED is absorbed, the amount of light that reaches the detector being inversely proportional to the turbidity of the sample.
  • Pigments (Chlorophyll, Phycocyanin): the optical sensors use the fluorescent properties of pigments, which, by exciting them at a given wavelength, emit light at a longer wavelength, in proportion to the number of pigments in the sample.

At Adasa, we select the most suitable sensors for each installation, depending on the characteristics of the water bodies. We offer bespoke solutions adapted to needs and can integrate existing systems into our multi-parametric solutions, such as:

  • aquaTest series: online measurement of physicochemical parameters and organic matter (optional).
  • AquaDam series: specially designed for measuring vertical profiles in dammed waters.

Our solutions for the continuous measurement of physical-chemical parameters are all easy-to-handle, have low operating costs and are environmentally friendly. There’s no need to use reagents, and they don’t generate harmful waste.



  • Precise and fast answers improve water quality monitoring networks.
  • Detect water pollution source and tracks wastewater treatment plants inflows and effluents.
  • Easily integrated into multi-parametric systems.
  • Environmentally friendly with no need for reagents and no harmful waste generated.

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