Monitoring and measurement method of a deposit layer on a surface in contact with a liquid medium and monitoring and measurement sensor implementing the same

Data di pubblicazione




Data di priorità



Politecnico di Milano


Department of Civil and Environmental Engineering


Marco Carminati; Andrea Turolla; Manuela Antonelli


Sensor for the continuous measurement (wireless and in real time) and at high fouling resolution of the surface in contact with water, as internal surfaces of piping and tanks. In particular the thickness of bacteria (biofilm) and chemical (limescale) deposits that forms on the surface. The operating principle is the measurement of the electric impedance between the planar electrode couples applied on the surface of the duct and placed at a comparable distance with the thickness to measure. It is possible to distinguish the type of deposit for how affects the ionic resistance as the thickness of the deposit increases: in the case of the biofilm, the resistance decreases as consequence of the bacteria metabolism, while in the case of insulating deposit (like the limestone), the resistance increases. In both the cases the response curve of the sensor is linear. As well as the distance, the sensible area (indicatively of few cm2) and the material of the insulating substrate (flexible or stiff) can be adapted to the specific application, industrial ore relative to the hydric service integrated.

Campo di applicazione

• Monitoring of the status of duct for the potable water distribution. • Active and precocious diagnostic of the status of probe surfaces and submerged electrodes for the continuous monitoring of water quality, for an on-demand maintenance. • Measurement of the thickness of the fouling in internal circuits of household appliances and hydric circuits of industrial systems. • Closed ring control of cleaning processes, sanitation and decalcification.


• Low cost. • Simplified embodiment and robustness (no mobile parts, passivables electrodes). • Adaptable to various geometries and dimensions of the duct and to the various thickness of deposits to measure (from µm to mm). • Quantitative measurement of the thickness with high resolution (1 micron). • Ability to discriminate biofilm from other non-biological deposits