Sensors for in-situ control of water quality, based on diamond nanocrystals, a material that pushes the limits of durability without maintenance, while maintaining an affordable price. Under the combined effect of global warming and demographic pressure, it is necessary to continuously monitor water quality at many points, before and after use. The large majority of sensors used for this task are electrochemical sensors, yet their large-scale deployment is limited by their purchase price, not to mention the maintenance costs (cleaning and recalibration), which can double the purchase price. DIAMSENS relies on the unique properties of diamond to develop and manufacture sensors that are both efficient and robust – “forever” even, some would say. A process patented by CEA-Leti, which consumes little energy, allows self-cleaning of submerged analysis surfaces. The sensor remains in as-new conditions, and the initial accuracy of the measurements is kept. This avoids frequent manual recalibrations and the associated maintenance costs. As for the price of the sensor itself, the solution is to use conventional microelectronics and electronics equipment to massively and quickly manufacture sensor arrays at an affordable price. DIAMSENS will successively serve the markets of the swimming pool water treatment, then agriculture - with the control of fertilizers - and finally the drinking water treatment associated with wastewater treatment.