NATM pressure cells are designed for the measurement of stresses and pressures acting within shotcrete linings and at the ground–structure interface, particularly in tunnelling applications using the NATM method. The instrument consists of a steel cell made of two plates welded along the perimeter, enclosing an incompressible fluid: changes in applied load generate variations in internal pressure, which are detected by a transducer and converted into an electrical signal. The cells can be installed to measure radial and tangential stresses in tunnel linings, enabling monitoring of structural behavior during excavation and consolidation phases. To ensure correct stress transfer over time, the cells are equipped with a re-pressurization valve that restores proper contact between the instrument plates and the surrounding material, even after volumetric changes in the concrete during curing. Robust construction and high protection rating make these instruments suitable for permanent installations in harsh environments where long-term measurement reliability and stability are required.