A modular fitting for immersion in a medium includes: a cylindrical fitting tube configured to accommodate a sensor as to enable contact with the medium at a first end, wherein at the first end a protective basket with at least two tines is arranged; a crown nut including an external thread and at least two slots; a ring; and a cylindrical fitting base including an internal thread complementary to the external thread of the crown nut at a first end region of the fitting base and a stop at a second end region of the fitting base, wherein the ring is configured to be slipped over a cable connected to the sensor, wherein the fitting base is configured to accommodate and fix the ring via the crown nut, and wherein the fitting base and the fitting tube each comprise connecting means to releasably connect them securely to each other.