Abstract: An optoelectronic theodolite sensor contains in a frame, a cylindrical measurement cell half filled with an opaque liquid or entirely filled with two overlying immiscible liquids, each of which fills half of the cell, the first one being opaque and the other transparent to light. In the normal position of the measurement cell, the liquid or the interface between the two liquids forms with opaque side surfaces of the cell faces, an exact quadrant through which the light of a light source reaches an optoelectronic element located on the opposite side of the measurement cell. An angular displacement of the measurement cell causes a change in the intensity of the light reaching the optoelectronic element, which is converted and then applied as a function of the displacement angle .phi..