Optochemical sensor and method

An optochemical sensor for determining a measurand correlated with a concentration of an analyte in a measuring fluid, comprising:

• a housing having an immersion region adapted to be immersed into the measuring fluid;
• a removable cap removably arranged at the immersion region of the housing, the removable cap including at least one sensor spot disposed on a lateral face of the removable cap;
• a radiation source disposed in the housing and configured to emit excitation radiation into the removable cap in an axial direction toward an end face of the removable cap, wherein the end face is perpendicular to the lateral face;
• a deflection module disposed in the removable cap and configured to deflect the excitation radiation in a direction of the at least one sensor spot such that the at least one sensor spot is irradiated with the excitation radiation, wherein the direction of the at least one sensor spot is perpendicular to the axial direction;
• a radiation receiver disposed in the housing and configured to receive received radiation emitted by the at least one sensor spot;
• and
• a sensor circuit disposed in the housing and configured to control the radiation source, to receive signals of the radiation receiver, and to generate and output output signals based on the signals of the radiation receiver.