Optochemical sensor and method for measured value correction

An optochemical sensor for determining a measurement signal that correlates with a physical or chemical measurand of a measuring fluid, the sensor comprising:

• a housing including at least one immersion region configured to be immersed in the measuring fluid;
• a removable sensor cap including a sensor spot,
• wherein the sensor cap is disposed in the immersion region of the housing, and
• wherein the sensor spot is disposed on a lateral surface of the sensor cap and comprises:
• an analyte-sensitive indicator dye, a luminescence of which is affected by an analyte in the measuring fluid;
• a hydrophobic matrix;
• and
• a state description indicator contained within the hydrophobic matrix,
• wherein the state description indicator is selected to absorb a polar solvent of the measuring fluid and to undergo a change of luminescence decay behavior or phase angle or a change of absorption and/or emission bands in presence of the polar solvent such that, when the polar solvent is absorbed into the hydrophobic matrix via cracks in the hydrophobic matrix, the cracks are detectable, wherein the cracks reflect an aging state of the sensor spot;
• at least one radiation source disposed in the housing and configured to radiate excitation radiation onto the sensor spot, to excite the luminescence of the indicator dye, and to excite a luminescence of the state description indicator;
• a first radiation receiver configured to receive reception radiation emitted by the sensor spot;
• a second radiation receiver configured to receive excitation radiation from the at least one radiation source after passing through the sensor spot;
• and
• a sensor circuit disposed in the housing and electrically connected to the at least one radiation source and the first and second radiation receivers, wherein the sensor circuit is configured to:
• control the at least one radiation source;
• generate, based on an intensity of luminescence and/or a phase angle of luminescence of the indicator dye detected by the first radiation receiver, a measurement signal representing the physical or chemical measurand in the measuring fluid in contact with the sensor spot;
• and
• based on the change of luminescence decay behavior or phase angle or the change of absorption and/or emission bands of the state description indicator in the presence of the polar solvent, detect the cracks in the hydrophobic matrix and thereby determine the aging state of the sensor spot.