Method for the energy-saving, continuous measuring of a quality of a liquid and measuring device for carrying out the method

A method for energy-saving, continuous measuring of a quality of a liquid using a measuring device having a sensor for detecting a measurement variable in the liquid, wherein:

• S1) the measuring device is arranged relative to the liquid and the sensor detects the measurement variable in the liquid;
• S2) the sensor is alternatingly activated for a duration of a switch-on phase and deactivated for a duration of a switch-off phase;
• S3) a switch-on phase in a steady state of the sensor is defined as a defined switch-on phase and a measurement value is detected as a comparison measurement value by the sensor during the defined switch-on phase when a value of the measurement variable differs by at most a predetermined difference from a value of the measurement variable during a previous switch-on phase;
• S4) a reference measurement is carried out to detect a reference measurement value representing a reference quality of the liquid;
• S5) during further switch-on phases following the defined switch-on phase, the sensor continuously detects measurement values in the liquid as operating measurement values representing operating qualities of the liquid;
• S6) a calculation rule assigns the comparison measurement value to correspond to the reference measurement value;
• and
• S7) a final measurement value representing a final quality of the liquid is determined based on the calculation rule and each of the operating measurement values;
• wherein
• in order to carry out the reference measurement
• S4b) the defined switch-on phase or a switch-on phase between the defined switch-on phase and the further switch-on phases for detecting the operating measurement values is extended compared to the preceding switch-on phases, and during the extended switch-on phase the reference measurement value is detected using the sensor.