Method for determining the necessity of cleaning and/or the success of cleaning

1. A method for determining necessity of a measure and/or success of a measure for a sensor in a retractable assembly, wherein the sensor is configured to measure one or more physical or chemical process variables of a process medium, the method comprising:

moving the sensor in a direction of a service chamber of the retractable assembly;

analyzing an attribute associated with the sensor using an analysis device, not the sensor, wherein the attribute is a state of at least a portion of a surface of the sensor and/or a composition of a service medium in the service chamber; and

deriving the measure based on the analysis of the analysis device.

2. The method of claim 1 , wherein the portion of the sensor is a membrane, a diaphragm, a filler opening for a bridge electrolyte, a sensor shaft, a glass shaft, an optical measuring window, or an electrode.

3. The method of claim 1 , wherein the analyzing is performed continuously during the moving of the sensor in the direction of the service chamber.

4. The method of claim 1 , wherein the service medium is cleaning liquid, flushing liquid or, at least in part, the process medium to be analyzed by the sensor, which enters the service chamber during the moving of the sensor.

5. The method of claim 1 , wherein the analyzing is performed at a location remote from the retractable assembly.

6. The method of claim 1 , wherein the deriving of the measure comprises at least one of the steps: starting a cleaning cycle, replacing the sensor, maintenance of the sensor, and further measurement.

7. A system for determining necessity of cleaning and/or success of cleaning of a sensor in a retractable assembly, the system comprising:

a retractable assembly including at least one service chamber;

a sensor disposed in the retractable assembly such that the sensor is movable between a service position and a process position, wherein in the service position the sensor is within the service chamber, and wherein the sensor is configured to measure one or more physical or chemical process variables of a process medium; and

an analysis device configured to analyze an attribute associated with the sensor, wherein the attribute is a state of at least a portion of a surface of the sensor and/or a composition of a service medium in the service chamber.

8. The system of claim 7 , wherein the analysis device is a spectrometer, a fluorescence measuring device, or a laser-based measuring device adapted to operate upon measuring scattering or reflection.

9. The system of claim 7 , wherein the retractable assembly comprises at least one optical window into the service chamber, and the analysis device is configured to determine the attribute via the at least one window.

10. The system of claim 9 , wherein the at least one optical window is one, single window.

11. The system of claim 9 , wherein the retractable assembly comprises at least two oppositely arranged optical windows into the service chamber.

12. The system of claim 9 , wherein the retractable assembly comprises at least two non-parallel optical windows into the service chamber, wherein the at least two windows are arranged orthogonally to one another.

13. The system of claim 7 , wherein the retractable assembly comprises at least one flushing connection, and the analysis device is configured to determine the attribute via the flushing connection.