Abstract: The invention relates to a waste water immersion probe (10) comprising a liquid-tight housing (11), a sensor (18) which is disposed in the housing (11) and a sensor window (20) formed on the housing (11). A wiper element (22) for cleaning the sensor window (20) is arranged on the outside of the sensor window (20), and the wiper element (22) is driven by a drive motor (24) which is arranged essentially in the housing (11). The housing is devoid of openings. A magnetic element (36, 37) is associated with the drive motor (24) and a magnetic element (34, 35) is associated with the wiper element (22) in such a manner that the magnetic drive motor element (36, 37) produces a magnetic field which transverses the housing wall and transmits a drive torque to the wiper element (22) without a shaft.

Abstract: The invention relates to a sedimentation plant comprising a sedimentation basin (12), a cleaner beam (18) and an ultrasonic sludge level probe (30) which is suspended in the sedimentation basin (12). The cleaner beam (18) collides with the sludge level probe (30) in a regular manner ensuring that the sludge level probe (30) is displaced from the vertical spatial position and that the distance measuring values supplied thereby are no longer required for evaluating the height (h) of the sludge level (40). A positional sensor (34) is associated with the ultrasonic measuring head (32), which determines the spatial position of the ultrasonic measuring head (32). As a result, an error position of the ultrasonic measuring head (32) can be determined and the distance measuring values supplied by the ultrasonic measuring head (32) when in the error position are suppressed when the height (h) of the sludge level (40) is determined.