Abstract: A method and a sensor (1) for oil-in-water measurement, in particular for the oil industry. In an electric measuring cell (7, 12) a capacitance is measured as a measure of an oil concentration in the water flowing through or in the accumulation filter (16, 16a, 16b). In order to reduce the maintenance requirement, the measuring cell (7, 12) is automatically calibrated at recurring time intervals with clean water (FIG. 1) and/or flushed with water, possibly oil-contaminated, in the back-flushing direction (FIG. 2). Advantages of the invention are reduced signal drift, improved long-term reliability and a long service life without monitoring or filter exchange.

Abstract: The present invention discloses a capacitive filling-level sensor, which is suitable in particular for filling-level determination in oil separator tanks. The capacitive sensor includes a measuring probe with at least one sensor electrode. According to the invention, the measuring probe is at least partially sheathed with at least one outer layer of a fluorinated plastic and at least one inner layer of a mica-filled plastic. Important exemplary embodiments concern an outer layer of perfluoroethylene-perfluoropropylene copolymer (FEP), an inner layer of mica-coated glass fiber tape impregnated with epoxy resin and possibly silanized and an incompressible, thermally adapted filling of the measuring-probe pipe with silicone oil and glass spheres or glass polyhedrons and/or an inner rod of AlMgSi-filled epoxy resin. The sheathing is electrically insulating, chemically inert, hydrophobic, oleophobic, waterproof, mechanically robust and easy to produce.

Abstract: The subject matter of the present invention is the optimization of a capacitive liquid level sensor which is suitable, in particular, for determining the location of a boundary layer 12 between water 10 and oil 11 in a separator tank. The known sensor principle is based on measuring the environmentally dependent capacitance between neighboring electrodes 13, 4; 4, 5; 5, 6 of a rod-shaped probe 1. According to the invention, the probe 1 is designed such that large ionic double-layer capacitors occur on the electrodes 4, 5, 6, 13 in the more conductive medium 10, and small capacitors occur between electrodes 4, 5, 6, 13 in the insulating medium 11. For this purpose, the electrode height h is selected to be large, the ratio of the electrode height h to the electrode spacing a is preferably selected to be in the range of 1<h/a<6 and, in particular, the measuring frequency f is selected to be in the dielectric cut-off frequencies of the media 10, 11.

Abstract: The present invention discloses a method and a sensor (1) for oil-in-water measurement, in particular for the oil industry. In an electric measuring cell (7, 12) a capacitance is measured as a measure of an oil concentration in the water flowing through or in the accumulation filter (16, 16a, 16b). In order to reduce the maintenance requirement, the measuring cell (7, 12) is automatically calibrated at recurring time intervals with clean water (FIG. 1) and/or flushed with water, possibly oil-contaminated, in the back-flushing direction (FIG. 2). Advantages of the invention are, inter alia, reduced signal drift, improved long-term reliability and a long service life without monitoring or filter exchange.

Abstract: A photoacoustic flow measuring cell (1a, 1b) for measuring oil residues in water including a photoacoustic sensor principle based on converting optical energy into acoustic energy by absorption of light on oil molecules in water. A measuring cell (1a, 1b) having contamination-free infeed optics (9, 10, 11, 21) is produced by providing a free fall stage (3) for a contactless feed (12) of light into an analyte (4). A sound detector (16) is an externally mounted piezoelectric transducer (16) or an optical interferometer (23) which measures vibrations of a liquid surface (6) without contacting the same. The photoacoustic free fall measuring cell (1a, 1b) provides a high level of detection, well into the ppm concentration range, low susceptibility to faults and is suitable, in particular, for use in high pressure separating tanks (28) for conveyance of crude oil.