Tube arrangement polished by forced electrolytic plasma polishing in sections, in particular a measuring tube arrangement, measuring sensor with such a measuring tube arrangement, and method for plasma polishing a measuring tube arrangement

A measuring tube arrangement, comprising:

• two support bodies, each with at least one bore;
• and
• at least one tube with a lumen for guiding a medium,
• wherein the at least one tube has a first end portion and a second end portion which are each connected to one of the support bodies,
• wherein the at least one bore of each of the support bodies communicates with one another via the lumen of the at least one tube,
• wherein the measuring tube arrangement has a portion which is polished by forced electrolytic plasma polishing and which, in a region in which a flow cross section has not more than a cross section of the at least one tube, extends over at least three diameters of the at least one tube, and
• wherein the portion polished by forced plasma polishing is followed by an etched portion that has a different surface structure from the portion polished by forced plasma polishing.

A measuring sensor, comprising:

• a measuring tube arrangement, including:
• two support bodies, each with at least one bore;
• and
• at least one tube with a lumen for guiding a medium,
• wherein the at least one tube has a first end portion and a second end portion which are each connected to one of the support bodies,
• wherein the at least one bore of each of the support bodies communicates with one another via the lumen of the at least one tube,
• wherein the measuring tube arrangement has a portion which is polished by forced electrolytic plasma polishing and which, in a region in which a flow cross section has not more than a cross section of the at least one tube, extends over at least three diameters of the at least one tube, and
• wherein the portion polished by forced plasma polishing is followed by an etched portion that has a different surface structure from the portion polished by forced plasma polishing;
• a base body that connects the two support bodies to one another in a rigid manner;
• an electrodynamic exciter for exciting bending vibration modes;
• and
• at least one vibration sensor for detecting bending vibrations of the at least one tube.

A method for a portion-wise plasma polishing of a measuring tube arrangement, comprising:

• positioning a cathode and an electrolyte supply line with respect to the measuring tube arrangement, wherein the cathode has a tip which is spaced no more than four inner diameters of a measuring tube of the measuring tube arrangement from an end face of the measuring tube arrangement;
• allowing an electrolyte to flow through the measuring tube arrangement;
• and
• applying an electrical voltage between the cathode and the measuring tube arrangement which is sufficient to maintain a plasma in a portion of the measuring tube arrangement that extends from an end face of the measuring tube arrangement over a length of not less than four inner diameters of the measuring tube into the measuring tube arrangement,
• wherein the measuring tube arrangement includes two support bodies, each with at least one bore;
• and at least one measuring tube with a lumen for guiding a medium, wherein end portions of the at least one measuring tube are each connected to one of the support bodies, wherein at least one end portion of the measuring tube is forced plasma polished.