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Contactless 2-dimensional laser sensor for 3-dimensional wire position and tension measurements

We have developed a contact-free 2-dimensional laser sensor with which the position of wires can be measured in 3 dimensions with an accuracy of better than 10 micrometer and with which the tension of the wires can be determined with an accuracy of 0.04 N. These measurements can be made from a distance of 15 cm. The sensor consists of commercially available laser pointers, lenses, color filters and photodiodes. In our application we have used this laser sensor together with an automated 3 dimensional coordinate table. For a single position measurement, the laser sensor is moved by the 3-dimensional coordinate table in a plane and determines the coordinates at which the wires intersect with this plane. The position of the plane itself (the third coordinate) is given by the third axis of the measurement table which is perpendicular to this plane. The control and readout of the table and the readout of the laser sensor were realized with LabVIEW. The precision of the position measurement in the plane was determined with wires of 0.2 mm and 0.3 mm diameter. We use the sensor for the quality assurance of the wire electrode modules for the KATRIN neutrino mass experiment. We expect that the precision is at least comparable or better if the wires are thinner. Such a device could be well suited for the measurement of wire chamber geometries even with more than one wire layer.