Patent ID: 8123480

Claim:
An elongated member of a wind turbine subjected to strain, comprising: a sensor unit for determining a deflection and/or a strain of the elongated member between a first point and a second point where the first and second points are assigned to a same side of the elongated member, the sensor unit having a proximity sensor for determining a distance between the second point and a third point, wherein the third point is connected to the first point by an inflexible support configured not to deflect when the elongated member deflects, the inflexible support thereby effective to maintain a constant distance between a first point and the third point, the distance between the first point and the third point is considerably longer than the distance between the second point and the third point, the third point is connected to the second point by a hollow, elastic element, and the distance between the second point and the third point is measured within the elastic element.