Patent ID: 8075267

Claim:
A wind turbine rotor blade, comprising a blade root; a leading edge extending away from the blade root along a centerline that is perpendicular to the blade root; a trailing edge opposite the leading edge and extending away from the blade root, wherein the leading edge and the trailing edges together form a hollow blade body, and a shoulder of the blade body resides at a maximum width location between the leading and trailing edges of the blade body; and a sensor unit arranged along the elongated member, where the sensor unit detects a deflection and/or strain of the elongated member between the first and second points, the sensor unit comprising a proximity sensor that determines a distance between the second point and the third point, an inflexible support that connects the first point to the third point, where the distance between the first point and the third point being longer than the distance between the second point and the third point, and a frequency detecting unit connected to the proximity sensor wherein the frequency detecting unit detects a frequency of a change of the distance between the second and third points.