One or more bolt gauges each with a built-in load cell are positioned on a blade bolt or a bearing bolt between a pitch bearing and a tightening means and tensioned by the securing means at the inside or the outside of a hub of a wind turbine. The bolt gauge then outputs a signal descending both from the tension from the bolt/securing means connection and the tension from the blade when the blade is vibrated due to wind forces and the rotation of the blade when the hub of the wind turbine is rotating.