Compact load cells

A force sensing apparatus for measuring forces in a load plane vertically offset from a sensor plane by a distance h, the force sensing apparatus comprising:

• at least one compact load cell comprising:
• at least three force sensing elements arranged in the sensor plane about a point and horizontally spaced a distance d from the point, each force sensing element comprising a pressure sensor encased in a force transmission medium such that the at least three force sensing elements form an array of pressure sensors;
• a load plate in contact with the force transmission medium;
• a load beam having a first end and a second end, the first end connected to the load plate and the second end extending axially from the point to the load plane;
• at least one rotor connected to the second end of the load beam located in the load plane;
• and
• wherein the load beam defines a motor shaft configured to drive the rotor such that forces acting on the rotor are transmitted to the sensor plane via the motor shaft, and a changing pressure field over the load plate produces measurements across the sensor elements from which axial and transverse forces applied to the rotor may be derived to calculate a local aerodynamic flow-field at the rotor;
• wherein the measurements obtained by the sensor elements include vertical and lateral components of force applied to the rotor;
• and
• wherein the force transmission medium is selected according to a desired degree of damping.