Method and apparatus for calibrating a torque measurement

An apparatus for calibrating a torque measurement of a rotatable object, the apparatus comprising:

• a structure to be coupled to the rotatable object, the structure comprising a first member and a second member, each extending along a length of a surface of the rotatable object and disposed on opposite sides of the rotatable object;
• an adapter to be coupled to the rotatable object, wherein the adapter is configured to apply a known torque to the rotatable object with the rotatable object in a stationary condition;
• a first pair of sensors coupled to the first member and the second member and positioned to measure a first rotational displacement of the rotatable object at a first axial location of the rotatable object, the first pair of sensors circumferentially spaced from each other at about 180 degrees, thereby compensating for bending of the rotatable object;
• and
• a second pair of sensors coupled to the first member and the second member and positioned to measure a second rotational displacement of the rotatable object at a second axial location of the rotatable object, the second pair of sensors circumferentially spaced from each other at about 180 degrees, thereby compensating for bending of the rotatable object.