A torque transducer unit for in-line calibration measurement of the output torque of a power wrench (S) includes a torque transferring spindle provided with a torque sensing device, two constant velocity universal joints, for instance Rzeppa-type couplings, and two coupling members for connecting the spindle at one end to the output shaft of a power wrench (S) and at the opposite end to a test joint. The spindle and the torque sensing device are protected from bending and friction related forces by the universal joints such that occurring misalignments between the power wrench (S) and the test joint do not jeopardize an accurate and reliable torque measurement.