radius at two independent phase angles imbalance data is obtained by measuring either acceleration velocity force or displacement at two independent locations on the vibrating system these measurements are processed to calculate a vector for each end representing the out of balance force nominally acting at each counterbalance axial location this vector is not raw signal data from the force sensors but has been compensated for forces that result from movement of the bearing mounts as the nominal out of balance force magnitude and phase angle at each of the two locations is calculated another process controls addition of correction mass to correct the imbalance the balancing system of the preferred embodiment uses electrical signals generated by load cells in the bearing mounts and by associated accelerometers to control the application of counterbalance mass in the preferred embodiment a pair of load cells 42 are located with one for each end of shaft 1 as shown in fig4 the load cell may measure small displacements in a very stiff elastically deforming support system a strain sensor suited to this application is the piezo disc this type of sensor produces a large signal output and so is not significantly affected by rfi figure shows an example of a possible bearing mount this bearing mount includes two concentric cylindrical rings 46 47 as illustrated in fig5 a pair of load bridges 40 41 are connected at the top and bottom of the inner ring 47 respectively and to opposite parts of the inner.