The dynamic force measuring system for the measurement of machinery vibration is based on the use of four piezoelectric force transducers. These transducers are installed between the feet of the machine under test and a terminating foundation, preferably a large seismic mass. The four signals are combined in two ways: (1) as a phasor sum to provide a single vertical force measurement and (2) as a sum and difference with equivalent moment arms to provide torque measurements. These fundamental measurements are based on force and torque equations developed from the six motions of an assumed rigid body. At the fundamental frequency of machinery vibration the two combined signals provide a measure of static and dynamic unbalance. The force spectrum may be analyzed by conventional means to provide frequency and amplitude information.