A compact portable device, which permits the measurement and determination of various properties of machinery using magnetic bearings, has been constructed. This mostly analog device has a white noise generator, a variable frequency, variable amplitude sine wave and square wave output and can generate a ramped frequency “rotating” electronic signal to simulate rotor speed run-up. It may be utilized during normal operation or when the rotor is in support, but not rotating. Probably it would be most helpful during initial test-stand testing. System dynamic properties, such as critical speeds, stiffness, damping, maximum and optimum clearances, rub angle locations, amplification factors, log decrements, structure resonances, cross coupling, etc., can be determined. A dynamic balancing feature using open-loop control, with the “rotating” electronic signal synchronized via a key-phasor, may be manually set at a given speed. This balancing feature may be automatically activated and then turned off at previously determined speeds. The open-loop control feature also may be used as a run-out compensator and for foundation vibration reduction. A block diagram description of the operational functions of this diagnostic device is presented, along with experimental results and dynamic properties gathered from its use on several magnetic bearing rigs.