Unbalance measuring systems

Claim 1

AN UNBALANCE MEASURING SYSTEM INCLUDING VIBRATION PICKUP MEANS HAVING AN OUTPUT UNBALANCE SIGNAL INCLUDING BOTH AN UNBALANCE COMPONENT PROPORTIONAL TO THE AMPLITUDE OF VIBRATION OF A ROTATING WORKPIECE WHOSE UNBALANCE IS BEING MEASURED AND MODULATING NOISE COMPONENTS, MEANS PRODUCING A SIMULATED UNBALANCE SIGNAL HAVING APPROXIMATELY THE FREQUENCY OF THE UNBALANCE SIGNAL COMPONENT, MEANS FOR CHANGING THE PHASE RELATIONSHIP BETWEEN THE ACTUAL AND THE SIMULATED UNBALANCE SIGNALS, MEANS FOR COMBINING THE SIGNALS, THE SIMULATED UNBALANCE SIGNAL BEING OF SUCH AN AMPLITUDE THAT DURING MODULATION OF THE COMBINED SIGNAL BY THE NOISE COMPONENTS THE COMBINED SIGNAL REMAINS AT SUBSTANTIALLY THE SAME POLARITY DURING EACH HALF CYCLE, AND MEASURING MEANS RESPONSIVE TO THE COMBINED SIGNAL AND OPERATIVE TO RECTIFY THE COMBINED SIGNAL SO AS TO PERMIT AMPLITUDE MEASUREMENTS BOTH WHERE THE ACTUAL AND THE SIMULATED SIGNALS ARE IN PHASE AND 180* OUT OF PHASE THEREBY ENABLING THE AMPLITUDE OF SAID UNBALANCE COMPONENT TO BE ISOLATED AND ACCORDINGLY THE ACTUAL UNBALANCE TO BE DETERMINED RELATIVELY UNINFLUENCED BY THE NOISE COMPONENTS.