Rapper Plunger

A rapper plunger displacement indicator for an electrostatic rapper control system of the type which supplies a pulse of controlled energy to the rapper coils. Means are provided for sensing current supplied to each rapper coil during the controlled energy pulse. The resultant sensed current is integrated with respect to time over the period of the pulse of controlled energy, and the result of the integration indicates plunger displacement. In a system where a short boost pulse of full lift energy is supplied immediately prior to the lift pulse of controlled energy for enhanced control accuracy, the integration is performed only during the controlled energy pulse, thus ignoring the boost pulse.