Abstract: 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.

Abstract: A comprehensive multiple rapper control system controls rapping intensity with enhanced accuracy, controls a large number of rappers in any desired sequence with intensity control for each individual rapper, and includes alarm circuitry for reliably indicating open circuited and short circuited conditions in the rapper coils or in the electrical connections to the rapper coils. For enhanced accuracy, a short boost pulse of full lift energy is applied immediately prior to a lift pulse of controlled energy. The boost pulse overcomes initial rapper plunger sticking forces so that total rapper plunger lift accurately reflects the electrical energy supplied during the subsequent controlled pulse. Advantage is taken of the relatively constant boost pulse which is supplied to every rapper in the system regardless of the energy supplied during the control pulse to provide an alarm circuit. Current through each rapper plunger lift coil is sensed during at least a portion of the boost pulse.