An apparatus for performing non-synchronous impact on object during operation is disclosed. The apparatus comprises an impact bar, a means to excite bar and a signal generator to provide pulse wave to energize and reset means to excite bar. The signal generator is set with sampling rate, block size, duty cycle and wave interval. These parameters are set to arrive at desired impact interval and energized time. The impact interval is not synchronous with load frequency. Assuming cyclic load frequency is provided at 20 Hz, synchronization of impact with cyclic load component can be avoided with impact frequency of 0.1538 Hz which is non-integer multiple of cyclic frequency. The apparatus was developed to replace manual impact hammer to enhance the accuracy of impact-synchronous modal analysis.