1. A method of monitoring the condition of a machine, said method comprising: receiving an input complex signal from the machine wherein the input complex signal comprises a plurality of signal components, the plurality of signal components comprising at least one signal component containing a pre-determined frequency of interest and at least one signal component containing noise; processing the input complex signal and generating an output complex signal comprising a plurality of signal components, the plurality of signal components comprising at least one signal component containing a pre-determined frequency of interest and at least one signal component containing noise, wherein said processing the input complex signal comprises executing a fixed time step integration algorithm using a fourth-order Runge-Kutta model of integration with a single, fixed integration time step that is defined to be substantially equal to a sampling time step of the input complex signal; and processing the output complex signal to assess whether a fault exists, wherein the pre-determined frequency of interest is extracted from the output complex signal; and wherein the pre-determined frequency of interest is displayed on a display.