Abstract: A magnetic fluid rotary feedthrough has a multi-stage magnetic fluid rotary seal adapted to provide a magnetic fluid seal about a shaft for extending between a first environment and a second environment, one or more sensors integrally mounted within the magnetic fluid rotary feedthrough to sense one or more physical parameters of the multi-stage magnetic fluid rotary seal, signal processing electronics mounted to or incorporated in the magnetic fluid rotary feedthrough to receive one or more sensor output signals from the one or more sensors, to process the one or more sensor output signals and to output one or more electronic processing signals, and one or more output devices operatively connected to receive the one or more electronic processing signals from the signal processing electronics to indicate the condition of the multi-stage magnetic fluid rotary seal.