Health-monitoring system for a device determining rotation frequency of a shaft

A system for sensing rotational frequency of a rotatable member and for monitoring health of the system, the system comprising:

• a radio-frequency signal generator that generates an electrical signal;
• a first magnetic speed probe configured as a transmitter;
• a second magnetic speed probe configured as a receiver, wherein the first and second magnetic speed probes are arranged in transmissive proximity with one another, each of the first and second magnetic speed probes includes:
• a magnet for generating a magnetic field proximate the rotatable member, rotation of the rotatable member causing changes in the magnetic field generated by the magnet;
• an inductive coil positioned proximate the rotatable member;
• and
• an electrical-current sensor coupled to the inductive coil, the electrical-current sensor sensing coil current induced within the inductive coil,
• wherein the first magnetic speed probe further includes a signal coupler that couples the electrical signal generated by the radio-frequency signal generator into the inductive coil of the first magnetic speed probe, thereby radiatively transmitting an electromagnetic signal;
• and
• a speed-probe monitor electrically coupled to each of the electrical-current sensors of the first and second magnetic speed probes, the speed-probe monitor determining health of the system based on the coil current sensed by the second magnetic speed probe in response to the electromagnetic signal radiatively transmitted by the first magnetic speed probe.