Target clearance measurement device

摘要

A target or rotor blade clearance measurement device is disclosed for indicating an interaction of a measurement probe with a target or rotor blade. In a preferred embodiment, the measurement device comprises a measurement probe containing a coil, a frequency source arranged to apply an input alternating signal to the measurement probe, and a frequency regulator arranged to regulate the input alternating signal at a frequency below the resonance frequency of the measurement probe. A detector is arranged to detect an output signal from the measurement probe at a frequency of the frequency source which varies in amplitude with an admittance and resonance frequency of the measurement probe. A circuit is arranged to scale the amplitude of the output signal detected by the detector according to the amplitude of the input signal provided by the frequency source.