Capacitance Probes

Capacitance probe based blade clearance systems see widespread use in turbomachinery applications to establish rotor blade tip clearance. The most suitable type of probe is the frequency modulated (FM) capacitance probe.

This technique was first developed by J Chivers (1989) and is superior to a DC system for on-engine applications as FM capacitance probes are unaffected by ionisation effects present in gas turbines. The capacitance tip clearance system measures the capacitance between the probe and the blade tip. This is then related to tip clearance using a pre-determined calibration factor in conjunction with the fundamental relationship for capacitance.

Capacitance Probe 1 Capacitance Probe 2

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