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Turbine Blade Tip Clearance Measurement

Triaxial FM and AM systems to handle high temperature high speed capacitance measurements for blade tip clearance and time of blade arrival
Real-time measurement of the clearance between turbine blades and the casing in which they run

The distance between a turbine blade and the turbine casing is a critical measurement for engineers. It is, however, a difficult measurement because of the typically high temperatures and rotational speeds involved. It’s usually difficult to locate electronic instruments close to the measurement and cables must be routed through a hostile environment before arriving at the electronic equipment’s location.

Fylde have a long history of supplying electronic equipment to make tip clearance measurement using triaxial capacitance probes. Probes are mounted in the casing and measure the capacitance formed by each blade tip as it passes the probe.

Techniques include using the capacitance between blade tip and probe to change an oscillator frequency (Frequency Modulation) or using the capacitance at a fixed frequency to vary the amplitude of an oscillator (Amplitude Modulation.)




  • It is important to state that Fylde do not supply probes or high temperature cables for blade tip clearance measurement. If you are not able to source probes, we advise you to contact our partners at GadCap CapaciSense
  • If you have probes and cable available, then you can obtain signal conditioning (either FM or AM from Fylde directly). Our FE-596-CDT A.M. system is the current product offering the highest available performance for this type of capacitance measurement.

  • Cable lengths can exceed 20m with resilience to high temperatures over the cable length, and measurement bandwidth is 400 kHz.
  • Fylde are able to supply triaxial low temperature cables (extension cables) suitable for this application for the low temperature portion of the cable routing.