Advances in through-the-case eddy current sensors

This paper discusses recent advances in tip clearance measurement systems for turbine engines using through-the-case eddy current sensors (TTC-ECS). Improved performance has been achieved through a combination of new designs for the magnetic components as well as the signal processing electronics. A novel preamplifier circuit eliminates the band-limiting effects of interwinding capacitance and cable capacitance. The system achieves wider bandwidths and higher signal-to-noise ratios compared to previous designs. Calibration techniques can improve system accuracy.