A system for the dynamic response characterization of turbomachinery tip clearance measurement instruments based on capacitive probes

This paper deals with the development of a system aimed at the characterization of turbomachinery tip clearance measurement instruments based on frequency modulated (FM) capacitance probes. The proposed system is able to accurately measure the dynamic response of the systems under testavoiding any mechanical moving part, ensuring in this way a faster, more accurate and versatile characterization procedure. The work introduces the characterization by means of a simple model of tip clearance measurement systems, which allows to obtain a straightforward relationship between the bandwidth and the clearance measurement accuracy. The experimental set-up of the proposed system is described, and some data related to two different clearance measurement systems are shown.