An In-Place Recalibration Technique to Extend the Temperature Capability of Capacitance-Sensing, Rotor-Blade-Tip-Clearance Measurement Systems

It is known that capacitance-sensing, rotor-blade-tip-clearance measurement systems suffer from a strong dependency on probe tip temperature and humidity. A novel in-place recalibration technique partly overcomes this problem through a simple modification of the electronics that permits a scale factor correction. The technique is used to reduce the errors in a commercial system by more than 50 percent up to a temperature of 370° C (700° F). A probe design is proposed to further raise the maximum temperature capability of the measurement system.