Patent ID: 8624604
Filing Date: 2014-01-07
Classification: F01D,G01B,G01S

Abstract:
1. Apparatus for determining the clearance between a member and a casing surface over and relative to which the member moves, comprising: a main waveguide, the waveguide having a proximal end and a distal end, the distal end being adjacent the casing surface and the proximal end being at a position recessed in the casing; a transmitter/receiver, provided at the proximal end of the main waveguide, and a reference element at a position intermediate the proximal and distal ends of the waveguide or at the distal end of the waveguide; wherein the transmitter receiver is arranged to transmit an electromagnetic signal through the main waveguide and receive: (i) a first portion of the electromagnetic signal reflected from the reference element; (ii) a second portion of the electromagnetic signal reflected from the casing surface, and (iii) a third portion of the electromagnetic signal reflected from the member.