Patent ID: 7890293

Claim:
A device for determining a distance between a rotor blade and a wall of a gas turbine surrounding the rotor blade, comprising: a waveguide that guides and emits electromagnetic waves in a direction to the rotor blade through a waveguide opening facing the rotor blade; a first unit connected to the waveguide that injects the electromagnetic waves into the waveguide; a second unit connected to the waveguide that receives reflected portions of the electromagnetic waves; and an evaluation unit that compares phases of the electromagnetic waves to be injected with phases of the reflected portions of the electromagnetic waves for each frequency and determines the distance based on the phase comparison, wherein the waveguide comprises at least two waveguide segments that are made from different materials, and wherein a temperature stability and an electromagnetic wave damping capacity of the materials increase starting from a segment connected to the first and the second units in a direction of a segment having the waveguide opening.