Abstract: A method (and corresponding apparatus) for monitoring gas turbine blades. The output from an eddy current sensor monitoring the movement of turbine blades past the sensor is processed to determine when the signal train from the sensor omits a signal or pulse corresponding to one of the shaft's full complement of blades. The signal processor compares sensed blade periods with average blade periods.

Abstract: A method is provided for determining timing points indicative of the passage of a blade in a turbine engine. The method comprises the steps of: providing a s first sensing coil proximate to a path of the blade, providing a second sensing coil proximate to the path of the blade, the second sensing coil spaced from the first sensing coil in a direction parallel to the path of the blade, and comparing a signal generated in the first sensing coil with a signal generated in the second sensing coil to derive a timing point indicative of the passage of the blade.

Abstract: A method (and corresponding apparatus) for monitoring the rotational speed of the shaft of a gas turbine having a number of spaced blades on or rotating with the shaft. The invention compensates for the errors which arise from the relative movement of turbine blade tips by deriving a correction factor for each blade and continually updating that correction factor.

Abstract: Method and apparatus for monitoring the rotational speed of a shaft, in particular a shaft having a number of spaced features on or rotating with the shaft. Preferred embodiments of the invention are concerned with methods and apparatuses for processing signals in order to calculate, with high accuracy and a fast response time, the rotational speed of a gas turbine shaft. The invention recognizes that it is possible to accurately measure speed between two eddy current sensors (5, 6) by determining the time take for a turbine blade to pass therebetween provided that appropriate compensation is made for the effect of apparent changes in the magnetic distance between the sensors.

Abstract: A method (and corresponding apparatus) for monitoring the rotational speed of the shaft of a gas turbine having a number of spaced blades on or rotating with the shaft. The invention compensates for the errors which arise from the relative movement of turbine blade tips by deriving a correction factor for each blade and continually updating that correction factor.

Abstract: A method (and corresponding apparatus) for monitoring gas turbine blades. The output from an eddy current sensor monitoring the movement of turbine blades past the sensor is processed to determine when the signal train from the sensor omits a signal or pulse corresponding to one of the shaft's full complement of blades. The signal processor compares sensed blade periods with average blade periods.

Abstract: Method and apparatus for monitoring the rotational speed of a shaft, in particular a shaft having a number of spaced features on or rotating with the shaft. Preferred embodiments of the invention are concerned with methods and apparatuses for processing signals in order to calculate, with high accuracy and a fast response time, the rotational speed of a gas turbine shaft. The invention recognises that it is possible to accurately measure speed between two eddy current sensors (5, 6) by determining the time take for a turbine blade to pass therebetween provided that appropriate compensation is made for the effect of apparent changes in the magnetic distance between the sensors.