Measurement of blade tip clearance and time of arrival in turbines using an optic sensor

Turbine blades suffer vibrations when they rotate inside a turbo machine. The measurement of those vibrations can indicate a problem in the working regime currently in use or can assess the quality of a manufactured rotating part. In order to evaluate the vibratory state of a spinning stage in a turbo machine, the measurement of the tip clearance and the time of arrival of the blades are computed. In this article the development of an electronic system based on an optic probe designed to measure those parameters will be introduced. An analog front end that will adapt the voltage coming from the sensor has been developed and an IP core has been synthesized to handle the digitalized signals from the analog front end. The IP core is embedded into an FPGA and will calculate the mentioned parameters for each blade before the following blade finishes passing in front of the sensor.