| 摘要 |
Method and apparatus for monitoring the rotational speed of a shaft having a number of spaced features on or rotating with the shaft, in which first and second spaced sensors 5, 6 are provided, the spacing between the sensors being variable e.g. due to thermal expansion of a sensor mounting fixture, the time of flight between the passage of a first feature past the first sensor and the second sensor is measured, the total time for a selected number of features to pass the sensors is determined, the period between the passage of a first feature past one of the sensors and the passage of the next feature past the same sensor is measured and the total time for the selected number of features to pass this sensor is determined and a correction factor for measured times of flight is determined from a ratio of the two total times referred to above. |
