| 摘要 |
A sensing system for sensing rotational speed of a shaft in a gas turbine engine, comprising: a target (phonic wheel) 40, the target fixed to the shaft in use, the target comprising at least one ferrous target element (teeth) 42 radially spaced from the shaft, and a first magnetic probe assembly comprising a first pole piece element 41 and a second pole piece element 48, wherein the first pole piece element and the second pole piece element are radially spaced from one another so that the at least one ferrous target element passes proximate to and between the first and second pole piece elements as the target rotates, so that radial movement of the at least one ferrous target element away from one of the first and second pole piece elements results in simultaneous and corresponding radial movement of the at least one ferrous target element towards the other of the first and second pole piece elements. By providing pole piece elements that are radially spaced from each other, radial movement of the target away from one pole piece element as a result of eccentric rotation of the shaft is compensated for by corresponding movement of the target towards the other pole piece element. |
