A system comprising: a component comprising at least a portion of a rotor blade of a turbine, configured to be moved cyclically past a sensor, and an apparatus for generating a timing signal for registering a passage of the component past the sensor, the apparatus comprising: the sensor, wherein the sensor is configured to output a signal that is dependent on a separation between a component and the sensor; and a timing signal generation device, characterized in that the timing signal generation device is configured to: perform a first passage event integral, defined as an integral of an output from the sensor over at least a portion of a first passage event of a reference component past the sensor; perform a second passage event integral, defined as an integral of an output from the sensor over at least a portion of a second passage event of a component to be measured past the sensor, the second passage event occurring after the first passage event; and generate a timing signal when the second passage event integral is equal to a predetermined fraction of the first passage event integral. a component comprising at least a portion of a rotor blade of a turbine, configured to be moved cyclically past a sensor, and an apparatus for generating a timing signal for registering a passage of the component past the sensor, the apparatus comprising: the sensor, wherein the sensor is configured to output a signal that is dependent on a separation between a component and the sensor; and a timing signal generation device, characterized in that the timing signal generation device is configured to: perform a first passage event integral, defined as an integral of an output from the sensor over at least a portion of a first passage event of a reference component past the sensor; perform a second passage event integral, defined as an integral of an output from the sensor over at least a portion of a second passage event of a component to be measured past the sensor, the second passage event occurring after the first passage event; and generate a timing signal when the second passage event integral is equal to a predetermined fraction of the first passage event integral. the sensor, wherein the sensor is configured to output a signal that is dependent on a separation between a component and the sensor; and a timing signal generation device, characterized in that the timing signal generation device is configured to: perform a first passage event integral, defined as an integral of an output from the sensor over at least a portion of a first passage event of a reference component past the sensor; perform a second passage event integral, defined as an integral of an output from the sensor over at least a portion of a second passage event of a component to be measured past the sensor, the second passage event occurring after the first passage event; and generate a timing signal when the second passage event integral is equal to a predetermined fraction of the first passage event integral. perform a first passage event integral, defined as an integral of an output from the sensor over at least a portion of a first passage event of a reference component past the sensor; perform a second passage event integral, defined as an integral of an output from the sensor over at least a portion of a second passage event of a component to be measured past the sensor, the second passage event occurring after the first passage event; and generate a timing signal when the second passage event integral is equal to a predetermined fraction of the first passage event integral.