1. A fluid measurement system comprising: an elongate member for location in a well bore, a signal generator for injecting a high frequency signal along the member; a data acquisition unit to record first reflected signals received from the member; a system criteria unit to maintain a data set relevant to the system, and a processor unit operable to act upon the first reflected signals and the data set to establish an output indicative of component fluid within the well bore from which the mixture of fluids flowing within the well bore can be determined.