Abstract: In a system for measuring the time delay existing between two pattern related random signals of similar but not identical modulated characteristics, utilizing the techniques of cross correlation, two analogue input signals are digitally quantized into binary form according to signal polarity. The first or leading quantized signal is delayed by a series of sequential time intervals or sampling periods to provide a time controlled sequence of delayed leading-signals at equal intervals. These delayed leading-signals are compared by a multiplication technique with the quantized second or lagging-signal, the occurrence when the signals correspond being summed in a series of overflow counters. The rate of filling of the responsive counters is proportional to the respective degree of correspondence and leads to one counter overflowing first, being indicative of the most probable time delay between the two signals.

Abstract: An ultrasonic transducer apparatus for sensing flow velocity through a pipe wall has a pair of strap-on transducer assemblies for securing to an unprepared pipe surface, the energy coupling between each transducer unit and the pipe or other working device being provided by an elastomeric contact pad, which also facilitates rapid replacement of the transducer crystal, by simplified assembly.