National Research Development Corporation

Robert Malcolm Henry

Maurice Sidney Beck

Two binary signals are compared by providing time signals to indicate the respective times at which the signals change their state, usually in the form of digital data strings corresponding to the times at which the signals change their state, and the two time signals are cross correlated. For example, if the two binary signals are in the same state between two consecutive times of the two data strings, a running total of time increments is increased by the numerical difference between the two times; if the two binary signals are in opposite states, the running total is decremented by the numerical difference. In a particular example the two binary signals are derived from two sensors spaced in the direction of flow of a flowing fluid; one binary signal is time shifted by adding or subtracting a series of numbers of increments; each time shifted signal and the other signal are cross correlated; and the transit time of the flow between the sensors is given by the time shift corresponding to the highest running total.

Correlation method

In a process for controlling a particle flow system which is to be operated at slightly above the velocity at which saltation occurs, a cross correlation technique is used to determine the spread of particle velocities in the system and this is compared with a signal representing the desired spread to produce an error signal indicating the desired mean velocity of particle flow. A second cross correlation technique, having a shorter integration period, is used to determine the actual mean particle velocity and this is compared with the first error signal to produce a second error signal to control the flow rate of the conveying fluid.

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Robert Malcolm Henry