I am revisiting some data I collected eons ago with a Hewlett Packard 3721A correlator (now obsolete). I used the cross-correlation facility to determine the transit time between two sensors from which I calculated the mean velocity of the fluid. I also measured the corresponding auto-correlation function values but never used them. I vaguely recollect being told at the time that signal coherence could be calculated from the auto-correlation peak values. Now, many years later, I would like to do this but am not sure how.

One example of the data: the auto-correlation peaks for Sensors A and B are 2.6 and 2.4 respectively and the cross-correlation peak (C) is 1.8. The units I believe are milli volts. Can signal coherence be calculated from these data? If so, what equation should be used?