...reasons

The velocity-push v is computed from differences in t and $\tau$.When t and $\tau$ are measured at the acquisition sampling interval, a difference of one or more samples will give in a velocity falling below the lowest velocity bin.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.