User manual

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Calculate dP/dt and run the result through some form of low pass filtering to smooth it.
Again, verify that the result is consistent with the recorded start and stop times. Pass the vertical
velocity measurements of the ACM through the same low pass filter. Two features, the velocity
ramp near the beginning and the stop near the end, will be readily identifiable in both filtered
records. An example using field data is shown Figure 8-9, “End Stop and Velocity Ramp”.
Figure 8-16: End Stop and Velocity Ramp
The top panel shows dP/dt and the bottom panel shows the vertical velocity
measurement. Both signals have been filtered. The time axes are initial estimates.
Calculate the means of both series. Align the velocity record to the pressure rate time
series by matching the points at which both reach half of their mean values. In each panel above
the blue line marks the level of half the mean value. The four panel plot below shows details of
the half mean value crossings. Interpolate the velocity record linearly between these two times.
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