Tools usually do not move up the well bore with a fixed velocity. Tool movement due to friction, sticking, rig-heave and cable movement all influence a tools actual speed within a well. As most dipmeter and borehole data are acquired in time rather than by depth we need to know this tool movement to place the data at a correct depth point. The use of speed buttons provides a way of correcting for anomalous tool speed.
On one dipmeter pad a second button is placed at a fixed distance from the first one. When these buttons pass over the same thin bed they will display the same response. If no acceleration is taking place, the distance between the two buttons will equal the given fixed distance. If the tool is accelerating or decelerating the apparent distance between responses will differ from the value of the fixed button distance. If this occurs a correction can be applied.
THEYS, P. 1999. Log Data Acquisition and Quality Control, Second Edition. Éditions Technip, Paris, 453.