Free Point Indicator Tool Procedure In Stuck Pipe
Electric wireline service companies run instruments on conductor lines inside the stuck drill pipe or tubing and are able to accurately determine the stuck point (check also stuck point calculations) of the pipe. The instruments called free point indicator tools are highly sensitive electronic devices that measure both stretch and torque movement in a drill string.
https://www.drillingmanual.com/free-point-indicator-tool-fpi/