in an open or non obstructing condition so that tools or other objects 14 can pass freely in and out of the tubular 12 as well as fluids in order to detect the speed of a passing object 14 two sensor devices 26 28 are provided on the tubular 12 at a location prior to the object 14 passing the closure system 24 by u201c on u201d the tubular 12 it should be understood that the sensor devices 26 28 may be located on a manifold on the tubular 12 or otherwise connected to the tubular 12 depending on the type of sensors employed in the sensor devices 26 28 the sensor devices 26 28 may be positioned on an interior surface 30 of the tubular wall 20 on an exterior surface 32 of the tubular wall 20 or within the tubular wall 20 itself such as in a pocket or opening in the tubular wall 20 to protect the sensor devices 26 28 from accidental dislodgement the sensor devices 26 28 are provided uphole of the closure system 24 closer to the uphole end 16 of the tubular 12 than the downhole end 18 of the tubular 12 the sensor.