A method and apparatus for determining whether a tubing conveyed perforating gun has fired by detecting a change in characteristics of the flow of an oil well. The sensor assembly includes a primary winding disposed adjacent the at least one blade to create a primary current from a disruption in the magnetic field by the moveable strings. In addition or alternatively, a tube hanger can be attached to the pump housing to allow insertion of a slack portion between the tube hanger and the pump housing. 0 to obtain a soluble napin-rich protein extract and a cruciferin-rich residue followed by performing aqueous extraction of the cruciferin-rich residue to obtain a soluble cruciferin-rich protein extract and a low-protein residue. The invention proposes that a core 9 of an inductive sensor unit 5 of the proximity sensor 1, which projects into a coil carrier 7, have a rectangular cross-sectional profile.