fig3 and 5 is shown a first displacement sensor 230 and second displacement sensor 240 are integrated into a non reciprocating element 602 of the reciprocating device 600 the first displacement sensor 230 senses a vibration signal produced by changes in the distance 232 between the reciprocating element 610 along the y axis i e along path b while the second displacement sensor 240 senses a vibration signal produced by changes in the distance 242 between the reciprocating element 610 along the x axis i e along path c that is each displacement sensor 230 240 measures a change in the clearance 606 between the reciprocating element 610 and the non reciprocating element 602 caused by anomalous or aberrant movement of the reciprocating element 610 in the embodiment of fig7 the displacement sensors 230 240 are integrated into the reciprocating element 610 rather than the non reciprocating element 602 as in the embodiment of fig6 each displacement sensor 230 240 measures a change in the clearance 606 between the reciprocating element 610 and the non reciprocating element 602 caused by anomalous or aberrant movement of the reciprocating element 610 referring now to fig8 and 9 graphical representations 900 902 respectively are shown as might be used in analyzing components of the vibration signal in fig8 the graphical representation 900 shows the displacement of the reciprocating element between its proximal 910 and distal 910 u2032 positions and a u201c low pass u201d component 912 of the vibration signal as can be seen the low pass component 912 exhibits increased amplitude 912 a as the reciprocating element reaches its distal position 910 u2032 i e as the reciprocating element is fully extended by the rod 112 in fig1 it is possible that the increased amplitude 912 a is expected at.