system and applied to the other similar systems depending on the system an acceptable change in k value would be established this could be set up as a range or a percentage change in the value if the diagnostic value k changes a certain percentage or falls outside a particular range a signal could be sent to an operator indicating that the circuit is in need of maintenance the present invention may be employed in a wide variety of cyclic systems in the preferred embodiment as shown in the schematic of fig1 the present invention is employed in a fluid power system the fluid power system 10 may include a variety of valves 12 operably connected to actuators 14 by fluid supply lines 15 one such valve and actuator is schematically represented in fig1 the system 10 may be driven by a control device 16 such as a plc or other control device as is well known in the art the control device 16 may be operatively connected to the various valves and actuators that make up the system and generates a control signal 17 which actuates valve 12 the location of flow sensor 18 can be chosen based upon the particular component in the system that is to be monitored in a pneumatic system including a valve and cylinder if the sensor were positioned to sense the flow in the fluid supply line to the valve then the condition of the valve and cylinder would be reflected in the k value alternatively if the sensor were disposed in the system to sense the flow between the valve and cylinder then the condition of the.