Abstract: A differential comparative pressure monitoring system (10) for monitoring the structural integrity of a structure (30) has a pressure source (12); a first fluidic circuit (14), and a reference fluidic circuit (16) which are connected in parallel to the pressure source (12); and a monitoring device (18). The first and reference fluidic circuits (14) and (16) have substantially matched characteristics. The first circuit (14) has a sensor element (20) which is sealed to a surface (28) on the structure (30). The reference circuit (16) is in fluidic isolation from the surface (28) of the structure (30). The monitoring device (18) takes simultaneous measurements of a common fluidic characteristic of the circuits (14) and (16), and produces a signal indicative the integrity of the structure based on a difference between the simultaneously measured common characteristic.

Abstract: A system for monitoring a structure includes cavities on an outer surface and a fluid source at substantially constant pressure coupled to the cavities through high fluid impedances to create pressure differentials therebetween. A telemetry system has pressure differential switches across each of the high impedances for monitoring differential pressure changes across the impedances and providing a signal indicative of the location of the cavity associated with the high impedance across which the change is monitored. A fluid capacitance is associated with each cavity and the corresponding impedances to facilitate a transient fluid flow through the impedances.

Abstract: A method for detecting separation in a structure that comprises at least two portions or layers affixed together comprises forming a cavity into the structure that passes through an interface formed between the two portions and plumbing the cavity to a monitoring system. A pressure differential is established between the cavity and a reference pressure to which the structure is exposed. A monitoring system monitors for a change in the pressure state of the cavity. Changes in the pressure state are indicative of a separation between the portions or layers.

Abstract: Apparatus 10 for condition monitoring the integrity of a rivet 12 joint holding together sheets 14 and 16 of a structure 18 includes a substantially fluid impervious pad 20 for covering the heads of the rivets 12 and an adjacent surface 24 of the structure 18. The pad 20 has a first surface 26 for placement over the rivets 12 and the surface 24. An inner portion of the surface 26 is formed or otherwise configured to define a fluid flow region 28 between the pad 20 and the rivets 12/surface 24 across which fluid can flow. The region 28 is coupled to a constant vacuum source 30 via a conduit 32 and a series coupled high fluid flow impedance 34. A transducer 38 and display 44 coupled in parallel across the impedance 34 provides an indication of change in differential pressure across the high impedance which in turn provides an indication of the presence or development of a flaw in the rivets joint.