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 comparative pressure monitoring instrument (10) houses a switch (14) having first and second ports (18) and (20), and a high flow impedance 16. The ports (18) and (20) are in fluidal communication with a first pressure source (72) and a second pressure source (82) respectively. The impedance (16) is coupled (i.e. shunted) across the switch ports (18) and (20) and the first and second pressure sources (72, 82). The switch (14) switches between a first state characterised by a pressure differential across the impedance (16) being less than a preset level and a second state characterised by the pressure differential across the impedance (16) being equal to or greater than the preset difference. Any difference in pressure between the sources (72) and (82) will cause an air/gas flow through the impedance (16) and thus a pressure drop across the impedance (16).

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.

Abstract: A laminated sensor comprises a base stratum and a terminal stratum. The base stratum has a first surface that is affixed to a surface of a structure to be monitored. The terminal stratum is affixed to the opposite second surface of the base stratum. A connector is attached to the terminal stratum. The base stratum is provided with first and second channels and that are cut through the thickness of the base stratum. The terminal stratum is provided with holes that extend through the thickness of the terminal stratum. A first pair of the holes are positioned to register with the first channel, while a second pair of the holes are positioned to register with the second channel. A first conduit is formed by the first channel and the holes; while a second conduit is formed by the second channel and the holes. The connector connects with tubes to provide fluid communication between the conduits and a differential pressure monitoring system.