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: 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 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: A differential comparative pressure monitoring system (10) for monitoring the structural integrity of a structure or component (30) comprises 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) are formed to have substantially matched characteristics. These characteristics include volumetric capacity of each of the circuits, fluid flow rates through the circuits, their temperature characteristics, and diffusion characteristics. The first circuit (14) comprises a sensor element (20) which is sealed to a surface (28) on the structure or component (30) being monitored by the system (10). The reference circuit (16) is in fluidic isolation from the surface (28) of the structure or component (30).