The photoelastic polyurethane resin has a Young's modulus at 25 C. of 2 to 5 MPa, a photoelastic constant at 25 C. of 100010.sup.12 Pa.sup.1 to 10000010.sup.12 Pa.sup.1, and a glass transition temperature of 60 C. to 21 C.

An apparatus for producing strain in an optical fibre proportional to dynamic pressure fluctuation in the surrounding substance. The apparatus includes a diaphragm having a first face that, in use, is exposed to dynamic pressure fluctuations in the substance, and a second, opposite face, the diaphragm being adapted to flex in response to dynamic pressure fluctuations applied to it. One or more optical fibres are mounted on either the first or the second face of the diaphragm, whereby strain is produced in the fibre when the diaphragm flexes.

A measuring system for detecting pressure and/or density, having at least one process connector, a diaphragm, a measuring unit, a housing and a display, wherein a process pressure acts via the process connector on the diaphragm and the measuring unit converts a stroke of the diaphragm caused thereby into a rotational movement of a pointer when the process pressure is changed via the measuring unit, and the pointer on the display shows the pressure applied on the diaphragm on a scale. The measuring system includes a connecting piece which includes the process connector, a meter base and a tubular extension.

A pressure measurement system includes a pressure pod with two chambers separated by a diaphragm such that a deformation/movement of the diaphragm is indicative of a difference between the pressures of the two chambers. Such deformation/movement is detected by a device that has no physical contact with the diaphragm, for example, by an optical detector that detects a change in the shape of the diaphragm or a movement of a protrusion on the diaphragm.

A displacement detector may include a substrate and a membrane having an inner surface facing the substrate. A mounting area may be arranged to fix the membrane along at least part of the perimeter of the membrane, wherein the mounting area, the inner surface and the substrate enclose a back volume. An acoustic compliance of the back volume may be arranged to be the same or larger than an acoustic compliance of the membrane. An optical sensor may be configured to generate a sensor signal indicative of a displacement of the membrane.

The present disclosure relates to a pressure gauge for an inflatable article. The pressure gauge comprises a housing. The pressure gauge comprises an indicating chamber defined within the housing. The pressure gauge comprises a resilient diaphragm located within the housing. The diaphragm is configured to expand upon an increase in pressure within the inflatable article. The diaphragm has a first surface and a second, opposing surface. The first surface of the diaphragm is configured to be in fluid communication with the interior of the inflatable article and the second surface of the diaphragm defines a boundary of the indicating chamber. The pressure gauge further comprises an indicating element located within the indicating chamber. The pressure gauge is configured so that the indicating element is moveable, by an expansion of the diaphragm, in a first direction away from a first position. The position of the indicating element relative to the housing provides an indication of the pressure within the inflatable article.

A pressure measurement system includes a pressure pod with two chambers separated by a diaphragm such that a deformation/movement of the diaphragm is indicative of a difference between the pressures of the two chambers. Such deformation/movement is detected by a device that has no physical contact with the diaphragm, for example, by an optical detector that detects a change in the shape of the diaphragm or a movement of a protrusion on the diaphragm.

An optical fiber sensor can be used to measure pressure with high sensitivity and fine resolution. As a cavity at the end of the sensor expands or contracts, the spectrum of a beam reflected from the end of fiber shifts, producing a change linked to pressure exerted on the sensor. Novel aspects of the present inventive sensor include the direct bonding of a silica thin film diaphragm to the optical fiber with localized or confined heating and a uniform thickness of the diaphragm. The resulting sensor has a diameter that matches the diameter of the optical fiber. Because the sensor is all silica, it does not suffer from temperature-induced error. In addition, the sensor can be very sensitive because the diaphragm can be very thin; it can also make highly repeatable measurements due to its very uniform thickness.

A sensor and methods of making a sensor are disclosed. The sensor may include a substrate including an opening, an optical source disposed in the substrate and configured to generate an optical source signal, an optical detector disposed in the substrate so that the opening is disposed between the optical source and the optical detector, a plurality of optical cavity structures disposed in the opening wherein each of the plurality of optical cavity structures contains an enclosed cavity so that the respective enclosed cavities are not in gas communication with each other, wherein the plurality of optical cavity structures are arranged in an optical path between the optical source and the optical detector, and a processing circuit coupled to the optical detector and configured to process an optical signal received by the optical detector.

Disclosed herein is a device which is intended to deliver and maintain reduced pressure to body surfaces for application of reduced pressure wound therapy (RPWT) also known as negative pressure wound therapy (NPWT). During application of this type of therapy, a substantially airtight seal is formed around a section of tissue to be treated. This seal is formed by a dressing which provides fluid communication from a section of tissue to a reduced pressure source. Disclosed herein is a dressing system which is configured to enhance usability and functionality of this dressing. First, the system may be configured to allow full rotation of the fluid communication conduit to the reduced pressure source along the axis substantially normal to the dressing. Second, the system may be configured to include a one-way valve to prevent backflow of any drainage fluids. Third, the system may be configured with transparent windows covered by opaque flaps to allow inspection through the dressing. Fourth, the system may be configured to include an indicator which visually makes clear whether reduced pressure is being applied or not. Fifth, the system is configured to minimize the profile of the dressing system.