SU1624290A1 - Device for measuring pressure - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the difference between two pressures of liquid or gaseous media. The purpose of the invention is to increase the linearity of the output characteristic. The device comprises a measuring device 1, a radiation source 2, a photodetector 3 and a pressure sensor 4 comprising a frame, which is a cylinder with an input channel for receiving pressure. The cylinder has a series of longitudinal channels located along the generator of the cylinder, and a transverse spiral groove, in the grooves of which is laid a fiber light guide sensitive to microbends. The frame is hermetically sealed with a rubber membrane with protrusions located in the middle of the longitudinal grooves. The depth of the spiral groove for a given width of the longitudinal grooves is chosen so that in the initial position, when the pressure difference above and below the membrane is zero, the protrusions of the membrane slightly bend the optical fiber laid in the spiral groove at the touch. The fiber portion in contact with the membrane, as a result of using a radial longitudinal protrusion with a height of 1-1.5 mm, practically reduces to a point, therefore, the deflection of the optical fiber will linearly depend on the deflection of the membrane, starting with a pressure difference equal to zero. 4 il. Ё About go you

Description

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The invention relates to a measurement technique and can be used to measure the difference between two pressures of liquid or gaseous media.

The purpose of the invention is to increase the linearity of the output characteristic.

FIG. 1 shows a block diagram of the device; in fig. 2 — pressure sensor; in fig. 3 shows section A-A in FIG. 2; in fig. 4 — node I in FIG. 3

The pressure measuring device comprises a measuring device 1, a light source 2, a photodetector 3, a pressure sensor 4 placed in a housing 5, connected to a radiation source 2 and a photo receiver 3 by means of a light-optical cable 6 and equipped with a pressure supply nozzle 7.

The pressure sensor comprises a frame 8, which is a cylinder with an inlet channel connected to fitting 7. On the outer surface of the cylinder there are made longitudinal grooves 9 and a spiral groove 10 in which the fiber light guide 11 is laid. The profile of the spiral groove is made in the form of a trapezium. The ratio of the width And the longitudinal grooves to the width i of the projections of the screw groove 10 is greater than one (h / l2 1).

The frame 8 is hermetically connected by a rubber membrane 12 to the protrusions 13 located on the inner surface of the membrane 12 above the middle of the longitudinal grooves 9. The diameter of the membrane is chosen to be smaller than the diameter of the frame so that the membrane fits tightly to the frame. For a given width of the longitudinal grooves 9, the depth of the helical groove 10 is chosen such that, after putting the membrane 12 on the frame, the projections 13 touch the optical fiber 11, which is laid in the helical groove 10, and partially deform it in the direction of the axis. This leads, provided that the length of the optical fiber in the ring does not change during deformation, to an additional deflection of the optical fiber away from the frame axis in the helical groove sections located on the projections, i.e. The fiber light guide moves away from the bottom of the groove in the indicated areas, maintaining its position in the plane of the winding ring passing through the middle of the bottom of the screw groove. The device works as follows.

The compared pressures Pi and P2 (assuming Pi P2) are supplied to the outside of the membrane 12 through the inlet of the housing 5 - PI, and to the inside of the membrane 12 through the input channel 7 of the sensor 4 - P2. Differential pressure bends the membrane

12 above the longitudinal grooves 9. The membrane 12 of the protrusions 13 further deforms the optical fiber 11. The deformation of the optical fiber leads to microbends in it.

As a result, a violation of the condition of complete internal reflection of the light propagating through the optical fiber, i.e. Part of the light radiation leaves the light guide and is absorbed by the polymer coating of the fiber. This leads to a decrease in the optical radiation power at the output of the fiber light, which is detected by the photodetector 3. appliances.

The sensitivity of the device can be adjusted over a wide range by

selection of the type of fiber, changes in the geometry of the deformer and the flexibility of the membrane.

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Claims (1)

Invention Formula A device for measuring pressure, containing a radiation source, a photodetector connected to a measuring device, a pressure sensor having a hollow a cylindrical frame with longitudinal grooves on the outer surface on which the optical fiber is wound, while the frame is placed in a flexible sealed envelope, the first end of the optical fiber connected to the output of the radiation source, and the second to the input of the photodetector, characterized in linearity of the output characteristic in the sensor on the outer surface the frame is made with a spiral groove, and the flexible shell is made with longitudinal protrusions on the inner surface, each protrusion being located in a plane passing through the middle of the longitudinal groove and the axis of the frame, with the height of the protrusion h being selected h (10-15) d, where d is the diameter of the fiber, and the length of the protrusion is equal to the length of the longitudinal grooves, while the light guide is laid on a spiral groove. ten FIG. 2 10 12 FIG. four