CN1448740A - Palladium film hydrogen sensing device based fibre-optical grating temperature non-responsiveness - Google Patents

Abstract

The hydrogen-sensitive Pd film device includes two V-shaped supports to form a V-shaped pliers structure via the connection of the middle hinge, fiber grating with plated hydrogen-sensitive Pd film adhered between two arms at one end of the V-shaped supports, and one metal filament with two ends connected two the adjusting screws between the other two arms at the other end of the V-shaped supports. Based on lever principle, regulating the length and position of the metal filament can change the stress on the fiber grating to one proper value to compensate the temperature drift in Bragg wavelength of the fiber grating. The said device is insensitive to temperature, reliable in performance and antijamming, and can detect hydrogen in relatively harsh environment in high precision, up to 0.05 %.

Description

A kind of based on the insensitive palladium film hydrogen sensor of optical fiber grating temperature

Technical field

The present invention relates to a kind of based on the insensitive palladium film hydrogen sensor of optical fiber grating temperature.

Background technology

In the hydrogen sensitive technology, generally adopt palladium (Pd) to make catalytic specie, work as H ₂Gas runs at first to be adsorbed then behind the Pd film and is absorbed, and this catalytic reaction is reversible.The Pd film of inhaling behind the hydrogen has two kinds of solid solution to exist usually, show as α mutually with β mutually, it is relevant with surperficial environment temperature with the concentration of hydrogen that α arrives the conversion of β phase mutually.Out of phase lattice parameter differs greatly, and absorption repeatedly and desorption can cause the dislocation of metal lattice, causes the Pd film to stand all after dates of several hydrogen sucting discharging hydrogens and just can twist down to damaged, so thereby must the compensate for ambient Temperature Influence slow down the transformation that α arrives the β phase mutually.At present, be to plate one or more layers Pd film at fiber end face to make it to constitute the lenticule method using maximum aspect the research of optical fiber hydrogen sensor; Use Pd film and non-crystal WO in addition ₃Making the hydrogen catalyzer also is one of early stage scheme, promptly except fiber end face plating Pd film, plates one deck WO again ₃Film, because this sensor can produce strong absorption to the light wave of 800nm, so this method has very high sensitivity to the sensitivity of hydrogen, but that unique deficiency is a response speed is slow; In recent years, about having report at the hydrogen sensor of optical fiber surface generation plasma resonance wave structure and the hydrogen sensor of evanescent wave (Evanescent) structure, these methods all have in various degree raising to the sensitivity of hydrogen sensitivity, but measuring accuracy generally is difficult to reach 0.1%.Therefore require than higher occasion at measuring accuracy, be higher than 0.05% occasion as the responsive precision of hydrogen, fiber grating is the scheme of our first-selection.When ultraviolet ray irradiation light-sensitive optical fibre can make its refractive index generation permanent change, according to this effect fibre core is periodically exposed, thereby obtain fiber grating.Fiber grating has that the reflection bandwidth scope is big, added losses are little, device miniatureization, be coupled with optical fiber, with a series of excellent properties such as other optical fibre devices are compatible and be not subjected to that environment dust influences.

Use the quick sensing principle of bragg grating (FBG) formation hydrogen to be: sputter Pd film on fiber grating, H ₂Be adsorbed very soon also and then absorption generation PdHx after meeting the Pd film, volume can produce contraction or expansion with the variation of density of hydrogen behind the generation PdHx, and the Pd membrane volume expands or contraction can cause the grating cyclomorphosis, causes bragg wavelengths _BChange.Temperature variation causes that the variation of grating cycle equally also can change bragg wavelengths in addition _B, therefore need make fiber grating insensitive to variation of ambient temperature.

Summary of the invention

In order to improve the sensitivity of hydrogen, reduce the influence of external environment to test macro, the purpose of this invention is to provide a kind of based on the insensitive Pd film of optical fiber grating temperature hydrogen sensor.

The technical solution adopted in the present invention is to achieve the above object of the invention: it comprises two V-type supports, be connected to form V shape forceps type structure by middle hinge, to be coated with and the fiber grating of the Pd film of hydrogen sensitivity is bonded between the two side arms of two V-type support one ends, the two ends of an one metal wire are contained in respectively that adjustment screw on the two side arms with the V-type support other end is connected and are fixing.

The beneficial effect that the present invention has is: be coated with the Pd film with the hydrogen sensitivity on a fiber grating, constitute the hydrogen sensitive sensor.Prop up by two V-types and to be configured to forceps type structure, tinsel has certain expansion coefficient, realizes insensitive to environment temperature thereby adjust prestress wiry by set screw.Because the tinsel thermal expansivity is bigger than optical fiber, its swell increment is also big than optical fiber, the lever principle of two V-type supports that dependence couples together by middle hinge, length and the position of regulating metal wire make the suffered STRESS VARIATION of fiber grating reach a suitable value, thereby have compensated the fiber grating bragg wavelengths that temperature causes _BDrift.It can make its variation to environment temperature insensitive, the test macro dependable performance, and strong interference immunity, precision height, it can accurately detect the concentration of hydrogen in relative rugged environment, and the general test precision can reach 0.05%.

Description of drawings

Fig. 1 is a hydrogen sensitive optical fibre optical grating construction synoptic diagram of the present invention;

Fig. 2 is a structural principle synoptic diagram of the present invention.

Among the figure: 1. fiber grating 2.Pd film 3.V type support 4.V type support 5. hinges

6. set screw 7. tinsels 8. are adjusted screw

Embodiment

As shown in Figure 1, in the sensor fibre grating, make fiber grating 1 on optical fiber, be coated with Pd film 2 on fiber grating 1, the thickness of Pd film 2 is between 10nm-30nm.

As shown in Figure 2, it comprises two V-type supports 3,4 the present invention, be connected to form V shape forceps type structure by middle hinge 5, with be coated with and the fiber grating 1 usefulness epoxy resin bonding of the Pd film 2 of hydrogen sensitivity between the two side arms of two V-type support 3,4 one ends, the two ends of an one metal wire 7 are connected with adjustment screw 6,8 on the two side arms that is contained in V-type support 3,4 other ends respectively and are fixing.Two adjust screw all can vertically move (promptly adjusting lever arm length).Elder generation's set screw 6, the bragg wavelength that makes fiber grating 3 is λ _B, this moment, density of hydrogen was zero, used epoxy resin bonding after mixing up.As after temperature raises, the cycle of the refractive index of fiber cores and fiber grating 1 all will become greatly, thereby the tuning wavelength of fiber grating 1 will move to the long wave direction, and tinsel 7 is bigger than optical fiber owing to thermal expansivity, and its swell increment is also big than optical fiber.Two V-type supports 3 that dependence couples together by middle hinge 5 and 4 levers that form, make suffered suitable the diminishing of stress of fiber grating 3, thereby wave length shift (if the overcompensation or not enough that the temperature that has compensated fiber grating raises and causes, then but suitable adjustable screw rod 6 and 8 vertically moves simultaneously, i.e. the adjustment (adjusting) lever brachium; Regulate to a certain temperature variation insensitive after, then also insensitive to other temperature variation).Therefore has only H ₂Concentration change can change bragg wavelengths _BMeasure bragg wavelengths _BThe drift size, then can measure the concentration of hydrogen.

Claims (2)

1. one kind based on the insensitive palladium film hydrogen sensor of optical fiber grating temperature, it is characterized in that: it comprises two V-type supports (3,4), be connected to form V shape forceps type structure by middle hinge (5), to be coated with and the fiber grating (1) of the Pd film (2) of hydrogen sensitivity is bonded between the two side arms of two V-type supports (3,4) end, the two ends of an one metal wire (7) are connected with adjustment screw (6,8) on the two side arms that is contained in V-type support (3, the 4) other end respectively and are fixing.

2. according to claim 1 a kind of based on the insensitive palladium film hydrogen sensor of optical fiber grating temperature, it is characterized in that: the thickness of said Pd film (2) is between 10nm-30nm.