CN105423893A - Axial deviation six sensitive grid full-bridge mixed-interdigital metal strain gauge capable of measuring two-side offset sensitive grid center axial partial derivative - Google Patents

Abstract

The invention provides an axial deviation six sensitive grid full-bridge mixed-interdigital metal strain gauge capable of measuring two-side offset sensitive grid center axial partial derivatives. The axial deviation six sensitive grid full-bridge mixed-interdigital metal strain gauge comprises a substrate and six sensitive grids fixed on the substrate, wherein each sensitive grid comprises sensitive sections and transition sections, and axes of all the sensitive sections are in the shape of parallel straight lines in the same plane; a direction along the direction of the axes in the plane is the axial direction, and a direction vertical to the axial direction is the transverse direction; centers of the sensitive grids have no deviation in the transverse direction and have deviation in the axial direction; the sensitive grids are respectively called a left third sensitive grid and a left first sensitive grid, then a middle A sensitive grid and a middle B sensitive grid, and finally a right first sensitive grid and a right third sensitive grid from the left to the right along the axial direction according to the central positions of the sensitive grids; total resistance variation values of the sensitive grids under the same strain are shown as 3:1:4:4:1:3; and the four sensitive grids in the front are arranged in an interdigital mode, the four sensitive grids in the rear are arranged in an interdigital mode, the two sensitive grids in the front can be arranged in an interdigital mode, and the two sensitive grids in the rear can be arranged in an interdigital mode. The axial deviation six sensitive grid full-bridge mixed-interdigital metal strain gauge can simultaneously measure axial first-order partial derivatives at the centers of the left third sensitive grid and the right third sensitive grid.

Description

Bilateral can be measured be biased sensitive grid central shaft and mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation

Technical field

The present invention relates to sensor field, especially a kind of metal strain plate.

Background technology

The principle of work of metal resistance strain gauge is resistance strain effect, and namely tinsel is when being subject to effects of strain, and its resistance, along with the size of occurred mechanically deform (stretching or compression), corresponding change occurs.The theoretical formula of resistance strain effect is as follows:

$R=\mathrm{\ρ}\frac{L}{S}---\left(1\right)$

Wherein R is its resistance value, and ρ is metal material resistivity, and L is metal material length, and S is metal material sectional area.Tinsel occurs in the process of mechanically deform bearing strain, and ρ, L, S three will change, thus will inevitably cause the change of metal material resistance value.When metal material is stretched, length increases, and sectional area reduces, and resistance value increases; When by compression, length reduces, and sectional area increases, and resistance value reduces.Therefore, as long as the change of resistance value can be measured, just known strained situation wiry.Metal material resistance change rate formula can be derived by relevant knowledges such as formula (1) and the mechanics of materials

$\frac{\mathrm{\Δ}R}{R}=K\frac{\mathrm{\Δ}L}{L}=K\mathrm{\ϵ}---\left(2\right)$

Wherein Δ R is resistance variation amount, and Δ L is the variable quantity of metal material length on pulling force or pressure action direction, and ε is that the strain on same direction is usually called axial strain, and K is metal material ga(u)ge factor.

In actual applications, metal resistance strain gauge is pasted onto the surface of Sensor Elastic Element or tested mechanical component.When the flexible member in sensor or tested mechanical component produce strain by acting force, also there is identical mechanically deform in the foil gauge pasted thereon thereupon, causes foil gauge resistance that corresponding change occurs.At this moment, mechanical quantity is just converted to the variable quantity output of resistance by resistance strain gage.

But we also need the partial derivative understanding workpiece strain sometimes, such as have three kinds of occasions below, but are not limited thereto three, need to use surface of the work strain partial derivative:

The first, concentrate owing to there will be strain near workpiece shapes sudden change place, often become workpiece and first occur damaging part, the strain partial derivative near sudden change place of monitoring shape, this place strain intensity can be obtained intuitively.

Second, exist in a large number by comer pieces in building, bridge, plant equipment, mechanics of materials relevant knowledge tells us, bent beam surface axial strain is directly proportional to section turn moment, the axial first-order partial derivative of section turn moment is directly proportional to cross section shearing strain, namely can know cross section shearing strain by the axial first-order partial derivative of surperficial axial strain, and this shearing strain directly cannot measure at surface of the work with foil gauge;

3rd, during applied elasticity research workpiece strain, internal strain is decided by partial differential equation, and equation solution needs boundary condition, and surface of the work strain partial derivative is exactly one of boundary condition, and this is that general foil gauge cannot provide.

In addition, to some position of workpiece, the such as position such as the shaft shoulder, part edge place, due to the sudden change of geomery, it strains the change that often corresponding existence is larger.But, just due to the sudden change of geomery, make the foil gauge that the more difficult arrangement in this place is general, need the product of a kind of energy inclined marginal position of monitor strain sheet instead of center position strain local derviation.

Summary of the invention

The deficiency of strain local derviation cannot be detected in order to overcome existing metal strain plate, the invention provides a kind of can being biased sensitive grid central shaft and mixing interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation by the monitor strain bilateral measured that more effectively can detect the axial local derviation of surface strain, particularly there is the axial single order local derviation of size restriction site at measuring workpieces corner, edge etc. to foil gauge.

The technical solution adopted for the present invention to solve the technical problems is:

A kind of bilateral of measuring is biased sensitive grid central shaft and mixes interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, comprise substrate, described metal strain plate also comprises six sensitive grids, the two ends of each sensitive grid connect a pin respectively, described substrate are fixed described six sensitive grids;

Each sensitive grid comprises sensitive segment and transition section, the two ends of described sensitive segment are transition section, described sensitive segment is elongated strip shaped, described transition section is tubbiness shape, the resistance of described sensitive segment is much larger than the resistance of described transition section, under same strain state, the increased resistance value of described sensitive segment is much larger than the increased resistance value of described transition section, and the increased resistance value of described transition section is close to 0;

All xsect centres of form of each sensitive segment form sensitive segment axis, this sensitive segment axis is straight line section, in described six sensitive grids each sensitive segment axis being parallel and be arranged in same plane, sensitive segment axis is determined in plane, along described sensitive segment axis direction namely axially, be laterally with axially vertical direction; Each sensitive segment exists the xsect that its both sides resistance value is equal, get this cross-section centroid position and with this sensitive segment resistance value for nominal mass is formed the nominal particle of place sensitive segment, the centroid position that the nominal particle of each sensitive segment is formed jointly is the center of sensitive grid;

, there is deviation at axial component in bias free in the horizontal between six sensitive grid centers; The order of sensitive grid center pressed by six sensitive grids, from left to right vertically, is first left three sensitive grids and the first from left sensitive grid, is then middle first sensitive grid and middle second sensitive grid, is finally a right sensitive grid and right three sensitive grids; The spacing at left three sensitive grid centers and the first from left sensitive grid center is 0, and the distance at left three sensitive grid centers and middle first sensitive grid center is Δ x ₁, the distance at middle first sensitive grid center and middle second sensitive grid center is 0, and the distance at middle second sensitive grid center and right three sensitive grid centers is Δ x ₂, Δ x ₁=Δ x ₂, the spacing at right three sensitive grid centers and a right sensitive grid center is 0;

Each sensitive segment axis is determined in plane, interdigital layout each other between first sensitive grid and middle second sensitive grid in left three sensitive grids, the first from left sensitive grid, middle part, middle first sensitive grid, middle second sensitive grid, interdigital layout each other between right three sensitive grids in the right and a right sensitive grid;

The sensitive segment all-in resistance of left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and right three sensitive grids is the proportionate relationship of 3:1:4:4:1:3, and left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and the all-in resistance changing value of sensitive segment sensitive segment under identical strain of right three sensitive grids are also the proportionate relationship of 3:1:4:4:1:3.

Accordingly, connect left three sensitive grids and a right sensitive grid, middle first sensitive grid, series connection the first from left sensitive grid and right three sensitive grids, middle second sensitive grid just in time forms four brachium pontis of measuring bridge.

Further, all shape of cross section consistent size of each sensitive segment, get the axis point midway of each sensitive segment and with this sensitive segment resistance value for nominal mass is formed the nominal particle of place sensitive segment, the sensitive segment total length of described left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and right three sensitive grids is the proportionate relationship of 3:1:4:4:1:3.The program is a kind of scheme that can select, as long as the position of nominal particle meets the equal xsect position of form center of its both sides resistance value, also can be other positions.

Further, in interdigital layout between equal and right three sensitive grids of left three sensitive grids, a right sensitive grid, in interdigital layout between equal and right three sensitive grids of the first from left sensitive grid, a right sensitive grid; Interdigital layout can be there is no yet.Described interdigital layout refers to: in the plane, in the sensitive segment distribution straggly with two sensitive grids on sensitive segment axes normal direction, the order occur respectively the sensitive segment of two sensitive grids in the direction in which and number of times do not limit in each sensitive segment axis institute of two sensitive grids.

Further again, first sensitive grid and middle second sensitive grid relatively, the sensitive segment axial length of right three sensitive grids and left three sensitive grids can be shorter and cross direction profiles can be closeer.Object reduces left three sensitive grid centers to the distance of foil gauge left side edge and right three sensitive grid centers to the distance of foil gauge right side edge.

Utilize the linear relationship between metal material increased resistance value and strain, this foil gauge may be used for monitor strain as common foil gauge.On the other hand, according to (" numerical computation method " 21 pages (1.4.11)-(1.4.14) formula as Yi Fengkang etc. compiles, National Defense Industry Press publishes in Dec, 1978 makes equidistant interpolation analysis) in numerical differentiation theory about the circular of single order local derviation, the numerical computation method of the x direction first-order partial derivative of f (x, y) is as follows:

$\frac{\∂f}{\∂x}{|}_{(x_2,y)}\≈\frac{1}{2h}\[f(x_0,y)-4f(x_1,y)+3f(x_2,y)\]---\left(3\right)$

Wherein x ₁=x ₀+ h, x ₂=x ₁+ h, paying special attention to above formula is (x ₂, y) the first-order partial derivative value formula of position, the truncation error of this formula is less is o (h ²) be the higher order indefinite small of step-length square.By the strain that formula (2) engineering be it is generally acknowledged sensitive grid resistance change direct ratio and sensitive grid center, in conjunction with the proportionate relationship of each sensitive grid resistance and the resistance change under same strain, resistance and the resistance value deducting middle first sensitive grid of left three sensitive grids and a right sensitive grid, distance again divided by left three sensitive grid centers and a right sensitive grid center is the axial single order numerical value local derviation strained, according to numerical differentiation theory, this is the axial single order numerical value local derviation of left three sensitive grid centers, equally, resistance and the resistance value deducting middle second sensitive grid of right three sensitive grids and the first from left sensitive grid, distance again divided by right three sensitive grid centers and the first from left sensitive grid center is the axial single order numerical value local derviation strained, according to numerical differentiation theory, this is the axial single order numerical value local derviation of right three sensitive grid centers.The axial single order local derviation of above-mentioned left three sensitive grids and right three sensitive grid centers can be measured simultaneously.Therefore the advantage of this foil gauge is that its both sides all can be used for the general foil gauge such as measuring workpieces corner, edge due to size and limit the axial single order local derviation at the position that cannot measure; And interdigital layout makes step-length h reduce, measuring error can be reduced like this according to analysis above.

Technique should be noted keep left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and right three sensitive grid transition section all-in resistances and the variable quantity of transition section resistance under external strain to be that the numerical relation of 3:1:4:4:1:3 is to heighten measuring accuracy, if the resistance of transition section and the lower resistance change of strain be can not ignore, also can be eliminated when detecting as systematic error.

Further, described metal strain plate also comprises cover plate, and described cover plate is covered in described sensitive grid and substrate.

Further again, described sensitive grid is wire form, foil, diaphragm type or thick-film type sensitive grid.

Further, described substrate is glued membrane substrate, glass fabric substrates, asbestos substrate, metallic substrates or temporary substrate.

Described six sensitive grid left, center, right are arranged in substrate.Certainly, also can be other arrangement.

Beneficial effect of the present invention is mainly manifested in: the arranged on left and right sides that foil gauge effectively can detect surface strain axial the single order local derviation, particularly foil gauge of left three sensitive grid centers and right three Liang Ge positions, sensitive grid center simultaneously all can have the axial single order local derviation of size restriction site in measuring workpieces corner, edge etc. to foil gauge.

Accompanying drawing explanation

Fig. 1 can measure bilateral to be biased sensitive grid central shaft mixes schematic diagram from interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation.

Fig. 2 can measure bilateral to be biased sensitive grid central shaft and to mix interdigital metal strain plate vertical view to the axial deviation six sensitive grid full-bridge of local derviation.

Fig. 3 is measuring bridge schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

With reference to Fig. 1 ~ Fig. 3, a kind of bilateral of measuring is biased sensitive grid central shaft and mixes interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, comprise substrate, described metal strain plate also comprises six sensitive grids, the two ends of each sensitive grid connect a pin respectively, described substrate are fixed described six sensitive grids;

Each sensitive grid comprises sensitive segment and transition section, the two ends of described sensitive segment are transition section, described sensitive segment is elongated strip shaped, described transition section is tubbiness shape, the resistance of described sensitive segment is much larger than the resistance of described transition section, under same strain state, the increased resistance value of described sensitive segment is much larger than the increased resistance value of described transition section, and the increased resistance value of described transition section is close to 0;

All xsect centres of form of each sensitive segment form sensitive segment axis, this sensitive segment axis is straight line section, in described six sensitive grids each sensitive segment axis being parallel and be arranged in same plane, sensitive segment axis is determined in plane, along described sensitive segment axis direction namely axially, be laterally with axially vertical direction; Each sensitive segment exists the xsect that its both sides resistance value is equal, get this cross-section centroid position and with this sensitive segment resistance value for nominal mass is formed the nominal particle of place sensitive segment, the centroid position that the nominal particle of each sensitive segment is formed jointly is the center of sensitive grid;

, there is deviation at axial component in bias free in the horizontal between six sensitive grid centers; The order of sensitive grid center pressed by six sensitive grids, from left to right vertically, is first left three sensitive grids and the first from left sensitive grid, is then middle first sensitive grid and middle second sensitive grid, is finally a right sensitive grid and right three sensitive grids; The spacing at left three sensitive grid centers and the first from left sensitive grid center is 0, and the distance at left three sensitive grid centers and middle first sensitive grid center is Δ x ₁, the distance at middle first sensitive grid center and middle second sensitive grid center is 0, and the distance at middle second sensitive grid center and right three sensitive grid centers is Δ x ₂, Δ x ₁=Δ x ₂, the spacing at right three sensitive grid centers and a right sensitive grid center is 0;

Each sensitive segment axis is determined in plane, interdigital layout each other between first sensitive grid and middle second sensitive grid in left three sensitive grids, the first from left sensitive grid, middle part, middle first sensitive grid, middle second sensitive grid, interdigital layout each other between right three sensitive grids in the right and a right sensitive grid;

The sensitive segment all-in resistance of left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and right three sensitive grids is the proportionate relationship of 3:1:4:4:1:3, and left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and the all-in resistance changing value of sensitive segment sensitive segment under identical strain of right three sensitive grids are also the proportionate relationship of 3:1:4:4:1:3.

Accordingly, connect left three sensitive grids and a right sensitive grid, middle first sensitive grid, series connection the first from left sensitive grid and right three sensitive grids, middle second sensitive grid just in time forms four brachium pontis of measuring bridge.

Further, all shape of cross section consistent size of each sensitive segment, get the axis point midway of each sensitive segment and with this sensitive segment resistance value for nominal mass is formed the nominal particle of place sensitive segment, the sensitive segment total length of described left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and right three sensitive grids is the proportionate relationship of 3:1:4:4:1:3.The program is a kind of scheme that can select, as long as the position of nominal particle meets the equal xsect position of form center of its both sides resistance value, also can be other positions.

Further, left three sensitive grids, the first from left sensitive grid and right three sensitive grids, a right sensitive grid are between any two in interdigital layout; Interdigital layout can be there is no yet.Described interdigital layout refers to: in the plane, in the sensitive segment distribution straggly with two sensitive grids on sensitive segment axes normal direction, the order occur respectively the sensitive segment of two sensitive grids in the direction in which and number of times do not limit in each sensitive segment axis institute of two sensitive grids.

Further again, first sensitive grid and middle second sensitive grid relatively, the sensitive segment axial length of right three sensitive grids and left three sensitive grids can be shorter and cross direction profiles can be closeer.Object reduces left three sensitive grid centers to the distance of foil gauge left side edge and right three sensitive grid centers to the distance of foil gauge right side edge.

The bilateral measured of the present embodiment is biased sensitive grid central shaft and mixes interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, comprise substrate 1, described metal strain plate also comprises six sensitive grids, the two ends of each sensitive grid connect a pin respectively, described substrate 1 are fixed described six sensitive grids.

Left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 can be fixed on substrate 1, for keep each sensitive grid fixing shape, position and size; Substrate 1 is very thin, thus the strain of surface of test piece is delivered to exactly left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7.Substrate 1 can be glued membrane substrate, glass fabric substrates, asbestos substrate, metallic substrates and temporary substrate.Usually with cohering, weld, substrate is fixed on the tested position of test block by the mode such as ceramic spraying.Substrate 1 also can be printed on the lines that some are located for foil gauge.

The materials such as cover plate paper using or glue are made, and are covered in left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6, right three sensitive grids 7 and substrate 1, play the protective seam of the effects such as protection against the tide, corrosion protection, loss prevention.

Pin 8 is for connecting sensitive grid and metering circuit, left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 respectively have two pins 8, to with foil and membrane type foil gauge, a left side three sensitive grid 2 that pin 8 is connected with it, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 combine as a whole.Two pins of left three sensitive grids 2 are 8-1 and 8-2, two pins of the first from left sensitive grid 3 are 8-3 and 8-4, two pins of middle first sensitive grid 4 are 8-5 and 8-6, two pins of middle second sensitive grid 5 are 8-7 and 8-8, two pins of a right sensitive grid 6 are 8-9 and 8-10, and two pins of right three sensitive grids 7 are 8-11 and 8-12.

Left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7, according to the difference of its metal sensitive material and processing technology, can be wire form, foil, diaphragm type, thick-film type.No matter the thickness of which kind of left three sensitive grid 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 is all very little, make left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 axial length with it depend on the deformation of workpiece and change.The basic crucial part of the present invention is left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, cooperation between a right sensitive grid 6 and right three sensitive grids 7, has following main points:

The first, six sensitive grids are arranged in substrate, is called left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7.

The second, left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 all can be divided into multiple sensitive segment 9 and multiple transition section 10, and each sensitive segment 9 is connected to form sensitive grid by each transition section 10.Comparatively speaking, sensitive segment 9 is in elongated shape, and resistance is comparatively large and its resistance is comparatively responsive to strain; Described transition section 10, substantially in tubbiness shape, makes the resistance of described transition section very little and insensitive to strain, and under duty, resistance variations is close to 0, and therefore the summation of sensitive segment resistance is the all-in resistance of single sensitive grid substantially.Fig. 2 has marked sensitive segment 9 and transition section 10 in more detail from angle more clearly.

3rd, the sensitive segment of each sensitive grid 9 is in elongated strip, and all xsect centres of form of each sensitive segment 9 form sensitive segment axis, and this sensitive segment 9 axis is straight line section, the axis being parallel of each sensitive segment 9 and be arranged in same plane.All xsects of each sensitive segment 9 are consistent along the projection of shape of sensitive segment axis direction.Get the axis point midway of each sensitive segment and with this sensitive segment resistance value for nominal mass is formed the nominal particle of place sensitive segment, the centroid position that the nominal particle of each sensitive segment is formed jointly is the center of sensitive grid.

4th, left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, the sensitive segment total length of a right sensitive grid 6 and right three sensitive grids 7 is the proportionate relationship of 3:1:4:4:1:3, left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, the sensitive segment all-in resistance of a right sensitive grid 6 and right three sensitive grids 7 is the proportionate relationship of 3:1:4:4:1:3, left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and the all-in resistance changing value of sensitive segment sensitive segment under identical strain of right three sensitive grids 7 are also the proportionate relationship of 3:1:4:4:1:3.Accordingly, connect left three sensitive grids 2 and a right sensitive grid 6, middle first sensitive grid 4, series connection the first from left sensitive grid 3 and right three sensitive grids 7, middle second sensitive grid 5 just in time forms four brachium pontis of measuring bridge.

5th, overlook left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7, they all have axis of symmetry and axis of symmetry overlaps (x-axis in Fig. 2), left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 sensitive segment 9 respective with right three sensitive grids 7 is all parallel with this axis of symmetry, and the sensitive segment 9 of each sensitive grid all distributes about this rotational symmetry.Therefore, left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 are coaxial, namely detect equidirectional strain and the center of left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 all in x-axis, their center bias free in the horizontal, there is deviation in part in the axial direction.According to the vertical view of foil gauge in Fig. 2, the sensitive segment 9 of left three sensitive grids 2 and the first from left sensitive grid 3 has lateral symmetry axle y _l, the center of left three sensitive grids 2 and the first from left sensitive grid 2 is at x-axis and y _lthe intersection point of axle, the sensitive segment 9 of middle first sensitive grid 4 and middle second sensitive grid 5 has lateral symmetry axle y _m, the center of middle first sensitive grid 4 and middle second sensitive grid 5 is at x-axis and y _mthe intersection point of axle, the sensitive segment 9 of a right sensitive grid 6 and right three sensitive grids 7 has lateral symmetry axle y _r, the center of a right sensitive grid 6 and right three sensitive grids 7 is at x-axis and y _rthe intersection point of axle.

6th, the spacing at the left center of three sensitive grids 2 and the center of the first from left sensitive grid 3 is 0, and the distance at the center of left three sensitive grids 2 and the center of middle first sensitive grid 4 is Δ x ₁, the distance at the center of middle first sensitive grid 4 and the center of middle second sensitive grid 5 is 0, and the distance at the center of middle second sensitive grid 5 and the center of right three sensitive grids 7 is Δ x ₂, Δ x ₁=Δ x ₂, the spacing at the center of right three sensitive grids 7 and the center of a right sensitive grid 6 is 0, as shown in Figure 2.Shown in Fig. 2, the axis of each sensitive segment 9 is determined in plane, left three sensitive grids 2, the first from left sensitive grid 3, interdigital layout each other between middle first sensitive grid 4 and middle second sensitive grid 5, a right sensitive grid 6, right three sensitive grids 7, interdigital layout each other between middle first sensitive grid 4 and middle second sensitive grid 5, left three sensitive grids 2, the first from left sensitive grid 3, can interdigital layout also can be contrary each other between a right sensitive grid 6 with right three sensitive grids 7, such as, in Fig. 2, these 4 sensitive grids are not formed interdigital, if but the length of these 4 sensitive grids tune up just can be formed interdigital.Described interdigital layout refers to: in the plane, in the sensitive segment distribution straggly with two sensitive grids on sensitive segment axes normal direction, the order occur respectively the sensitive segment of two sensitive grids in the direction in which and number of times do not limit in each sensitive segment 9 axis of two sensitive grids institute.Because the relative position of left three sensitive grids 2, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and right three sensitive grids 7 is ensured quite accurately to be secured by foil gauge production technology, this is also that the present invention can detect the key one of of workpiece strain axis to partial derivative.

In sum, left three sensitive grids 2 of the present invention, the first from left sensitive grid 3, middle first sensitive grid 4, middle second sensitive grid 5, a right sensitive grid 6 and the all-in resistance changing value of sensitive segment sensitive segment under identical strain of right three sensitive grids 7 are also the proportionate relationship of 3:1:4:4:1:3, each sensitive grid center bias free in the horizontal, there is deviation in part in the axial direction, the spacing at the left center of three sensitive grids 2 and the center of the first from left sensitive grid 3 is 0, and the distance at the center of left three sensitive grids 2 and the center of middle first sensitive grid 4 is Δ x ₁, the distance at the center of middle first sensitive grid 4 and the center of middle second sensitive grid 5 is 0, and the distance at the center of middle second sensitive grid 5 and the center of right three sensitive grids 7 is Δ x ₂, Δ x ₁=Δ x ₂, the spacing at the center of right three sensitive grids 7 and the center of a right sensitive grid 6 is 0.

The first from left sensitive grid 3 resistance under free state is made to be R _l0, middle second sensitive grid 5 resistance is R _m0, right three sensitive grid 7 resistance are R _r0, should R be had _l0+ R _r0=R _m0=R ₀.Foil gauge of the present invention is placed in certain when having a surface strain, the first from left sensitive grid 3 resistance is R ₀+ Δ R _l, middle sensitive grid 4 resistance is R ₀+ Δ R _m0, right three sensitive grid 7 resistance are R ₀+ Δ R _r; On the other hand, the center of the first from left sensitive grid 3 and right three sensitive grids 7 lays respectively at x-axis and y in Fig. 2 _lintersection point and x-axis and y _rintersection point, axially at a distance of 2 Δ x ₁.The formula of the relation of sensitive grid resistance and surface strain and numerical differentiation (3) is utilized to have:

$\frac{\∂\mathrm{\ϵ}}{\∂x}{|}_{\stackrel{\‾}{x}}\≈\frac{{\mathrm{\ϵ}}_L-4{\mathrm{\ϵ}}_M+3{\mathrm{\ϵ}}_R}{2{\mathrm{\Δx}}_1}\≈\frac{K({\mathrm{\ΔR}}_L-{\mathrm{\ΔR}}_M+{\mathrm{\ΔR}}_R)}{2{\mathrm{\Δx}}_1}.---\left(4\right)$

Wherein for the center of right three sensitive grids 7, ε _lfor the strain of the first from left sensitive grid 3 center, ε _mfor the strain of middle second sensitive grid 5 center, ε _rfor the strain of right three sensitive grid 7 centers.Namely this is the principle of the present embodiment measured surface strain axis to local derviation.Pay special attention to, the numerical differentiation that above formula calculates is that the strain axis of the center of right three sensitive grids 7 is to single order local derviation, this position is the right side of foil gauge, therefore has and is convenient to there are the axial single order local derviation of size restriction site in measuring workpieces corner, edge etc. advantage to foil gauge.Composition graphs 2, notice the sensitive segment 9 short (in fact in Fig. 2, sensitive segment 9 length of right three sensitive grids 7 is the half of the sensitive segment 9 of middle second sensitive grid 5) of the comparatively middle sensitive grid 4 of the sensitive segment 9 of right three sensitive grids 7, laterally the sensitive segment 9 of upper right three sensitive grids 7 is arranged closeer (in fact in Fig. 2, the hop count of the sensitive segment 9 of right three sensitive grids 7 is 3/2 times of the hop count of the sensitive segment 9 of middle second sensitive grid 5), its object is all to reduce the distance of right three sensitive grid 7 centers to foil gauge right side edge as far as possible, so that play above-mentioned advantage further.Equally, left three sensitive grids 2, middle first sensitive grid 4 and a right sensitive grid 6 can coordinate the strain axis calculating left three sensitive grid 2 centers to first-order partial derivative; Strengthen the density of transversely arranging by the length of the sensitive segment 9 shortening left three sensitive grids 2, reduce the distance of left three sensitive grid 2 centers to foil gauge left side edge as far as possible.The strain axis of the center of above-mentioned right three sensitive grids 7 can be measured to the strain axis of single order local derviation and left three sensitive grid 2 centers to first-order partial derivative simultaneously.

Coordinated by the present embodiment electric bridge to can be used for monitor strain, strain axis to single order local derviation, suppose that bridge input voltage is u _i, output voltage is u _o, Fig. 3 is shown in by the schematic diagram of measuring bridge.When without workpiece effects of strain, each arm resistance of electric bridge is labeled as R respectively according to clockwise direction ₁, R ₂, R ₃, R ₄, when obscuring also with these sign flag resistance place electric bridges.Each electric bridge can be laid sensitive grid or the resistance of foil gauge.Arrange identical with general foil gauge, if settle sensitive grid on multiple brachium pontis, to the order of each installation position, the requirement of strain difinite quality.During without workpiece effects of strain, the Output Voltage Formula of electric bridge is

$u_o=\frac{R_1{R}_3-R_2{R}_4}{(R_1+R_2)(R_3+R_4)}{u}_i;---\left(5\right)$

Now, bridge balance i.e. u is required _o=0, so so-called bridge balance condition R must be met ₁r ₃-R ₂r ₄=0, the electric bridge of employing meets further

R ₁＝R ₂＝R ₃＝R ₄，(6)

Because, the first, satisfy condition (6) time, the highest according to relevant theoretical foil gauge sensitivity; The second, monitor strain or strain axis are set up to the equal requirement condition of method (6) of local derviation.When foil gauge, with external world's strain, strain also occurs, above-mentioned bridge balance condition is generally no longer set up, now

$\begin{array}{c}{u}_o=\frac{\left(R_1+{\mathrm{\ΔR}}_1\right)\left(R_3+{\mathrm{\ΔR}}_3\right)-\left(R_2+{\mathrm{\ΔR}}_2\right)\left(R_4+{\mathrm{\ΔR}}_4\right)}{\left(R_1+{\mathrm{\ΔR}}_1+R_2+{\mathrm{\ΔR}}_2\right)\left(R_3+{\mathrm{\ΔR}}_3+R_4+{\mathrm{\ΔR}}_4\right)}{u}_i\\ \≈\frac{R_3{\mathrm{\ΔR}}_1+R_1{\mathrm{\ΔR}}_3-R_4{\mathrm{\ΔR}}_2-R_2{\mathrm{\ΔR}}_4+{\mathrm{\ΔR}}_1{\mathrm{\ΔR}}_3-{\mathrm{\ΔR}}_2{\mathrm{\ΔR}}_4}{\left(R_1+R_2\right)\left(R_3+R_4\right)}{u}_i\\ \≈\frac{\left({\mathrm{\ΔR}}_1-{\mathrm{\ΔR}}_2\right)+\left({\mathrm{\ΔR}}_3-{\mathrm{\ΔR}}_4\right)}{4R_1}{u}_i\end{array}---\left(7\right)$

Due to Δ R _i< < R _i(i=1,2,3,4) event first ≈ sets up, and second ≈ is as Δ R ₁-Δ R ₂with Δ R ₃-Δ R ₄jack per line or contrary sign but | Δ R ₁-Δ R ₂| with | Δ R ₃-Δ R ₄| not very close to time set up, in engineering, choose reasonable foil gauge installation position can realize completely.The voltage measurement strain that general available formula (7) obtains; Can convolution (4) and formula (7) to the axial local derviation of strain, reasonable design arranges each brachium pontis sensitive grid and resistance, such as brachium pontis R ₁second sensitive grid 5 in layout, brachium pontis R ₂right three sensitive grids 7 of arranged in series and the first from left sensitive grid 3, all the other brachium pontis configuration substitutional resistance, can obtain with right three sensitive grid 7 center strain axis to the linear magnitude of voltage u of single order local derviation _o, this voltage is that feeble signal need be amplified.

Claims (8)

1. can measure bilateral and be biased sensitive grid central shaft and mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation for one kind, comprise substrate, it is characterized in that: described metal strain plate also comprises six sensitive grids, the two ends of each sensitive grid connect a pin respectively, described substrate are fixed described six sensitive grids;

Each sensitive grid comprises sensitive segment and transition section, the two ends of described sensitive segment are transition section, described sensitive segment is elongated strip shaped, described transition section is tubbiness shape, the resistance of described sensitive segment is much larger than the resistance of described transition section, under same strain state, the increased resistance value of described sensitive segment is much larger than the increased resistance value of described transition section, and the increased resistance value of described transition section is close to 0;

All xsect centres of form of each sensitive segment form sensitive segment axis, this sensitive segment axis is straight line section, in described six sensitive grids each sensitive segment axis being parallel and be arranged in same plane, sensitive segment axis is determined in plane, along described sensitive segment axis direction namely axially, be laterally with axially vertical direction; Each sensitive segment exists the xsect that its both sides resistance value is equal, get this cross-section centroid position and with this sensitive segment resistance value for nominal mass is formed the nominal particle of place sensitive segment, the centroid position that the nominal particle of each sensitive segment is formed jointly is the center of sensitive grid;

, there is deviation at axial component in bias free in the horizontal between six sensitive grid centers; The order of sensitive grid center pressed by six sensitive grids, from left to right vertically, is first left three sensitive grids and the first from left sensitive grid, is then middle first sensitive grid and middle second sensitive grid, is finally a right sensitive grid and right three sensitive grids; The spacing at left three sensitive grid centers and the first from left sensitive grid center is 0, and the distance at left three sensitive grid centers and middle first sensitive grid center is Δ x ₁, the distance at middle first sensitive grid center and middle second sensitive grid center is 0, and the distance at middle second sensitive grid center and right three sensitive grid centers is Δ x ₂, Δ x ₁=Δ x ₂, the spacing at right three sensitive grid centers and a right sensitive grid center is 0;

Each sensitive segment axis is determined in plane, interdigital layout each other between first sensitive grid and middle second sensitive grid in left three sensitive grids, the first from left sensitive grid, middle part, middle first sensitive grid, middle second sensitive grid, interdigital layout each other between right three sensitive grids in the right and a right sensitive grid, can have interdigital layout also can not have interdigital layout between left three sensitive grids, the first from left sensitive grid and right three sensitive grids, a right sensitive grid;

The sensitive segment all-in resistance of left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and right three sensitive grids is the proportionate relationship of 3:1:4:4:1:3, and left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and the all-in resistance changing value of sensitive segment sensitive segment under identical strain of right three sensitive grids are also the proportionate relationship of 3:1:4:4:1:3.

2. can measure bilateral to be as claimed in claim 1 biased sensitive grid central shaft and to mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, it is characterized in that: all shape of cross section consistent size of each sensitive segment, get the axis point midway of each sensitive segment and with this sensitive segment resistance value for nominal mass is formed the nominal particle of place sensitive segment, the sensitive segment total length of described left three sensitive grids, the first from left sensitive grid, middle first sensitive grid, middle second sensitive grid, a right sensitive grid and right three sensitive grids is the proportionate relationship of 3:1:4:4:1:3.

3. can measure bilateral to be as claimed in claim 1 or 2 biased sensitive grid central shaft and to mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, it is characterized in that: in interdigital layout between equal and right three sensitive grids of described left three sensitive grids, a right sensitive grid, in interdigital layout between equal and right three sensitive grids of the first from left sensitive grid, a right sensitive grid.

4. can measure bilateral to be as claimed in claim 1 or 2 biased sensitive grid central shaft and to mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, it is characterized in that: first sensitive grid and middle second sensitive grid relatively, the sensitive segment axial length of right three sensitive grids and left three sensitive grids can be shorter and cross direction profiles can be closeer.

5. can measure bilateral to be as claimed in claim 1 or 2 biased sensitive grid central shaft and to mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, it is characterized in that: described metal strain plate also comprises cover plate, described cover plate is covered in described sensitive grid and substrate.

6. can measure bilateral to be as claimed in claim 1 or 2 biased sensitive grid central shaft and to mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, it is characterized in that: described sensitive grid is wire form, foil, diaphragm type or thick-film type sensitive grid.

7. can measure bilateral to be as claimed in claim 1 or 2 biased sensitive grid central shaft and to mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, it is characterized in that: described substrate is glued membrane substrate, glass fabric substrates, asbestos substrate, metallic substrates or temporary substrate.

8. can measure bilateral to be as claimed in claim 1 or 2 biased sensitive grid central shaft and to mix interdigital metal strain plate to the axial deviation six sensitive grid full-bridge of local derviation, it is characterized in that: described six sensitive grid left, center, right are arranged in substrate.