CN103175465A - Minisize resistance-type displacement meter based on full-bridge electrometric method - Google Patents

Abstract

The invention relates to a minisize resistance-type displacement meter based on a full-bridge electrometric method, belonging to the technical field of geomechanical model tests. The minisize resistance-type displacement meter mainly comprises a thin copper sheet, a test bolt, a protective shell, four strain sheets, lead wires and a perforated base, wherein the test bolt is fixed on the upper end of the thin copper sheet; the intermediate part and the lower end of the thin copper sheet are arranged in the protective shell; the relative positions of two side surfaces of the intermediate part of the thin copper sheet are adhered with the four strain sheets; the lower part of the thin copper sheet and the base are fixed together; and the four strain sheets are respectively connected with the lead wires to form a full-bridge circuit. The minisize resistance-type displacement meter disclosed by the invention can be used for measuring the displacement of the surface of a dam body or the inside of the a rock body, has the characteristics of minisize, light weight, high sensitivity and good stability and is especially suitable for the geomechanical model tests.

Description

Micro electric resistive displacement meter based on the full-bridge electrical measuring method

Technical field

The invention belongs to the geomechanical model testing technology field; Specially refer to a kind of structural design of the Simple miniature resistance-type displacement meter for geomechanical model test.

Background technology

Geomechanical model test can the model engineering structure strain, displacement characteristics, again can approximate simulation rock mass tomography etc. geologic agent on the impact of engineering structure stability, therefore it has extremely important effect and is widely used in the engineering designs such as water conservancy, mining, tunnel, and for example the big-and-middle-sized arch dam of China was substantially all done geomechanical model test.

In geomechanical model test, the displacement situation of body structure surface and basic rock mass inside is main measurement content under load action, can reflect the security and stability at stress, strained situation and each position of structure and basic rock mass by displacement, and then obtain the final safety analysis result of engineering.But geomechanical model test need to be measured many some displacements, and sometimes measuring point need to be arranged in the inside of strata model; But the size of model own is little, and displacement measuring device can not be excessive so that structure and rock mass stress distribution situation are exerted an influence.To sum up, geomechanical model test needs the displacement measuring device of a kind of miniature, lightweight, highly sensitive, good stability.Although emerge in recent years the high-tech measurement mechanisms such as Fibre Optical Sensor, these costs are higher, and easily are disturbed, and seriously hindered its popularization.

Shandong University applied for once the miniature built-in suspension beam type displacement meter of geomechanical model test " be used for " that (open (bulletin) day: 2009.01.14 disclosed (bulletin) number: CN101344372).This is a kind of miniature built-in cantilever beam type displacement gage for geomechanical model test, comprises spring leaf, wire rope, foil gauge, it is characterized in that: the two ends of wire rope are connected to the stator at spring leaf upper end and measuring point place, model inside; Be provided with adjusting bolt in the spring leaf upper end, the spring leaf lower end is fixed on thick steel bar, and foil gauge is arranged near the root of spring leaf lower end and is connected with the signal receiving and processing device by signal wire.This displacement meter adopts the half-bridge method to measure, and measuring accuracy is not high; And the internal displacement value of measuring rock mass structure is more laid particular stress in this invention.

Summary of the invention

The objective of the invention is for overcoming the weak point of prior art, a kind of micro electric resistive displacement meter based on the full-bridge electrical measuring method is proposed, the present invention can measure the displacement on dam body or rock mass surface, and have the characteristics of miniature, lightweight, highly sensitive, good stability, be specially adapted to geomechanical model test.

A kind of micro electric resistive displacement meter based on the full-bridge electrical measuring method that the present invention proposes is characterized in that, is used for the displacement measurement of geomechanical model test, this displacement meter mainly comprises scale copper, test bolt, containment vessel, 4 foil gauges and wire thereof, base with holes; Wherein, test is bolted to the upper end of scale copper, and middle part and the lower end of scale copper are placed in containment vessel, bonding four foil gauges of the relative position of the middle part both side surface of scale copper, and bottom and the base of scale copper are fixed; 4 foil gauges composition full-bridge circuit that is connected with wire respectively.

This base can be plastic feet, can be comprised of base plate and riser, and base plate one end is a circular hole, is used for fixing with geomechanics model, and the base other end also has a small sircle hole, is used for interspersed 4 wires; Riser is combined in and has two holes on base plate one end, is used for base and scale copper bottom are fixed by set bolt.

This scale copper is about the thick scale copper of 0.5mm, highly is about 3.6cm, and is up-narrow and down-wide, and the narrowest place, top is about 0.9cm, and bottom the widest part is about 1.5cm, and the scale copper bottom is fixed on plastic feet; 4 foil resistance foil gauges are placed in copper sheet both side surface middle part, and wherein, the first foil gauge and the 4th foil gauge, the second foil gauge and the 3rd foil gauge are in respectively copper sheet both sides same position.

This each foil gauge surface all scribbles paraffin and adds the vaseline sealing, is used for protection against the tide and thermal insulation, to improve stability;

The size of population of this displacement meter can be 1cm*2cm*3.5cm.

Characteristics of the present invention and useful result:

This displacement meter can the buried foundation strata model inside, also can be arranged in the measuring point of body structure surface.This displacement meter one end is fixed on brandreth, and when the other end was subjected to displacement, copper sheet can produce bending; Use the full-bridge method to measure the strain differential on copper sheet two sides, and then conversion obtain the shift value of copper sheet; This displacement meter is converted into extremely sensitive electric signal with shift value and measures; And this displacement meter only uses the simple material such as resistor disc, scale copper, thin wire, plastic plate, and cost has been saved in processing, easy to use greatly.

This displacement meter constructs, uses simple, and cost is lower; Use the full-bridge method highly sensitive; The displacement meter arrangement convenience can be measured dam body or strata model surface displacement, also can measure the strata model internal displacement; The displacement meter size is less, and is less to the structural stress distribution influence; Measuring technique is easy to learn, and cost is low, is easy to promote the use of.

Description of drawings

Fig. 1 is displacement meter side view of the present invention;

Fig. 2 is vertical view of the present invention;

Fig. 3 is the positive view of the A-A section of Fig. 2;

Fig. 4 is displacement meter rear view of the present invention;

Fig. 5 is circuit reduction figure of the present invention;

Wherein, 1 scale copper, 2 test bolt (2-1 nuts, the 2-2 nut), 3 containment vessels, 4 foil gauges (4-1 foil gauge 1,4-2 foil gauge 2,4-3 foil gauge 3,4-4 foil gauge 4), 5 set bolts (5-1 set bolt 1,5-2 set bolt 2), 6 bases, 7 wires (wire A, wire B, wire C, wire D); R1, R2, R3, R4 be corresponding foil gauge 1,2,3,4 respectively, A/C wire connecting power, B/D two ends connection surveying instrument.

Embodiment

The micro electric resistive displacement meter based on the full-bridge electrical measuring method that the present invention proposes reaches by reference to the accompanying drawings embodiment and is described in detail as follows:

A kind of micro electric resistive displacement meter based on the full-bridge electrical measuring method that the present invention proposes is characterized in that, is used for the displacement measurement of geomechanical model test, this displacement meter mainly comprises scale copper, test bolt, containment vessel, 4 foil gauges and wire thereof, base with holes; Wherein, test is bolted to the upper end of scale copper, and middle part and the lower end of scale copper are placed in containment vessel, bonding four foil gauges of the relative position of the middle part both side surface of scale copper, and bottom and the base of scale copper are fixed; 4 foil gauges composition full-bridge circuit that is connected with wire respectively.

The structure of the present embodiment is as shown in Fig. 1～4, and the size of population of this displacement meter is 1cm*2cm*3.5cm approximately, can ignore than the dam body moulded dimension, so less on the stress distribution impact of model.The present embodiment mainly comprises scale copper 1, test bolt 2(is comprised of nut 2-1 and nut 2-2), containment vessel 3,4 foil gauge 4(the first foil gauge 4-1, the second foil gauge 4-2, the 3rd foil gauge 4-3 and the 4th foil gauge 4-4) and wire (wire A, wire B, wire C, wire D), base 6 with holes; Wherein, test bolt 2 is fixed on the upper end of scale copper 1, the middle part of scale copper 1 and lower end are placed in containment vessel 3, bonding four foil gauges 4 of the relative position of the middle part both side surface of scale copper 1, and the bottom of scale copper 1 is fixing by gib screw 5-1,5-2 and base 6; The first foil gauge 4-1, the second foil gauge 4-2, the 3rd foil gauge 4-3 and the 4th foil gauge 4-4 respectively with wire A, wire B, wire C, the wire D composition full-bridge circuit that is connected.

The embodiment of each parts of this displacement meter is respectively described below:

The base 6 of the present embodiment is plastic feet, as shown in Fig. 2,3, formed by base plate and riser, the high approximately 0.6cm of base plate is about 3cm, thick approximately 0.8cm, base plate one end is a circular hole 6-1, diameter 0.5cm, the point of fixity of bolt and geomechanics model outside of be used for interting is fixed, and base is placed on the point of fixity of model outside; The base other end also has a small sircle hole, and diameter 0.3cm is used for interspersed 4 wires; Riser is combined on base plate one end, and high approximately 1cm is about 1.5cm, thick approximately 0.8cm,, have two holes, be used for scale copper 1 bottom is fixed by set bolt 5-1,5-2, as shown in Figure 3.

The scale copper 1 thick scale copper of thickness 0.5mm of the present embodiment, highly approximately 3.6cm, up-narrow and down-wide, the narrowest 0.9cm of place in top, the bottom is the widest goes out 1.5cm, the scale copper bottom use 2 fixedly universal source hook bolt 5 be fixed on plastic feet 6; A test bolt 2 is settled at copper sheet 1 top, and screw is about 1cm, adopts general snap head bolt; 2 foil resistance foil gauges 4 that length is 0.5mm have respectively been arranged at copper sheet both side surface middle part, wherein, the first foil gauge 4-1 and the 4th foil gauge 4-4, the second foil gauge 4-2 and the 3rd foil gauge 4-3 are in respectively the both sides same position, as shown in Figure 2; Each foil gauge surface all scribbles paraffin and adds the vaseline sealing, is used for protection against the tide and thermal insulation, to improve stability; The present embodiment adopts 4 wires 7, and every wire is separated into 2 thin wires again, uses the full-bridge method to connect 8 thin wires are connected with 4 foil gauges, and connected mode is seen accompanying drawing 3,4 and Fig. 5; The containment vessel 3 thick thin plastic sheets of use 0.5mm are made, and just the middle and lower part with copper sheet is trapped among wherein, are used for preventing dust etc. to the pollution of foil gauge and to the interference of test figure, and are cementing fixing between containment vessel bottom and pedestal.

Measuring principle and the course of work of this displacement meter are described as follows: during use, when measuring the rock mass internal displacement, the bolt head on displacement meter top is imbedded the measuring position; When measuring the body structure surface displacement, the adjacent measuring position of bolt head on displacement meter top makes copper sheet that less bending occurs simultaneously; During measurement, base is fixed on the outer point of fixity of model; When the measuring position was subjected to displacement, bolt was also along with the measuring position produces identical displacement together; Copper sheet is bent, copper sheet two ends produce equal and opposite in direction, opposite direction strain stress ₁=ε ₂=-ε ₃=-ε ₄).

The foil gauge measure equation:

$\frac{\mathrm{\ΔR}}{R}=K\·\mathrm{\ϵ}---\left(1\right);$

Full-bridge method measure equation:

$\mathrm{\&Delta;U}=\frac{U}{4}(\frac{{\mathrm{\&Delta;R}}_1}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA00002936377500011.png,HDA00002936377500021.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}+\frac{{\mathrm{\&Delta;R}}_2}{R_2}-\frac{{\mathrm{\&Delta;R}}_3}{R_3}-\frac{{\mathrm{\&Delta;R}}_4}{R_4})=\frac{\mathrm{UK}}{4}({\mathrm{\&epsiv;}}_1+{\mathrm{\&epsiv;}}_2-{\mathrm{\&epsiv;}}_3-{\mathrm{\&epsiv;}}_4)---\left(2\right);$

Strainmeter full-bridge method place in circuit reading:

${\mathrm{\&epsiv;}}_{\mathrm{ds}}=\frac{4\mathrm{\&Delta;U}}{\mathrm{KU}}={\mathrm{\&epsiv;}}_1+{\mathrm{\&epsiv;}}_2-{\mathrm{\&epsiv;}}_3-{\mathrm{\&epsiv;}}_4={4\mathrm{\&epsiv;}}_1---\left(3\right);$

(ε ₁, ε ₂, ε ₃, ε ₄Be respectively foil gauge 1,2,3,4 strain value; R ₁, R ₂, R ₃, R ₄Be respectively foil gauge 1,2,3,4 resistance value; U is magnitude of voltage; K is the coefficient of strain);

Because the displacement exact value of measuring in model test is in a small amount with respect to the copper sheet size, so the bending value of the shift value of bolt and copper sheet can be approximated to be linearity, namely shift value is similar to and ε again ₁Linear, namely with strain-ga(u)ge reading ε _dsBeing linear closes.Before use, use clock gauge, strainmeter to carry out calibration to displacement meter on the calibration frame, the data that record are carried out linear fit, obtain strain-displacement curve slope; During test, then the strainmeter difference of reading be multiply by the displacement difference that slope is exactly measurement.

(1) displacement meter is accessed in strainmeter according to the full-bridge method, as shown in Figure 5, use clock gauge to carry out calibration to displacement meter on the calibration frame, the multi-group data that same displacement meter is recorded carries out linear fit, obtains strain-displacement curve slope;

When (2) measuring internal displacement, the top bolt of displacement meter is imbedded the measuring position; When measuring surface displacement, with the top bolt of the displacement meter surface near the measuring position, make simultaneously copper sheet that less bending occurs; Use bolt that the base of displacement meter is fixed on the point of fixity of model outside;

(3) full-bridge circuit and the strainmeter with displacement meter connects, as shown in Figure 5;

The initial measurement data of the strainmeter when (4) reading model is without loading;

(5) after model begins to load, the strain-ga(u)ge reading when reading each heap(ed) capacity;

(6) the poor slope that multiply by of any twice strain-ga(u)ge reading is exactly twice displacement difference in the heap(ed) capacity situation, because initial displacement is 0, be exactly shift value in corresponding each heap(ed) capacity situation that records so measure constantly with the poor slope that multiply by calibration of the strain-ga(u)ge reading of initial time.

Claims (5)

1. the micro electric resistive displacement meter based on the full-bridge electrical measuring method, is characterized in that, is used for the displacement measurement of geomechanical model test, and this displacement meter mainly comprises scale copper, test bolt, containment vessel, 4 foil gauges and wire thereof, base with holes; Wherein, test is bolted to the upper end of scale copper, and middle part and the lower end of scale copper are placed in containment vessel, bonding four foil gauges of the relative position of the middle part both side surface of scale copper, and bottom and the base of scale copper are fixed; 4 foil gauges composition full-bridge circuit that is connected with wire respectively.

2. displacement meter as claimed in claim 1, is characterized in that, this base is plastic feet, is comprised of base plate and riser, and base plate one end is a circular hole, is used for fixing with geomechanics model, and the base other end also has a small sircle hole, is used for interting 4 wires; Riser is combined in and has two holes on base plate one end, is used for base and scale copper bottom are fixed by set bolt.

3. displacement meter as claimed in claim 1, is characterized in that, this scale copper is the thick scale copper of 0.5mm, and height 3.6cm is up-narrow and down-wide, the narrowest 0.9cm of place in top, and the bottom is the widest goes out 1.5cm, and the scale copper bottom is fixed on plastic feet; 4 foil resistance foil gauges are placed in copper sheet both side surface middle part, and wherein, the first foil gauge and the 4th foil gauge, the second foil gauge and the 3rd foil gauge are in respectively copper sheet both sides same position.

4. displacement meter as claimed in claim 1, is characterized in that, this each foil gauge surface all scribbles paraffin and adds the vaseline sealing, is used for protection against the tide and thermal insulation, to improve stability.

5. displacement meter as claimed in claim 1, is characterized in that, the size of population of this displacement meter is 1cm*2cm*3.5cm.

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