CN102506687A - High-accuracy thickness gauge - Google Patents

Abstract

The invention relates to a high-accuracy thickness gauge, comprising a microprocessor, a display module and a keyboard which are connected with the microprocessor as well as a differential transformer displacement transducer, a stepping motor and a pressure transducer, wherein the secondary side of a differential transformer is connected with the microprocessor by virtue of a sampling circuit, an amplifying circuit and an A/D (analogue-to-digital) conversion circuit sequentially, a control terminal of the stepping motor is connected with the microprocessor, an output shaft of the stepping motor is connected with the upper end of an iron core of the differential transformer by virtue of a meshing device, the pressure transducer is arranged at the lower end of the iron core, the pressure transducer is connected with the microprocessor by virtue of the A/D conversion circuit; and a driving signal terminal of the sampling circuit is also connected with the microprocessor. The thickness gauge has the beneficial effect that an ATmega16 microprocessor is used as a processing core and is matched with the pressure transducer; moreover, through structural optimization, the thickness gauge has the advantages of high measuring accuracy, use convenience and the like and can be used for measuring thicknesses of multiple articles.

Description

A kind of high precision thicknessmeter

Technical field

The invention belongs to light industry and make the field, relate to a kind of thicknessmeter, especially a kind of high precision thicknessmeter that is applicable to that light industry leather, plastics, paper equal thickness are measured.

Background technology

In recent years, along with improving constantly of light industry production technology and means, there is the measurement of related parameter (such as thickness) to have higher requirement aborning to leather, glass, paper, plastics etc.What at present China's light industry still adopted for the measurement of thickness is traditional pointer thicknessmeter; Yet this thicknessmeter adopts pointer header; Through measuring the size of induction electromotive force; The thickness that reflects measured object; Shortcomings such as this measurement device precision is not high, human error is bigger are very outstanding, though some digital thickness measuring instruments have also appearred on the market, these thickness measuring instruments also the presence bit displacement sensor adopt unreasonable, precision is not high, can only measure shortcoming such as single article.

Summary of the invention

The objective of the invention is to overcome the shortcoming of above-mentioned prior art; A kind of high precision thicknessmeter is provided; It is its processing core that this thicknessmeter adopts microprocessor, cooperates pressure transducer, through structural optimization; Make it not only have measuring accuracy height, advantage such as easy to use, and can be fit to measure multiple article thickness.

The objective of the invention is to solve through following technical scheme:

This high precision thicknessmeter; Comprise microprocessor and be connected in display module and the keyboard on the microprocessor; Also include differential transformer displace, stepper motor and pressure transducer; The differential transformer secondary of said differential transformer displace is connected on the microprocessor through sample circuit, amplifying circuit and A/D change-over circuit successively, and said Stepping Motor Control end is connected with microprocessor, and the output shaft of stepper motor is connected with the upper end of the iron core of differential transformer displace through geared assembly; Said pressure transducer is located at the lower end of iron core, and pressure transducer is connected with microprocessor through the A/D change-over circuit; Described control signal sampling terminal is connected on the microprocessor.

The lower end of above-mentioned iron core is provided with the concave shape connector of a back-off; Said pressure transducer is located in the connector; The pressure-sensitive contact of pressure transducer stretches out a connecting link downwards, and the lower end of said connecting link is provided with a horizontal surface of contact, also has thick of a horizontally disposed side under the horizontal surface of contact.

Above-mentioned microprocessor adopts the Atmegal6 single-chip microcomputer.

The present invention has following beneficial effect:

The present invention adopts the high precision differential transformer displace, and (precision can reach 1 μ m; Ordinary numbers formula thicknessmeter is merely 10-100 μ m); Can be applicable to the measurement of different article through the stressed size of keyboard according to national standard setting testee unit area.Microprocessor through the detected pressures sensor and and the keyboard to set up value between difference; Calculate the control corresponding amount through pid control algorithm; Control step driven by motor iron core motion, and realized from the single-measurement to the duplex measurement, low precision measure is to high-acruracy survey, vertically measure the leap that the optional position is measured.

Description of drawings

Fig. 1 is a principle of work structured flowchart of the present invention;

Fig. 2 is a measure portion MECH plot of the present invention;

Fig. 3 is a sensor force diagram of the present invention;

Fig. 4 is the structural equivalents figure of differential displacement sensor;

Fig. 5 is the output characteristic curve of differential transformer.

Wherein: 1 is stepper motor; 2 is geared assembly; 3 is differential transformer displace; 4 is pressure transducer; 5 is connecting link; 6 is thick of side; 7 is horizontal surface of contact; 8 is connector; 9 is guide rod.

Embodiment

Below in conjunction with accompanying drawing structural principle of the present invention and principle of work are done further explain.

Referring to Fig. 1, high precision thicknessmeter of the present invention consists predominantly of microprocessor, display module, keyboard, differential transformer displace 3, stepper motor 1 and pressure transducer 4.Annexation between them is: the differential transformer secondary of differential transformer displace 3 is connected on the microprocessor through sample circuit, amplifying circuit and A/D change-over circuit successively, and the control end of stepper motor 1 is connected with microprocessor.Like Fig. 2; The output shaft of stepper motor 1 is connected with the upper end of the iron core a of differential transformer displace 3 through geared assembly 2; Geared assembly 2 can realize that geared assembly 2 specifically comprises a gear and a guide rod 9 by gear and tooth bar, and gear is located on the output shaft of stepper motor 1; The bar shaped tooth engagement that is provided with on itself and the guide rod 9; Guide rod 9 lower ends are fixedly connected with the upper end of iron core a, thereby stepper motor 1 rotates and drives guide rod vertical moving about in the of 9, thereby iron core a is moved up and down in coil.Pressure transducer 4 is located at the lower end of iron core a, and the signal output part of pressure transducer 4 is connected with microprocessor through the A/D change-over circuit, and the drive signal end of said sample circuit is also connected on the microprocessor.

Referring to Fig. 2; The lower end of iron core a is provided with the concave shape connector 8 of a back-off, and pressure transducer 4 is located in the connector 8, and the pressure-sensitive contact of pressure transducer 4 stretches out a connecting link 5 downwards; The lower end of this connecting link 5 is provided with a horizontal surface of contact 7, also has thick 6 of a horizontally disposed side under it.

In optimal case of the present invention, microprocessor (following general designation MCU) adopts the Atmegal6 single-chip microcomputer to realize.

Below introduce the principle of work of critical piece-differential transformer displace 3 of the present invention in detail:

Differential transformer displace 3 is made up of differential transformer and iron core a; For differential transformer, when iron core a was positioned at the center, two Secondary Winding mutual inductances were identical; The output voltage size of two secondary is identical; The defence line is opposite, because two Secondary Winding anti-phase series connection, thereby output voltage U.=0; When if iron core is not positioned at the centre position, the different output of mutual inductance electromotive force U ₂Non-vanishing.

As shown in Figure 4: as to load sinusoidal voltage U at primary coil _i, then the induced potential of secondary is:

$E=\frac{\mathrm{d\Φ}}{\mathrm{dt}}=\frac{\mathrm{Md}{I}_0}{\mathrm{dt}}---\left(1\right)$

In the following formula, M is the mutual inductance between former limit and secondary; I ₀Be electric current through primary coil; Φ is the total magnetic flux through secondary.

If I _MBe the current peak of primary coil, ω is the angular frequency of driving voltage, then:

$\frac{d_I}{\mathrm{dt}}=-\mathrm{j\ω}{I}_M{e-}^{\mathrm{j\ωt}}---\left(2\right)$

E＝-JωMI (3)

U _o=E ₂₁-E ₂₂=-j ω M ₁I ₀-(j ω M ₂I ₀)=j ω I ₀(M ₂-M ₁) (4) have according to the definition of mutual inductance:

${\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="HDA0000096522360000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_1=\frac{{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000096522360000011.png"\; state="\{\{state\}\}">N</figure-callout>}}_1{\mathrm{\&Phi;}}_1}{I_0},$ $M_2=\frac{N_2{\mathrm{\&Phi;}}_2}{I_0}---\left(5\right)$

If the number of turn of two secondary coils is identical, be the N circle, Φ ₁Be L ₂₁Magnetic flux, Φ ₂Be L ₂₂Magnetic flux, then have:

U _o＝ωN(Φ ₂-Φ ₁) (6)

$\mathrm{\&Phi;}=\frac{\mathrm{KB}}{\mathrm{hx}}---\left(7\right)$

In the formula, K is a constant; B is a magnetic induction density; H is an iron core thickness; X is the effective width of iron core in magnetic field.When iron core move up Δ x apart from the time, have:

${\mathrm{\&Phi;}}_1=\frac{\mathrm{KB}}{h(x+\mathrm{\&Delta;x})}$

${\mathrm{\&Phi;}}_2=\frac{\mathrm{KB}}{h(x-\mathrm{\&Delta;x})}---\left(8\right)$

Then: $U_o=\mathrm{\&omega;\; N}*(\frac{\mathrm{KB}}{h(x+\mathrm{\&Delta;\; x})}-\frac{\mathrm{KB}}{h(x-\mathrm{\&Delta;\; x})})=\frac{-2\mathrm{\&omega;\; NKB}}{h(x^2-\mathrm{\&Delta;}{x}^2)}*\mathrm{\&Delta;\; x}---\left(9\right)$

When Δ x＜＜during x, can be similar to and ignore Δ x ², then:

$U_o\&ap;\frac{-2\mathrm{\&omega;NKB}}{h{x}^2}*\mathrm{\&Delta;x}=K_1*\mathrm{\&Delta;x}---\left(10\right)$

In like manner: when iron core move down Δ x apart from the time, have:

$U_o\&ap;\frac{2\mathrm{\&omega;NKB}}{h{x}^2}*\mathrm{\&Delta;x}={-K}_1*\mathrm{\&Delta;x}---\left(11\right)$

When iron core is in the centre position, Δ x=0, U _o=0

The output characteristic curve of differential transformer displace is as shown in Figure 5, E among the figure ₂₁, E ₂₂Be respectively the output induction electromotive force of two Secondary Winding, solid line 1 is the ideal output characteristic of differential transformer displace, and the actual output characteristics of dotted line 2 expressions.E ₀Be expressed as remaining electromotive force at zero point, this is because the factors such as asymmetric and core center position that differential transformer is made cause.

Thicknessmeter of the present invention has utilized differential transformer secondary output voltage to become these characteristics of pure linear relationship to make with the distance X of iron core off-center position.And this differential transformer displace is 3 simple in structure, the measure linear scope is big, and metering circuit is reliable, highly sensitive and cheap.Therefore the thicknessmeter that adopts this way to make can improve measuring accuracy greatly.

Principle of work of the present invention is:

The control signal of sample circuit is provided by MCU, and after having received the order of MCU acquisition controlling, sample circuit can be gathered the secondary output voltage of differential transformer.And the electric signal of gathering usually is very little, need carry out processing and amplifying, and this function is realized by amplifying circuit.Signal is sent into the A/D change-over circuit and is carried out digital-to-analog conversion after amplifying, the digital signal after its conversion is sent into MCU handle, and the testing sample thickness that obtains is after treatment sent into display module show.

The course of work of the present invention is following:

When realizing the measurement of testing sample thickness; At first testing sample is positioned on the thickness measuring platform 6; MCU transmits control signal to stepper motor 1 then; The iron core a that drives differential transformer displace 3 by stepper motor 1 moves up and down, when surface of contact 7 does not touch testing sample, and pressure transducer 4 no-outputs.As iron core a during not in the centre position, the secondary of the differential transformer of anti-series (i.e. the first secondary coil c and second subprime coil d anti-series) voltage U _oNon-vanishing.The value that pressure transducer 4 is set on microprocessor through keyboard is pressure (its value is different with the difference of testing sample) current corresponding value or a magnitude of voltage; When iron core a moves down; When the value of feedback that touches testing sample and pressure transducer 4 at surface of contact 7 reached setting value, microprocessor (MCU) sent brake command to stepper motor 1 and carries out 5 seconds programs of time-delay simultaneously, and the time then; MCU sends sampling control signal to sample circuit; The control sampling thief reads the transformer output voltage, after amplifying circuit amplification and analog to digital conversion, sends into the conversion that MCU carries out voltage and thickness, at last conversion value is sent into display apparatus module and shows.

The present invention can come adjustment gaging pressure flexibly according to testing sample, is fit to various samples.As, when testing sample was leather, the pressure that requires every square centimeter of testing sample to bear was F ₁=500 ± 10g can be got by Fig. 3, and be research object with the sensor this moment, and the gravity of establishing guide rod and iron core is G, and pressure transducer 4 suffered pressure are F ₂, can get by condition of balance on force: F ₁=G+F ₂, can get pressure F thus ₂Value, so the setting value of pressure transducer is F ₂Corresponding voltage value or current value.

In sum, displacement measurement of the present invention adopts high-precision differential transformer displace, and the suffered pressure size of determinand can pass through to press key assignments, thereby realizes measuring the purpose of different determinand thickness; Can measure determinand thickness in the optional position, space, change the shortcoming that traditional thicknessmeter can only in the vertical direction be measured.Thicknessmeter output pressure control signal of the present invention in addition is to adopt PID control, the precision and the accuracy that when measuring automatically, can also improve sample thickness greatly.

Claims (4)

1. high precision thicknessmeter; Comprise microprocessor and be connected in display module and the keyboard on the microprocessor; It is characterized in that: also include differential transformer displace (3), stepper motor (1) and pressure transducer (4); The differential transformer secondary of said differential transformer displace (3) is connected on the microprocessor through sample circuit, amplifying circuit and A/D change-over circuit successively; The control end of said stepper motor (1) is connected with microprocessor; The output shaft of stepper motor (1) is connected with the upper end of the iron core (a) of differential transformer displace (3) through geared assembly (2), and said pressure transducer (4) is located at the lower end of iron core (a), and pressure transducer (4) is connected with microprocessor through the A/D change-over circuit; The drive signal end of said sample circuit is connected on the microprocessor.

2. high precision thicknessmeter according to claim 1; It is characterized in that: the lower end of said iron core (a) is provided with the concave shape connector (8) of a back-off; Said pressure transducer (4) is located in the connector (8); The pressure-sensitive contact of pressure transducer (4) stretches out a connecting link (5) downwards, and the lower end of said connecting link (5) is provided with a horizontal surface of contact (7), also has thick of a horizontally disposed side (6) under the horizontal surface of contact (7).

3. high precision thicknessmeter according to claim 1 is characterized in that: said microprocessor adopts the Atmega16 single-chip microcomputer.

4. high precision thicknessmeter according to claim 1 is characterized in that: said geared assembly (2) is made up of gear and tooth bar.

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