CN2854506Y - Electric balance differential capacitance minimeter - Google Patents

Abstract

The utility model discloses a new balance-type differential condenser micrometer, wherein, a cylindrical capacitor moving plate is inserted into a cylindrical capacitor measuring plate and the capacitor moving plate is inserted with a central plate and one end of the outer casing of central plate exceeding the moving plate is positioned with a reference plate with standard capacitor. Such end of the central plate is connected with a charge amplifier and measuring circuit and a LabVIEW device, while the LabVIEW device is connected with the reference plate with standard capacitor. The other end of the center plate, namely the moving plate, is connected with the measuring lever. Measuring plate connects the excitation voltage, while the moving plate connects the grounding. The beneficial effect of the utility model is: the systematic measurement is more stable and reliable so that the measuring system is higher in precision and sensitivity to realize the automatization, promptness and intelligentization of capacitor micrometer and to let the application of capacitor micrometer perfect.

Description

Novel electrobalance formula differential capacitor dial gauge

Technical field:

The utility model relates to measuring technique, is a kind of dial gauge, specifically, is a kind of novel electrobalance formula differential capacitor dial gauge

Background technology:

Capacitance gage is the very high surveying instrument of a kind of precision requirement, the automatization level of existing capacitance gage is lower, do not have real time implementation and intelligent functions yet, especially the stability of system testing and reliability are not ideal enough, thereby the precision of test macro and sensitivity all are affected, are difficult to the requirement that reaches higher.

Summary of the invention:

The purpose of this utility model provides a kind of system testing and has more stability and reliability, the test macro precision is higher, sensitivity is also higher thereby make, and has realized robotization, real time implementation and the intelligentized novel electrobalance formula differential capacitor dial gauge of capacitance gage.

Technical solution of the present utility model is: a kind of novel electrobalance formula differential capacitor dial gauge, it is characterized in that: the capacitance measurement pole plate that tubular is arranged, be fitted with the electric capacity movable plate electrode of tubular in the measuring pad, be fitted with the center pole plate in the electric capacity movable plate electrode, an end that exceeds movable plate electrode of center pole plate is set with the reference pole plate of reference capacitance outward, this end of center pole plate is connected with the LabVIEW device through charge amplifier and metering circuit, the LabVIEW device is connected with the reference pole plate of reference capacitance in addition, the movable plate electrode end at the other end place of center pole plate connects measuring staff, measuring pad connects driving voltage, movable plate electrode ground connection.

The capacitance measurement pole plate of the tubular described in the utility model has two sections that are not connected, and two sections measuring pads connect positive and negative driving voltage respectively.Reference capacitance C ₂The reference pole plate connect signal conditioning circuit in the LabVIEW device, and connect the center pole plate through metering circuit and charge amplifier, movable plate electrode connects measuring staff.The LabVIEW device is made up of the display of signal conditioning circuit, signal acquisition circuit and PC.A rp-op amp is arranged in the charge amplifier, and its inverting input is connected to the center pole plate.Adopt the integral instrument amplifier in the metering circuit.

The beneficial effects of the utility model are: system testing has more stability and reliability, and the test macro precision is higher, sensitivity is also higher thereby make.Robotization, real time implementation and the intellectuality of capacitance gage have been realized.Make the application in practice of capacitance gage more attain perfection.

Below in conjunction with drawings and Examples the utility model is further described:

Description of drawings:

Fig. 1 is the structural representation of a kind of novel electrobalance formula differential capacitor dial gauge of the present utility model;

Fig. 2 is the electrical schematic diagram of the charge amplifier in the novel electrobalance formula differential capacitor dial gauge of the present utility model;

Fig. 3 is the metering circuit figure in the novel electrobalance formula differential capacitor dial gauge of the present utility model;

Fig. 4 is the electrical schematic diagram of novel electrobalance formula differential capacitor dial gauge of the present utility model;

Fig. 5 is the process flow diagram of the LabVIEW in the novel electrobalance formula differential capacitor dial gauge of the present utility model.

Embodiment:

Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 have described an embodiment of the present utility model jointly.

The hardware configuration of electrobalance formula differential capacitor dial gauge is seen Fig. 1.Can be divided into micrometer head and metering circuit two parts.Signal condition 8 belongs to the hardware circuit of LabVIEW, can use modules such as SCXI-1200, SCXI-1100, SCXI-1122.It is cylindric that micrometer head is, by reference capacitance C ₂And capacitor C _S1, C _S2The differential capacitor that makes up combines.The fixed plate of differential capacitor is measuring pad 1 and center pole plate 2; C ₂Be made up of reference pole plate 3 and center pole plate 2, electric capacity is constant.1 of the measuring pad of differential capacitor inserts movable plate electrode 4, and movable plate electrode 4 ground connection have the electrostatic screening function.Driving voltage U ₁With-U ₁Be anti-phase each other and same, act on differential capacitor C respectively frequently with the square wave constant pressure source of the width of cloth _S1, C _S2Measuring pad 1 on, U ₂Be reference capacitance C ₂Excitation power supply, also be square wave, frequency and U ₁Identical, but U ₂Amplitude follow the displacement of measuring staff 5 and change.So U ₂It is variable.

Charge amplifier 6 is front end circuits of metering circuit 7.It becomes voltage signal with charge conversion.Circuit adopts the rp-op amp device.

Metering circuit 7 is the integral instrument amplifier, and this amplifier has characteristics such as low in energy consumption, that precision is high, noise is low.

The measuring principle of electrobalance formula differential capacitor dial gauge as shown in Figure 4, this is a closed loop charge balance equation measuring system as we can see from the figure, feedback mechanism is reference capacitance C ₂

Comprise rp-op amp 11, integral instrument amplifier (AD620), resistance R, R1, capacitor C among Fig. 2, Fig. 3 ₂, C _S1, C _S2Deng.

6 is charge amplifier among Fig. 4, and 7 is metering circuit, and 8 is modulate circuit, and 9 is signal acquisition circuit, and 10 is display.In also comprise capacitor C ₂, C _S1, C _S2Deng.

At synchronization, driving voltage ± U ₁And U ₂Act on the measuring pad and the reference capacitance C of differential capacitor respectively ₂The reference pole plate on, the specific inductive capacity of establishing capacitor dielectric is ε, during as initial zero-bit, differential capacitor C _S1=C _S1 ^*, C _S2=C _S2 ^*, its urceolus internal diameter is D, the external diameter of center pole plate is d.When the measuring staff displacement x, then the differential capacitor electric capacity is

$C_{S1}=C_{S1}^{*}\±\frac{2\mathrm{\π\ϵx}}{\ln (D/d)}---\left(1\right)$

${\mathrm{<figure-callout\; id="2"\; label="C\; S"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">C</figure-callout>}}_S={\mathrm{<figure-callout\; id="2"\; label="C\; S"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">C</figure-callout>}}_S^2\&PlusMinus;\frac{2\mathrm{\&pi;\&epsiv;x}}{\ln (D/d)}---\left(2\right)$

By formula (1), (2) displacement of following measuring staff of differential capacitor electric capacity as can be known make linear change, are the functions of x.When movable plate electrode is in the geometric center position of differential capacitor, C _S1=C _S2, because the same same width of cloth frequently of their driving voltage, but anti-phase each other, so the electric charge of responding on the pole plate of center is respectively Q _S1With-Q _S2, establish by C this moment _S1And C _S2The quantity of electric charge that the differential capacitor that makes up is responded on the pole plate of center is Q ₁, Q then ₁=Q _S1-Q _S2=0.Because dielectric losses such as differential capacitor air are little, residual charge is almost nil for dial gauge processing precise, so zero point in addition.Amplify though metering circuit is carried out high power, instrument still has very high sensitivity and precision; The symmetry error that compensates caused effectively of structure.As movable plate electrode right lateral, Q ₁＞0 is regularity, and left lateral then is negative then property.Reference capacitance C ₂Capacity be definite value, its excitation power supply U ₂Be the function of measuring staff displacement, phase place also changes.Q ₁During for positive charge, since the inverting function of charge amplifier, U ₂Be negative value, Q ₂Be negative charge; Q ₁During for negative charge, Q ₂Be positive charge.If the total amount of induced charge is Q on the pole plate of center ₃, during system balancing, Q ₃Be zero, then have

U ₁(C _S1-C _S2)＝U ₂C ₂ (3)

This moment charge amplifier output U ₀Also be zero.When the measuring staff displacement, the differential capacitor linear change, the balance of system is broken.Q ₃≠ 0, convert voltage signal U to through charge amplifier ₀, input to metering circuit and signal conditioning circuit, then with original driving voltage U ₂ ^*Stack, U at this moment ₂=U ₂ ^*+ Δ U ₂, U ₂Amplitude change the power on total amount Q of lotus of final center pole plate ₃Belong to zero heavily again, the balance that measuring system promptly becomes new.Get by formula (1), (2), (3)

$U_1(C_{S1}^{*}-{\mathrm{<figure-callout\; id="2"\; label="C\; S"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">C</figure-callout>}}_S^2\&PlusMinus;\frac{4\mathrm{\&pi;\&epsiv;x}}{\ln (D/d})=({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^{*}+\mathrm{\&Delta;}{U}_2)C_2---\left(4\right)$

System is when new position balance

$U_1(C_{S1}^{*}-{\mathrm{<figure-callout\; id="2"\; label="C\; S"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">C</figure-callout>}}_S^2)={\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^{*}{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">C</figure-callout>}}_2,$ So

$\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">U</figure-callout>}}_2=\&PlusMinus;\frac{4U_1\mathrm{\&pi;\&epsiv;}/\ln (D/d)}{C_2}x---\left(5\right)$

U ₁, C ₂, D, d be constant, so U ₂Displacement x with measuring staff is made linear change."+" number expression movable plate electrode initial position is when the geometric center position of differential capacitor in the formula, U during the measuring staff right lateral ₂Variable quantity; "-" number expression movable plate electrode U during the measuring staff left lateral under above-mentioned operating mode ₂Variable quantity.Dial gauge has the function of identification measuring staff direction of motion.The sensitivity that is got direction finder by formula (5) is

$S_1=\left|\frac{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">U</figure-callout>}}_2}{\mathrm{\&chi;}}\right|=\frac{4U_1\mathrm{\&pi;\&epsiv;}/\ln (D/d)}{C_2}---\left(6\right)$

Because measuring electric capacity is difference structure, so eliminated the even item in the output, kept odd item, the linearity improves greatly.Adopt one pole mode, then its output as capacitance gage

$\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">U</figure-callout>}}_2=\frac{-2U_1\mathrm{\&pi;\&epsiv;}/\ln (D/d)}{C_2}x---\left(7\right)$

Sensitivity is

$S_1=\left|\frac{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="Y20052007802500081.png"\; state="\{\{state\}\}">U</figure-callout>}}_2}{\mathrm{\&chi;}}\right|=\frac{2U_1\mathrm{\&pi;\&epsiv;}/\ln (D/d)}{C_2}---\left(8\right)$

In the high-order term of output, contain even-order harmonic, so linearity relative mistake is a little.Can know from formula (5), (6), (7), (8), novel differential capacitor dial gauge has improved 1 times than the sensitivity of monopolar type capacitance gage, and the linearity also is greatly improved.

After the non-electric charge quantity signalling of novel differential capacitor dial gauge converted electric signal output to, the software platform by LabVIEW detected.The output signal one tunnel of metering circuit inputs to the signal regulating device of LabVIEW, carries out isolation, the filtering of sensor signal, formation voltage signal U ₂, another road feeds back to C ₂Make up closed-loop system.Utilizing wavelet packet to carry out filtering is a vital link.When the wavelet packet algorithm makes LabVIEW handle the data of large amount of complex not only accurately but also quick.Improved the speed and the precision of A/D conversion greatly, system testing has more stability and reliability, and the test macro precision is higher, sensitivity is also higher thereby make.

Data collecting card adopts PCI-6024E, and it carries out the A/D conversion to the signal from signal conditioner, and sampling keeps, thereafter the program code by LabVIEW to digital signal analyze, computing, storage and demonstration.The displacement measurement program is the displacement measurement virtual instrument software of developing on the LabVIEW platform.Fig. 5 is the program circuit of LabVIEW.

The characteristics of new Type Charge Balance Differential Capacitance Micrometer of the present utility model are:

(1) utilizes feedback control technology to combine with differential capacitor and make up closed loop electric equilibrium formula sensing Device. With Open-loop sensors other being arranged is to have increased feedback element, has constructed the feedback-Department of Survey of closed loop System.

(2) detection system is used the hardware and software development platform of LabVIEW. LabVIEW makes Substitute text language with a kind of graphical language, programing work is very convenient, with the hardware system perfect adaptation, For high accuracy, high-sensitivity measurement are established rich basis.

(3) can test bidirectional displacement, any position zero setting in total travel.

The sensing system of Novel differential capacitance gage of the present utility model is as nuclear take differential capacitor Heart device, and detection system is the carrier of computer as LabVIEW, both perfect adaptations, real Automation, real time implementation and the intellectuality of capacitance gage have been showed. LabVIEW has powerful fortune The Presentation Function of calculation ability and data, curve, image and printing function make the reality of capacitance gage Trample application and more attain perfection.

Claims (6)

1, a kind of novel electrobalance formula differential capacitor dial gauge, it is characterized in that: the capacitance measurement pole plate that tubular is arranged, be fitted with the electric capacity movable plate electrode of tubular in the measuring pad, be fitted with the center pole plate in the electric capacity movable plate electrode, an end that exceeds movable plate electrode of center pole plate is set with the reference pole plate of reference capacitance outward, this end of center pole plate is connected with the LabVIEW device through charge amplifier and metering circuit, the LabVIEW device is connected with the reference pole plate of reference capacitance in addition, the movable plate electrode end at the other end place of center pole plate connects measuring staff, measuring pad connects driving voltage, movable plate electrode ground connection.

2, novel electrobalance formula differential capacitor dial gauge according to claim 1, it is characterized in that: the capacitance measurement pole plate of tubular has two sections that are not connected, and two sections measuring pads connect positive and negative driving voltage respectively.

3, novel electrobalance formula differential capacitor dial gauge according to claim 2 is characterized in that: reference capacitance C ₂The reference pole plate connect signal conditioning circuit in the LabVIEW device, and connect the center pole plate through metering circuit and charge amplifier, movable plate electrode connects measuring staff.

4, according to claim 1,2 or 3 described novel electrobalance formula differential capacitor dial gauges, it is characterized in that: the LabVIEW device is made up of signal conditioning circuit, signal acquisition circuit and display.

5, according to claim 1,2 or 3 described novel electrobalance formula differential capacitor dial gauges, it is characterized in that: a rp-op amp is arranged in the charge amplifier, and its inverting input is connected to the center pole plate.

6, according to claim 1,2 or 3 described novel electrobalance formula differential capacitor dial gauges, it is characterized in that: adopt the integral instrument amplifier in the metering circuit.

Images