CN101608928B - Detection method for detecting physical quantity to be detected based on general capacitor and detection system thereof - Google Patents

Abstract

The invention discloses a detection method for detecting physical quantity to be detected based on a general capacitor and a detection system thereof; and the general capacitor is composed of an actual electrode and a virtual electrode, the actual electrode is one or more electrified metal conductors and the virtual electrode is a space at an infinite distance. Changes of the physical quantity to be detected of an object between the actual electrode and the virtual electrode can result in change of a capacitance value of the general capacitor or change of the physical quantity related to the capacitance value, and changes of the physical quantity of the object to be detected can be detected by measuring the capacitance value or the related physical quantity of the general capacitor. The detection method and the detection system overcome problems of difficulties in designing, arranging or manufacturing one of the electrodes of the capacitor in certain occasions, and provide a novel configuration and design method of a capacitor in a capacitive sensor.

Description

A kind of method and detection system of carrying out the measured physical quantity detection based on general capacitor

Technical field

The invention belongs to signalling arrangement and detection range, the formation of capacitor and method for designing, a kind of measured physical quantity detection method and detection system of carrying out in particularly a kind of capacitance type transducers based on this capacitor.

Background technology

Capacitor is a kind of circuit devcie in order to temporary transient store charge, generally by two or multi-disc by dielectric separately and the metal electrode of insulation form.When the distance between all metal electrodes was finite value, this capacitor can be called ordinary capacitor; When wherein at least one plate electrode and other distance between electrodes were the infinite distance, this capacitor can be called general capacitor.Electrode nearer with respect to the observer in the general capacitor is necessary in esse electrode, is called virtual electrode; Be the electrode of infinite distant place with respect to the observer in the general capacitor, can think not exist, or the electrode of virtual presence, dummy electrodes be called.In other words, general capacitor is made up of virtual electrode and dummy electrodes.Capacitor in the current capacitance type transducers is ordinary capacitor, comprises two or more virtual electrode, and does not comprise dummy electrodes.Like 200710057356.9 dual inside-and-outside ring capacitance sensors announced, include ring in and outer shroud two electrodes as electric capacity.At 200710305370.6 electrostatic capacitance sensors mentioned, its capacitor is made up of signal electrode and bias electrode.Tubular type capacitive transducer in 89219440.5 announcements is two electrodes that are made up of electric capacity emitter tube and receiving pole tube.

General capacitor is the same with ordinary capacitor, also possibly be that a plurality of electrodes constitute.As being to constitute electric capacity by the electrode more than three by the capacitor in the 97111084.0 known multielectrode capacitance sensors.By the general capacitor that a plurality of electrodes constitute, it is dummy electrodes that an electrode is wherein arranged.At some special occasions, when a certain electrode of ordinary capacitor is difficult to design or makes or install, just bring obstacle for the application of capacitive transducer.At this moment, the building method of Applying Generalized electric capacity comes design capacitance, is used as dummy electrodes to the electrode that is difficult to design or make or install, thereby the principle that can use capacitive transducer is carried out the detection of physical quantity to be measured.

Summary of the invention

Based on existing state of the art, the object of the present invention is to provide and a kind ofly carry out the method that physical quantity to be measured detects based on general capacitor, have simple in structure, easy for installation, advantage of wide range of application.

The following technical scheme of the concrete employing of the present invention:

A kind ofly carry out the method that the measured physical quantity of target object detects based on general capacitor, said general capacitor be by one or more charged objects as virtual electrode, the space of infinite distant place constitutes as dummy electrodes is common; Said physical quantity to be measured is meant the amount of the portrayal target object proterties that can detect through capacitance type transducers, and this method detects physical quantity to be measured according to the variation of general capacitor capacitance, it is characterized in that, said method comprising the steps of:

(1) design virtual electrode, said virtual electrode can be the metal polar plate of one or more conductions;

(2) choose dummy electrodes, said dummy electrodes is the space of infinite distant place;

(3) the original capacitance value of the said general capacitor of estimation, the original capacitance value of said general capacitor when not having target object between estimation virtual electrode and the dummy electrodes;

(4) confirm corresponding relation, estimation is also measured the corresponding relation of numerical value of capacitance of numerical value and the general capacitor of the measured physical quantity be in the target object between virtual electrode and the dummy electrodes, and the match relation curve;

(5) measure when having target object between virtual electrode and the dummy electrodes, because the variable quantity of the capacitance of the general capacitor that variation caused of measured physical quantity;

(6) obtain the numerical value of variable quantity of numerical value or the physical quantity to be measured of physical quantity to be measured according to the relation curve of the variable quantity of step (5) measured capacitance value and the match in the step (4).

The general capacitor that a kind of measured physical quantity that is used for target object detects; When target object as for said capacitor in the time, utilize the variation of the capacitance of general capacitor to detect measured physical quantity, said general capacitor is made up of two or more electrodes; Wherein having an electrode at least is virtual electrode; Having an electrode at least is dummy electrodes, and said virtual electrode can be the metal polar plate of one or more conductions, and said dummy electrodes is the space of infinite distant place.

The present invention also discloses a kind of detection system of carrying out the measured physical quantity detection of object based on general capacitor simultaneously; Said detection system comprises general capacitor, electric capacity/voltage transformation module, signal processing module, analog to digital conversion and the display module that is made up of virtual electrode and dummy electrodes, it is characterized in that:

The output of the capacitance value measuring apparatus of said general capacitor links to each other with the input of said electric capacity/voltage transformation module; The output of said electric capacity/voltage transformation module links to each other with the input end of signal processing module, and the output terminal of said signal processing module links to each other with the input end of said analog to digital conversion and display module;

Said general capacitor is as the transformation device of physical quantity to be measured, the conversion of the measured physical quantity of target object converted to the conversion of the capacitance of said general capacitor; Through electric capacity/voltage transformation module, the capacitance of measured general capacitor is transformed into magnitude of voltage and is input to signal processing module; In said signal processing module, the voltage signal that electric capacity/voltage transformation module is exported carries out filtering, processing and amplifying; At last through analog to digital conversion and display module, convert the voltage signal of analog quantity the voltage signal of digital quantity to, and voltage signal is shown.

The invention has the beneficial effects as follows; Overcome an electrode design, the installation in some occasion capacitor or made difficult obstacle; The structure of capacitor in a kind of novel capacitive transducer and the method for design are provided, have had advantage easy for installation, simple in structure and applied widely.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention is done further explain; But a kind of method of carrying out physical quantity to be measured based on general capacitor of the present invention is not limited to embodiment.

Fig. 1 is the synoptic diagram of general capacitor among the present invention.

Fig. 2 utilizes general capacitor to carry out the functional block diagram of the detection system of physical quantity detection among the present invention.

Fig. 3 is the virtual electrode of general capacitor in the present embodiment.

Fig. 4 is the installation site synoptic diagram of virtual electrode on automatically-controlled door of general capacitor in the present embodiment.

Fig. 5 utilizes general capacitor to carry out the circuit theory diagrams of the detection system of physical quantity detection among the present invention.

Fig. 6 is the relation curve of the capacitance of general capacitor in the present embodiment with variable in distance between target object and the virtual electrode.

Embodiment

Of the present inventionly a kind ofly carry out the method that physical quantity to be measured detects, comprise the design virtual electrode, choose the demarcation of the estimation of dummy electrodes, original capacitance value, physical values to be measured and five processes such as aftertreatment of detection signal based on general capacitor.

A. design virtual electrode.Said virtual electrode is meant in the general capacitor nearer from the observer, in esse electrode.Need to combine capacitance type transducers to carry out physical quantity to be measured and detect occasion, condition and the purpose of using, material, size, shape and the quantity etc. of design virtual electrode.Such as, under the environment that poisonous gas exists, need avoid material during the material of selection virtual electrode with poisonous gas generation chemical reaction.The size of virtual electrode not only need be considered to improve the sensitivity that measured physical quantity detects, and also need combine field erected condition to weigh.Such as, obstacle distance detects when carrying out reversing automobile based on broad sense electric capacity, and the size of virtual electrode will be avoided excessive outward appearance and kinetic balance characteristic to influence automobile as far as possible.The size of virtual electrode has specific (special) requirements in some occasion, therefore needs to design to on-the-spot condition.Such as, carrying out detection of dynamic for the gas content of oil gas two-phase flow in the oil pipeline, the shape of virtual electrode should have similarity with the shape of pipeline in the broad sense capacitive transducer, is designed to the part of tubulose or tubulose as far as possible.In addition, at some special occasions, sensitivity and precision in order to improve detection can design a plurality of virtual electrode.These virtual electrode and dummy electrodes all can constitute broad sense electric capacity.Such as, when the capacitance type transducers that utilizes broad sense electric capacity detects solid disperse fraction of particle in the limited confined space, can design a plurality of virtual electrode that are parallel to each other, to improve sensitivity and the precision that detects.

B. choose dummy electrodes.Be in the electrode of infinite distant place in the general capacitor with respect to the observer, can think not exist that perhaps the electrode of virtual presence is called dummy electrodes.In general capacitor, the space of choosing infinite distant place is a dummy electrodes.

C. estimate the original capacitance value.When not having target object between virtual electrode and the dummy electrodes, the original capacitance value of general capacitor can be according to definition C=Q/U or its formula C=2W that derives of capacitor intrinsic capacitance value _e/ U ²Or C=Q ²/ (2W _e) estimate.Wherein C is the capacitance of general capacitor, unit: F (farad); Q is the quantity of electric charge on the virtual electrode, unit: C (enclosed pasture); U is the current potential of virtual electrode with respect to the earth, unit: V (volt); W _eBe the electrostatic energy that stores in the general capacitor, unit: J (joule).Comparatively practical evaluation method can be estimated through two-dimensional electromagnetic field analysis software Ansoft Maxwell or other electromagnetical analogies software.Its evaluation method is at first to set up the Electromagnetic Simulation model that comprises virtual electrode and dummy electrodes, through model is carried out the characteristic equation that relevant electric capacity is set up in finite element analysis, and then carries out the size that numerical evaluation obtains capacitance.This capacitance is the estimated value of original capacitance value actual size.

D. confirm corresponding relation.Estimation is also measured the corresponding relation of numerical value of capacitance of numerical value and the general capacitor of the measured physical quantity be in the target object between virtual electrode and the dummy electrodes, and the match relation curve.The physical characteristics of the target object between virtual electrode and the dummy electrodes is (like the composition of target object; The temperature of target object; The size of target object or target object are with respect to the distance of virtual electrode) when changing, the capacitance of general capacitor can change thereupon.Dielectric physical characteristics parameter promptly is the measured physical quantity of target object.Adopt evaluation method among the above-mentioned steps c to having target object between virtual electrode and the dummy electrodes, and its physical characteristics when changing the size and the capacitance variation amount of capacitance estimate.Through enough repeatedly changing the size of the physical characteristics parameter of target object, can obtain the data of one group of corresponding capacitance.Utilize the method for data fitting, can obtain the measured physical quantity of target object and the corresponding relation curve between the capacitance.Carry out actual measurement to limited unique point in the matched curve scope (maximal value, minimum value and the relation curve that comprises the physical characteristics parameter changes the physical characteristics parameter value corresponding when comparatively violent) again, and relation curve is revised according to measurement result.Revised physical characteristics parameter and capacitance corresponding relationship curve promptly can be as the calibration curves of corresponding relation between measured physical quantity and the capacitance.

E. measure capacitance.Measure when having target object between virtual electrode and the dummy electrodes, because the variable quantity of the capacitance of the general capacitor that variation caused of target object measured physical quantity.

F. obtain the numerical value of variable quantity of numerical value or the physical quantity to be measured of target object physical quantity to be measured according to the corresponding relation relation curve of confirming in the variable quantity of step e measured capacitance value and the steps d.

The present invention utilizes general capacitor to carry out physical quantity to be measured and detects, and wherein the principle of general capacitor is:

General capacitor as shown in Figure 1 is made up of two concentric spherical pole plates.The radius of sphere pole plate 1 is R ₁, institute's carried charge is+q; The radius of another sphere pole plate 2 is R ₂, carried charge is-q.Two sphere pole plates 1 and 2 are respectively that radius is R ₁And R ₂The part of concentric spherical, have identical solid angle ω.The surface density of charge of sphere pole plate 1 is

under the situation of CONSIDERING EDGE effect not; According to Gauss theorem, the electric field intensity that can try to achieve sphere pole plate 1 outer distance centre of sphere r place is:

$E=\frac{1}{4{\mathrm{\&pi;\&epsiv;}}_0}\frac{\frac{q}{\mathrm{\&omega;}{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009101043319E00022.png,H2009101043319E00032.png"\; state="\{\{state\}\}">R</figure-callout>}}_1^2}\&times;4{\mathrm{\&pi;<figure-callout\; id="1"\; label="R"\; filenames="H2009101043319E00022.png,H2009101043319E00032.png"\; state="\{\{state\}\}">R</figure-callout>}}_1^2}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2009101043319E00011.png,H2009101043319E00022.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}=\frac{q}{{\mathrm{\&omega;\&epsiv;}}_0{r}^2}---\left(1\right)$

Then the potential difference (PD) between sphere pole plate 1 and the sphere pole plate 2 is:

$U={\&Integral;}_{R_1}^{R_2}E\left(r\right)\mathrm{dr}={\&Integral;}_{R_1}^{R_2}\frac{q}{{\mathrm{\&omega;\&epsiv;}}_0{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="H2009101043319E00011.png,H2009101043319E00022.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}\mathrm{dr}=\frac{q}{{\mathrm{\&omega;\&epsiv;}}_0}(\frac{1}{R_1}-\frac{1}{R_2})---\left(2\right)$

Electric capacity between sphere pole plate 1 and the sphere pole plate 2 is:

$C=\frac{q}{U}={\mathrm{\&omega;\&epsiv;}}_0\frac{R_1{R}_2}{R_1+R_2}---\left(3\right)$

Hence one can see that, when the radius R of sphere pole plate 2 ₂During →+∞, the electric capacity between sphere pole plate 1 and the sphere pole plate 2 is C → ω ε ₀R ₁

Therefore, when the electric capacity between sphere pole plate 1 and the sphere pole plate 2 changes, can think between sphere pole plate 1 and the sphere pole plate 2 dielectric since specific inductive capacity change and cause.Dielectric 3 occurs, near, away from, disappear or water cut increase etc. all can cause the variation of specific inductive capacity.Dielectric average dielectric constant is by ε ₀Become ε ' ₁At this moment, the capacitor C between sphere pole plate 1 and the sphere pole plate 2 ' → ω ε ' ₁R ₁As long as physical quantity to be measured causes dielectric specific inductive capacity to change, all can cause the change in dielectric constant between sphere pole plate 1 and the sphere pole plate 2, thereby cause corresponding capacitance variations.This changes in capacitance can be confirmed through the capacitance of Measurement of capacitor, also can confirm like electric charge, current potential, electric energy, magnetic energy, electromagnetic energy and Li Lai through measuring the physical quantity relevant with capacitance.

Fig. 2 utilizes general capacitor to carry out the detection system that physical quantity detects among the present invention, comprising:

General capacitor, said general capacitor be by one or more charged objects as virtual electrode, the space of infinite distant place constitutes as dummy electrodes is common;

Electric capacity/voltage conversion circuit, when near the measured physical quantity of the object under test being in broad sense electric capacity changed, the capacitance of general capacitor can change, and described electric capacity/voltage conversion circuit converts the variable quantity of capacitance into voltage variety;

Signal processing circuit, for degree of accuracy and the sensitivity that improves metering circuit, said amplifying circuit can amplify the output voltage values ratio of electric capacity/voltage conversion circuit;

Analog to digital conversion circuit, analog-digital conversion circuit as described can convert the analog voltage signal of amplifying circuit output to digital signal output.

The said circuit theory diagrams that utilize general capacitor to carry out the detection system that physical quantity detects are as shown in Figure 5.

Said electric capacity/voltage conversion circuit comprises that (first integrated chip in the present embodiment is the CAV424 of German AMG Co. to first integrated chip, and its driving voltage is+5V), resistance R 1, resistance R 2, resistance R 3, resistance R 4, resistance R 5, resistance R 6, capacitor C 1, capacitor C 2, capacitor C 3, capacitor C 4.Said resistance R 1 be connected on first integrated chip pin 11 and+the 5V driving power between; Said resistance R 2 is connected between the pin 3 and ground of first integrated chip; Said resistance R 3 is connected between the pin 2 and ground of first integrated chip, and said resistance R 4 is connected between the pin 1 and ground of first integrated chip, and said resistance R 5 is connected between the pin 4 and pin 5 of first integrated chip; Said resistance R 6 is connected between the pin 4 and pin 6 of first integrated chip; Said capacitor C 1 is connected between the pin 12 and ground of first integrated chip, and said capacitor C 2 is connected between the pin 13 and ground of first integrated chip, and said capacitor C 3 is connected between the pin 15 and ground of first integrated chip; Said capacitor C 4 is connected between the pin 16 and ground of first integrated chip; The pin 10 of said first integrated chip directly links to each other with ground, and the pin 14 of the virtual electrode of said broad sense electric capacity and first integrated chip links to each other, the pin 5 of said first integrated chip and two difference output ports of pin 6 as electric capacity/voltage conversion circuit.

The principle of work of said electric capacity/voltage conversion circuit is: the first integrated chip inside is one and confirms that by capacitor C 1 reference oscillator of frequency controlling the integrator of the constant symmetric construction identical with the cycle of two phase places.The amplitude of these two integrators confirms with Cx through capacitor C 4, C4 electric capacity (also can be used as Measurement of capacitor sometimes) as a reference here, and Cx is as Measurement of capacitor.Relatively the voltage amplitude difference of two integrators just can provide the relative capacitance variations difference of capacitor C 4 and Cx.This differential signal converts d. c. voltage signal to through a second-order low-pass filter and exports through the adjustable differential signal output stage of output.As long as the simple adjustment first integrated chip outside element seldom just can change the filter constant and the enlargement factor of low-pass filter.This metering circuit can be measured 5% to 100% variation capacitance of reference capacitance value.The inner reference oscillator of first integrated chip charges and discharge to external oscillator capacitor C 1 and the inner additional capacitor of first integrated chip, and the value of the capacitance of C1 is approximate according to following formula:

C ₁＝1.6C ₄ (4)

Wherein C4 is the reference capacitance value.

The reference oscillator electric current I _OSCThe reference voltage V that is connect by outer meeting resistance R4 and first integrated chip the 6th pin _MConfirm:

$I_{\mathrm{osc}}=\frac{V_M}{R_4}---\left(5\right)$

The frequency of reference oscillator is:

$f_{\mathrm{OSC}}=\frac{{\mathrm{<figure-callout\; id="2"\; label="I\; osc"\; filenames="H2009101043319E00011.png,H2009101043319E00022.png"\; state="\{\{state\}\}">I</figure-callout>}}_{\mathrm{osc}}}{2\&CenterDot;{\mathrm{\&Delta;V}}_{\mathrm{OSC}}\&CenterDot;({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="H2009101043319E00022.png,H2009101043319E00032.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_{\mathrm{OSC},\mathrm{PAR},\mathrm{INT}}+C_{\mathrm{OSC},\mathrm{PAR},\mathrm{EXT}})}---\left(6\right)$

Wherein, Δ V _OSCBe the peak valley voltage difference of reference oscillator, this value is 2.1V by the internal resistance decision of first integrated chip.

The differential voltage of first integrated chip output

$V_{\mathrm{DIFF}}=G_{\mathrm{LP}}\&CenterDot;V_{\mathrm{DIFF},0}=G_{\mathrm{LP}}\&CenterDot;\frac{3}{8}\&CenterDot;(V_{C4}-V_{\mathrm{CX}})---\left(7\right)$

Enlargement factor wherein

$G_{\mathrm{LP}}=1+\frac{R_5}{R_6}---\left(8\right)$

The relevant electrical equipment parameter of said electric capacity/voltage conversion circuit is:

Electrical equipment	Parameter
		Resistance R
1	50Ω
		Resistance R
2	500kΩ
		Resistance R
3	500kΩ
		Resistance R
4	250kΩ
		Resistance R
5	75kΩ
		Resistance R
6	75kΩ
		Capacitor C
1	16pF
		Capacitor C
2	2000pF
		Capacitor C
3	2000pF
		Capacitor C
4	13pF

As shown in Figure 5, said signal processing circuit comprises second integrated chip (second integrated chip in the present embodiment is the AD8138 of U.S. ADI company, and its driving voltage is 5V), resistance R 7, resistance R 8, resistance R 9, resistance R 10, capacitor C 5.Said resistance R 7 is connected between the pin 8 of pin 6 and second integrated chip of first integrated chip; Said resistance R 8 is connected between the pin 1 of pin 5 and second integrated chip of first integrated chip; Said resistance R 9 is connected between the pin 8 and pin 5 of second integrated chip; Said resistance R 10 is connected between the pin 1 and pin 4 of second integrated chip, and said capacitor C 5 is connected between the pin 2 and ground of second integrated chip, and the power supply of the pin 3 of said second integrated chip and+5V directly links to each other; The pin 6 of said second integrated chip directly links to each other with ground, the pin 4 of said second integrated chip and two difference output ports of pin 5 as amplifying circuit.

Second integrated chip can carry out exporting with the form of differential signal behind the linear amplification to differential signal in the said signal processing circuit.Its enlargement factor depends on the ratio of resistance R 9 and R7 or R10 and R8.It is enlargement factor

$G_{\mathrm{DI}}=\frac{R_9}{{\mathrm{<figure-callout\; id="7"\; label="R"\; filenames="H2009101043319E00022.png"\; state="\{\{state\}\}">R</figure-callout>}}_7}=\frac{R_{10}}{R_8}---\left(9\right)$

The relevant electrical equipment parameter of said signal processing circuit is:

Electrical equipment	Parameter
		Resistance R
7	499Ω
		Resistance R
8	499Ω
		Resistance R 9	1000Ω
Resistance R
	10	1000Ω
Capacitor C
	5	100pF

Below for using a specific embodiment of the principle of the invention, present embodiment is used the capacitance type transducers based on general capacitor, measures the distance of biosome and automatically-controlled door.The measurement result of present embodiment can be used as the basis for estimation whether automatically-controlled door of building or plant is opened.

The realization of present embodiment comprises the steps:

A. design virtual electrode.The virtual electrode of broad sense electric capacity is the high-purity red copper of rectangle in the present embodiment, and the surface reaches smooth through meticulous abrasive paper for metallograph polishing, and handles with the acetone cleaning by degreasing.As shown in Figure 3, the length of side l and the thickness h of rectangle red copper electrode are respectively (unit: cm): l=10, h=0.5.In order to reduce other energized conductors of virtual electrode annex, add anhydride curing agent in the back side of electrode and side with epoxy resin and carry out surface-coated for the influence of measuring.

The installation site of said virtual electrode on automatically-controlled door is as shown in Figure 4. Virtual electrode 1 and 2 is installed in respectively on the two fan glass slides 3 and 4 of automatically-controlled door, and wherein virtual electrode 2 is installed in the front of glass slide 4, and virtual electrode 1 is installed in the back side of glass slide 3.Virtual electrode 1 and virtual electrode 2 constitute general capacitor with the space of infinite distant place respectively; The size of capacitance is transferred to the size of capacitance on the testing circuit 8 respectively through signal transmssion line 5 and 6; After detection and judging, whether decision starts drive motor 7.

B. choose dummy electrodes.The space, axial infinite distant place that present embodiment is chosen glass slide plane in the automatically-controlled door dummy electrodes in the object detection circuit of making a living.

C. estimate the original capacitance value.Utilize two-dimensional electromagnetic field analysis software Ansoft Maxwell that the general capacitor that comprises virtual electrode and dummy electrodes is simulated, the size of capacitance is about 14pF.

D. confirm corresponding relation.Suppose standard heights the is arranged adult of (H=175cm) near automatically-controlled door, (d=500cm) walks close to (d=10cm) automatically-controlled door from afar.Get adult relative dielectric constant ε in the estimation ₁=1.0 * 10 ⁶, conductivity is γ=1.67 * 10 ^-3, through two-dimensional electromagnetic field analysis software Ansoft Maxwell to the adult of above-mentioned standard heights near general capacitor in the situation of virtual electrode simulate, d=500cm during to d=10cm, electric capacity is increased to 18.040pF from 14.683pF.The data that estimation obtains are following:

Distance (cm)	Capacitance (pF)
		500	14.683
400	14.683
		300	14.706
200	14.763
		100	14.993
50	15.583
		10	18.040

Utilize physical quantity testing circuit based on general capacitor shown in Figure 5 that a height is walked close to (d=10cm) when the virtual electrode automatically-controlled door is installed, the situation of change of capacitance for the adult of 175cm from (d=500cm) far away.Measurement result is following:

Distance (cm)	Capacitance (pF)
		500	14.3
100	15.0
		50	16.1
10	18.0

Result according to above-mentioned actual measurement revises relation curve shown in dotted lines in Figure 6, and the corresponding relation of the adult of the standard heights that obtains and the capacitance of distance between the virtual electrode and general capacitor size is shown in the positive triangle among Fig. 6.Align the actual measured value shown in the triangle number carry out capacitance that match obtains general capacitor with the relation curve of distance between target object and the virtual electrode shown in solid line among Fig. 6.

When the adult who e. measures a standard heights walks close to automatically-controlled door, the size of the capacitance of the general capacitor that the virtual electrode of installing on the automatically-controlled door and the space of infinite distant place constitute.When walking close to automatically-controlled door like the adult a standard heights, the capacitance that at a time records broad sense electric capacity is 17.4pF.

F obtains the numerical value of variable quantity of numerical value or the physical quantity to be measured of physical quantity to be measured according to the relation curve of the variable quantity of step e measured capacitance value and the match in the steps d.According to the above-mentioned capacitance that measures, i.e. 17.4pF and combine the matched curve shown in the solid line in the corresponding relation curve map 6 can know that this moment, the adult was 20cm apart from the distance of virtual electrode.

The foregoing description only is used for further specifying a kind of method of utilizing the broad sense capacitive transducer to carry out physical quantity to be measured of the present invention; But the present invention is not limited to embodiment; Every foundation technical spirit of the present invention all falls in the protection domain of technical scheme of the present invention any simple modification, equivalent variations and modification that above embodiment did.

Claims (2)

1. one kind is carried out the method that the measured physical quantity of target object detects based on general capacitor, said general capacitor be by one or more charged objects as virtual electrode, the space of infinite distant place constitutes as dummy electrodes is common; Said physical quantity to be measured is meant the amount of the portrayal target object proterties that can detect through capacitance type transducers, and this method detects physical quantity to be measured according to the variation of general capacitor capacitance, it is characterized in that, said method comprising the steps of:

(1) design virtual electrode, by one or more charged metal polar plates as virtual electrode;

(2) choose dummy electrodes, said dummy electrodes is the space of infinite distant place;

(3) the original capacitance value of the said general capacitor of estimation, the original capacitance value of said general capacitor when not having target object between estimation virtual electrode and the dummy electrodes; When not having target object between virtual electrode and the dummy electrodes; The original capacitance value of general capacitor is estimated according to the definition C=Q/U of capacitor intrinsic capacitance value; Wherein C is the capacitance of general capacitor; Q is the quantity of electric charge on the virtual electrode, and U is the current potential of virtual electrode with respect to the earth; Perhaps set up the Electromagnetic Simulation model comprise virtual electrode and dummy electrodes, through model is carried out the characteristic equation that relevant capacitance is set up in finite element analysis, and then carry out the size that numerical evaluation obtains said general capacitor original capacitance value;

(4) confirm corresponding relation; Target object between virtual electrode and the dummy electrodes causes that dielectric specific inductive capacity changes between virtual electrode and the dummy electrodes; Thereby the capacitance variation that causes said general capacitor; Estimation is also measured the corresponding relation of numerical value of capacitance of numerical value and the general capacitor of the measured physical quantity that causes said dielectric change in dielectric constant be in the target object between virtual electrode and the dummy electrodes, and the match relation curve;

(5) measure when having target object between virtual electrode and the dummy electrodes, because the variable quantity of the capacitance of the general capacitor that variation caused of measured physical quantity;

(6) obtain the numerical value of variable quantity of numerical value or the physical quantity to be measured of physical quantity to be measured according to the relation curve of the variable quantity of step (5) measured capacitance value and the match in the step (4).

2. one kind is carried out the detection system that the measured physical quantity of object detects based on general capacitor; Said detection system comprises general capacitor, electric capacity/voltage transformation module, signal processing module, analog to digital conversion and the display module that is made up of virtual electrode and dummy electrodes, it is characterized in that:

Constitute said virtual electrode by one or more charged objects, the space of infinite distant place is as said dummy electrodes;

Said electric capacity/voltage conversion circuit comprises the first integrated chip CAV424, resistance R 1, resistance R 2, resistance R 3, resistance R 4, resistance R 5, resistance R 6, capacitor C 1, capacitor C 2, capacitor C 3, capacitor C 4; Said resistance R 1 be connected on the first integrated chip CAV424 pin 11 and+the 5V driving power between; Said resistance R 2 is connected between the pin 3 and ground of the first integrated chip CAV424; Said resistance R 3 is connected between the pin 2 and ground of the first integrated chip CAV424; Said resistance R 4 is connected between the pin 1 and ground of the first integrated chip CAV424; Said resistance R 5 is connected between the pin 4 and pin 5 of the first integrated chip CAV424, and said resistance R 6 is connected between the pin 4 and pin 6 of the first integrated chip CAV424, and said capacitor C 1 is connected between the pin 12 and ground of the first integrated chip CAV424; Said capacitor C 2 is connected between the pin 13 and ground of the first integrated chip CAV424; Said capacitor C 3 is connected between the pin 15 and ground of the first integrated chip CAV424, and said capacitor C 4 is connected between the pin 16 and ground of the first integrated chip CAV424, and the pin 10 of the said first integrated chip CAV424 directly links to each other with ground; The pin 14 of the virtual electrode of said broad sense electric capacity and the first integrated chip CAV424 links to each other, the pin 5 of the said first integrated chip CAV424 and two difference output ports of pin 6 as electric capacity/voltage conversion circuit;

Said signal processing module comprises the second integrated chip AD8138, resistance R 7, resistance R 8, resistance R 9, resistance R 10, capacitor C 5; Said resistance R 7 is connected between the pin 8 of pin 6 and the second integrated chip AD8138 of the first integrated chip CAV424; Said resistance R 8 is connected between the pin 1 of pin 5 and the second integrated chip AD8138 of the first integrated chip CAV424; Said resistance R 9 is connected between the pin 8 and pin 5 of the second integrated chip AD8138; Said resistance R 10 is connected between the pin 1 and pin 4 of the second integrated chip AD8138; Said capacitor C 5 is connected between the pin 2 and ground of the second integrated chip AD8138; The power supply of the pin 3 of the said second integrated chip AD8138 and+5V directly links to each other, and the pin 6 of the said second integrated chip AD8138 directly links to each other with ground, the pin 4 of the said second integrated chip AD8138 and two difference output ports of pin 5 as amplifying circuit;

The output terminal of said signal processing module links to each other with the output terminal of said analog to digital conversion and display module; Said general capacitor is as the transformation device of physical quantity to be measured, the conversion of the measured physical quantity of target object converted to the conversion of said general capacitor capacitance; Through electric capacity/voltage transformation module, the capacitance of measured general capacitor is transformed into magnitude of voltage and is input to signal processing module; In said signal processing module, the voltage signal that electric capacity/voltage transformation module is exported carries out filtering, processing and amplifying; At last through analog to digital conversion and display module, convert the voltage signal of analog quantity the voltage signal of digital quantity to, and voltage signal is shown.

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