CN2534570Y - Capacitance level gauage - Google Patents

Abstract

A novel capacitor fluid level gage is provided with two sensors D1 and D2 with output capacitance respectively Cs1'=B1'S1'+A1' and Cs2=B2S2+A2; wherein, S1' and S2 are the area of the capacitor in the liquid; A1' and A2 are an equivalent capacitor which is a fixed value. Two inductive reactances XL1 and XL2 are respectively in harmonic resonance with the two equivalent capacitors A1' and A2; due to infinite resistance of the harmonic resonance circuit, the formation of the two sensors D1 and D2 and the two output capacitors Cs1' and Cs2 is not relevant to A1' and A2 but to B1'S1' and B2S2. When measuring the voltage ratio, the two sensors D1 and D2 are connected in series and a voltage meter is connected with D1 in parallel. When measuring the current ratio, the two sensors D1 and D2 are connected in parallel and the current meter is connected with D2 in series. Therefore, the output signals B1'S1' and B2S2 of the two sensors D1 and D2 can be compared and the measured value is only relevant to the area S1' and S2 of the two sensors D1 and D2 in the liquid, not other factors and no impact of SIC changes.

Description

A kind of new-type capacitance liquid level meter

(1) technical field:

The present invention relates to a kind of capacitance liquid level meter of measuring liquid measure, be used in particular for measuring the gasoline storage capacity in the vehicles petrol tank.

(2) background technology:

The reading of capacitance liquid level meter often is subjected to the variable effect of dielectric Constant and produces error on the market.

(3) summary of the invention:

It is irrelevant that the object of the invention provides a kind of capacitance liquid level meter reading and dielectric change in dielectric constant of making, only relevant with the area in electric capacity is immersed in liquid, accurately measures a kind of capacitance liquid level meter of storage liquid measure.

The present invention seeks to realize like this, this capacitance liquid level meter comprises sensor and Displaying Meter, and its principle of work is: two of sensor D are set, external alternate electrical signal, as survey conductive body, the capacitor plate of sensor will apply one deck insulating material, first sensor D ₁Capacitor C s ₁With second sensor D ₂Capacitor C s ₂Be immersed in the liquid as electrode, be immersed in the long-pending S that is respectively in liquid the inside ₁And S ₂When changing between the electrode of liquid level at capacitance type sensor of fluid to be measured, be equivalent to the variation of medium between pole plate, thereby cause the variation of electric capacity, the 120th page of record of " sensor practical application circuit design " first published that the Huang Xianwu that publishes according to publishing house of University of Electronic Science and Technology etc. writes: capacitance liquid level meter sensor output capacitance Cx=A+Bx, A, B are and the sensor construction size that the constant that measured medium is relevant, x are liquid level.Also can be scaled sensor output capacitance Cs=A+BS by this formula, S is immersed in the liquid area for capacitor C s, and A, B are and the capacitance structure size the relevant constant of measured medium.It is in parallel with equivalent capacity BS that the equivalent electrical circuit of capacitor C s can be equivalent capacity A, and equivalent capacity A is a definite value, capacitor C s and inductive reactance X _L(inductive reactance X in parallel _LWith equivalent capacity A resonance), form sensor D, because inductive reactance X _LWith the resonant circuit resistance infinity that equivalent capacity A forms, the electric current that external circuit flows into this resonant circuit is zero, and so, sensor D output capacitance Cs just becomes with equivalent capacity A irrelevant, and is only relevant with equivalent capacity BS.This point, also available mathematical formulae represent that sensor D output capacitance Cs=A+BS is as capacitor C s and inductive reactance X _LWhen in parallel, reactance is: $\frac{1}{\mathrm{j\ωCs}+\frac{1}{j{X}_L}}=\frac{1}{\mathrm{j\ω}(\mathrm{BS}+A)+\frac{1}{j{X}_L}}=\frac{1}{\mathrm{j\ωBS}+\mathrm{j\ωA}-\frac{j}{X_L}}$ As A and X _LResonance $\mathrm{\ωA}=\frac{1}{X_L}$ The time, the reactance of sensor D equals $\frac{1}{\mathrm{j\ωBS}}.$ So first sensor D ₁Output capacitance Cs ₁At this moment be B only ₁S ₁, second sensor D ₂Output capacitance Cs ₂At this moment be B only ₂S ₂Sensor output voltage or electric current respectively with B ₁S ₁, B ₂S ₂Proportional.In order on display instrument, to show sensor voltage or current indication ratio, at above-mentioned first sensor D ₁Capacitor C s ₁The bottom cuts out one, and remaining electric capacity is Cs ₁', second sensor D ₂Capacitor C s ₂The shape size is the same with that piece electric capacity that cuts out, and high together the end of with, establishes capacitor C s ₁, Cs ₁', Cs ₂Be immersed in the long-pending S that is respectively in liquid the inside ₁, S ₁', S ₂No matter liquid level raises or reduces like this, and S is arranged all the time ₁'+S ₂=S ₁, according to Cs ₁'=B ₁' s ₁'+A ₁', Cs ₂=B ₂S ₂+ A ₂, capacitor C s ₁', Cs ₂Respectively with inductive reactance X _L1, X _L2(inductive reactance X in parallel _L1, X _L2Respectively with A ₁', A ₂Resonance) form sensor D respectively ₁And D ₂, because resonant circuit resistance infinity, at this moment sensor D ₁, D ₂Output capacitance Cs ₁', Cs ₂, become and A ₁', A ₂Irrelevant, only and B ₁' s ₁', B ₂S ₂Relevant, make B ₁'=B ₂, when surveying voltage ratio, with sensor D ₁And D ₂Series connection (is equivalent to electric capacity B ₁' s ₁' and B ₂S ₂Series connection), voltage table is connected in parallel on sensor D ₁On, establish D ₁Voltage is V ₁,

When surveying current ratio, with sensor D ₁And D ₂Parallel connection (is equivalent to electric capacity B ₁' s ₁' and B ₂S ₂In parallel), reometer is connected on sensor D ₂On, establish D ₂Electric current is I ₂, Therefrom can find out, the final output capacitance value of sensor only with two capacity area S that are immersed in the liquid ₁, S ₂Ratio relevant, the A relevant with specific inductive capacity, B are irrelevant.So, just realized that the reading of capacitance liquid level meter is not influenced by dielectric change in dielectric constant, only be immersed in liquid in capacity area relevant.

Because the design of capacitance liquid level meter of the present invention, the output capacitance that makes sensor only be immersed in liquid in two capacity areas than relevant, irrelevant with other factors, so influenced by the medium change in dielectric constant and the shortcoming that produces error with regard to having overcome capacitance liquid level meter reading on the market, if it being used the vehicles such as automobile gets on, replace present automobile float-type sensor, can cancel mechanical transmission mechanism, overcome existing float-type sensor error and reach the 10-25% shortcoming.Improve measuring accuracy, volume simple in structure is little.

(4) description of drawings:

Fig. 1, sensor device synoptic diagram.(1) be container, (2) are split pin, Cs ₁, Cs ₂Be electric capacity, X _L1, X _L2Be inductive reactance, D ₁, D ₂Be sensor.

Fig. 2, sensor equivalent circuit diagram.A ₁, A ₂, B ₁S ₁, B ₂S ₂Be equivalent capacity, X _L1, X _L2Be inductive reactance.

Frame of broken lines interior resonance circuit.

Fig. 3, " realizing that sensor voltage or current indication are than new equipment " structural representation.X _L1, X _L2Be inductive reactance, D ₁, D ₂Be sensor, Cs ₁, Cs ₂Be electric capacity, Cs ₁' be capacitor C s ₁The bottom cuts out a remaining electric capacity, s ₁', S ₂Be capacitor C s ₁', Cs ₂It is long-pending to be immersed in the liquid the inside respectively.

Fig. 4 (a), " realizing sensor voltage read-around ratio new equipment " are surveyed the voltage synoptic diagram.X _L1, X _L2Be inductive reactance, B ₁' S ₁', A ₁', A ₂, B ₂S ₂Be equivalent capacity,

Voltage table.

(b) " realize sensor current read-around ratio new equipment " and survey current diagram.X _L1, X _L2Be inductive reactance, B ₁' S ₁', A ₁', A ₂, B ₂S ₂Be equivalent capacity, the  reometer.

(5) embodiment:

From Fig. 1, Fig. 2, this capacitance liquid level meter is provided with two sensors, capacitor C s ₁, Cs ₂The lower end is positioned at container (1) bottom, and it is fixing that the upper end is exported pin (2), capacitor C s ₁With inductive reactance X _L1(inductive reactance X in parallel _L1With equivalent capacity A ₁Resonance), form first sensor D ₁, capacitor C s ₂With inductive reactance X _L2(inductive reactance X in parallel _L2With equivalent capacity A ₂Resonance), form second sensor D ₂, capacitor C s ₁And Cs ₂As sensor D ₁, D ₂Electrode be immersed in the liquid, along with liquid measure changes, an electrode part has appearred in air, a part is immersed in the liquid, S ₁And S ₂Be respectively capacitor C s ₁And Cs ₂Be immersed in the area in the liquid, when changing between the electrode of liquid level at capacitance type sensor of fluid to be measured, be equivalent to the dielectric variation of interpolar, thereby cause electric capacitance change, first sensor D ₁Output capacitance Cs ₁=A ₁+ B ₁S ₁, second sensor D ₂Output capacitance Cs ₂=A ₂+ B ₂S ₂, A ₁, A ₂, B ₁, B ₂For with capacitor arrangement size, the relevant constant of measured medium, capacitor C s ₁Equivalent electrical circuit be equivalent capacity A ₁With equivalent capacity B ₁S ₁Parallel connection, capacitor C s ₂Equivalent electrical circuit be equivalent capacity A ₂With equivalent capacity B ₂S ₂Parallel connection, equivalent capacity A ₁, A ₂Be a definite value, at this moment inductive reactance X _L1, X _L2Respectively with electric capacity A ₁, A ₂Form resonant circuit, because resonant circuit resistance infinity, the electric current that external circuit flows into this resonant circuit is zero, so, and sensor D ₁, D ₂Shu Chu capacitor C s respectively ₁, Cs ₂Just become and equivalent capacity A ₁, A ₂Irrelevant, only and B ₁S ₁, B ₂S ₂Relevant, see Fig. 2.The voltage of two sensors output or electric current respectively with B ₁S ₁, B ₂S ₂Proportional.In order on display instrument, to demonstrate sensor voltage or current indication ratio, design a kind of " realizing the new equipment of sensor voltage or current indication ratio ", be introduced capacitor C s in conjunction with Fig. 3 ₁The bottom cuts out one, and remaining partition capacitance is Cs ₁', capacitor C s ₂Shape size and capacitor C s ₁That piece that cuts out is the same, and high together the end of with, establishes capacitor C s ₁, Cs ₁', Cs ₂The area that is immersed in the liquid is respectively S ₁, S ₁', S ₂No matter liquid level raises or reduces like this, and S is arranged all the time ₁'+S ₂=S ₁, according to, Cs ₁'=B ₁' S ₁'+A ₁', Cs ₂=B ₂S ₂+ A ₂, capacitor C s ₁', Cs ₂Respectively with inductive reactance X _L1, X _L2(inductive reactance X in parallel _L1, X _L2Respectively with A ₁', A ₂Resonance), form sensor D respectively ₁, D ₂, owing to wipe the circuitous resistance infinity of shaking, at this moment sensor D ₁, D ₂Output capacitance Cs ₁', Cs ₂Just become and A ₁', A ₂Irrelevant, only and B ₁' S ₁', B ₂S ₂Relevant, make B ₁'=B ₂, when surveying voltage ratio, with sensor D ₁, D ₂Series connection (is equivalent to electric capacity B ₁' S ₁', B ₂S ₂Series connection), with voltage table parallel sensor D ₁, establish D ₁Voltage is V ₁, see Fig. 4 (a) When surveying current ratio, with sensor D ₁And D ₂Parallel connection (is equivalent to electric capacity B ₁' S ₁' and B ₂S ₂In parallel), with reometer series connection sensor D ₂, establish D ₂Electric current is I ₂, see Fig. 4 (b)

Therefrom can find out, the final output capacitance value of sensor only with two capacity area S that are immersed in the liquid ₁, S ₂Ratio relevant, the A relevant with specific inductive capacity, B are irrelevant.So, just realized that the reading of capacitance liquid level meter is not influenced by dielectric change in dielectric constant, only be immersed in liquid in capacity area relevant.

Claims (1)

1. One, a kind of new-type capacitance liquid level meter comprises voltage table, reometer and capacitor C s ₁, Cs ₂With inductive reactance X _L1, X _L2, capacitor C s ₁With inductive reactance X _L1Parallel connection, inductive reactance X _L1With equivalent capacity A ₁Resonance is formed a sensor D ₁, capacitor C s ₂With inductive reactance X _L2Parallel connection, inductive reactance X _L2With equivalent capacity A ₂Resonance is formed another sensor D ₂It is characterized in that: at sensor D ₁Capacitor C s ₁The lower end cuts out one, and the electric capacity of remaining part is Cs ₁', sensor D ₂Capacitor C s ₂Shape size and capacitor C s ₁That piece electric capacity that cuts out is the same, and with the end with high, when surveying voltage ratio with sensor D ₁, D ₂Series connection, voltage table D in parallel ₁, when surveying current ratio with sensor D ₁, D ₂Parallel connection, reometer  and D ₂Series connection.

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