CN103292863A - Capacitive liquid level sensor and resistance coupling method of liquid level measurement - Google Patents

Abstract

The invention discloses a capacitive liquid level sensor and a resistance coupling method of liquid level measurement. The capacitive liquid level sensor comprises an outer metal pipe and an inner metal pipe which constitute a cylindrical capacitor. A containing chamber for containing liquid is formed between the inner wall of the outer metal pipe and the outer wall of the inner metal pipe. When the containing chamber is filled with liquid, height of the liquid in the containing chamber can be calculated by measuring changes of the capacitance of the outer metal pipe and the inner metal pipe. Accuracy of oil level data measured by the resistance coupling method is several times higher than that by a conventional method; non-contact measurement is free of structural abrasion, so that service life is prolonged and long-term stability is good; further, since resistances are adjustable in measurement and cover all output ranges of oil float resistances, vehicle oil float can be substituted with additional arrangement of positioning drills.

Description

The method of capacitive liquid level sensor and resistance coupling measurement liquid level

Technical field

The present invention relates to the liquid level detection technique, particularly relate to the method for a kind of capacitive liquid level sensor and resistance coupling measurement liquid level.

Background technology

At present, the fuel level sensor that automobile market is used mostly is slide rheostat formula liquid level sensor, and its working method is by float because the leverage that buoyancy causes makes the change in resistance of slide rheostat come work.But fuel sensor is not formulated corresponding standard owing to domestic, cause the way of output of the fuel sensor that market uses ever-changing, according to incompletely statistics, the kind of employed oil float reaches kind more than 400 on the home market, except the resistance variation was various, its size of current that can bear also all had difference.The installation dimension formulated of different manufacturers also has multiple in addition, so just cause the interchangeability of fuel sensor on the market very poor, and oil float of traditional mechanical contact all can produce wearing and tearing in various degree in use for some time, cause the skew of loose contact or resistance, may have influence on accuracy of detection even may cause detecting inefficacy.

Summary of the invention

Technical matters to be solved by this invention is: a kind of capacitive liquid level sensor is provided, can reduce liquid level detect in to the wearing and tearing of surveying instrument, and promote the precision that liquid level detects.

The further technical matters to be solved of the present invention is: a kind of method of resistance coupling measurement liquid level is provided, can reduces in the liquid level detection surveying instrument is worn and torn, and promote the precision that liquid level detects.And can adapt to the diversified way of output on the market, to improve the interchangeability of product.

For solving the problems of the technologies described above, the present invention proposes a kind of capacitive liquid level sensor, comprises metal outer pipe and metal inner pipe; Described metal outer pipe and metal inner pipe constitute column capacitance;

Wherein, the accommodation space of receiving fluids between described metal outer pipe inwall and the metal inner pipe outer wall; When being placed with liquid in the described accommodation space, by detecting the variation of metal outer pipe and the capacitance of metal inner pipe, the height of liquid in the calculating accommodation space.

Preferably, the variation △ C=C of described capacitance _H-C ₀The concrete computing formula of △ C is:

$\mathrm{\ΔC}=\frac{2\mathrm{\π}(\mathrm{\ϵ}-{\mathrm{\ϵ}}_0)H}{\ln (R_1/R_0)};$

Described C ₀Be the initial capacitance between metal outer pipe and the metal inner pipe, unit is F;

Described ε ₀Be the effective dielectric constant of gas in the accommodation space, unit is F/m;

Described L is the liquid level maximum height, and unit is m;

Described R ₁Be the metal outer pipe radius, unit is m;

Described R ₀For managing radius in the stainless steel, unit is m;

Described ε is the effective dielectric constant of liquid in the accommodation space, and unit is F/m.

Preferably, described capacitive liquid level sensor also is provided with housing, and described housing is the cast aluminium material.

Preferably, described capacitive liquid level sensor is fixed in the sub-installation site of vehicle oil float by the ring flange that is processed with different center bore groove lines.

On the other hand, the present invention also proposes a kind of method of resistance coupling measurement liquid level, comprises step:

Detect the variation of capacitance by the capacitive liquid level sensor, calculate the height of liquid in the accommodation space;

According to the amount of liquid that the height by described liquid level obtains, the corresponding resistance value of coupling output;

Amount of liquid is shown according to described resistance value by panel board.

Preferably, the variation △ C=C of described capacitance _H-C ₀The concrete computing formula of △ C is:

$\mathrm{\ΔC}=\frac{2\mathrm{\π}(\mathrm{\ϵ}-{\mathrm{\ϵ}}_0)H}{\ln (R_1/R_0)};$

Described C ₀Be the initial capacitance between metal outer pipe and the metal inner pipe, unit is F;

Described ε ₀Be the effective dielectric constant of gas in the accommodation space, unit is F/m;

Described L is the liquid level maximum height, and unit is m;

Described R ₁Be the metal outer pipe radius, unit is m;

Described R ₀For managing radius in the stainless steel, unit is m;

Described ε is the effective dielectric constant of liquid in the accommodation space, and unit is F/m.

Preferably, described basis is by the amount of liquid of the height acquisition of described liquid level, and the step of the corresponding resistance value of coupling output specifically comprises:

High computational amount of liquid according to described liquid level;

From default corresponding tables, find the corresponding resistance value of described amount of liquid;

Resistance value in the match circuit is adjusted into the corresponding resistance value of described amount of liquid.

Preferably, the reference point of described amount of liquid or resistance value is provided with 4 to 16 according to the precision needs.

The detectable oil level data accuracy of the present invention exceeds several times than classic method, and owing to be non-contact measurement, does not have the structure wearing and tearing, long service life, and long-time stability are good; In addition, because resistance value is adjustable in the above-mentioned detection, contain the sub-resistance output area of all oil floats, added to locate and join brill, can realize the replacement to vehicle oil float.

Description of drawings

Fig. 1 is the structural representation of capacitive liquid level sensor one embodiment of the present invention.

Fig. 2 is the structural representation of capacitive liquid level sensor one embodiment match resistance circuit of the present invention.

Fig. 3 is the structural representation that capacitive liquid level sensor one embodiment of the present invention processes the ring flange of different center bores.

Fig. 4 is another structural representation that capacitive liquid level sensor one embodiment of the present invention processes the ring flange of different center bores.

Fig. 5 is the steps flow chart synoptic diagram of method one embodiment of resistance coupling measurement liquid level of the present invention.

Fig. 6 is the steps flow chart synoptic diagram that the method one embodiment liquid level of resistance coupling measurement liquid level of the present invention is converted to resistance value.

The realization of the object of the invention, functional characteristics and advantage will be in conjunction with the embodiments, are described further with reference to accompanying drawing.

Embodiment

Should be appreciated that specific embodiment described herein only in order to explaining the present invention, and be not used in restriction the present invention.

With reference to Fig. 1, an embodiment of a kind of capacitive liquid level sensor of the present invention is proposed.This capacitive liquid level sensor can comprise metal outer pipe 11 and metal inner pipe 12; This metal outer pipe 11 constitutes column capacitance with metal inner pipe 12; Wherein, the accommodation space 13 of receiving fluids between these metal outer pipe 11 inwalls and metal inner pipe 12 outer walls; When being placed with liquid 14 in this accommodation space 13, by the variation of detection metal outer pipe 11 with the capacitance of metal inner pipe 12, calculate the height of liquid 14 in the accommodation space 13.

Capacitive liquid level sensor in the present embodiment can be used for automobile oil level and detects, and replaces the oil float seed oil position detection mode of passing through.

Above-mentioned capacitive liquid level sensor can mainly (radius be R by elongated stainless steel outer tube ₁), in the stainless steel pipe (radius is R0) and with accommodation space 13 in the fluid to be measured 14 common round metal cylindricality electric capacity that constitute.The area coverage that this capacitive liquid level sensor can utilize its two electrode changes with the variation of fluid to be measured 14 liquid levels, thereby the relation that causes corresponding electric capacitance change is carried out level gauging.

When liquid level H=0 measured in the accommodation space 13 (not having liquid), there is capacitor C between the round metal cylindricality electric capacity that pipe constitutes in stainless steel outer tube and the stainless steel ₀, obtain electric capacity according to formula and be:

$C_0=\frac{2\mathrm{\π}{\mathrm{\ϵ}}_{0}L}{\ln (R_1/R_0)};---\left(1\right)$

When liquid level tested in the accommodation space 13 was H, having electric capacity between the pipe in stainless steel outer tube and the stainless steel was C _H:

$C_H=\frac{2\mathrm{\π}{\mathrm{\ϵ}}_0(L-H)}{\ln (R_1/R_0)}+\frac{2\mathrm{\π\ϵH}}{\ln (R_1/R_0)}$

$=\frac{2\mathrm{\π}{\mathrm{\ϵ}}_{0}L}{\ln (R_1/R_0)}+\frac{2\mathrm{\π}(\mathrm{\ϵ}-{\mathrm{\ϵ}}_0)H}{\ln (R_1/R_0)};---\left(2\right)$

When liquid level tested in the accommodation space 13 was increased to H by zero, its changes in capacitance amount Δ C can be drawn by formula (1) and formula (2):

$\mathrm{\ΔC}=\mathrm{CH}-C0=\frac{2\mathrm{\π}(\mathrm{\ϵ}-{\mathrm{\ϵ}}_0)H}{\ln (R_1/R_0)};---\left(3\right)$

By formula (3) as can be known, parameter ε ₀, ε, R ₁, R ₀All be definite value, so changes in capacitance amount Δ C and liquid level variable quantity H are the near-linear relation.Be out of shape by formula (2):

C _H=a ₀+ b ₀H (a ₀And b ₀Be constant) (4)

This shows the capacitance C of above-mentioned capacitive liquid level sensor _HSize and the electric capacity depth H that immerses liquid 14 linear.Above-mentioned C ₀Be the initial capacitance between metal outer pipe 11 and the metal inner pipe 12, unit is F; Above-mentioned ε ₀Be the effective dielectric constant of gas in the accommodation space 13, unit is F/m; Above-mentioned L is the liquid level maximum height, and unit is m; Above-mentioned R ₁Be metal outer pipe 11 radiuses, unit is m; Above-mentioned R ₀For managing radius in the stainless steel, unit is m; Above-mentioned ε is the effective dielectric constant of liquid 14 in the accommodation space 13, and unit is F/m.

Because the length of pipe can be formulated as required in stainless steel outer tube and the stainless steel, so above-mentioned capacitive liquid level sensor is suitable for the oil measurement that carries out of any specification size oil tank of vehicle.

In the present embodiment, can can be according to the needs of measuring accuracy with liquid level zero point to full scale with the capacitance that measures, evenly be divided into 4 to 16 (such as 8) reference point, simultaneously also be divided into 8 reference point with the resistance value of automotive oil float output is also corresponding, when measuring capacitance between adjacent two reference point wherein, output resistance is also exported corresponding resistance value on an equal basis, and namely corresponding automobile instrument is indicated corresponding oil quantity scale.Thereby replaced oil float by its float height, resistance change and electric current changes thereupon and be shown in structure and the principle of panel board.

Set up the corresponding tables of oil mass and resistance value, oil mass and resistance value can be divided into 8 parts (also can be divided into 4 parts or 16 parts according to the precision needs) respectively equally, again fuel tank is demarcated then, namely every past fuel tank is poured a oil mass into, and sensor can receive a resistance signal; Can be with above-mentioned corresponding tables burned software in advance.

If certain automotive oil tank is 140L, the sub-resistance output area of former car oil float is 0 Ω～105 Ω, then automotive oil tank oil mass, resistance value output can be divided into 8 equal portions, and is corresponding as follows respectively:

?	1	2	3	4	5	6	7	8
									Oil mass (L)	0	20	40	60	80	100	120	140

Resistance value (Ω)

0

15

30

45

60

75

90

105

(capacitance signal when even oil mass is 0L is equal to resistance value 0 Ω to the burned above corresponding relation of software, after capacitance signal during 20L is equal to resistance value 15 Ω, with reference to match resistance circuit shown in Figure 2, wherein R is variable resistor, adjusts R=105 Ω/7=15 Ω in this example.

By above-mentioned Fig. 2 as can be known, when fuel tank fuel quantity was full (140L), three resistance all were connected in series, combination R _AB=7R=7*15 Ω=105 Ω, this moment, gauge pointer can point to instrument full scale part according to the resistance value size.When a fuel tank fuel quantity consumption part, when being left 120L, two resistance serial connections of resistance 2R, 4R, combined resistance R _AB=6R=6*15 Ω=90 Ω, in like manner gauge pointer can be indicated to 7/8ths position of panel board full scale.By that analogy, the every consumption part of automotive oil tank oil mass, gauge pointer can carry out the indication of different oil masses position according to the resistance value that changes at panel board.

Above-mentioned capacitive liquid level sensor also can be provided with housing, and described housing can be the cast aluminium material.Above-mentioned capacitive liquid level sensor can be fixed in the sub-installation site of vehicle oil float by the ring flange that is processed with different center bore groove lines.

Because the installation of automotive oil float in the market only five hole flange forms installs that angle differs between hole size, via hole because center bore, bolt are crossed, the mounting means of generation has tens of kinds.Feasible oil float does not on the market possess universal, causes the user need exchange the difficulty of former car oil float for.

In the present embodiment, above-mentioned capacitive liquid level sensor housing is selected the cast aluminium material of good processability for use, and at the groove line (with reference to the center bore D1 to D8 shown in 3) of the different center bores of ring flange processing, when using, the user only needs to carry out mark according to center bore size and spiro keyhole position, such as being labeled as some D2 shown in Figure 4, and the good screw thread via hole of available common drill bit secondary processing can adapt to the installation of any five hole flanges.

The used rubber sheet gasket of former car oil float places on the capacitive transducer ring flange, with marking pen its mounting hole site is imprinted on the ring flange, clamps capacitive transducer and has bored the corresponding mounting hole position with hand drill with simple tool.Bore the capacitive liquid level sensor of position, hole and inserted the sub-installation site of former car oil float, and the good screw of fixing and locking.The resistance output line is connected to former automobile oil gauge, and connects automobile power source to capacitance liquid level meter, thereby replaces former car oil float fully.

The detectable oil level data accuracy of above-mentioned capacitive liquid level sensor exceeds several times than classic method and (reaches about 0.8% such as static accuracy, dynamic accuracy reaches about 2%), and owing to be non-contact measurement, do not have the structure wearing and tearing, long service life, long-time stability are good; In addition, because resistance value is adjustable in the above-mentioned detection, contain the sub-resistance output area of all oil floats, added to locate and join brill, can realize obtaining vehicle oil float.

With reference to Fig. 5, method one embodiment of a kind of resistance coupling measurement of the present invention liquid level is proposed.This method can comprise:

Step S11, detect the variation of capacitance by the capacitive liquid level sensor, calculate the height of liquid in the accommodation space;

Step S12, according to the amount of liquid that is obtained by the height of described liquid level, the corresponding resistance value of coupling output;

Step S13, amount of liquid is shown according to described resistance value by panel board.

Capacitive liquid level sensor in the present embodiment can be described in above-mentioned embodiment, and the measurement of liquid level can not repeat them here described in above-mentioned embodiment yet.

With reference to Fig. 6, above-mentioned steps S12 can specifically comprise:

Step S121, according to the high computational amount of liquid of described liquid level;

Step S122, from default corresponding tables, find the corresponding resistance value of described amount of liquid;

Step S123, the resistance value in the match circuit is adjusted into the corresponding resistance value of described amount of liquid.

In the present embodiment, can can be according to the needs of measuring accuracy with liquid level zero point to full scale with the capacitance that measures, evenly be divided into 4 to 16 (such as 8) reference point, simultaneously also be divided into 8 reference point with the resistance value of automotive oil float output is also corresponding, when measuring capacitance between adjacent two reference point wherein, output resistance is also exported corresponding resistance value on an equal basis, and namely corresponding automobile instrument is indicated corresponding oil quantity scale.Thereby replaced oil float by its float height, resistance change and electric current changes thereupon and be shown in structure and the principle of panel board.

Set up the corresponding tables of oil mass and resistance value, oil mass and resistance value can be divided into 8 parts (also can be divided into 4 parts or 16 parts according to the precision needs) respectively equally, again fuel tank is demarcated then, namely every past fuel tank is poured a oil mass into, and sensor can receive a resistance signal; Can be with above-mentioned corresponding tables burned software in advance.

The detectable oil level data accuracy of the method for above-mentioned resistance coupling measurement liquid level exceeds several times than classic method and (reaches about 0.8% such as static accuracy, dynamic accuracy reaches about 2%), and owing to be non-contact measurement, do not have the structure wearing and tearing, long service life, long-time stability are good; In addition, because resistance value is adjustable in the above-mentioned detection, contain the sub-resistance output area of all oil floats, added to locate and join brill, can realize obtaining vehicle oil float.

The above only is the preferred embodiments of the present invention; be not so limit claim of the present invention; every equivalent structure or equivalent flow process conversion that utilizes instructions of the present invention and accompanying drawing content to do; or directly or indirectly be used in other relevant technical fields, all in like manner be included in the scope of patent protection of the present invention.

Claims (8)

1. a capacitive liquid level sensor is characterized in that, comprises metal outer pipe and metal inner pipe; Described metal outer pipe and metal inner pipe constitute column capacitance;

Wherein, the accommodation space of receiving fluids between described metal outer pipe inwall and the metal inner pipe outer wall; When being placed with liquid in the described accommodation space, by detecting the variation of metal outer pipe and the capacitance of metal inner pipe, the height of liquid in the calculating accommodation space.

2. capacitive liquid level sensor according to claim 1 is characterized in that, the variation △ C=C of described capacitance _H-C ₀The concrete computing formula of △ C is:

$\mathrm{\ΔC}=\frac{2\mathrm{\π}(\mathrm{\ϵ}-{\mathrm{\ϵ}}_0)H}{\ln (R_1/R_0)};$

Described C ₀Be the initial capacitance between metal outer pipe and the metal inner pipe, unit is F;

Described ε ₀Be the effective dielectric constant of gas in the accommodation space, unit is F/m;

Described L is the liquid level maximum height, and unit is m;

Described R ₁Be the metal outer pipe radius, unit is m;

Described R ₀For managing radius in the stainless steel, unit is m;

Described ε is the effective dielectric constant of liquid in the accommodation space, and unit is F/m.

3. capacitive liquid level sensor according to claim 1 and 2 is characterized in that, described capacitive liquid level sensor also is provided with housing, and described housing is the cast aluminium material.

4. capacitive liquid level sensor according to claim 3 is characterized in that, described capacitive liquid level sensor is fixed in the sub-installation site of vehicle oil float by the ring flange that is processed with different center bore groove lines.

5. the method for a resistance coupling measurement liquid level is characterized in that, comprises step:

Detect the variation of capacitance by the capacitive liquid level sensor, calculate the height of liquid in the accommodation space;

According to the amount of liquid that the height by described liquid level obtains, the corresponding resistance value of coupling output;

Amount of liquid is shown according to described resistance value by panel board.

6. the method for resistance coupling measurement liquid level according to claim 5 is characterized in that, the variation △ C=C of described capacitance _H-C ₀The concrete computing formula of △ C is:

$\mathrm{\ΔC}=\frac{2\mathrm{\π}(\mathrm{\ϵ}-{\mathrm{\ϵ}}_0)H}{\ln (R_1/R_0)};$

Described C ₀Be the initial capacitance between metal outer pipe and the metal inner pipe, unit is F;

Described ε ₀Be the effective dielectric constant of gas in the accommodation space, unit is F/m;

Described L is the liquid level maximum height, and unit is m;

Described R ₁Be the metal outer pipe radius, unit is m;

Described R ₀For managing radius in the stainless steel, unit is m;

Described ε is the effective dielectric constant of liquid in the accommodation space, and unit is F/m.

7. according to the method for claim 5 or 6 described resistance coupling measurement liquid levels, it is characterized in that described basis is by the amount of liquid of the height acquisition of described liquid level, the step of the corresponding resistance value of coupling output specifically comprises:

High computational amount of liquid according to described liquid level;

From default corresponding tables, find the corresponding resistance value of described amount of liquid;

Resistance value in the match circuit is adjusted into the corresponding resistance value of described amount of liquid.

8. according to the method for claim 5 or 6 described resistance coupling measurement liquid levels, it is characterized in that the reference point of described amount of liquid or resistance value is provided with 4 to 16 according to the precision needs.

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