WO2007048736A1 - Capacitive gauge comprising interdigital electrodes on an insulating substrate - Google Patents

Capacitive gauge comprising interdigital electrodes on an insulating substrate Download PDF

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Publication number
WO2007048736A1
WO2007048736A1 PCT/EP2006/067503 EP2006067503W WO2007048736A1 WO 2007048736 A1 WO2007048736 A1 WO 2007048736A1 EP 2006067503 W EP2006067503 W EP 2006067503W WO 2007048736 A1 WO2007048736 A1 WO 2007048736A1
Authority
WO
WIPO (PCT)
Prior art keywords
gauge
electrodes
cylinder
insulating substrate
interdigital
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP2006/067503
Other languages
French (fr)
Inventor
Volodia Naydenov
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Plastic Omnium Advanced Innovation and Research SA
Original Assignee
Inergy Automotive Systems Research SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from FR0510930A external-priority patent/FR2892507B1/en
Application filed by Inergy Automotive Systems Research SA filed Critical Inergy Automotive Systems Research SA
Priority to JP2008537060A priority Critical patent/JP2009513962A/en
Priority to EP06807349A priority patent/EP1943487A1/en
Priority to US12/091,066 priority patent/US20080223128A1/en
Priority to BRPI0617815A priority patent/BRPI0617815A2/en
Publication of WO2007048736A1 publication Critical patent/WO2007048736A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
    • G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
    • G01F23/268—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors mounting arrangements of probes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm

Definitions

  • Capacitive gauge comprising interdigital electrodes on an insulating substrate
  • the present invention relates to a capacitive gauge comprising interdigital electrodes on an insulating substrate, a method for manufacturing such a gauge and its use as a level gauge in fuel tanks.
  • these level sensors or gauges comprise an electrical capacitor used for measurement and an electrical capacitor used for reference.
  • the capacitor used for measurement is normally present over the entire height of the tank, and its capacitance varies according to the height of fuel in the tank.
  • the capacitor used for reference is permanently immersed in the fuel and supplies a reference value of the dielectric constant of the fuel.
  • An appropriate electronic circuit determines the level of the fuel in the tank.
  • the capacitors of these sensors can be flat or cylindrical plates between which the fuel can fall and rise and influence the capacitance by skin effect. Alternatively, they can be interdigital (engaged comblike) electrodes which interact by interference effect; the latter are affixed to a substrate and look like printed circuits. Such electrodes can moreover be manufactured by manufacturing methods similar to those of printed circuits.
  • US patent 4,296,630 discloses both capacitive gauges with interference effect comprising interdigital electrodes obtained by eroding a metallic layer affixed to a ribbon-shaped flat and flexible substrate, and capacitive gauges with skin effect in the form of cables obtained by overmoulding electrodes disposed in an annular fashion in an extrusion process.
  • the first variant has the drawback of a low active surface and the need for a protective casing, particularly to avoid the effect of the waves.
  • the second variant is difficult to produce in practice, and moreover its production is not explained in the patent concerned.
  • the present application seeks to resolve these problems by providing a capacitive gauge with large active surface, not requiring a protective casing (in particular, hydraulic protection against waves) and being easy to produce in practice.
  • the present invention relates to a capacitive gauge comprising interdigital electrodes on an insulating substrate having the form of a hollow cylinder having an internal surface and an external surface, the interdigital electrodes being disposed on the internal surface of this cylinder.
  • gauge is used to denote a device that supplies a signal representative of a liquid level in a tank.
  • This device can include an electronic circuit for processing this signal, making it possible to determine the level and quantity of fuel in the tank. Alternatively, it can be linked to such a circuit.
  • the use of an integrated circuit is advantageous, particularly because of the similarity in manufacturing processes mentioned previously.
  • these are preferably covered by the insulating substrate so as not to disturb the measurement.
  • interdigital electrodes is used to denote electrodes having the form of coils with loops in the form of digits engaged comblike with each other, and this as described in the abovementioned US patent.
  • these digits extend vertically, along internal generatrices of the cylinder. The fact of having the gauge positioned vertically in the tank makes it then possible to obtain a substantially linear signal according to the level of liquid to be measured.
  • the gauge according to the invention can comprise a pair of interdigital measurement electrodes and a pair of reference electrodes, also interdigital.
  • the latter is preferably located at one end of the substrate, which will be placed/fixed on the bottom of the tank (preferably, even, in a spare tank, if appropriate) so as to ensure its constant immersion in the liquid present in the tank. It makes it possible to disregard variations of temperature, pressure, nature of the liquid, and other interference factors likely to disturb the measurement.
  • the relative cylinder height that it occupies is preferably small relative to that occupied by the pair of measurement electrodes, so that the latter can be present over substantially the entire height of the liquid.
  • the loops of the measurement electrode and of the reference electrode are both vertical.
  • the interdigital electrodes are present on a cylindrical insulating substrate.
  • This substrate can be based on any known insulating material used as a printed circuit substrate, for example based on an insulating polymer chosen from the polyimides (such as the resins known by the trade name Capton®), epoxy resins and polyesters.
  • This cylinder can be continuous or discontinuous along a generatrix. In particular, it can be obtained by welding, bonding etc. a flat insulating substrate.
  • the cylindrical substrate comprises, on its external surface, a conductive coating, for example metallic, acting as an electrostatic protection screen.
  • a conductive coating for example metallic, acting as an electrostatic protection screen.
  • a copper-based coating with a thickness of 35 to 70 ⁇ m, is ideal.
  • the height of the cylindrical substrate is normally dependent on the maximum height of liquid in the tank. Its diameter is normally a trade-off between a good measurement accuracy and an acceptable size.
  • the present invention also relates to a method for manufacturing a gauge as described above.
  • This method consists in manufacturing a flat gauge by any known method (such as erosion, photolithography, etc) and then winding the latter with electrodes turned inwards so as to form a cylinder.
  • a flexible substrate that is a substrate made of a material and having a thickness enabling it to be wound.
  • a substrate based on an insulating polymer as described previously is ideal.
  • the cylindrical form can be preserved by joining the two ends of the substrate by welding, bonding, etc, and/or by inserting the wound substrate into a plate of appropriate shape (metallic rings, for example).
  • the invention also relates to the use of a gauge as described previously as a level gauge in a fuel tank.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
  • Level Indicators Using A Float (AREA)

Abstract

Capacitive gauge comprising interdigital electrodes on an insulating substrate having the form of a hollow cylinder having an internal surface and an external surface, the interdigital electrodes being disposed on the internal surface of this cylinder.

Description

Capacitive gauge comprising interdigital electrodes on an insulating substrate
The present invention relates to a capacitive gauge comprising interdigital electrodes on an insulating substrate, a method for manufacturing such a gauge and its use as a level gauge in fuel tanks.
Many devices have been proposed to date for measuring the level of liquid in the tanks, and in particular, in the fuel tanks of motor vehicles. These known devices normally use level sensors or gauges delivering a signal representative of the level of fuel in the tank.
In a variant, these level sensors or gauges comprise an electrical capacitor used for measurement and an electrical capacitor used for reference. The capacitor used for measurement is normally present over the entire height of the tank, and its capacitance varies according to the height of fuel in the tank. The capacitor used for reference is permanently immersed in the fuel and supplies a reference value of the dielectric constant of the fuel. An appropriate electronic circuit determines the level of the fuel in the tank. The capacitors of these sensors can be flat or cylindrical plates between which the fuel can fall and rise and influence the capacitance by skin effect. Alternatively, they can be interdigital (engaged comblike) electrodes which interact by interference effect; the latter are affixed to a substrate and look like printed circuits. Such electrodes can moreover be manufactured by manufacturing methods similar to those of printed circuits.
Thus, US patent 4,296,630 discloses both capacitive gauges with interference effect comprising interdigital electrodes obtained by eroding a metallic layer affixed to a ribbon-shaped flat and flexible substrate, and capacitive gauges with skin effect in the form of cables obtained by overmoulding electrodes disposed in an annular fashion in an extrusion process. The first variant has the drawback of a low active surface and the need for a protective casing, particularly to avoid the effect of the waves. The second variant is difficult to produce in practice, and moreover its production is not explained in the patent concerned. The present application seeks to resolve these problems by providing a capacitive gauge with large active surface, not requiring a protective casing (in particular, hydraulic protection against waves) and being easy to produce in practice.
To this end, the present invention relates to a capacitive gauge comprising interdigital electrodes on an insulating substrate having the form of a hollow cylinder having an internal surface and an external surface, the interdigital electrodes being disposed on the internal surface of this cylinder.
The term "gauge" is used to denote a device that supplies a signal representative of a liquid level in a tank. This device can include an electronic circuit for processing this signal, making it possible to determine the level and quantity of fuel in the tank. Alternatively, it can be linked to such a circuit. The use of an integrated circuit is advantageous, particularly because of the similarity in manufacturing processes mentioned previously.
Regarding the electrical connections between the electrodes and the electronic signal processing circuit, these are preferably covered by the insulating substrate so as not to disturb the measurement.
The term "interdigital" electrodes is used to denote electrodes having the form of coils with loops in the form of digits engaged comblike with each other, and this as described in the abovementioned US patent. Preferably, these digits extend vertically, along internal generatrices of the cylinder. The fact of having the gauge positioned vertically in the tank makes it then possible to obtain a substantially linear signal according to the level of liquid to be measured.
Advantageously, and as described in the abovementioned US patent, the gauge according to the invention can comprise a pair of interdigital measurement electrodes and a pair of reference electrodes, also interdigital. The latter is preferably located at one end of the substrate, which will be placed/fixed on the bottom of the tank (preferably, even, in a spare tank, if appropriate) so as to ensure its constant immersion in the liquid present in the tank. It makes it possible to disregard variations of temperature, pressure, nature of the liquid, and other interference factors likely to disturb the measurement. The relative cylinder height that it occupies is preferably small relative to that occupied by the pair of measurement electrodes, so that the latter can be present over substantially the entire height of the liquid. Preferably, the loops of the measurement electrode and of the reference electrode are both vertical. Furthermore, they advantageously have at least a part of an electrode in common. According to the invention, the interdigital electrodes are present on a cylindrical insulating substrate. This substrate can be based on any known insulating material used as a printed circuit substrate, for example based on an insulating polymer chosen from the polyimides (such as the resins known by the trade name Capton®), epoxy resins and polyesters. This cylinder can be continuous or discontinuous along a generatrix. In particular, it can be obtained by welding, bonding etc. a flat insulating substrate.
According to an advantageous variant, the cylindrical substrate comprises, on its external surface, a conductive coating, for example metallic, acting as an electrostatic protection screen. A copper-based coating, with a thickness of 35 to 70 μm, is ideal. The height of the cylindrical substrate is normally dependent on the maximum height of liquid in the tank. Its diameter is normally a trade-off between a good measurement accuracy and an acceptable size.
The present invention also relates to a method for manufacturing a gauge as described above. This method consists in manufacturing a flat gauge by any known method (such as erosion, photolithography, etc) and then winding the latter with electrodes turned inwards so as to form a cylinder.
In this method, preference is given to the use of a flexible substrate, that is a substrate made of a material and having a thickness enabling it to be wound. To this end, a substrate based on an insulating polymer as described previously is ideal.
The cylindrical form can be preserved by joining the two ends of the substrate by welding, bonding, etc, and/or by inserting the wound substrate into a plate of appropriate shape (metallic rings, for example).
Finally, the invention also relates to the use of a gauge as described previously as a level gauge in a fuel tank.

Claims

C L A I M S
1 - Capacitive gauge comprising interdigital electrodes on an insulating substrate, characterized in that the insulating substrate has the form of a hollow cylinder having an internal surface and an external surface and in that the interdigital electrodes are disposed on the internal surface of the cylinder.
2 - Gauge according to the preceding claim, characterized in that it transmits a signal representative of a liquid level in a tank and that it incorporates an electronic circuit for processing said signal.
3 - Gauge according to the preceding claim, characterized in that the electrical connections between the electrodes and the electronic signal processing circuit are covered by the insulating substrate so as not to disturb the measurement.
4 - Gauge according to any one of the preceding claims, characterized in that the electrodes have the form of coils with loops in the form of digits engaged comblike with each other and in that these digits extend vertically, along internal generatrices of the cylinder.
5 - Gauge according to the preceding claim, characterized in that it comprises a pair of measurement electrodes and a pair of reference electrodes, both interdigital with vertical digits, the latter being located at one end of the cylinder and occupying a small height of the latter, and the former extending over substantially the entire height of the cylinder.
6 - Gauge according to the preceding claim, characterized in that the pair of measurement electrodes and the pair of reference electrodes have a part of an electrode in common.
7 - Gauge according to any one of the preceding claims, characterized in that the cylinder comprises, on its external surface, a conductive coating acting as an electrostatic protection screen.
8 - Method of manufacturing a gauge according to any one of the preceding claims, according to which a capacitive gauge is manufactured comprising interdigital electrodes on a flat insulating substrate, and said gauge is wound with electrodes turned inwards so as to form a cylinder.
9 - Method according to the preceding claim, characterized in that the cylindrical form of the gauge is preserved by welding, bonding and/or the use of a plate of appropriate shape.
10 - Use of a gauge according to any one of Claims 1 to 8, or obtained by a method according to Claim 9, as a level gauge in a fuel tank.
PCT/EP2006/067503 2005-10-26 2006-10-17 Capacitive gauge comprising interdigital electrodes on an insulating substrate Ceased WO2007048736A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
JP2008537060A JP2009513962A (en) 2005-10-26 2006-10-17 Capacitance gauge with crossed finger electrodes on an insulating substrate
EP06807349A EP1943487A1 (en) 2005-10-26 2006-10-17 Capacitive gauge comprising interdigital electrodes on an insulating substrate
US12/091,066 US20080223128A1 (en) 2005-10-26 2006-10-17 Capacitive Gauge Comprising Interdigital Electrodes On An Insulating Substrate
BRPI0617815A BRPI0617815A2 (en) 2005-10-26 2006-10-17 capacitive meter, method of fabricating a meter, and use of a meter

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FR0510930 2005-10-26
FR0510934 2005-10-26
FR0510934 2005-10-26
FR0510930A FR2892507B1 (en) 2005-10-26 2005-10-26 CAPACITIVE GAUGE COMPRISING ELECTRODES INTERDIGITED ON AN INSULATING SUPPORT

Publications (1)

Publication Number Publication Date
WO2007048736A1 true WO2007048736A1 (en) 2007-05-03

Family

ID=37607086

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Application Number Title Priority Date Filing Date
PCT/EP2006/067503 Ceased WO2007048736A1 (en) 2005-10-26 2006-10-17 Capacitive gauge comprising interdigital electrodes on an insulating substrate

Country Status (6)

Country Link
US (1) US20080223128A1 (en)
EP (1) EP1943487A1 (en)
JP (1) JP2009513962A (en)
KR (1) KR20080063366A (en)
BR (1) BRPI0617815A2 (en)
WO (1) WO2007048736A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115683275A (en) * 2022-11-02 2023-02-03 河源市嘉辰科技有限公司 Cross-buckling interdigital electrode structure, capacitive water level sensor and precise water level detection device

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2892509B1 (en) * 2005-10-26 2007-12-21 Inergy Automotive Systems Res CAPACITIVE GAUGE FOR FUEL TANK
WO2008049913A1 (en) 2006-10-26 2008-05-02 Inergy Automotive Systems Research (Société Anonyme) Process for measuring a liquid level in a tank and associated system
US8549910B2 (en) * 2010-01-07 2013-10-08 Federal-Mogul Corporation Fuel system electro-static potential differential level sensor element and hardware/software configuration

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FR2662249A1 (en) * 1990-05-17 1991-11-22 Jaeger DEVICE FOR MEASURING THE LEVEL AND / OR VOLUME OF A LIQUID CONTAINED IN A CAPACITIVE PROBE TANK.
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CN115683275A (en) * 2022-11-02 2023-02-03 河源市嘉辰科技有限公司 Cross-buckling interdigital electrode structure, capacitive water level sensor and precise water level detection device

Also Published As

Publication number Publication date
KR20080063366A (en) 2008-07-03
BRPI0617815A2 (en) 2016-08-23
EP1943487A1 (en) 2008-07-16
JP2009513962A (en) 2009-04-02
US20080223128A1 (en) 2008-09-18

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