DE10118061A1 - Capacitative sensor element comprises numerous electrodes which interlock, made of metal plates that are held by a plastic holding element - Google Patents

Capacitative sensor element comprises numerous electrodes which interlock, made of metal plates that are held by a plastic holding element

Info

Publication number
DE10118061A1
DE10118061A1 DE2001118061 DE10118061A DE10118061A1 DE 10118061 A1 DE10118061 A1 DE 10118061A1 DE 2001118061 DE2001118061 DE 2001118061 DE 10118061 A DE10118061 A DE 10118061A DE 10118061 A1 DE10118061 A1 DE 10118061A1
Authority
DE
Germany
Prior art keywords
electrodes
sensor
plastic
liquid
frame
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
DE2001118061
Other languages
German (de)
Inventor
Bernhard Jakoby
Matthias Buskies
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.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
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
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Priority to DE2001118061 priority Critical patent/DE10118061A1/en
Publication of DE10118061A1 publication Critical patent/DE10118061A1/en
Ceased legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01VGEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS
    • G01V3/00Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/088Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices operating with electric fields
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm
    • G01F23/22Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of 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
    • G01F23/26Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of 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
    • G01F23/263Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of 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 using capacitors
    • G01F23/265Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of 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 using capacitors for discrete levels
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm
    • G01F23/22Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of 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
    • G01F23/26Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of 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
    • G01F23/263Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of 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 using capacitors
    • G01F23/268Indicating or measuring liquid level, or level of fluent solid material, e.g. indicating in terms of volume, indicating by means of an alarm by measurement of 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 using capacitors mounting arrangements of probes

Abstract

A capacitative sensor element comprises numerous electrodes (1,2) which interlock with each other. The electrodes consist of metal plates and are held by a plastic holding element (3). The latter has a plastic frame, and the electrodes are arranged in a frame inner area so that when it is dipped into a liquid the electrode sections are coated. A capacitative sensor element comprises numerous electrodes (1,2) which interlock with each other. The electrodes consist of metal plates and are held by a plastic holding element (3). The latter has a plastic frame, and the electrodes are arranged in a frame inner area so that when it is dipped into a liquid the electrode sections are coated. The electrodes are arranged in a comb structure. The sensor is formed by placing a sheet metal structure for interlocking electrodes in a mould and then filling the mould with plastic e.g. by injection molding. The metal structure is formed by stamping or etching sheet metal.

Description

State of the art

The invention is based on a capacitive sensor element or of a method for producing a capacitive Sensor element according to the genre of the independent Claims.

Capacitive sensor elements are already known, which serve as level sensors. Such sensor elements are shown in FIG. 1. The sensor elements have a printed circuit board 100 , on the upper side of which electrode structures 101 , 102 are formed as thin surface layers. The electrodes 101 are all electrically connected to one another. Likewise, the electrodes 102 are all connected to one another. A measurement capacitance consisting of the electrode group 101 and the electrode group 102 is thus formed. The capacitance between these electrodes depends on the electrode geometry and the dielectric constant of the surrounding medium. A corresponding partial capacitance is formed both on the upper side of the electrodes 101 , 102 and on the lower side of the electrodes. The partial capacitance which forms between the electrodes 101 , 102 downward is essentially determined by the dielectric constant of the carrier substrate 100 . The upper partial capacitance between the electrodes 101 , 102 is determined by the dielectric constant of the medium above the electrodes. When used as a level sensor, the sensor element according to FIG. 1 is arranged such that part of the electrodes 101 , 102 is immersed in the liquid and, depending on the level of the liquid, part of the electrodes 101 , 102 are not immersed in the liquid. Thus, if the dielectric constant of the liquid differs from the dielectric constant of air, the total capacitance measured between the electrodes 101 , 102 depends on how many of the electrodes 101 , 102 are immersed in the liquid and how many are not. Since the carrier 100 is arranged at the bottom, the capacity cannot be changed in this direction, so that the change in capacity due to the immersion or non-immersion in the liquid is relatively small. Furthermore, a printed circuit board 100 is usually used as a carrier, which has a relatively large dielectric constant. This also contributes to the fact that the measurement effect is relatively small. Furthermore, such circuit boards 100 can change over time, either due to aging or due to the diffusion of part of the measurement medium. There is then a slow shift in the measured capacitance, which is very difficult to compensate for in terms of measurement technology.

Advantages of the invention

The capacitive sensor element according to the invention and the method for producing a capacitive sensor element have the advantage over the fact that the electrodes no longer have to be attached to a surface of a carrier 100 due to the formation of the electrodes from a metal sheet. It is therefore possible to apply liquid to both the top, the bottom and the space between the electrodes and to measure a capacitance which changes in this way. Furthermore, sensor elements can be formed particularly easily from such metal sheets by forming a holding element by filling a mold with plastic, in which the metal sheets are also inserted.

The advantages of the dependent claims. It will be particularly easy Holding element formed as a frame, because the Electrode structures are held on both sides can. Electrodes can be especially simple as one piece Comb structures formed in the associated supply lines become. By adding electrodes you can easily Reference capacities are formed. Filling the form is particularly easy to do by injection molding or reaction molding. The metal sheets from which the electrodes are formed can be particularly easy by punching or etching to be edited. During production, the individual structures especially the sensitive ones Electrode structures through metallic bridges with each other can be connected, which makes handling particularly easy becomes.

drawings

Embodiments of the invention are shown in the drawings shown and in the following description explained. Show it

Fig. 1, a capacitive sensor element according to the prior art,

Fig. 2 is an external view of a sensor element according to the invention,

FIGS. 3 and 4 cross sections through the Fig. 2 and

Fig. 5 is a metal sheet as used for the manufacture.

description

In Figs. 2 to 4 show different views are shown of a sensor element according to the invention. In FIG. 2 an external view is shown in a top view, in the figure a cross section along the line III-III of FIG. 2 is shown and in FIG. 4 a cross section through the element of FIG. 2 parallel to the paper plane of FIG Fig. 2 shown.

FIG. 2 shows a sensor element which has a multiplicity of measuring electrodes 1 , 2 which are held in a frame 3 . The measuring electrodes 1 and 2 are designed as thin metal sheets, while the frame 3 is made of an insulating plastic. As can be seen in the top view according to FIG. 2 or in the section according to FIG. 3, the electrodes 1 and 2 are arranged in such a way that the electrodes interlock, ie an electrode 1 is always followed by an electrode 2 and an electrode 2 is always followed by an electrode 1 . Electrically, it is the case that the electrodes 1 are short-circuited to one another and that the electrodes 2 are short-circuited to one another. The electrodes 1 and 2 thus form two electrodes of a measuring capacity. The sensor is designed so that it can be immersed in a liquid medium. The level of the liquid can then be determined by measuring the capacitance between the interdigitated electrodes 1 , 2 . Depending on the dielectric constant of the liquid, the capacitance that is measured between the electrodes 1 , 2 will change. It is essential that this dielectric constant differs from the dielectric constant of air. The measured capacitance is influenced depending on how many of the electrodes 1 , 2 are immersed in the liquid and how many of the electrodes 1 , 2 are not immersed in the liquid. In contrast to the previously known sensors, in the sensor according to the invention the electrodes 1 , 2 which are immersed in the liquid are acted upon from all sides by the liquid, so that the measuring effect is greater than in conventional sensors in which the measuring electrodes are formed on the upper side of a substrate are. Furthermore, conventional sensors have the problem that the dielectric constant of the carrier substrate can change, in particular if the medium to be measured is diffused into the carrier plate. Then there is a slow temporal offset, which is difficult to compensate for in terms of measurement technology.

In FIGS. 2 and 3 2 also other electrodes 4, 5 in addition to the level electrodes 1 shown forming a reference capacitance. The sensor is introduced into a measuring liquid so that the further electrodes 4 , 5 , which form the reference capacitance, are always surrounded by the liquid. By measuring the capacitance between the electrodes 4 , 5 of the reference capacitance, the dielectric constant of the liquid can thus be calculated. On the basis of this calculation, it can then be concluded for the measuring capacity how large the number of measuring electrodes 1 , 2 contained in the liquid or not immersed in the liquid is.

However, the invention is not based on level sensors limited. In particular, such Electrode structures are always used wherever Capacity is measured in a liquid. This is  for example when determining the composition the liquid based on a capacity measurement, e.g. Example at Fuel type sensors, the case.

In FIG. 4 is a further view of the sensor is shown which represents a cross-section through the sensor element of FIG. 2 parallel to the plane of the paper. The cut is made in such a way that the electrodes 1 , 2 , 4 , 5 are exposed so that the embedding in the material of the frame 3 can be seen. As can be seen in the figure, the electrodes 1 are attached in one piece to a corresponding feed line 11 . Furthermore, the electrodes 2 are all attached in one piece to a corresponding feed line 12 . The feed lines 11 and 12 are completely embedded in the plastic material of the frame 3 and only protrude at the lower end in order to form connecting elements 21 and 22 . The electrode fingers 5 of the reference capacitance are also connected in one piece to the feed line 12 . The electrode fingers 4 of the reference capacitance have their own supply line 14 and their own connection 24 . The supply line 24 is also embedded in the material of the plastic frame 3 . The electrodes 1 , 2 , 4 , 5, the feed lines 11 , 12 , 14 and the connection elements 21 , 22 , 24 are formed in one piece by stamping or etching out of a metal sheet. The individual coherent metal pieces can be manufactured individually or it is possible to structure all of them from one piece at the same time. The structuring out of a single piece is explained in more detail in FIG. 5.

In FIG. 5 is a plan view is shown on a machined metal strip 51, as they are shown in FIGS. 2 to 4 from the basic structures for the electrodes are structured out. All metallic elements as explained in FIG. 4 are structured out of the metal strips 51 . In particular, the supply lines 11 , 12 , 14 and the electrodes 1 , 2 , 4 and 5 connected to them . However, a large number of connecting elements 31 , 32 are provided. The electrodes 1 , 2 and 4 , 5 are connected to one another by short connecting elements 31 so that they are joined to form a mechanically fixed grid. The conductor tracks 11 , 12 are connected by long connecting rods 32 to an outer edge 33 of the metal strip 51 . Starting from the strip 51 as it is shown in Fig. 5 is carried out the production of the plastic frame 3 by the strip is placed in a mold 51 and the plastic by injection molding or reaction casting is filled into the mold as the frame 3 that forms. The connecting elements 31 and 32 are then cut through a further processing step, in particular a stamping or sawing step, so that the electrodes 1 , 2 and 4 , 5 are then separated from one another and are no longer connected by metallic connecting elements 31 . Furthermore, the longer connecting elements 32 are severed, so that there is no longer any connection to an outer edge 33 of the metal strip 51 .

The connecting elements 31 and 32 ensure that the individual electrodes 1 , 2 , 4 , 5 and conductor tracks 11 , 12 , 14 cannot move relative to one another in the manufacturing phase. Handling is therefore particularly simple, in particular machining can be carried out without any problems. After parts of these sheet metal elements are then embedded in the plastic of the frame 3 , the individual elements are held by the frame 3 . The individual connecting elements 31 , 32 can then be severed without the relative position of the individual elements being able to be influenced thereby. A particularly simple manufacturing process can be realized in this way.

This is particularly possible to design the sheet metal strip 51 as a very long sheet metal strip, so that a large number of metal structures for a large number of sensor elements are arranged in succession on a sheet metal strip 51 . It is even possible to use a material for the sheet metal strip 51 which is of such thickness that a large number of elements 51 are located in a rolled sheet metal strip. In terms of production technology, a large number of elements can be automatically fed to a processing machine.

Claims (7)

1. Capacitive sensor element with a plurality of interlocking electrodes ( 1 , 2 ), characterized in that the electrodes ( 1 , 2 ) are designed as metal plates which are held by a holding element ( 3 ) made of plastic.
2. Sensor element according to claim 1, characterized in that the holding element ( 3 ) is designed as a plastic frame and that the electrodes ( 1 , 2 ) are arranged in an interior of the frame such that when the frame ( 3 ) is immersed in a liquid an upper side, a lower side and spaces between the electrodes ( 1 , 2 ) are acted upon by the liquid.
3. Sensor elements according to one of the preceding claims, characterized in that the electrodes ( 1 , 2 ) are designed as interdigitated comb structures, each of which is connected to supply lines ( 11 , 12 ) on one side.
4. Sensor element according to one of the preceding claims, characterized in that further electrodes ( 4 , 5 ) are provided and that at least one further supply line ( 14 ) is provided for the further electrodes ( 4 , 5 ).
5. A method for producing a capacitive sensor, characterized in that a metal sheet with metallic structures for interlocking electrodes ( 1 , 2 ) is inserted into a mold, and that a holding element ( 3 ) is formed from a plastic by filling the mold with plastic becomes.
6. The method according to claim 5, characterized in that because the mold is filled by injection molding or reaction molding he follows.
7. The method according to any one of the preceding method claims, characterized in that the metal structures are formed by stamping or etching a sheet ( 51 ).
DE2001118061 2001-04-11 2001-04-11 Capacitative sensor element comprises numerous electrodes which interlock, made of metal plates that are held by a plastic holding element Ceased DE10118061A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE2001118061 DE10118061A1 (en) 2001-04-11 2001-04-11 Capacitative sensor element comprises numerous electrodes which interlock, made of metal plates that are held by a plastic holding element

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2001118061 DE10118061A1 (en) 2001-04-11 2001-04-11 Capacitative sensor element comprises numerous electrodes which interlock, made of metal plates that are held by a plastic holding element
PCT/DE2002/001332 WO2002084228A1 (en) 2001-04-11 2002-04-10 Capacitive sensor element and method for producing a capacitive sensor element

Publications (1)

Publication Number Publication Date
DE10118061A1 true DE10118061A1 (en) 2002-10-24

Family

ID=7681219

Family Applications (1)

Application Number Title Priority Date Filing Date
DE2001118061 Ceased DE10118061A1 (en) 2001-04-11 2001-04-11 Capacitative sensor element comprises numerous electrodes which interlock, made of metal plates that are held by a plastic holding element

Country Status (2)

Country Link
DE (1) DE10118061A1 (en)
WO (1) WO2002084228A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003060438A1 (en) * 2002-01-18 2003-07-24 Robert Bosch Gmbh Device for measuring levels
DE102008013530A1 (en) 2007-10-02 2009-04-09 Robert Bosch Gmbh Fluid level sensor for fluid, particularly for fuel tank of motor vehicle, has printed circuit board and has outbound resistance structure at top of printed circuit board

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITTO20030219A1 (en) * 2003-03-25 2004-09-26 Eltek Spa Device for detecting physical variables of a fluid,
JP2014021073A (en) * 2012-07-23 2014-02-03 Aisan Ind Co Ltd Liquid sensor

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07218318A (en) * 1994-01-31 1995-08-18 Kajima Corp Liquid level and precipitate height measuring device
DE19644777C1 (en) * 1996-10-28 1998-06-04 Sican Gmbh Filling level indicator sensors for automobile fuel tank

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1498404B2 (en) * 1965-05-17 1973-05-30 Capacitive measuring transducer for level measurement hoehe
US5005409A (en) * 1989-01-13 1991-04-09 Teleflex Incorporated Capacitive liquid sensor
JPH04110618A (en) * 1990-08-30 1992-04-13 Murata Mfg Co Ltd Liquid level sensor
DE4313418A1 (en) * 1993-04-24 1994-10-27 Spohr Mestechnik Gmbh Method and device for the digital determination and remote interrogation of filling levels and levels in liquids or media of limited high viscosity, using discrete sensor positions
GB9422911D0 (en) * 1994-11-14 1995-01-04 Moonstone Technology Ltd Capacitive touch detectors

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07218318A (en) * 1994-01-31 1995-08-18 Kajima Corp Liquid level and precipitate height measuring device
DE19644777C1 (en) * 1996-10-28 1998-06-04 Sican Gmbh Filling level indicator sensors for automobile fuel tank

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Measur-Sci. Technol.7(1996), S. 79-86 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003060438A1 (en) * 2002-01-18 2003-07-24 Robert Bosch Gmbh Device for measuring levels
US6988405B2 (en) 2002-01-18 2006-01-24 Robert Bosch Gmbh Device for measuring levels
DE102008013530A1 (en) 2007-10-02 2009-04-09 Robert Bosch Gmbh Fluid level sensor for fluid, particularly for fuel tank of motor vehicle, has printed circuit board and has outbound resistance structure at top of printed circuit board

Also Published As

Publication number Publication date
WO2002084228A1 (en) 2002-10-24

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