EP1102981A1 - Detecteur de gaz avec grille de protection pour minimiser les influences de courants de fuite, et utilisation d'un tel detecteur - Google Patents

Detecteur de gaz avec grille de protection pour minimiser les influences de courants de fuite, et utilisation d'un tel detecteur

Info

Publication number
EP1102981A1
EP1102981A1 EP99942722A EP99942722A EP1102981A1 EP 1102981 A1 EP1102981 A1 EP 1102981A1 EP 99942722 A EP99942722 A EP 99942722A EP 99942722 A EP99942722 A EP 99942722A EP 1102981 A1 EP1102981 A1 EP 1102981A1
Authority
EP
European Patent Office
Prior art keywords
current
gas sensor
shield electrode
sensor according
temperature
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.)
Withdrawn
Application number
EP99942722A
Other languages
German (de)
English (en)
Inventor
Andreas Bausewein
Eric Chemisky
Susanne Kornely
Hans Meixner
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.)
Siemens AG
Siemens Corp
Original Assignee
Siemens AG
Siemens Corp
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 Siemens AG, Siemens Corp filed Critical Siemens AG
Publication of EP1102981A1 publication Critical patent/EP1102981A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/122—Circuits particularly adapted therefor, e.g. linearising circuits

Definitions

  • the present invention relates to heated gas sensors as they have recently been used for the precise control and monitoring of combustion processes and exhaust gas purification devices with e.g. Catalysts are provided and used.
  • Such high-temperature gas sensors usually consist of a substrate (platelet or film) which is coated with a gas-sensitive layer provided with electrodes as a sensor element and which is heated to temperatures of, for example, platinum by means of an electrical heating element. 700 to 900 ° C is heated. This heating solves the task of keeping the sensor temperature constant irrespective of the flow conditions in the exhaust tract and the exhaust gas temperature, as a result of which the cross sensitivity of the sensor to the temperature is minimized.
  • Such an electric heating element is usually in the
  • Substrate e.g. made of aluminum oxide, embedded. This protects it from the oxidation effects that occur at high temperatures.
  • the heating is supplied with unipolar rectangular PW signals (pulse width modulation), namely in order to save electrical energy for the sensor heating.
  • the gas-sensitive sensor element located on the top of the substrate generally only supplies weak electrical signals in the ⁇ A range, e.g. depending on the gas to be detected / measured. approx. 1 volt operating voltage.
  • the problem arises that the effect of the current flow through the heating element has a disruptive influence on the measuring sensitivity of the sensor. This influence is also due to the use of good insulators
  • the substrate cannot be ruled out because the insulator materials available for the substrate have a disturbingly high electrical conductivity at temperatures above 600 ° C.
  • a known remedy is to measure the gas-sensitive sensor signals during breaks in the otherwise flowing heating current.
  • the object of the present invention is to provide a measure with which the problems set out above can be solved in a satisfactory manner and, in particular, sensor signals of the gas sensor which are unaffected by the operation of the heating of the sensor can be obtained over the period of time.
  • the present invention is based on the idea of changing the usual structure of a gas sensor with integrated heating in such a way that influences of the heater on the measuring sensitivity are largely excluded, in particular for sensors with heating temperatures between 500 and 1000 ° C.
  • the invention or as a supplement to this is here also achieved that not only high-quality, electrically highly insulating insulator substrates, for example only high-purity aluminum oxide, can be used.
  • the principle of the invention provides for a shielding electrode to be inserted into the structure of the gas sensor element provided with a heating element, by means of which leakage currents originating from the area of the heating element are prevented from penetrating into the physically effective sensor area. It is further provided that unipolar fractions of leakage currents from the sensor element to the shield electrode (or vice versa) are minimized by the potential of the shield electrode chosen according to the invention.
  • Figure 1 shows a schematic diagram of the invention.
  • FIG. 2 shows in relation to FIG. 1 a circuit structure with adjustment / regulation of the potential of the shield electrode.
  • Figure 3 shows a circuit structure with a potential control, connected to a temperature measuring device.
  • FIG. 1 which serves only as a schematic overview, shows sensor 1 and 11 denotes the sensor element.
  • the heating element which is fed from a controllable heating current source 112, is designated by 12.
  • the shield electrode provided according to the invention is designated by 13. This is able to absorb both leakage currents Ih originating from the heating element 12 and leakage currents Is originating from the sensor element 11 and derives them (Ih + Is), namely insofar as a suitably dimensioned potential P with a low internal resistance is applied to this shield electrode 13.
  • the electrical potential applied to the shield electrode 13 is preferably dimensioned such that the mean value measured over time periods ( ⁇ t) between gas sensor element 11 and shield electrode 13 of the amount of charge ( ⁇ Q x ⁇ t) of unipolar components of leakage currents occurring is minimized.
  • this potential provided according to the invention is kept constant and is dimensioned such that the time average of a current Is determined as described below is minimized.
  • a development of the invention makes it possible to carry out the minimization “on-lme”, in particular for the detection of currents in the nA range.
  • This development provides that the potential of the shield electrode 13 is continuously controlled with the aid of sensor-internal signals and the current Is is continuously increased 2 shows a circuit diagram as an example of an embodiment according to the invention, the circuit of FIG. 2 contains, in addition to the details 11 to 13 already mentioned, a regulator circuit 14 and a controllable potential source 15. The latter is the circuit of the shield electrode inserted as shown.
  • a measuring current Im flows through the sensor element 11 via the connections 111, namely for measuring the actual gas sensor measurement signal.
  • This measuring current is allowed to flow with a continuously, in particular periodically changing direction Im + and Im-.
  • the gas sensor measurement signal is measured so that it is not influenced by the heating current at times when no heating current flows through the heating element. With e.g. clocked heating current, this measurement takes place in the clock breaks. This rule also applies to the invention.
  • the difference value Im + minus Im- of the two measuring currents of the sensor element measured as above is determined and this differential current value is fed to the controller 14 of the control circuit provided according to the invention as a signal of a unipolar current.
  • This difference measured value is the above-mentioned current value Is between the sensor element and the shield electrode, obtained by indirect measurement.
  • the control of the potential source 15 by the output signal of the controller 14 then takes place and has the result that, according to the invention, the shield electrode 13 is preferably kept continuously at such an electrical potential that the current value Is is continuously minimized, at least averaged over time.
  • a low-pass filter 26 can also preferably be provided in the control circuit, which protects the actual control system against possible disturbances that could come from the heating power supply.
  • the material of the or. the shield electrode 13 must be at least an order of magnitude better electrically conductive than the electrical insulation between the sensor element and the Shield electrode.
  • the shield electrode 13 is a metallic layer made of, for example, platinum, platinum metal and the like. within the construction. However, it is also sufficient to provide a mesh / grid that is not too wide-meshed.
  • FIG. 3 A further embodiment of the embodiment according to FIG. 2 is shown in FIG. 3. Reference numerals already described for FIG. 2 also apply to FIG. 3.
  • the shield electrode 13 is also used and designed as an integrated temperature sensor. Such a constructively integrated temperature sensor is of great advantage.
  • the measurement of the temperature is carried out by measuring the electrical resistance of the material of the shield electrode 13.
  • the material of the shield electrode 13 has a temperature-dependent specific electrical resistance.
  • FIG. 3 shows an AC voltage source 21 for a measuring current that flows through a measuring resistor 22 as a measuring element through at least a portion of the shield electrode 13.
  • the temperature value of the shield electrode 13 can be detected as a voltage drop across the measuring resistor 22.
  • a relatively low frequency is preferred for the electrical current of the AC voltage source 21 flowing through the shield electrode 13 in its function as a temperature sensor.
  • the bandpass filter 24 is designed so that it only passes the frequency of the temperature measuring current. If necessary, a rectifier stage 25 is also provided, at whose output the temperature signal can then be obtained.
  • the controller 14 is advantageously additionally preceded by a low-pass filter 26 with which (also) disturbances generated by the temperature measurement can be kept away from the control loop.
  • the potential value to be set / regulated for the shield electrode can be determined from the measured variable I s , which is determined as stated above.
  • the actual measurement of the gas-sensitive sensor value Us is carried out, as in the prior art, preferably using alternating current as the measuring current.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)

Abstract

L'invention concerne un détecteur de gaz et un procédé permettant de le faire fonctionner, ledit détecteur comportant, entre son élément de détection (11) et son dispositif de chauffage (12), une grille de protection (13) qui doit être raccordée à un potentiel (P) de préférence régulé, cela pour minimiser des courants unipolaires (Is).
EP99942722A 1998-07-24 1999-07-01 Detecteur de gaz avec grille de protection pour minimiser les influences de courants de fuite, et utilisation d'un tel detecteur Withdrawn EP1102981A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19833453 1998-07-24
DE1998133453 DE19833453C2 (de) 1998-07-24 1998-07-24 Vorrichtung und Betriebsverfahren an/in geheizten Gassensoren zur Minimierung von Leckstrom-Einflüssen
PCT/DE1999/001902 WO2000007005A1 (fr) 1998-07-24 1999-07-01 Detecteur de gaz avec grille de protection pour minimiser les influences de courants de fuite, et utilisation d'un tel detecteur

Publications (1)

Publication Number Publication Date
EP1102981A1 true EP1102981A1 (fr) 2001-05-30

Family

ID=7875256

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99942722A Withdrawn EP1102981A1 (fr) 1998-07-24 1999-07-01 Detecteur de gaz avec grille de protection pour minimiser les influences de courants de fuite, et utilisation d'un tel detecteur

Country Status (4)

Country Link
EP (1) EP1102981A1 (fr)
JP (1) JP2002521688A (fr)
DE (1) DE19833453C2 (fr)
WO (1) WO2000007005A1 (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10011562C2 (de) 2000-03-09 2003-05-22 Daimler Chrysler Ag Gassensor
DE10133160C1 (de) * 2001-07-07 2003-01-30 Bosch Gmbh Robert Sensorelement mit leitfähiger Abschirmung
DE10200052A1 (de) * 2002-01-03 2003-07-24 Bosch Gmbh Robert Sensorelement
DE10339967A1 (de) 2002-08-30 2004-04-15 Denso Corp., Kariya Mehrschicht-Gassensorelement
DE102005018438A1 (de) * 2005-04-21 2006-10-26 Robert Bosch Gmbh Beheizter amperometrischer Sensor sowie Verfahren zu seinem Betrieb
DE102019202242A1 (de) * 2019-02-19 2020-08-20 Inficon Gmbh Gasdetektor mit einer Ionisiervorrichtung

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4332225A (en) * 1980-10-02 1982-06-01 General Motors Corporation Internal combustion engine with oxygen sensor heater control
DE3120159A1 (de) * 1981-05-21 1982-12-09 Bosch Gmbh Robert Elektrochemischer messfuehler fuer die bestimmung des sauerstoffgehaltes in gasen
JPS59197851A (ja) * 1983-04-26 1984-11-09 Ngk Insulators Ltd 電気化学的素子および装置
US4839019A (en) * 1986-11-20 1989-06-13 Fuji Electric Co., Ltd. Oxygen sensor
JPH0684950B2 (ja) * 1987-03-03 1994-10-26 日本碍子株式会社 電気化学的装置
DE3807603C2 (de) * 1988-03-08 1994-01-20 Fraunhofer Ges Forschung Halbleitender Gassensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0007005A1 *

Also Published As

Publication number Publication date
DE19833453C2 (de) 2000-06-15
DE19833453A1 (de) 2000-02-10
WO2000007005A1 (fr) 2000-02-10
JP2002521688A (ja) 2002-07-16

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