EP1370853A2 - Capteur de detection de gaz - Google Patents

Capteur de detection de gaz

Info

Publication number
EP1370853A2
EP1370853A2 EP02727198A EP02727198A EP1370853A2 EP 1370853 A2 EP1370853 A2 EP 1370853A2 EP 02727198 A EP02727198 A EP 02727198A EP 02727198 A EP02727198 A EP 02727198A EP 1370853 A2 EP1370853 A2 EP 1370853A2
Authority
EP
European Patent Office
Prior art keywords
sensor
signal
sensor element
sensor according
gas
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Withdrawn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
EP02727198A
Other languages
German (de)
English (en)
Inventor
Michael Bauer
Isolde Simon
Christian Krummel
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.)
Paragon AG
Original Assignee
Robert Bosch GmbH
Paragon AG
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, Paragon AG filed Critical Robert Bosch GmbH
Publication of EP1370853A2 publication Critical patent/EP1370853A2/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Withdrawn legal-status Critical Current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
    • G01N27/123—Circuits particularly adapted therefor, e.g. linearising circuits for controlling the temperature
    • G01N27/124—Circuits particularly adapted therefor, e.g. linearising circuits for controlling the temperature varying the temperature, e.g. in a cyclic manner

Definitions

  • the invention is based on a sensor for detecting gases according to the category of the independent claim.
  • a gas sensor realized in micromechanical technology has become known, which is used for targeted Development of a selectivity to a given type of gas is heated to different operating temperatures.
  • the micromechanical sensor is heated in pulsed operation, the sensor element being at least approximately in thermal equilibrium at all times due to its low heat capacity.
  • the sensor signal is obtained from a measurement of the conductivity of the sensor element, which takes place during heating breaks.
  • the duration of the heating pulses varies, for example, from 6 to 300 milliseconds.
  • a complete detection cycle for example in the minute range, contains numerous heating pulses, the operating temperature being increased either from heating pulse to heating pulse or from heating pulse packet to heating pulse packet.
  • the signals recorded in the pulse pauses are put together to form a curve, the one has different course depending on the temperature, which is characteristic of the type of gas to be detected.
  • the invention has for its object a sensor for
  • Specify detection of gases in which a weighting factor can be specified when the sensor element is exposed to at least two different types of gas.
  • the sensor according to the invention for the detection of gases provides that in an evaluation circuit for the sensor signal emitted by a sensor element, an evaluation of the temporal signal curve after a temperature change is provided, the sensor signal being at least in a time interval in which the chemical equilibrium in the sensor element not available. Based on tests, it was found that after a temperature change in the sensor element, the sensor element being at least approximately in thermal equilibrium, the concentrations of more than one type of gas are inferred from the signal curve, which lies at least partially before chemical equilibrium is reached in the sensor element can be applied to the sensor element. If more than one gas type is applied to the sensor element, the signal curve therefore depends on the ratio of the concentrations of the least two gas types involved.
  • the sensor according to the invention for the detection of gases therefore makes it possible, by specifying special operating conditions of the sensor element, to provide a sensor signal in which the at least two gas types involved are provided with a predetermined ratio of their concentrations influence the sensor signal.
  • a particularly simple evaluation of the sensor signal curve results if at least a first and then at least a second signal value are recorded, the information being contained in the difference or quotient of the least two signal values.
  • An advantageous embodiment provides that the second signal value is detected when the sensor element has at least approximately reached its chemical equilibrium.
  • the evaluation of the signal curve extends from an area in which the chemical equilibrium has not been reached to an area in which this is the case.
  • the expected signal changes are maximum and, due to the higher signal swing, enable a simplified technical implementation in the evaluation circuit.
  • a particularly simple setting of the weighting factor of the at least two predetermined types of gas with which the sensor element is acted on is achieved by specifying the amount of the temperature changes.
  • the weighting factor can also be influenced by a suitable definition of the starting temperature before the temperature change.
  • the weighting factor can also be specified by specifying the evaluation of the time interval and by specifying the time of detection of the first and / or the second signal value.
  • the sensor according to the invention can advantageously be used for the simultaneous detection of existing nitrogen oxides and carbon monoxide in the breathing air. Such a sensor is more advantageous than air sensor in a force
  • switching signals for an air conditioning system are determined from the sensor signal curve in the evaluation circuit, which can include these switching signals for controlling the ventilation flap, fans or air filters.
  • FIG. 1 shows a block diagram of a sensor according to the invention for detecting gases
  • FIGS. 2a-2c show signal curves as a function of the time that occur in the sensor according to the invention according to FIG.
  • FIG. 1 shows a signal generator 10 which outputs a heating control signal 11 both to a heating controller 12 and to a time control 13.
  • the heating controller 12 outputs 35 a heating signal 14 to a heating element 15, which a sensor heated element 16.
  • the raw sensor signal 17 provided by the sensor element 16 is processed in a sensor signal processing 18 to the sensor signal S.
  • the sensor signal S reaches both a first and a second sample / hold memory 19, 20.
  • the heating control signal 11 causes the heating controller 12 to change the heating signal 14 from the first heating signal level Hl to the second heating signal level H2 at a first time Tl.
  • the temperature in the heating element 15 and accordingly in the sensor element 16 then drops from the first temperature Tempi to the second temperature Temp2.
  • a thermal time constant is achieved which can be in the range of a few milliseconds, for example 10-30 milliseconds.
  • the temperature change from the first temperature Tempi to the second temperature Temp2 takes place correspondingly quickly.
  • the first time interval II is followed by the second time interval 12, within which a thermal equilibrium has been reached in the sensor element 16, but no chemical equilibrium has been reached by the gas acting on the sensor element 16.
  • an evaluation of the course of the sensor signal S shown in FIG. 2a is provided as a function of the time t, the sensor signal S being at least partially in the second time interval II, in which the chemical equilibrium is not present.
  • the sensor signal S provides the sensor signal processing 18, which converts the raw sensor signal 17 into a signal suitable for further signal processing.
  • the sensor rest signal 17 lies, for example, as a signal element 16 flowing current, the amount of which depends on the electrical resistance or conductance of the sensor element 16 at a predetermined operating voltage.
  • a pulsed operation of the sensor element 16 can be provided.
  • the sensor signal S provided by the sensor signal conditioning unit 18 according to FIG. 2a should be a measure of the time course of the electrical resistance of the sensor element 16.
  • the sensor signal S Starting from an output signal level S1, the sensor signal S increases in the first time interval II during the temperature reduction of the sensor element 16 to a final value which is not specified in more detail, from which a signal drop can be determined at constant temperature Temp2 while the chemical balance is being divided.
  • the two sample / hold memories 19, 20 are provided, which are controlled by the sample signals 21, 22, which the time control 13 determines from the heating control signal 11.
  • the / Hold signal 21 is generated at the second time TA1 and causes the first sample / hold memory 19 to take over the first signal value S2 of the sensor signal S present at the second time TAl and stores it.
  • an evaluation of the signal curve of the sensor signal S is provided, which lies at least partially in the second time interval 12.
  • the evaluation of the signal curve is possible, for example, by forming a difference between signal levels.
  • the sampling is therefore provided at the third point in time TA3 of the sensor signal S at which S has a second signal value S3.
  • the sampling can be, for example, towards the end of the second time interval 12.
  • the third point in time TA2 is at which the second sampling / Hold memory 20, caused by the second sample / hold signal 22, takes over and stores the second signal value S3 in a third time interval 14, in which the chemical equilibrium in sensor element 16 is at least approximately established or has already approximately been set.
  • the determination of the evaluation in the third time interval 13 enables the greatest possible level change in the sensor signal S to be detected and simplifies the requirements for the signal evaluation 23, which include, for example, the difference between the first and second signal values S2, S3 of the sensor signal S or other computing operations described in more detail below performs.
  • the determination of the beginning of the third time interval 13, at which it is assumed that the chemical equilibrium in the sensor element 16 is at least approximately adjusted, can be carried out on the basis of experiments and is determined at a point in time after which the sensor signal S changes until a saturation level S4 is reached only changes a predetermined percentage of, for example, 10 or 5%.
  • the time duration of the second and third time intervals 12, 13 is, for example, in the range of 100-200 milliseconds, it being possible for the two time intervals 12, 13 to be at least approximately the same length, for example.
  • the heating signal level changes, starting from the second heating signal level H3, back to the first heating signal level H1, which leads to an increase in temperature from the second temperature Temp2 to the first temperature Tempi in the sensor element 16.
  • the renewed temperature change takes place in the fourth time interval 14, the duration of which corresponds to that of the first time interval II.
  • the sensor signal S falls from the saturation level S4 to a return level S5 during the fourth interval 14.
  • the amount of change in sensor signal S during First time interval II, on the one hand, and during fourth time interval 14, depending on the concentration of the different types of gas with which sensor element 16 is acted upon, can differ considerably in some cases.
  • a further signal evaluation in the further signal course after the fourth time interval 14 can be provided, since at this point in time there is a thermal equilibrium in the sensor element 16 and on the other hand the chemical equilibrium has not been reached.
  • the signal evaluation 23 can provide an output signal 24 which reflects more detailed information about the curve shape of the signal S, which lies at least partially in the second subinterval 12. For example, considerably more signal values S2, S3 can be recorded than shown in the exemplary embodiment. In addition or as an alternative to the determination of signal differences, the determination of quotients can be provided.
  • the signal evaluation 23 determines a mathematical function that describes the signal curve of the sensor signal S as at least approximately.
  • An evaluation by interpolation of several signal values S2, S3 can provide parameters of the underlying functional relationships. For example, it can be determined whether there is at least approximately a linear course or an exponential signal course. In the case of an exponential signal curve, the signal offset and the exponent can be specified. It has been demonstrated experimentally that a gradual change from an exponential course to a linear signal course of the sensor signal S is based on an aging process of the sensor element 16. It is therefore possible to set a threshold give that indicates that the sensor element 16 should be replaced if necessary. The thresholds can be given by the parameters of the exponential or linear curve shape.
  • a further advantageous embodiment provides for the sensor element 16 to be initially exposed to a gas type or a gas mixture to be detected and then to be exposed to air. By evaluating a relative signal change in both cases, a statement can be made about the sensitivity of the sensor element 16 to the type of gas or the gas mixture.
  • the sensor according to the invention for the detection of gases can be used, for example, as an air quality sensor in a motor vehicle, in which at least one output signal 24 is passed on to an air conditioning system (not shown in more detail).
  • the air conditioning system can take into account the switching signal 24 when actuating an air flap, when operating fans or, for example, when operating air filters.
  • the sensor element 16 for example a tin oxide semiconductor gas sensor, is provided, for example, for determining the concentration of
  • the weighting factor can preferably take place by determining the amount of the temperature change from the first temperature Tempi to the second temperature Temp2. Another possibility is given by specifying the initial temperature, in the exemplary embodiment shown the first temperature tempi. Another way to add the weighting factor influence, lies in the determination of the duration of the second time interval 12, during which the chemical equilibrium is not present in the sensor element 16.
  • a further possibility for influencing the weighting factor lies in the determination of the temporal position of the scanning signals 21, 22 at the second and third times TAl, TA2.
  • the influence of the parameters mentioned on the sensitivity to individual types of gas and in particular to the weighting factor when the sensor element 16 is exposed to different types of gas can preferably be determined experimentally.

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 Fluid Adsorption Or Reactions (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

L'invention concerne un capteur de détection de gaz. Selon l'invention, une évaluation de signal (23) émet un signal de sortie (24), et un facteur de pondération est défini pour au moins deux types de gaz appliqués à l'élément capteur (16). Par ailleurs, un chauffage de capteur (15) effectue une modification de température (temp1, temp2) de l'élément capteur (16) dans un premier intervalle de temps (I1) inférieur au temps requis par l'élément capteur (16) pour créer un équilibre chimique, l'élément capteur (16) étant au moins approximativement en équilibre thermique. L'évaluation de signal (23) évalue une caractéristique temporelle du signal de capteur après la modification de température (temp1, temp2), le signal de capteur (S) étant au moins partiellement situé dans un deuxième intervalle de temps (I2) dans lequel l'équilibre chimique de l'élément capteur (16) n'est pas créé.
EP02727198A 2001-03-09 2002-03-05 Capteur de detection de gaz Withdrawn EP1370853A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE2001111269 DE10111269A1 (de) 2001-03-09 2001-03-09 Sensor zur Detektion von Gasen
DE10111269 2001-03-09
PCT/DE2002/000799 WO2002073176A2 (fr) 2001-03-09 2002-03-05 Capteur de detection de gaz

Publications (1)

Publication Number Publication Date
EP1370853A2 true EP1370853A2 (fr) 2003-12-17

Family

ID=7676796

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02727198A Withdrawn EP1370853A2 (fr) 2001-03-09 2002-03-05 Capteur de detection de gaz

Country Status (3)

Country Link
EP (1) EP1370853A2 (fr)
DE (1) DE10111269A1 (fr)
WO (1) WO2002073176A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9945023B2 (en) 2010-06-30 2018-04-17 H.C. Starck, Inc. Touch screen device comprising Mo-based film layer and methods thereof

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10255703A1 (de) * 2002-11-29 2004-07-01 Robert Bosch Gmbh Schaltungsanordnung zum Betreiben eines Sensors mit einem Heizelement
US7803039B2 (en) * 2004-06-18 2010-09-28 Denso Corporation Method of controlling air intake into air conditioned enclosure
DE102007057500A1 (de) * 2007-11-29 2009-06-10 Siemens Ag Gassensorelement
GB2499842A (en) * 2012-03-02 2013-09-04 Crowcon Detection Instr Ltd Temperature regulated multiple gas sensor
DE102012210525A1 (de) * 2012-06-21 2013-12-24 Robert Bosch Gmbh Verfahren zur Funktionskontrolle eines Sensors zur Detektion von Teilchen und Sensor zur Detektion von Teilchen

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2911928B2 (ja) * 1989-12-14 1999-06-28 フィガロ技研株式会社 ガス検出方法
DE19543296C2 (de) * 1995-11-21 2001-02-22 I T V I Internat Techno Ventur Verfahren zur Ermittlung absoluter Gaskonzentrationen unter Verwendung halbleitender Gassensoren
DE19959925C2 (de) * 1999-12-11 2003-09-18 Eads Deutschland Gmbh Verfahren zur Bestimmung von Gaskonzentrationen mit einem Dünnschicht-Halbleiter-Gassensor und Dünnschicht-Halbleiter-Gassensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO02073176A3 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9945023B2 (en) 2010-06-30 2018-04-17 H.C. Starck, Inc. Touch screen device comprising Mo-based film layer and methods thereof

Also Published As

Publication number Publication date
WO2002073176A2 (fr) 2002-09-19
DE10111269A1 (de) 2002-09-12
WO2002073176A3 (fr) 2003-10-02

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