DE3939386C2 - Device for detecting the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures - Google Patents

Device for detecting the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures

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Publication number
DE3939386C2
DE3939386C2 DE3939386A DE3939386A DE3939386C2 DE 3939386 C2 DE3939386 C2 DE 3939386C2 DE 3939386 A DE3939386 A DE 3939386A DE 3939386 A DE3939386 A DE 3939386A DE 3939386 C2 DE3939386 C2 DE 3939386C2
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DE
Germany
Prior art keywords
concentration
detecting
signal output
differential amplifier
explosive
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Expired - Fee Related
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DE3939386A
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German (de)
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DE3939386A1 (en
Inventor
Werner Woelke
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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
    • G01N27/14—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature
    • G01N27/16—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
    • 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
    • G01N27/14—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature
    • G01N27/18—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature caused by changes in the thermal conductivity of a surrounding material to be tested
    • G01N27/185—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature caused by changes in the thermal conductivity of a surrounding material to be tested using a catharometer

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  • 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)

Description

Die Erfindung betrifft ein Gerät zur Erfassung der Konzen­ tration explosibler oder gesundheitsgefährdender Gase oder zum Nachweis der Konzentration von Sauerstoff in brennbaren Gasgemischen, mit einem in einem Meßkopf angeordneten, nach dem Prinzip der Wärmetönung katalytisch arbeitenden Sensor­ widerstand in einer konstantstrom- oder konstantspannungs­ gespeisten Brückenschaltung, deren Diagonalzweig an einen Signalausgang geführt ist.The invention relates to a device for recording the concents tration of explosive or hazardous gases or to detect the concentration of oxygen in flammable Gas mixtures, with one arranged in a measuring head, after the principle of the heat tone catalytic sensor resistance in a constant current or constant voltage fed bridge circuit, the diagonal branch of one Signal output is guided.

Bei bekannten Geräten der genannten Art (vgl. z. B. DE-PS 36 22 307) ist der Diagonalzweig der Brückenschaltung im all­ gemeinen unmittelbar an den Signalausgang geführt. Das hat erhebliche Nichtlinearitäten des Meßbereiches durch die zur katalytischen Aufheizung zusätzlichen elektrothermischen Änderungen des Sensorwiderstandes bei Konstantstromversor­ gung bzw. des Sensorwiderstandes und des Referenzwider­ standes bei Konstantspannungsversorgung der Brückenschal­ tung zur Folge. Hier will die Erfindung Abhilfe schaffen.In known devices of the type mentioned (see, for example, DE-PS 36 22 307) is the diagonal branch of the bridge circuit in space mean led directly to the signal output. That has considerable non-linearities of the measuring range due to the catalytic heating additional electrothermal Changes in sensor resistance with constant current suppliers supply or the sensor resistance and the reference resistance with constant voltage supply of the bridge scarf result. The invention seeks to remedy this.

Bekannt ist es zwar auch (DE 22 14 027 C3), einen Diagonal­ zweig und einen Signalausgang einer Brückenschaltung einen Regelverstärker zwischenzuschalten, jedoch in ganz anderem Zusammenhang.It is also known (DE 22 14 027 C3), a diagonal branch and a signal output of a bridge circuit Interpose control amplifier, but in a completely different way Context.

Der Erfindung liegt die Aufgabe zugrunde, das Gerät der eingangs genannten Art so weiter zu entwickeln, daß die Linearität des von der Konzentration des gemessenen Gases abhängigen Brückensignals verbessert wird. The invention has for its object the device the kind mentioned at the outset so that the Linearity of the concentration of the measured gas dependent bridge signal is improved.  

Hierzu lehrt die vorliegende Erfindung, daß dem Diagonal­ zweig und dem Signalausgang ein Shunt-Regelverstärker zwischengeschaltet ist. Hierzu ist nach einer bevorzugten Ausführungsform dem Diagonalzweig ein Differenzverstärker und dem Differenzverstärker ein Transistor nachgeschaltet, dessen Drainageschluß mit dem positiven Eingang des Differenzverstärkers sowie dem zugeordneten Diagonal­ zweigpunkt der Brückenschaltung und dessen Arbeitswiderstand mit dem Signalausgang verbunden ist.To this end, the present invention teaches that the diagonal branch and the signal output a shunt control amplifier is interposed. This is according to a preferred one Embodiment of the diagonal branch a differential amplifier and a transistor connected downstream of the differential amplifier, whose drainage closure with the positive  Input of the differential amplifier and the assigned diagonal branch point of the bridge circuit and its load resistance with the signal output is connected.

Die durch die Erfindung erreichten Vorteile sind zunächst darin zu sehen, daß die Linearität des am Signalausgang anstehenden Signals erheblich verbessert ist; die Verbesserung der Linearisie­ rung kann bis zum Faktor 10 gehen. Diese Linearitätsverbesserung ist auf die geringere Erwärmung des Sensorwiderstandes während des Wärmetönungsprozesses zurückzuführen. Seine elektrische Be­ lastung wird nämlich durch den Shunt-Regelverstärker entsprechend verringert. Vorteilhaft ist auch, daß der Strombedarf im Gegensatz zum bekannten Gerät bei zunehmender Gaskonzentration abnimmt, so daß die Explosions- und Eigensicherheit leichter erreichbar ist.The advantages achieved by the invention are initially in it to see that the linearity of the pending at the signal output Signal is significantly improved; the improvement of linearization tion can go up to a factor of 10. This linearity improvement is due to the lower heating of the sensor resistance during attributed to the toning process. Its electrical loading load is namely correspondingly by the shunt control amplifier decreased. It is also advantageous that the electricity requirement in contrast to the known device decreases with increasing gas concentration, so that explosion and intrinsic safety is easier to achieve.

Im folgenden wird die Erfindung anhand einer ein Ausführungs­ beispiel darstellenden Zeichnung erläutert.The invention is based on an embodiment example illustrative drawing explained.

Die einzige Figur zeigt ein Gerät zur Erfassung der Konzentration explosibler oder gesundheitsgefährdender Gase oder zum Nachweis der Konzentration von Sauerstoff in brennbaren Gasgemischen. Das Gerät arbeitet mit einem nach dem Prinzip der Wärmetönung kata­ lytisch arbeitenden Sensorwiderstand 1, der in einem Meßkopf 2 angeordnet ist. Der Meßkopf 2 ist lediglich schematisch angedeutet und kann auch weitere Teile des Gerätes beinhalten. Der Sensor­ widerstand 1 befindet sich mit drei weiteren Widerständen 3, 4, 5 in einer Brückenschaltung 6. Der Widerstand 3 ist baugleich mit dem Sensorwiderstand 1, es fehlt ihm lediglich eine katalytisch wirksame Oberfäche, die die Wärmetönung bewirkt; dieser Wider­ stand 3 kompensiert unter anderem Meßwertverfälschungen, die durch Änderungen der Feuchte und Temperatur des zu messenden Gases entstehen können.The only figure shows a device for detecting the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures. The device works with a cata lytically working sensor resistor 1 , which is arranged in a measuring head 2 , on the principle of heat toning. The measuring head 2 is only indicated schematically and can also contain other parts of the device. The sensor resistor 1 is located with three further resistors 3 , 4 , 5 in a bridge circuit 6 . The resistor 3 is structurally identical to the sensor resistor 1 , it only lacks a catalytically active surface which causes the heat to be released; This opposed 3 was compensated for, among other things, falsifications of measurement values, which can arise from changes in the humidity and temperature of the gas to be measured.

Zur Verstärkung der Brückensignalspannung an den Diagonalzweig­ punkten 7, 8 ist ein Differenzverstärker 9 nachgeschaltet. Die mit diesem verstärkte Brückensignalspannung wird vom Arbeitswider­ stand 10 eines nachgeschalteten Transistors 11 auf einen Signal­ ausgang 12, 13 geführt. Der Drainanschluß 14 des Transistors 11 ist sowohl mit dem positiven Eingang 15 des Differenzverstärkers 9 als auch mit dem Diagonalzweigpunkt 7 der Brückenschaltung 6 verbunden. Damit besteht eine Parallelschaltung des Transistors 11 mit seinem in Reihe liegenden Arbeitswiderstand 10 zum Wärme­ tönungssensor bzw. Sensorwiderstand 1. In Verbindung mit dem Differenzverstärker 9 ist die Schaltung somit als Shunt-Regelver­ stärker 9, 10, 11 wirksam, dessen Bezugsspannung die Teilspan­ nung der beiden Widerstände 4, 5 ist; das gilt insbesondere, wenn die durch die katalytische Verbrennung gebildete Reaktionswärme des Sensorwiderstandes 1 dessen ohmschen Wert vergrößert.To amplify the bridge signal voltage at the diagonal branch points 7 , 8 , a differential amplifier 9 is connected downstream. The amplified with this bridge signal voltage is from the working resistance 10 of a downstream transistor 11 to a signal output 12 , 13 out. The drain connection 14 of the transistor 11 is connected both to the positive input 15 of the differential amplifier 9 and to the diagonal branch point 7 of the bridge circuit 6 . So there is a parallel connection of the transistor 11 with its series resistance 10 to the thermal tint sensor or sensor resistor. 1 In connection with the differential amplifier 9 , the circuit is thus effective as a shunt control amplifier 9 , 10 , 11 , the reference voltage of which is the partial voltage of the two resistors 4 , 5 ; this applies in particular if the heat of reaction of the sensor resistor 1 formed by the catalytic combustion increases its ohmic value.

Claims (2)

1. Gerät zur Erfassung der Konzentration explosibler oder gesund­ heitsgefährdender Gase oder zum Nachweis der Konzentration von Sauerstoff in brennbaren Gasgemischen, mit einem in einem Meß­ kopf angeordneten, nach dem Prinzip der Wärmetönung katalytisch arbeitenden Sensorwiderstand in einer konstantstrom- oder konstant­ spannungsgespeisten Brückenschaltung, deren Diagonalzweig an einen Signalausgang geführt ist, gekennzeichnet durch einen dem Diagonalzweig (7. 8) und dem Signalausgang (12, 13) zwischenge­ schalteten Shunt-Regelverstärker (9, 10, 11).1.Device for detecting the concentration of explosive or health-endangering gases or for detecting the concentration of oxygen in flammable gas mixtures, with a sensor head arranged in a measuring head, which works catalytically according to the principle of heat toning, in a constant current or constant voltage-fed bridge circuit, the diagonal branch of which is led to a signal output, characterized by a diagonal branch (7. 8) and the signal output ( 12 , 13 ) interposed shunt control amplifier ( 9 , 10 , 11 ). 2. Gerät nach Anspruch 1, dadurch gekennzeichnet, daß dem Dia­ gonalzweig (7, 8) ein Differenzverstärker (9) und dem Differenz­ verstärker (9) ein Transistor (11) nachgeschaltet ist, dessen Drain­ anschluß (14) mit dem positiven Eingang (15) des Differenzver­ stärkers (9) sowie dem zugeordneten Diagonalzweigpunkt (7) der Brückenschaltung (6) und dessen Arbeitswiderstand (10) mit dem Signalausgang (12, 13) verbunden ist.2. Apparatus according to claim 1, characterized in that the slide gonalzweig (7, 8), a differential amplifier (9) and the differential amplifier (9) is followed by a transistor (11) whose drain connection (14) to the positive input ( 15 ) of the differential amplifier ( 9 ) and the associated diagonal branch point ( 7 ) of the bridge circuit ( 6 ) and its load resistor ( 10 ) is connected to the signal output ( 12 , 13 ).
DE3939386A 1989-02-17 1989-11-29 Device for detecting the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures Expired - Fee Related DE3939386C2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE3939386A DE3939386C2 (en) 1989-02-17 1989-11-29 Device for detecting the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE8901861U DE8901861U1 (en) 1989-02-17 1989-02-17 Device for measuring the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures
DE3939386A DE3939386C2 (en) 1989-02-17 1989-11-29 Device for detecting the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures

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DE3939386A1 DE3939386A1 (en) 1990-08-23
DE3939386C2 true DE3939386C2 (en) 1998-12-24

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DE8901861U Expired DE8901861U1 (en) 1989-02-17 1989-02-17 Device for measuring the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures
DE3939386A Expired - Fee Related DE3939386C2 (en) 1989-02-17 1989-11-29 Device for detecting the concentration of explosive or hazardous gases or for detecting the concentration of oxygen in flammable gas mixtures

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006011117A1 (en) * 2006-03-08 2007-09-13 Esders Gmbh Combustible gas detecting device for use in e.g. chemical system, has sensor arranged in measuring space, where value for humidity contained in gas mixture and/or temperature of gas mixture is determined by another sensor

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2670291B1 (en) * 1990-12-07 1994-11-04 Icare Sa TEMPERATURE MONITORING DEVICE FOR A SENSITIVE ELEMENT OF A FILAMENT FUEL GAS DETECTOR.

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2214027C3 (en) * 1972-03-20 1976-04-08 Siemens AG, 1000 Berlin und 8000 München Control device with a control amplifier in the diagonal output of a bridge circuit
DE3622307C2 (en) * 1986-07-03 1988-08-04 Draegerwerk Ag, 2400 Luebeck, De

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2214027C3 (en) * 1972-03-20 1976-04-08 Siemens AG, 1000 Berlin und 8000 München Control device with a control amplifier in the diagonal output of a bridge circuit
DE3622307C2 (en) * 1986-07-03 1988-08-04 Draegerwerk Ag, 2400 Luebeck, De

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006011117A1 (en) * 2006-03-08 2007-09-13 Esders Gmbh Combustible gas detecting device for use in e.g. chemical system, has sensor arranged in measuring space, where value for humidity contained in gas mixture and/or temperature of gas mixture is determined by another sensor

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DE8901861U1 (en) 1989-04-06
DE3939386A1 (en) 1990-08-23

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