CN202814906U - Catalytic combustion type gas sensor - Google Patents
Catalytic combustion type gas sensor Download PDFInfo
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- CN202814906U CN202814906U CN 201220066736 CN201220066736U CN202814906U CN 202814906 U CN202814906 U CN 202814906U CN 201220066736 CN201220066736 CN 201220066736 CN 201220066736 U CN201220066736 U CN 201220066736U CN 202814906 U CN202814906 U CN 202814906U
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- triode
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- catalytic combustion
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Abstract
The utility model relates to a catalytic combustion type gas sensor which comprises a detection element and a compensation element. The catalytic combustion type gas sensor further comprises two same triodes. One ends of the detection element and the compensation element are jointly connected with the emitting electrode of the second triode, and the other end of the compensation element is grounded. The base electrode of the second triode is connected with the base electrode of the first triode. The collector electrode of the second triode is connected with the base electrode of the second triode, the collector electrode of the second triode is connected with one end of a fourth resistor, and the other end of the fourth resistor is grounded. The other end of the detection element is connected with the emitting electrode of the first triode through a first resistor and connected with a voltage negative feedback circuit through an adjustable voltage source module. The collector electrode of the first triode is connected with one ends of a third resistor and a second resistor respectively. The other end of the third resistor is grounded. The other end of the second resistor is connected with a negative voltage feedback circuit module and a signal conditioning module respectively.
Description
Technical field
The utility model relates to a kind of catalytic combustion type gas sensor, relates in particular to the circuit of this catalytic combustion type gas sensor.
Background technology
The catalytic combustion sensor is made of detecting element and compensating element.Detecting element is to turn to coil by platinum filament, outside coil, be coated with the paste coat that is formed by aluminium oxide-silicon oxide, sinter spherical porous body under the uniform temperature into, salt solusion with the dipping of the bead behind sintering noble metal platinum, palladium etc., pyroprocessing again, make at oxide carrier and form the precious metal catalyst layer, be packaged at last element, and the difference of compensating element, and detecting element is not have Catalytic Layer.
In detecting element surface flameless catalytic combustion, heating power raises the platinum filament temperature of detecting element, the corresponding increase of resistance value when inflammable gas (such as methane etc.).Be lower than in 10% (volume fraction) situation, airborne inflammable gas can perfect combustion, and its thermal value is directly proportional with the concentration of inflammable gas.The concentration of inflammable gas is larger in the air, and the heating power that burning produces is more, and the increase in temperature of platinum filament is larger, and it is more that its resistance value increases.As long as measure the increased resistance value of detecting element platinum filament, just can detect the concentration of inflammable gas in the air.
The catalytic combustion type gas sensor principle of work of prior art is as shown in Figure 1: detecting element and compensating element, series connection, and peripheral circuit consists of Wheatstone bridge.
Peripheral circuit provides constant voltage to electric bridge, and balance between original state A, B does not have pressure reduction.When detecting element contacts with inflammable gas, the detecting element temperature that makes heating power rises, and (nothing is burnt on the compensating element,, its platinum filament resistance is constant), the platinum filament resistance increases, the current potential of A increases and the current potential of B is constant, utilize the potential difference (PD) that produces between A, B to be directly proportional with combustable gas concentration, the test combustable gas concentration.Wherein the effect of compensating element, is beyond the compensation inflammable gas catalytic combustion, by caused deviations of factor such as environment temperature, supply voltage and gas flow rates.For example, the flow velocity of clean air increases suddenly, element high temperature bead (about 450 ℃) can increase by the heat of convection type loss, and the bead temperature can reduce, but because compensating element, is similar with the detecting element bead, thermal loss also approaches, both thermal resistances together with etc. the reduction of amplitude, the voltage of A is constant, does not have signal output on Wheatstone bridge, also just avoided causing the generation of the situation of reporting by mistake because the clean air flow velocity strengthens.This principle is owing to inflammable gas catalytic combustion heat on detecting element, and its bead working temperature raises with the increase of combustable gas concentration.
Summary of the invention
The utility model provides a kind of catalytic combustion type gas sensor, and by variable voltage source and voltage negative feedback, working current on the control detecting element is intended to make the detecting element bead to work under steady temperature all the time.
In order to solve the problems of the technologies described above, the utility model is achieved through the following technical solutions:
The utility model comprises: detecting element and compensating element; Also comprise: the first triode and the second triode; Described the first triode is identical with the second triode; One end of detecting element and compensating element, and the emitter of the second triode connect altogether, the other end ground connection of compensating element; The base stage of the second triode links to each other with the base stage of the first triode; The collector of the second triode links to each other with the base stage of the second triode, and the collector of the second triode connects an end of the 4th resistance, the other end ground connection of the 4th resistance; The other end of detecting element links to each other with the emitter of the first triode by the first resistance respectively and links to each other with voltage negative feedback circuit by the adjustable voltage source module; The collector of the first triode links to each other with an end of the 3rd resistance and an end of the second resistance respectively; The other end ground connection of the 3rd resistance; The other end of the second resistance links to each other with the voltage negative feedback circuit module; The other end of the second resistance links to each other with the signal condition module simultaneously, and the signal after the conditioning is exported to external circuit.
Compared with prior art, the beneficial effects of the utility model are: can obviously reduce detecting element sensitivity decay and signal drift, reduce power consumption, prolong sensor life-time.
Description of drawings
Fig. 1 is the circuit module figure of catalytic combustion type gas sensor in the prior art.
Fig. 2 is circuit module figure of the present utility model.
Embodiment
Below in conjunction with accompanying drawing and embodiment the utility model is described in further detail:
The utility model comprises: detecting element and compensating element; Also comprise: the first triode T1 and the second triode T2; Described the first triode T1 is identical with the second triode T2; One end of detecting element and compensating element, and the emitter of the second triode T2 connect altogether, the other end ground connection of compensating element; The base stage of the second triode T2 links to each other with the base stage of the first triode T1; The collector of the second triode T2 links to each other with the base stage of the second triode T2, and the collector of the second triode T2 connects an end of the 4th resistance R 4, the other end ground connection of the 4th resistance R 4; The other end of detecting element links to each other with the emitter of the first triode T1 by the first resistance R 1 respectively and links to each other with voltage negative feedback circuit by the adjustable voltage source module; The collector of the first triode T1 links to each other with an end of the 3rd resistance R 3 and an end of the second resistance R 2 respectively; The other end ground connection of the 3rd resistance R 3; The other end of the second resistance R 2 links to each other with the voltage negative feedback circuit module; The other end of the second resistance R 2 links to each other with the signal condition module simultaneously, and the signal after the conditioning is exported to external circuit.
Thermal resistance when described the first resistance R 1, the second resistance R 2 and the 3rd resistance R 3 and detection, compensating element, work approaches; The resistance of the 4th resistance R 4 is greater than the first resistance R more than 1 1000 times.
Voltage negative feedback circuit module in the utility model is Voltage Series or the negative-feedback circuit in parallel that adopts prior art commonly used.The signal condition module also is to adopt prior art convectional signals modulate circuit, is intended to enlarge dynamic range of signals, adopts the input range coupling of circuit with follow-up A/D.Variable voltage source also is the module that adopts prior art commonly used.
The utility model and former principle of work are different, and detecting element adopts the constant temperature mode of operation, namely when detecting inflammable gas, by constant temperature control circuit, automatically regulate the heating current of detecting element, make it to be in temperature constant state.Output signal is taken from the variable quantity of catalysis sensing element working current.
The utility model has been used a mirror current source design, adopt transistor T 1 and the T2 of full symmetric, parameter is identical, wherein more than 1000 times, the thermal resistance of other resistance and detection and compensating element, approaches the resistance of R4 in the circuit greater than the thermal resistance (both thermoelectric resistances approach) of detection and compensating element.If flowing through transistor T 1 basic emitter voltage is V
BE1, emitter current I
C1, base current I
B1Flowing through transistor T 2 basic emitter voltages is V
BE2, emitter current I
C2, base current I
B2Because two transistor base current potentials are identical, and I1*R is then arranged
Detecting element+ V
BE2=I
C1* R1+V
BE1Because two transistor parameters are identical, V
BE2=V
BE1, I1*R is then arranged
Detecting element=I
C1* R1, i.e. electric current I by R1
C1Be the mirror image of detecting element working current I1, have
I
C1Be converted to voltage sampling signal by R3, regulate detecting element working current I1 by negative feedback.The specific works process is: at first adjust detecting element working current I1 by negative-feedback circuit, make the electric current of the detecting element of flowing through equal its rated operational current, detecting element is in the initialization state, and working temperature is about 450 ℃.When detecting inflammable gas, catalyst combustion reaction occurs on the detecting element surface in inflammable gas, and detecting element catalysis porous small ball surface temperature is raise, and passes to rapidly inner platinum filament, platinum filament temperature rising resistance is increased, i.e. R
Detecting elementIncrease.The reduction of detecting element working current I1 is flow through the electric current I of R1 by its mirror image
C1Obtain embodying I
C1Be converted to voltage sampling signal by R3, by negative-feedback circuit, reduction detecting element working current I1 by a larger margin makes R
Detect ElementReturn to initial value, guarantee the work of detecting element constant temperature.Simultaneously, by voltage sampling signal, can obtain to reduce one to one voltage signal of amplitude with the detecting element working current, adopt in advance the normal concentration inflammable gas to determine both linear relationships, signal can go out actual combustable gas concentration by inverse thus.
Under traditional Wheatstone bridge duty, because what add on detection and the compensating element, series circuit is constant voltage, the detecting element thermal resistance increases, and its working current also can reduce, impact on catalysis porous small ball surface temperature is negative sense, namely reduces little spherical surface temperature.But the heat that the inflammable gas catalytic combustion produces, the effect that the bead surface temperature is raise is far longer than the former, and the effect of its stack is still detecting element catalysis bead surface temperature and raises, and the platinum filament resistance increases.And the utility model is in order to keep the temperature constant of detecting element catalysis bead, inner platinum filament, for reaching this point, by feedback the reduction amplitude of detecting element working current wanted large many in the circuit.
In addition, because the resistance of R4 is very large, make I
C2Little I2 far away can ignore to the shunting action of I1, and I1 ≈ I2 is then arranged, and basic identical by the electric current of detecting element and compensating element.The compensating action of compensating element, in Wheatstone bridge obtains keeping equally.For example, when there being environment temperature by a small margin to raise, the temperature of operation element and compensating element, raises simultaneously, because the little spherical structure of work of two elements approaches, its intensification ratio approaches, and then the current potential between two elements remains unchanged, i.e. I1*R
Detecting elementRemain unchanged.Because I1*R
Detecting element=I
C1* R1, its image current I
C1Remain unchanged, then feedback circuit can not act on yet, and the voltage source constant voltage remains unchanged, and does not just have wrong report and produces.
The utility model is for improving detecting element sensitivity, and the element alumina support adopts porous structure in the making, and improves the specific surface area of catalyst layer as far as possible.Because detecting element is operated in about 450 ℃, long-time high temperature sintering, the aluminium oxide of porous can become low activity and fine and close α phase structure gradually, and carrier surface area is reduced; The noble metal catalyst particle can become large by sintering, and the specific surface area of catalyst layer can descend, and catalytic activity reduces; When the inflammable gas of high concentration burns at detecting element, moment, high temperature also can make noble metal active particle distillation be gaseous state, make on the compensating element, carrier that is in same air chamber and adsorb trace catalyst, make inflammable gas can be on compensating element, catalytic combustion, these all can make the electric bridge output sensitivity descend.Adopt detecting element constant temperature mode of operation, can significantly delay the Woelm Alumina densified sintering product, with change mutually to SA corundum, the sintering that suppresses the noble metal catalyst particle becomes large, avoid simultaneously occurring moment high temperature and make the situation of noble metal active particle distillation, obviously reduce detecting element sensitivity decay and signal drift, prolong sensor life-time.
Since the catalytic combustion sensor need to be in measuring process continuous heating, therefore power consumption is larger, generally can reach 80-150mA (2.5-4.5V direct current supply), so in portable apparatus, usually need to adopt jumbo rechargeable battery to the power supply of whole instrument.During inflammable gas below alarm set point concentration appears in testing environment for a long time, the power-saving effect of this constant temperature mode of operation will be clearly.
When contact high concentration inflammable gas environment (methane that for example surpasses 10% percent by volume), the change in resistance of detecting element is no longer linear with combustable gas concentration, and this can't the Measurement accuracy combustable gas concentration.Can overcome this problem by the Constant Temperature Detection method, the measurement range of the sensor that in fact this enlarge.
Moment contacts the high concentration inflammable gas simultaneously, " activation " phenomenon can appear in the catalytic combustion sensor, namely since element surface moment acutely burn, the steep temperature rise that produces, the effect of aforementioned desensitization is amplified rapidly, transducer sensitivity descends rapidly, and for avoiding damaging sensor, the method for taking at present is to surpass after the sensing range with regard to power-off shutdown.If the high and low concentration change of the frequent appearance of testing environment, detecting instrument can't work, adopt Constant Temperature Detection pattern of the present utility model, the power supply of giving detecting element is one and reduces gradually, until the process of cutting off the power supply fully, when avoiding the detecting element damage, can largely alleviate this phenomenon.
Claims (2)
1. a catalytic combustion type gas sensor comprises: detecting element and compensating element; Characterized by further comprising: the first triode and the second triode; Described the first triode is identical with the second triode; One end of detecting element and compensating element, and the emitter of the second triode connect altogether, the other end ground connection of compensating element; The base stage of the second triode links to each other with the base stage of the first triode; The collector of the second triode links to each other with the base stage of the second triode, and the collector of the second triode connects an end of the 4th resistance, the other end ground connection of the 4th resistance; The other end of detecting element links to each other with the emitter of the first triode by the first resistance respectively and links to each other with voltage negative feedback circuit by the adjustable voltage source module; The collector of the first triode links to each other with an end of the 3rd resistance and an end of the second resistance respectively; The other end ground connection of the 3rd resistance; The other end of the second resistance links to each other with the voltage negative feedback circuit module; The other end of the second resistance links to each other with the signal condition module simultaneously, and the signal after the conditioning is exported to external circuit.
2. catalytic combustion type gas sensor according to claim 1 is characterized in that: the thermal resistance when described the first resistance, the second resistance and the 3rd resistance and detection, compensating element, work approaches; The resistance of the 4th resistance is greater than the first resistance more than 1000 times.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220066736 CN202814906U (en) | 2012-02-27 | 2012-02-27 | Catalytic combustion type gas sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220066736 CN202814906U (en) | 2012-02-27 | 2012-02-27 | Catalytic combustion type gas sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN202814906U true CN202814906U (en) | 2013-03-20 |
Family
ID=47873765
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 201220066736 Withdrawn - After Issue CN202814906U (en) | 2012-02-27 | 2012-02-27 | Catalytic combustion type gas sensor |
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| Country | Link |
|---|---|
| CN (1) | CN202814906U (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102590289A (en) * | 2012-02-27 | 2012-07-18 | 上海恩尼克思工业仪器有限公司 | Catalytic combustion type gas sensor |
| CN106596836A (en) * | 2017-01-23 | 2017-04-26 | 河南驰诚电气股份有限公司 | Apparatus and method for preventing catalytic combustion sensor from poisoning |
| CN111537664A (en) * | 2020-05-07 | 2020-08-14 | 江苏集萃智能集成电路设计技术研究所有限公司 | Catalytic multi-gas sensing system |
| CN115013738A (en) * | 2022-06-09 | 2022-09-06 | 西安航天神舟建筑设计院有限公司 | Natural gas line leakage detection device |
-
2012
- 2012-02-27 CN CN 201220066736 patent/CN202814906U/en not_active Withdrawn - After Issue
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102590289A (en) * | 2012-02-27 | 2012-07-18 | 上海恩尼克思工业仪器有限公司 | Catalytic combustion type gas sensor |
| CN106596836A (en) * | 2017-01-23 | 2017-04-26 | 河南驰诚电气股份有限公司 | Apparatus and method for preventing catalytic combustion sensor from poisoning |
| CN111537664A (en) * | 2020-05-07 | 2020-08-14 | 江苏集萃智能集成电路设计技术研究所有限公司 | Catalytic multi-gas sensing system |
| CN115013738A (en) * | 2022-06-09 | 2022-09-06 | 西安航天神舟建筑设计院有限公司 | Natural gas line leakage detection device |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| AV01 | Patent right actively abandoned |
Granted publication date: 20130320 Effective date of abandoning: 20140514 |
|
| RGAV | Abandon patent right to avoid regrant |