CN202974931U - Gas sensor - Google Patents
Gas sensor Download PDFInfo
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- CN202974931U CN202974931U CN 201220609793 CN201220609793U CN202974931U CN 202974931 U CN202974931 U CN 202974931U CN 201220609793 CN201220609793 CN 201220609793 CN 201220609793 U CN201220609793 U CN 201220609793U CN 202974931 U CN202974931 U CN 202974931U
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Abstract
The utility model discloses a gas sensor composed of a gas sensitive element, gas chambers and gas diffusion channels, wherein the gas sensitive element is arranged in the measured air chamber; the measured air chamber is communicated with the flow-limited air chamber through at least two different gas diffusion channels; air in the flow-limited air chamber is allowed to be diffused to the surface of the sensitive element through the different gas diffusion channels; and each gas diffusion channel comprises a gas diffusion resistance element.
Description
Technical field
The present invention relates to the mensuration that gas sensor is used for the gas sample concentration.
Background technology
Most of current mode electrochemical gas sensors are by oxidation or the measure gas concentrations that concerns between the current-responsive value of tested gas gained and gas concentration of reducing.During measurement, gas first is diffused into electrode surface by the gas flow-limiting device that sensor is preset, be dissolved in electrolytic solution, then in electrode surface absorption, generation redox reaction, the reaction product desorption leaves electrode surface, any one step of this cascade process is the possibility limit reaction rates all, thereby has influence on the sensitivity of sensor.
in order to improve the stability of commercialization gas sensor, generally all wish the response of sensor is designed in gas phase limiting diffusion current district when carrying out sensor design, this can be by improving catalytic activity, strengthening diffusional resistance realizes, the response of sensor is determined by the mass transferring in gas phase speed of gas fully like this, and gas mass transferring in gas phase speed is substantially by gas flow rate, the mechanical form meter size of the gas flow-limiting device that the physicochemical characteristics of gas to be measured (gas diffusivity) and sensor are default or scattering and permeating characteristic determine, it is better linear that this moment, sensor had response, response is subjected to the impact of control of Electric potentials fluctuation less, sensitivity is also comparatively stable, be subjected to temperature, the characteristics such as the such environmental effects such as pressure are less.
And in fact, the response of most of sensors is in and mixes the control zone, it is the impact that the response of sensor is subjected to above-mentioned a plurality of processes, this moment, the response characteristic of sensor became complicated, environment and electrode self activated state becomes large to the impact of response, and unpredictable, and to carry out also more complicated of quantitative mathematical expression to above-mentioned all processes in theory.In order to obtain measurement result accurately and reliably, common way is: demarcate to reduce above-mentioned interference under the airflow rate, pressure, temperature, humidity and the gas composition that approach with the actual measurement condition, condition before sensor uses, and nominal time and Measuring Time approach the impact that, inactivation aging due to sensitive element with the minimizing transducer sensitivity, activation or the impact variation such as poisoning cause measurement result as far as possible.
Frequent and the specialty of demarcating requires to have brought inconvenience and increased operation and use cost for manufacturer and user.Improving the stability of sensor, do not sacrifice accuracy when reducing the transducer calibration frequency is also the huge challenge that sensor and detecting instrument manufacturer face.
Summary of the invention
The present invention utilizes sensor to the characteristics of gas response, sensor construction and measuring process is controlled to improve the stability of sensor measurement, reduces the transducer calibration frequency.
Gas sensor of the present invention is comprised of gas detecting element, air chamber, gas diffusion paths, its architectural feature is: described gas detecting element is in one and measures in air chamber, described measurement air chamber contacts with gas to be measured by at least two different gas diffusion paths, allow gas to be diffused into the sensitive element surface by different diffusion admittances, described diffusion admittance comprises gas diffusion resistance spare.Described gas diffusion paths resistance piece comprises diffusion hole, capillary module, porous membrane, gas-permeable membrane etc.
Described measurement air chamber can communicate with corresponding current limliting air chamber respectively by at least two different gas diffusion resistance spares, the resistance of gas diffusion resistance spare is different, the current limliting air chamber connects gas piping by valve or kapillary door, allows gas to be measured to enter respectively different current limliting air chambers and measures.
The measurement air chamber of described sensor, at least two gas diffusion resistance spares, current limliting air chambers can be connected according to this and be communicated, and allow to arrive sensitive electrode by different diffusion admittances surperficial, and the current limliting air chamber connects gas piping by valve or kapillary.
Described sensitive element absorption or consume gas to be measured, and the response relation between gas concentration to be measured is linear, and response magnitude is subjected to the impact of gas diffusion velocity; Described gas detecting element comprises electrochemical sensor, catalytic combustion sensor, semiconductor transducer.
The response of this sensor is mainly by the mass transferring in gas phase process control in the sensor air chamber, this mass transport process is determined by the mechanical form of flowing gas state, gas diffusion resistance spare and size mainly, comparatively stablize controlled, and the larger process affected by environment such as gas dissolution, liquid phase diffusion, gas absorption, redox reaction and reaction product desorption and the variation of sensor catalytic activity are deducted by twice measurement the impact of sensor response, thereby can increase substantially stability and the accuracy of measurement.
This measuring method can be used for direct measure gas concentrations, also can be used for transducer sensitivity is demarcated and do not needed the calibrating gas of concentration known.
Description of drawings
Fig. 1: one of gas sensor configuration schematic diagram of the present invention
Fig. 2: two of gas sensor configuration schematic diagram of the present invention
Embodiment:
Application Example one
Course of reaction for gasmetry, can simply it be divided into two classes: the first kind is the mass transferring in gas phase process, the characteristics of this process are: mass transfer velocity mainly determines (it is Rm that this paper defines this process resistance) by gas flow rate, gas physicochemical characteristics and gas phase diffusion resistance, and stability better; Equations of The Second Kind is referred to as course of reaction, it comprises the processes such as gas dissolution, liquid phase diffusion, gas absorption, redox reaction and reaction product desorption, this process is comparatively complicated, and influence factor more (it is Rcat that this paper defines its overall process resistance), if sensor is linear to the response of gas concentration, following relation is satisfied in the response of sensor: (resistance of gas mass transfer and other process resistances)
S =KC/(Rm+Rcat ) （1）
Or
KC/S = Rm +Rcat （2）
Wherein K is constant, and C is gas concentration.
If when sensor measurement, the Equations of The Second Kind process is deducted the impact of sensor response, the response of sensor is mainly determined by mechanical form and the size of sensor current limliting resistance piece, can greatly reduce by the impact of various environmental factors and sensor catalytic activity factor, thereby can increase substantially its stability.
Fig. 1 is the structural representation according to a kind of gas sensor 10 of above-mentioned theory thinking design, this sensor 10 is comprised of gas detecting element, air chamber, gas diffusion resistance spare current-limiting apparatus, described gas detecting element 100 is in to be measured in air chamber 201, described sensitive element adsorbs or consumes gas to be measured, and the element responds size is subjected to the gas mass transfer velocity to affect control, described measurement air chamber 201 is by two different gas diffusion paths 301, 302 (gas diffusion resistance spares) respectively with two current limliting air chambers 202 independently, 203 communicate, allow the gas in the current limliting air chamber to be diffused into the sensitive element surface by gas diffusion paths, but the gas diffusion resistance of two gas diffusion paths is different, two current limliting air chambers connect gas piping (when using kapillary by valve or kapillary, should guarantee that the diffusional resistance of gas in kapillary is much larger than the diffusional resistance of gas flow-limiting device, gas rate of propagation therein is rate of propagation in gas flow-limiting device much smaller than it), allowing gas to be measured to enter respectively different current limliting air chambers measures.
What the present embodiment disclosed is a kind of galvanochemistry these hydrogen sulfide gas sensor, gas sensor is galvanochemistry sulfuretted hydrogen electrode, gas diffusion resistance spare 301 is diameter 2.6mm, the diffusion hole of thickness 1mm, gas diffusion resistance spare 302 is diameter 3.2mm, the diffusion hole of thickness 1mm, air chamber 202,203 volume are 0.5ml.
First use the standard hydrogen sulphide gas measuring transducer constant P of 25ppm when using, its process is as follows:
1) control by valve, the 25ppm stink damp is passed through sensor with fixed flow rate through air chamber 202, recording sensor steady-state response value S1 is 24.63uA, and relation is satisfied in this response:
nFC/S1 = Rm1 +Rcat （3）
Wherein Rm1 is the diffusional resistance of air chamber 1, and under the condition that gas flow rate is fixed, mainly mechanical form and the size by gas diffusion resistance spare 301 in air chamber 202 determines.
2) control by valve, the 25ppm stink damp is passed through sensor with fixed flow rate through air chamber 203, recording sensor steady-state response value S2 is 37.65uA, and relation is satisfied in this response:
nFC/S2 = Rm2 +Rcat （4）
Wherein Rm2 is the diffusional resistance of air chamber 203, and under the condition that gas flow rate is fixed, mainly the mechanical dimension by gas diffusion resistance spare 302 in air chamber 203 determines.
3) got by (4)-(3):
nFC(1/S2-1/S1) = Rm2-Rm1 =K （5）
Because Rm2, Rm1 mainly determine by the gas diffusion resistance spare in air chamber 301,302 mechanical form and size, time to time change not substantially, thereby can be used as a constant K and process, as definition sensor constants P=nFK, have
P =(1/S2-1/S1)C=35.10 （6）
Repeat said process during measurement, the present embodiment accuracy of the sulfuretted hydrogen Standard Gases verification method of 50ppm, the sensor steady-state response value that 50ppm H2S is passed into air chamber 202 acquisitions is 49.06uA, and the steady-state response value that sensor is passed into air chamber 203 acquisitions is 75.37uA, is got by (6):
C = P/(1/S2-1/S1)=49.3（ppm） （7）
Substantially identical by gas concentration value and Standard Gases concentration that formula (7) calculates, error is less than 1%.After obtaining gas concentration, when utilizing separately gas diffuser 301 and 302 to measure, the sensitivity of sensor also can calculate.
In actual application, if the drift of transducer sensitivity is little, the method for above-mentioned twice measurement can only carry out only carrying out one-shot measurement during conventionally test from the timing signal use to transducer sensitivity.
Explained as seen by above-described embodiment and principle, this sensor is not limited to electrochemical sensor to the selection of sensitive element, so long as the response of sensor is controlled by the gas mass transfer velocity, this structure all is suitable for, the gas sensitization of relation (1) can be used this sensor construction and method is measured as long as its response is satisfied, and the gas detecting element of the type includes but not limited to electrochemical sensor, catalytic combustion sensor, semiconductor transducer.
The present embodiment two gas with various diffusional resistances of Gas flow-limiting hole acquisition of different-diameter, adopt a plurality of metering holes also can reach same purpose, the method that reaches effect same also has but is not limited to realize with capillary module, porous membrane, gas-permeable membrane, but requires the diffusional resistance of twice measurement gas different.
By the analysis of above-described embodiment as can be known, the response of this sensor is mainly determined by the mechanical dimension of the gas phase current-limiting apparatus in the sensor air chamber, the larger process affected by environment such as gas dissolution, liquid phase diffusion, gas absorption, redox reaction and reaction product desorption and sensor catalytic activity change to be deducted by twice measurement the impact of sensor response, thereby can increase substantially stability and the accuracy of sensor measurement, reduce the frequency that sensor need to be demarcated.
Application Example two:
Fig. 2 is the structural representation according to the another kind of self-calibration gas sensor 20 of above-mentioned theory thinking design, this sensor 20 is comprised of gas detecting element, air chamber, gas diffusion resistance spare, described gas detecting element 100a directly is in and measures in air chamber 201a, described sensitive element adsorbs or consumes gas to be measured, and the element responds size is affected by the gas mass transfer velocity; Described measurement air chamber 201a, gas diffusion resistance spare 301a, current limliting air chamber 202a, gas diffusion resistance spare 302a communicate with current limliting air chamber 203a series connection, two current limliting air chambers connect gas piping (when using kapillary by valve or kapillary, should guarantee the diffusional resistance of gas in kapillary much larger than the diffusional resistance of gas flow-limiting device, gas rate of propagation therein is rate of propagation in gas flow-limiting device much smaller than it.) allow gas to be measured to enter respectively different current limliting air chambers to measure.。
What the present embodiment disclosed is a kind of from demarcating the galvanochemistry these hydrogen sulfide gas sensor, gas sensor is galvanochemistry sulfuretted hydrogen electrode, gas diffusion resistance spare 301a is diameter 2.6mm, the diffusion hole of thickness 1mm, gas diffusion resistance spare 302a is diameter 4.4mm, the diffusion hole of thickness 1mm, the volume of air chamber 202a, 203a is 0.5ml.
First use the standard hydrogen sulphide gas measuring transducer constant P of 25ppm when using, its process is as follows:
1) control by valve, the 25ppm stink damp is flowed out through air chamber 203a with fixed flow rate, this moment, gas diffusion path was: arrive sensitive element from current limliting air chamber 203a through gas diffusion resistance spare 302a, current limliting air chamber 202a, gas diffusion resistance spare 301a and measurement air chamber 201a surperficial, recording sensor steady-state response value S1 is 25.12uA, and relation is satisfied in this response:
nFC/S1 = Rm1 +Rcat （8）
Wherein Rm1 is the diffusional resistance of air chamber 1, and mainly mechanical form and the size by gas diffusion resistance spare 301a in air chamber 202a determines.
)Control by valve, the 25ppm stink damp is flowed out through air chamber 202a with fixed flow rate, this moment, gas diffusion path was: from current limliting air chamber 202a, surperficial through gas diffusion resistance spare 301a and measurement air chamber 201a arrival sensitive element, recording sensor steady-state response value S2 is 38.76uA, and relation is satisfied in this response:
nFC/S2 = Rm2 +Rcat （9）
Wherein Rm2 is the diffusional resistance of air chamber 203a, and mainly mechanical form and the size by gas diffusion resistance spare 302a in air chamber 203a determines.
3) got by (9)-(8):
nFC(1/S2-1/S1) = Rm2-Rm1 =K （10）
Because Rdm2, Rdm1 mainly determine by the mechanical form size of gas flow-limiting device 301a, 302a in air chamber, time to time change not substantially, thereby can be used as a constant K and process, as definition sensor constants P=nFK, have
P =(1/S2-1/S1)C=35.02 （11）
Repeat said process during measurement, the present embodiment accuracy of the sulfuretted hydrogen Standard Gases verification method of 50ppm, the sensor steady-state response value that 50ppm H2S is passed into air chamber 202a acquisition is 50.11uA, the steady-state response value that sensor is passed into air chamber 203a acquisition is 77.55uA, is got by (11):
C = P/(1/S2-1/S1)=49.6（ppm） （12）
Substantially identical by gas concentration value and Standard Gases concentration that formula (12) calculates, error is less than 1%.After obtaining gas concentration, when separately gas being passed into 202a or 203a and measuring, the sensitivity of sensor also can calculate.
In actual application, if the drift of transducer sensitivity is little, the method for above-mentioned twice measurement can only transducer sensitivity being carried out only carry out one-shot measurement during conventionally test from the timing signal use, pass into 202a or 203a with gas.
Just two kinds of sensor construction designs that realize this measuring method of above two embodiment introductions; in fact the professional person utilizes described Method And Principle; can be by the different sensor construction of composite design realizing described measuring method, they are at the row of the protection of measuring method of the present invention.
Claims (6)
1. gas sensor, formed by gas detecting element, measurement air chamber, current limliting air chamber, gas diffusion paths, it is characterized in that: described gas detecting element is in one and measures in air chamber, described measurement air chamber is communicated with the current limliting air chamber by at least two different gas diffusion paths, allow the gas in the current limliting air chamber to be diffused into the sensitive element surface by different diffusion admittances, described diffusion admittance comprises gas diffusion resistance spare.
2. gas sensor as claimed in claim 1, it is characterized in that described measurement air chamber communicates with corresponding current limliting air chamber respectively by the different gas diffusion resistance spare of at least two diffusional resistances, the current limliting air chamber connects gas piping by valve or kapillary door, allows gas to be measured to enter respectively different current limliting air chambers and measures.
3. gas sensor as claimed in claim 1, it is characterized in that described measurement air chamber, at least two gas diffusion resistance spares, current limliting air chambers connect successively and communicate, allow gas to arrive sensitive electrode by one or more diffusion admittances respectively surperficial, the current limliting air chamber connects gas piping by valve or kapillary.
4. gas sensor as claimed in claim 1, is characterized in that wherein said sensitive element absorption or consume gas to be measured, and the response relation between gas concentration to be measured is linear, and response magnitude is subjected to the impact of gas diffusion velocity.
5. gas sensor as claimed in claim 1, is characterized in that wherein said gas detecting element comprises electrochemical sensor, catalytic combustion sensor, semiconductor transducer.
6. gas sensor as claimed in claim 1, is characterized in that wherein said gas diffusion resistance spare comprises diffusion hole, capillary module, porous membrane, gas-permeable membrane.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220609793 CN202974931U (en) | 2012-08-14 | 2012-11-19 | Gas sensor |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
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| CN201220401175 | 2012-08-14 | ||
| CN201220401175.X | 2012-08-14 | ||
| CN 201220609793 CN202974931U (en) | 2012-08-14 | 2012-11-19 | Gas sensor |
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| CN202974931U true CN202974931U (en) | 2013-06-05 |
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| CN 201220609793 Expired - Lifetime CN202974931U (en) | 2012-08-14 | 2012-11-19 | Gas sensor |
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- 2012-11-19 CN CN 201220609793 patent/CN202974931U/en not_active Expired - Lifetime
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Granted publication date: 20130605 |