KR20090056731A - The device of measuring carbon dioxide - Google Patents

Abstract

A carbon dioxide measuring device capable of temperature compensation and control is provided to improve the accuracy of the carbon dioxide concentration measurement in the situation in which the change of the external environment is severe. A carbon dioxide measuring device capable of the temperature compensation and control comprises: a carbon dioxide sensor; a heating unit(20) formed on the one side of the carbon dioxide sensor; a first sensor(30) in which a first sensor lead line(31) is extended; an electric circuit board(60) electrically connected to the carbon dioxide sensor, the heating unit, and the first sensor through an electromotive force lead line(11), a voltage applying lead line(21) and a first sensor lead line; and a second sensor(50) which is closely located in a contact point in which the first sensor lead line and an electric circuit board are bonded. The carbon dioxide sensor comprises: a solid electrolyte(12); a standard electrode(13) and a sensing electrode(14) formed on both sides of the solid electrolyte; and a pair of electromotive force lead lines connected to the standard electrode and the sensing electrode. A pair of voltage applying lead lines are formed on the heating unit.

Description

CO2 measuring device with temperature compensation and control {THE DEVICE OF MEASURING CARBON DIOXIDE}

The present invention relates to a carbon dioxide measurement device capable of temperature compensation and control, and more particularly, temperature compensation that can increase the accuracy and reliability of carbon dioxide measurement by maintaining a constant driving temperature required for the measurement regardless of the ambient temperature change and The present invention relates to an electrochemical carbon dioxide meter that can be controlled.

Carbon dioxide is the main cause of global warming as a chemically stable gas in the atmosphere, and the necessity of adjusting the concentration of carbon dioxide for indoor air conditioning and horticulture of buildings, including the environmental problems, is increasing. Research into how to measure the concentration of is actively conducted.

Currently, the optical method (NDIR method) is most commonly used to measure the concentration of carbon dioxide gas in the atmosphere. This method measures the degree of absorption of infrared rays using the principle that carbon dioxide absorbs only infrared rays of a specific wavelength. By measuring the carbon dioxide concentration.

This device has the advantage of excellent selectivity, quantification and reproducibility, but requires a closed space for measurement and has a problem of being bulky and very heavy due to the physical size of components and filters. In addition, since the driving unit and the measuring device are very expensive and the configuration of the processing unit for the control is complicated, the cost of the overall measuring equipment is inevitably high. In particular, since the optical system is easily contaminated when exposed to a harsh environment, the use range is limited to indoors.

Another method for measuring the carbon dioxide concentration is a semiconductor gas sensor using a semiconductor compound such as SnO ₂ or TiO ₂ . The semiconductor type gas sensor is a principle of measuring the concentration of gas through a resistance change that appears when gas particles are adsorbed on the surface of a semiconductor compound. Since the particles are difficult to distinguish, there is a disadvantage that the gas selectivity is remarkably inferior.

In order to solve the above problems, a gas meter using a solid electrolyte has been proposed, and the gas meter using the solid electrolyte has a simple structure and enables the fabrication of a sensor in the form of a small element, and selectively detects only a specific gas. By using the sensing electrode, gas selectivity is improved and gas concentration can be measured quantitatively. In addition, because of the low cost and the use of oxides, there is an advantage in that it can be used stably in extreme environments.

The gas measuring instrument using the solid electrolyte has been continuously developed since the research of carbon dioxide sensor using potassium carbonate of Gauthier and Chamberland in the 1970s, and the solid electrolytes such as NASICON, LISICON, and beta alumina (NBA) Combined electromotive-type carbon dioxide sensors have been actively researched and developed for many years.

However, the biggest reason why it is not widely commercialized even though it is an electrochemical carbon dioxide meter using a solid electrolyte having many advantages, it is essential to maintain a constant operating temperature of high temperature for the smooth operation of the electrochemical carbon dioxide meter using the solid electrolyte. It is very difficult to maintain a constant driving temperature due to a sudden change in temperature and a large temperature difference between the inside of the heater and the ambient temperature. As the output signal of the sensor changes according to the temperature deviation, the accuracy of carbon dioxide concentration measurement is lowered and the reliability is bad. This is because it affects.

More specifically, the conventional electrochemical carbon dioxide meter is a sensing electrode using a mixed carbonate phase and a noble metal membrane in which a gas to be detected and a thermodynamic equilibrium reaction take place, and a wide range of carbon dioxide concentrations without a reaction with carbon dioxide, and electrolytes in a wide temperature range. Galvanic battery cells (Type III) employing a metal oxide / oxide mixed phase as a reference electrode capable of constantly fixing Na ₂ O activity at a reference electrode interface have been mainly used. Carbon dioxide detection sensor of the galvanic cell structure follows the principle that the electromotive force measured at the electrodes located on both sides of the electrolyte is changed by the Nernst equation according to the concentration of the surrounding carbon dioxide gas, and the appropriate driving temperature (350 ℃ ~ 550 ℃) ) Shows a fairly stable measured value (EMF) behavior for carbon dioxide gas partial pressure.

However, the carbon dioxide meter based on this principle shows a constant electromotive force value according to the carbon dioxide concentration when the driving temperature is always kept constant. If the driving temperature is not constant, the signal change according to the temperature change, not the signal change due to the concentration. Will cause. This can be a real stumbling block to actual use because it can show false information about the gas concentration to be measured.

, (여기서 E₀ = 일정 온도에서 주어지는 열역학적 물질 상수, R=8.3144 (J/molK), T=구동온도(℃), F=96440 (C/mol), P_CO2=이산화탄소 농도) 와 같이 나타낼 수 있다. 위의 식을 통해 주변 이산화탄소 농도가 500ppm으로 일정하다고 가정하고, 구동온도 499℃와 500℃하에서의 기전력 편차를 이론적으로 계산해 보면 약 1.094mV의 차이가 유발된다. 이것은 실제로 사용되는 주변 환경의 온도가 10℃이상 차이가 나게 되면 그 기전력 값의 차이는 10mV이상 벌어져 정밀한 이산화탄소 농도 측정이 불가능하게 된다.In the following example, the change in sensor electromotive force measurement value according to the change of driving temperature is explained.

, (Where E ₀ = Thermodynamic material constant given at a constant temperature, R = 8.3144 (J / molK), T = drive temperature (° C), F = 96440 (C / mol), P _CO2 = carbon dioxide concentration). Assuming that the ambient carbon dioxide concentration is constant at 500ppm through the above equation, the theoretical calculation of the electromotive force deviation under the operating temperature of 499 ℃ and 500 ℃ causes a difference of about 1.094mV. This means that when the temperature of the surrounding environment actually differs by more than 10 ℃, the difference in the electromotive force value is increased by more than 10mV, which makes precise CO2 concentration measurement impossible.

The present invention has been made to solve the above-described problems, an object of the present invention is to use a first sensor located in close proximity to the carbon dioxide sensor, the first sensor lead wire and the second sensor located in the bonding portion of the electrical circuit board temperature It is to provide a carbon dioxide measuring device capable of temperature compensation and control that can maintain a constant operating temperature of the carbon dioxide sensor even in a severe environment to prevent the degradation of reliability caused by temperature changes.

The carbon dioxide measuring apparatus capable of temperature compensation and control of the present invention includes a solid electrolyte, a reference electrode and a sensing electrode formed on both sides of the solid electrolyte, and a pair of electromotive force lead wires respectively connected to the reference electrode and the sensing electrode. A carbon dioxide sensor configured to; Heating means provided at one side of the carbon dioxide sensor and having a pair of voltage applying lead wires for applying a voltage; A first sensor provided close to the carbon dioxide sensor and having a first sensor lead wire extended; An electrical circuit board electrically connected to the carbon dioxide sensor, the heating means, and the first sensor by the electromotive force lead wire, the voltage applying lead wire, and the first sensor lead wire; And a second sensor provided in close proximity to the contact at which the first sensor lead wire and the electric circuit board are bonded. Characterized in that it is formed to include.

The electric circuit board may be configured to compare a measured value measured by the first sensor and the second sensor to correct a temperature error, and to form a controller for adjusting a driving temperature or a heating time of the heating means according to the result. It features.

The first sensor may be a contact thermocouple, and the electromotive force measured by the first sensor may be amplified and filtered before being transmitted to the controller.

In addition, the second sensor is characterized in that thermistor (Thermistor).

In addition, the heating means uses a substrate having a predetermined pattern formed by screen printing platinum (Pt) on one side, characterized in that the voltage application lead wire is connected to both ends of the pattern.

In addition, the carbon dioxide measuring device is characterized in that the carbon dioxide sensor, the heating means, and the first sensor is provided inside the housing, the carbon dioxide measuring device further includes a protection means so that the second sensor is not exposed to the outside. It is characterized by.

Accordingly, the carbon dioxide measuring apparatus capable of temperature compensation and control according to the present invention requires a carbon dioxide sensor using a first sensor located close to the carbon dioxide sensor, and a second sensor located at a bonding portion of the first sensor lead wire and the electric circuit board. Maintaining a constant operating temperature has the advantage of increasing the accuracy of carbon dioxide concentration measurement even in the situation of severe changes in the external environment.

In addition, the carbon dioxide measuring apparatus capable of temperature compensation and control of the present invention can be used not only for indoor use but also for indoor and outdoor air purifiers, home appliances including air conditioners, building air conditioning control, and food service industries, thereby reducing constraints on the places provided. There is an advantage to widen the use of the carbon dioxide sensor.

Hereinafter, the carbon dioxide measuring apparatus 100 capable of temperature compensation and control according to the present invention having the characteristics as described above will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of the carbon dioxide measuring apparatus 100 according to the present invention, FIG. 2 is another cross-sectional view of the carbon dioxide measuring apparatus 100 according to the present invention, and FIG. 3 is a plan view of the heating means 20 according to the present invention. 4 is an operation schematic diagram of the control unit 61 according to the present invention, and FIG. 5 is another operation schematic diagram of the control unit 61 according to the present invention.

As shown, the carbon dioxide measuring apparatus 100 of the present invention includes a carbon dioxide sensor 10, heating means 20, the first sensor 30, the electric circuit board 60 and the second sensor 50. Is formed.

The carbon dioxide sensor 10 includes a solid electrolyte 12, a reference electrode 13 and a sensing electrode 14 formed on both sides of the solid electrolyte 12, and the reference electrode 13 and a sensing electrode 14, respectively. It is configured to include a pair of electromotive force lead wires 11 connected to each other.

The carbon dioxide sensor 10 has an electromotive force measured by the sensing electrode 14 and the reference electrode 13 provided on both sides of the electrolyte in the galvanic cell structure according to the concentration of carbon dioxide gas in the vicinity of the Nernst equation. Following the principle, the solid electrolyte 12 constituting the carbon dioxide sensor 10 may be an alkali ion (lithium ion, sodium ion, potassium ion) conductor, and more preferably NBA (Na ₂ O.11Al). ₂ O ₃ ), NasiCON (NASICON: Na _{1 + X} Zr ₂ Si _X P _3-X O ₁₂ ), Beta-alumina (Na ₂ O.χ Al ₂ O ₃ ), Na ₂ CO ₃ , Li Alkali metal carbonates such as ₂ CO ₃ , K ₂ CO ₃ , Li ₃ PO ₄ or Lithium Phosphorous Oxy Nitride (LIPON), LISICON (Li _{1 + y} Zr ₂ Si _y P _3-y O ₁₂ ), or mixtures thereof may be used. (The X and Y are each independently a constant of 1-2).

In addition, the constituent material of the sensing electrode 14 is carbonate, which is Na ₂ CO ₃ , BaCO ₃ , Li ₂ CO ₃ , SrCO ₃ , CaCO ₃ , Cs ₂ CO ₃ , MnCO ₃ , MgCO ₃ , K ₂ CO ₃ , Rb ₂ CO ₃ , CuCO ₃ or a mixture thereof may be used, more preferably BaCO ₃ , Na ₂ CO ₃ , Li ₂ CO ₃ , K ₂ CO ₃ or a mixture thereof may be used.

Finally, the material of the reference electrode 13 is Na ₂ ZrO ₃ -ZrO ₂ , Na ₂ MoO ₄ -MoO ₃ , Na ₂ WO ₄ -WO ₃ , Na ₂ SnO ₃ -SnO ₂ , Na ₂ Ti ₆ O ₁₃ -TiO ₂ , Na ₂ Ti ₆ O ₁₃ -Na ₂ Ti ₃ O ₇ , Na ₂ Si ₂ O ₅ -SiO ₂ , Na ₂ Si ₂ O ₅ -Na ₂ Si ₁ O ₃ , Na ₂ Ge ₄ O ₃ -GeO ₂ , Li ₂ TiO ₃ -TiO ₂ , LiCoO ₂ -Co ₃ O ₄ , or a mixture thereof may be used, more preferably Na ₂ Ti ₆ O ₁₃ -TiO ₂ , LiCoO ₂ -Co ₃ O ₄ , Li ₂ TiO ₃ -TiO ₂ , or mixtures thereof, may be used.

Since the carbon dioxide sensor 10 using the solid electrolyte 12 has a simple structure, it is possible to manufacture a small form of the sensor and has a low production cost, and by using a sensing electrode 14 to selectively detect only a specific gas. It has the advantage of increasing gas selectivity and quantitative measurement of gas concentration.

However, in order to correctly measure the carbon dioxide sensor 10, the ion conductivity of the electrolyte must be high, and the equilibrium reaction between the carbon dioxide gas and the electrode must be maintained, so that the carbon dioxide measuring device 100 maintains a high temperature of about 400 to 500 ° C. 20 is required, the conventional carbon dioxide measuring apparatus 100 detects this through a sensor located in close proximity to the carbon dioxide sensor 10 and controls the operation of the heating means 20.

However, in the case of using the local resistance heat by the voltage applied to the heating means 20, even a slight voltage difference may cause a temperature deviation, the temperature deviation ultimately of the concentration measurement of the carbon dioxide measuring device 100 This hinders accuracy.

In addition, when the carbon dioxide measuring device 100 is used to monitor the indoor environment, the temperature change range of the actual measured place does not change significantly at room temperature, but when the carbon dioxide measuring device 100 is used to monitor the outdoor environment, the change in the ambient temperature is large. Accurate measurements will be more difficult.

The present invention allows a more precise measurement of carbon dioxide concentration by adjusting the driving temperature or heating time of the heating means 20 through temperature correction regardless of the external temperature change. Explain.

The heating means 20 is provided on one side of the carbon dioxide sensor 10 and a pair of voltage applying lead lines 21 for applying a voltage are formed.

As shown in FIG. 3, the heating means 20 may use a substrate on which one surface of platinum (Pt) is screen printed to form a predetermined pattern. The voltage application lead line 21 may be formed at both ends of the pattern. Is connected to. In this case, it is preferable to use a paste including platinum Pt to facilitate screen printing of the pattern.

The first sensor 30 is provided in close proximity to the carbon dioxide sensor 10 and is a means for measuring temperature to extend the first sensor lead wire 31 to transmit the electromotive force detected by the first sensor 30.

1 and 2, the first sensor 30 and the carbon dioxide sensor 10 are shown as an example provided on one side of the heating means 20, the position of the first sensor 30 is In addition to the parts shown in FIGS. 1 and 2, the carbon dioxide sensor 10 may be formed in various ways as long as it is located close to the carbon dioxide sensor 10 to measure the driving temperature of the carbon dioxide sensor 10.

In this case, the first sensor 30 has heat resistance even at a high temperature by the heating means 20, and is attached to the first sensor 30 to increase the accuracy of temperature sensing. Is preferably.

The electric circuit board 60 is connected to the carbon dioxide sensor 10, the heating means 20, and the first sensor by the electromotive force lead wire 11, the voltage applying lead wire 21, and the first sensor lead wire 31. Means for being electrically connected with 30.

The second sensor 50 is provided in close proximity to the contact point B where the first sensor lead wire 31 and the electric circuit board 60 are bonded.

Since the electric circuit board 60 is not easily driven at a high temperature in general, the electric circuit board 60 is shown in FIG. 1 to minimize the influence of the heating means 20. The carbon dioxide measuring apparatus 100 includes the carbon dioxide sensor 10, the heating means 20, and the first sensor 30 inside the housing 40.

Accordingly, the second sensor 50 can measure a temperature in the range of -40 to 150 ° C., and a relatively inexpensive thermistor may be used. The position of the second sensor 50 may be determined by the first sensor. The lead wire 31 and the electric circuit board 60 are formed to be closest to each other in a feasible range so that the temperature of the contact point B to be bonded can be measured so that more accurate temperature correction can be made.

On the other hand, the first sensor 30 is the first sensor (a) when the temperature difference between the place (A) is detected and the first sensor lead wire 31 is connected to the electrical circuit board 60 is large Since a difference from the actual value also occurs in the temperature (electromotive force value) detected from 30, the present invention provides a method in which the first sensor lead wire 31 is close to a contact bonded to the electric circuit board 60, and thus a second sensor ( 50 is provided, and the electric circuit board 60 compares the measured values measured by the first sensor 30 and the second sensor 50 to correct a temperature error, and accordingly the heating means ( The controller 61 for adjusting the driving temperature or the heating time of the 20 is formed.

In addition, as shown in FIG. 5, the controller 61 should compare the measured values measured by the first sensor 30 and the second sensor 50, but the thermocouple as the first sensor 30. When the thermistor is used as the second sensor 50, the thermocouple has a very small electromotive force change according to temperature compared to the thermistor, and thus may not be easily compared to the first sensor 30. The electromotive force measured from the (thermocouple) is preferably amplified and filtered before being transmitted to the controller 61.

The controller 61 of the electric circuit board 60 may apply PID control (Proportional Integral Derivative Control) to perform functions such as comparing measured values, checking temperature error, and controlling the heating means 20. Temperature control of the heating means 20 is controlled by controlling the time that the current applied through the voltage application lead line 21 of the heating means 20 by using a pulse width modulation (PWM, Pulse Width Modulation) method, Accordingly, it is possible to maintain a constant temperature.

In addition, as shown in FIG. 2, a protection means 70 may be further provided to protect the second sensor 50, and the protection means 70 may be provided in addition to the shape shown in FIG. 2. If the means for protecting the two sensors 50 can be applied in various ways.

1 and 2 illustrate an example in which the heating means 20 is formed on the upper surface of the carbon dioxide sensor 10 and the first sensor 30 is attached to the lower surface of the carbon dioxide sensor 10. Corresponding to one embodiment of the present invention, the present invention is not limited to the above-described embodiment, and the scope of application is not limited, of course, various modifications are possible without departing from the gist of the present invention claimed in the claims. Of course.

EXAMPLE

An embodiment of the present invention is a carbon dioxide measuring apparatus 100 of the type shown in Figure 2, the solid oxide of the carbon dioxide sensor 10 is NBA (Na ₂ O · 11Al ₂ O ₃ ), the sensing electrode 14 is A mixture of BaCO ₃ and Na ₂ CO ₃ , the reference electrode 13 is formed of a mixture of Na ₂ Ti ₆ O ₁₃ and TiO ₂ , the heating means 20 is platinum on the surface in contact with the carbon dioxide sensor 10 The carbon dioxide measuring apparatus 100 is screen-printed in a predetermined pattern, and the contact thermocouple is provided in close proximity to the carbon dioxide sensor 10, and the thermistor is formed on the electric circuit board 60. By maintaining the relative humidity at 50%, the measured value of the carbon dioxide sensor 10 according to the temperature change of 20 ℃ to 25 ℃ 30 ℃ was tested.

As a comparative example of the above embodiment, the contact thermocouple and thermistor are not provided, but other conditions were measured by measuring the carbon dioxide sensor 10 of the same carbon dioxide measuring apparatus 100.

6 is a graph measuring a change in carbon dioxide concentration according to a change in ambient temperature of the conventional carbon dioxide measuring apparatus 100, and FIG. 7 measures a change in carbon dioxide concentration according to a change in ambient temperature of the carbon dioxide measuring apparatus 100 according to the present invention. In one graph,

As shown in FIG. 6, a comparative example in which only a constant voltage is applied to the heating means 20 to maintain a constant driving temperature has a signal value (CO ₂ concentration) measured from the carbon dioxide sensor 10 as the ambient temperature changes. It can be seen that the change is also caused by).

On the contrary, the embodiment of the carbon dioxide measuring apparatus 100 of the present invention has a constant output signal value (CO ₂ concentration) because it compensates and controls the driving temperature of the actual sensor according to the ambient temperature change as shown in FIG. It can be seen that.

1 is a cross-sectional view of a carbon dioxide measuring apparatus according to the present invention.

2 is another cross-sectional view of the carbon dioxide measuring apparatus according to the present invention.

3 is a plan view of the heating means according to the invention.

4 is a schematic operation diagram of a control unit according to the present invention;

5 is another operation schematic diagram of a control unit according to the present invention;

Figure 6 is a graph measuring the change in carbon dioxide concentration according to the ambient temperature change of the conventional carbon dioxide measuring apparatus.

Figure 7 is a graph measuring the carbon dioxide concentration change according to the ambient temperature change of the carbon dioxide measuring apparatus according to the present invention.

** Description of the symbols for the main parts of the drawings **

100: carbon dioxide measuring device capable of temperature compensation and control according to the present invention

10: carbon dioxide sensor 11: electromotive force lead wire

12: solid electrolyte 13: reference electrode

14: sensing electrode

20: heating means 21: voltage applied lead wire

30: first sensor 31: first sensor lead wire

40 housing

50: second sensor

60: electric circuit board 61: control unit

70: means of protection

Claims (8)

A pair of solid electrolytes 12 and reference electrodes 13 and sensing electrodes 14 formed on both sides of the solid electrolyte 12, respectively, connected to and extending from the reference electrode 13 and the sensing electrodes 14, respectively. A carbon dioxide sensor 10 including an electromotive force lead wire 11 of the carbon dioxide sensor 10; Heating means 20 provided on one side of the carbon dioxide sensor 10 and having a pair of voltage applying lead lines 21 for applying a voltage; A first sensor 30 in which a first sensor lead wire 31 extends close to the carbon dioxide sensor 10; Electrically connected to the carbon dioxide sensor 10, the heating means 20, and the first sensor 30 by the electromotive force lead wire 11, the voltage applying lead wire 21, and the first sensor lead wire 31. A circuit board 60; And A second sensor 50 provided in close proximity to the contact point where the first sensor lead wire 31 and the electric circuit board 60 are bonded; Carbon dioxide measuring device capable of temperature compensation and control, characterized in that formed, including. The method of claim 1, The electrical circuit board 60 Control unit for comparing the measured value measured by the first sensor 30 and the second sensor 50 to correct the temperature error, and adjust the driving temperature or heating time of the heating means 20 according to the result ( Carbon dioxide measuring device capable of temperature compensation and control, characterized in that 61) is formed. The method of claim 2, The first sensor (30) is a carbon dioxide measuring device capable of temperature compensation and control, characterized in that the contact thermocouple (Thermocouple). The method of claim 3, The electromotive force measured from the first sensor (30) is a carbon dioxide measuring device capable of temperature compensation and control, characterized in that the amplification and filtering before being transmitted to the control unit (61). The method according to claim 2 or 3, The second sensor 50 is a carbon dioxide measuring device capable of temperature compensation and control, characterized in that thermistor (Thermistor). The method of claim 2, The heating means 20 uses a substrate having a predetermined pattern formed by screen printing platinum (Pt) on one side, and the voltage applying lead line 21 is connected to both ends of the pattern and temperature compensation and Carbon dioxide measuring device that can be controlled. The method of claim 2, The carbon dioxide measuring device 100 is the carbon dioxide sensor 10, the heating means 20, and the first sensor 30, the temperature compensation and controllable carbon dioxide measurement, characterized in that provided in the housing 40 Device. The method of claim 2, The carbon dioxide measuring device 100 is a carbon dioxide measuring device capable of temperature compensation and control, characterized in that the protection means 70 is further provided so that the second sensor 50 is not exposed to the outside.

Images