JP3321315B2 - Atmospheric gas detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmospheric gas detecting device, and more particularly, to an atmospheric gas detecting device such as nitrogen, oxygen,
The present invention relates to an atmospheric gas detection device that detects atmospheric gases such as argon, carbon dioxide, and water vapor.

[0002]

2. Description of the Related Art Conventionally, a platinum thin-film resistor (note that a case where a platinum thin-film resistor is used as a sensor will be described below as an example, but the sensor in the present invention is not limited to a platinum thin-film resistor). There are many methods of detecting atmospheric gas using a method of detecting only a specific atmospheric gas. For example, in the case of detecting water vapor, a platinum thin film resistor (hereinafter referred to as a resistor or a temperature detection sensor as necessary) , A water vapor detection sensor, or simply a sensor) reacts to both temperature and water vapor. (1) Use two sensors, a temperature detection sensor and a water vapor detection sensor, which have the same temperature sensitivity, and subtract both reaction amounts. By doing so, the amount of water vapor is determined by comparing the remaining reaction amount with the reference reaction amount. (2) Using two sensors having different temperature sensitivities, a temperature detection sensor and a water vapor detection sensor, and detecting the temperature with the temperature detection sensor, removing the reaction amount of the water vapor detection sensor with respect to the temperature, and removing the remaining water vapor detection sensor. The amount of water vapor is determined by comparing the reaction amount with the reference reaction amount. However, in (1), it is difficult to obtain a temperature detection sensor and a water vapor detection sensor having the same temperature sensitivity in terms of manufacturing. In (2), since the temperature detection sensor is also affected by the water vapor, an error occurs depending on the amount of the water vapor. In particular, when the temperature increases, the amount of the water vapor rapidly increases, so that the influence is strongly affected. There were drawbacks such as.

FIG. 3 is a graph showing the relationship between the terminal voltage of a platinum thin-film resistor and the amount of gas in the atmosphere or the ambient temperature when a constant current is passed through the platinum thin-film resistor using the current as a parameter. FIG. 3A shows the relationship between the amount of water vapor in the atmosphere and the terminal voltage of the resistor, and FIG. 3B shows the relationship between the helium concentration in the atmosphere and the terminal voltage of the resistor. ) Shows the relationship between the ambient temperature and the terminal voltage of the resistor. As is clear from these figures, when a current is passed through the platinum thin film resistor,
The gas concentration in the atmosphere or the atmospheric temperature can be detected.

[0004]

[Problems to be solved by the invention]

(1) Humidity detection using a platinum thin film resistor is affected by the temperature of the resistor itself.
The temperature change of the resistor had to be removed.
For this reason, separate sensors must be prepared for temperature detection and humidity detection. (2) If a difference between the output voltages is obtained by using a temperature detection sensor and a humidity detection sensor having the same temperature sensitivity, the change in temperature can be removed. Therefore, the humidity is obtained from the remaining change in humidity. However, it is difficult to manufacture a temperature detection sensor and a humidity detection sensor having the same temperature sensitivity in terms of manufacturing. (3) When a temperature detection sensor and a humidity detection sensor with unequal temperature sensitivity are used, first obtain the temperature with the temperature detection sensor, and then use that temperature value to remove the temperature influence of the humidity detection sensor. The humidity is determined from the remaining value. However, the temperature detection sensor loses thermal equilibrium when humidity is added, and cannot obtain a correct temperature. This tendency is more susceptible to higher temperatures as the absolute amount of humidity increases. (4) A self-temperature compensation method in which temperature detection is performed by a humidity detection sensor is also considered, but this principle is realized by adjusting the humidity detection sensor to a current at a point where the humidity sensitivity becomes zero. However, it is difficult to adjust the humidity sensitivity of the humidity detection sensor to zero, and when the ambient temperature changes, the zero point shifts.

[0005]

In order to solve the above-mentioned problems, the present invention provides (1) a sensor having a terminal voltage which changes in response to an ambient gas when a predetermined constant current is passed, the sensor comprising: In response to the number of types of atmospheric gas to be determined, currents having different peak values are applied to determine the response value of the sensor to each amount of atmospheric gas as an estimation formula, and the sensor is placed under the condition of the atmospheric gas to be determined. A method in which currents having different peak values are applied to obtain a response value of the sensor, and the response value is substituted into the estimation formula to obtain a solution, thereby detecting an amount of atmospheric gas to be obtained. And (2)
When a predetermined constant current is passed, the terminal voltage changes in response to the surrounding gas. At least as many sensors as the number of types of atmospheric gas desired to be obtained. The response value of the sensor to the sensor is obtained as an estimation formula, and the current having the different peak value is simultaneously applied to each sensor under the condition of the atmospheric gas for which the sensor is to be obtained, thereby obtaining the response value of each sensor. Substituting the value into the above estimation formula to obtain the solution, and detecting the amount of the atmospheric gas to be obtained, and (3) the terminal voltage reacts with the surrounding gas when a predetermined constant current is passed. It has a single sensor that changes, and when there is only one kind of atmospheric gas to be sought, utilizing the property of responding to the ambient temperature of the sensor,
A current having a different peak value is applied twice to the sensor to obtain a response value to the atmospheric gas and the ambient temperature as an estimated value, and the current having a different peak value is applied under the condition of the atmospheric gas for which the sensor is to be obtained. Then, a reaction value is obtained, and the reaction value is substituted into the above-mentioned estimation formula to obtain a solution, and the amount of the atmospheric gas is obtained therefrom.

[0006]

[Function] When a current is applied to a platinum thin film resistor, a voltage corresponding to temperature or humidity is generated, and when the current applied to the platinum thin film resistor is changed, the degree of the reaction is changed and the voltage is changed. Is used, the platinum thin film resistor is arranged in a two-dimensional arrangement of temperature and humidity, and currents having different peak values of two factors (temperature and humidity) are added, and the voltage change in that case is obtained as an estimation formula, respectively. By giving orthogonality to those estimation formulas, an unknown value is obtained from the estimation formulas (in this case, the currents with different peak values are within the current range applied to the humidity detection sensor, and if the current value is such that a response can be obtained,
Any value). In this way, the temperature or humidity can be obtained by one humidity detection sensor, and the current of zero humidity sensitivity, which is difficult in the self-temperature compensation method in which the humidity detection is performed by one humidity detection sensor, is not required.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is to change the property of reacting to a gas such as nitrogen, oxygen, argon, carbon dioxide and water vapor when a current is applied to a platinum thin film resistor and the peak value of the current. Utilizing the property that the degree of reaction changes,
Currents having different peak values for the number of types of atmospheric gas to be obtained are applied to the resistor in advance, and the reaction value of the resistor with respect to the amount of atmospheric gas is obtained as an estimation formula. Is installed, the reaction value of the resistor when the current having a different peak value is applied is substituted into the above-mentioned estimation formula and is made simultaneous, and the solution of the estimation formula is obtained, whereby the amount of the atmospheric gas to be obtained is obtained. It is intended to be obtained directly.

For simplicity, the description will be made by taking water vapor, helium, temperature and the like as an example. When an electric current is applied to a platinum thin film resistor, the platinum thin film resistor is made of these water vapor and helium in the atmospheric gas. It shows characteristics as shown in FIG. 3 with respect to concentration or temperature. From this, it is possible to obtain the amount or temperature of atmospheric gas (water vapor, helium) by multiplely arranging the amount or temperature of atmospheric gas, giving orthogonality to the estimation formulas, and combining each estimation formula. become. Here, an example will be described in which an estimation formula is obtained using Chebyshev orthogonal polynomials shown in (Equation 1) and (Equation 2) in which the order of two variables of water vapor and temperature is linear.

[0009]

(Equation 1)

Here, I _1, I ₂ : current [A] applied to the resistor V _1, V ₂ : terminal voltage [V] of the resistor at I ₁ and I ₂ dH: change in water vapor amount, H ^{_{-H b [g / m 3]}} H: water vapor content _{^{[g / m 2] H b}} : mean value of the water vapor content [g / m ^3] dT: change in _{temperature, T-T b [℃]} T: temperature [° C.] T _b : average value of temperature [° C.] m ₁ : terminal voltage [V] of the resistor at I _{1, Hb} and T _b h ₁ : coefficient [v] / of the linear expression of H at I ₁ [G /
m ^3] t _1: coefficient of linear expression of T in _{I 1 [v] / [℃} ] m 2: I 2, H b and T terminal voltage of the resistor in the _b [V] h _2: H in I ₂ Coefficient [V] / [g /
m ³ ] t ₂ : Coefficient [V] / [° C.] of the linear expression of T in I ₂ Coefficients m _1, h _1, t _1, m _2, h ₂ and t ₂ are described in mathematical formulas and the like It can be easily obtained from a table of the Chebyshev orthogonal polynomials or the like. Thus, if V ₁ and V ₂ are given, dH and dT can be obtained.

FIG. 1 is a view for explaining an example of a detection circuit for obtaining water vapor and temperature using the above-mentioned (Equation 1) and (Equation 2) as an embodiment of an atmospheric gas detection apparatus according to the present invention. In the figure, I _{1 to} In are constant current circuits (and constant currents), Rs is a platinum thin film resistor, and CH is an environment to be obtained.
A / D is an analog / digital conversion circuit, ALU is an arithmetic circuit, DISP is a display device, and CONT is a control circuit.

In FIG. 1, first, a platinum thin film resistor Rs
Is set in the channel under the environment in which it is desired to obtain, and then the currents I ₁ and I ₂ having different peak values are sequentially applied, and the terminal voltages V ₁ and V ₂ of the platinum thin-film resistor Rs generated at this time are converted to the analog / digital converter A / D to the arithmetic circuit ALU. The arithmetic circuit ALU incorporates a determinant solving program shown in (Equation 3). The obtained variation dH of the amount of water vapor and the variation dT of the temperature include the average value _{Hb of} water vapor and the average value T of temperature. _The steam amount H and the temperature T are calculated by adding _b . The control circuit CONT activates the switch SW for switching the current value and simultaneously supplies the voltage appearing in the analog / digital converter A / D to the arithmetic circuit ALU in order. Also, the display circuit DISP
Indicates the water vapor amount H and the temperature T. The above example is for two unknowns, water vapor and temperature.
Even in the case of three or more, if the same procedure is performed, this unknown number can be obtained.

FIG. 2 is a diagram for explaining a current application method. FIGS. 2 (a) and 2 (b) are diagrams showing a detection method when one detection sensor is used. As described above, the currents I _{1 and} I ₂ having different peak values are applied with a time lag, and the pulse width of each current may be about 50 ms. FIG. 2C shows a case where a plurality of types of atmospheric gas are obtained. In the case where a plurality of types of atmospheric gas are obtained, the detection state is delayed in time and an error is caused. If currents having different peak values are applied to these at the same time, atmospheric gas can be detected at high speed.

[0014]

As is apparent from the above description, according to the first aspect of the present invention, a plurality of types of atmospheric gases can be detected using a single sensor without affecting the ambient temperature. . According to the second aspect of the present invention, a plurality of sensors are used to detect the reaction values of all the sensors within the same time. Even if there is, the atmospheric gas can be detected without causing a time lag. Furthermore, according to the third aspect of the present invention, even if there is only one atmospheric gas to be obtained, the atmospheric gas can be detected without being affected by the ambient temperature by utilizing the reaction to the ambient temperature. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an atmospheric gas detection device according to the present invention.

FIG. 2 is a diagram for explaining the timing of a current applied to the atmospheric gas detection device according to the present invention.

FIG. 3 is a diagram showing an example of a reaction characteristic of a sensor used in the present invention.

[Explanation of symbols]

I _{1 to} In: constant current circuit, Rs: platinum thin film resistor, CH
... Ambient atmosphere, A / D ... Analog / digital conversion circuit, ALU ... Calculation circuit, DISP ... Display device, CONT
... Control circuit.

Continuation of the front page (56) References JP-A-60-198446 (JP, A) JP-A-1-311260 (JP, A) JP-A-1-311261 (JP, A) JP-A-2-1-115757 (JP) , A) JP-A-56-648 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/00-27/24 G01K 1/00-19/00 JICST file (JOIS )

Claims (3)

(57) [Claims] 1. A sensor whose terminal voltage changes in response to ambient gas when a predetermined constant current is passed, and a current having a different peak value is applied to the sensor by the number of types of atmospheric gas to be obtained. The reaction value of the sensor with respect to each atmospheric gas amount is obtained as an estimation formula, and the reaction value of the sensor is obtained by applying a current having a different peak value under the condition of the atmospheric gas for which the sensor is to be obtained. An atmospheric gas detection device, wherein a value is substituted into the above-mentioned estimation formula to obtain a solution, and an amount of the atmospheric gas to be obtained is detected based on the solution. 2. A sensor in which a terminal voltage changes in response to ambient gas when a predetermined constant current is passed has at least as many types of atmospheric gases as desired, and currents having different peak values are simultaneously applied to each sensor. The reaction value of the sensor with respect to each atmospheric gas amount is obtained as an estimation formula, and the current having the different peak value is simultaneously applied to each sensor under the condition of the atmospheric gas for which the sensor is to be obtained, and the reaction value of each sensor is obtained. An atmospheric gas detection apparatus for determining the amount of atmospheric gas to be obtained by substituting the reaction value into the estimation formula and obtaining a solution. 3. A sensor having a single sensor whose terminal voltage changes in response to ambient gas when a predetermined constant current is passed. When only one type of atmospheric gas is required, the ambient temperature of the sensor is reduced. Utilizing the property of reacting, a current having a different peak value is applied twice to the sensor to obtain a reaction value with respect to the atmospheric gas and the ambient temperature as an estimated value, and under the condition of the atmospheric gas for which the sensor is desired to be obtained. An atmospheric gas detection device, wherein a reaction value is obtained by applying the currents having different peak values, the reaction value is substituted into the estimation formula to obtain a solution, and the amount of the atmospheric gas is obtained therefrom.