KR101131958B1 - Method for measuring concentriation of gas and device for the same - Google Patents

Abstract

A gas concentration measuring method and a gas concentration measuring apparatus are provided. Gas concentration measurement method, the step of injecting the measurement gas into the gas sensor; Measuring the output voltage of both ends of the load resistance connected in series with the gas sensor or the internal resistance of the gas sensor (hereinafter, referred to as the output voltage and the internal resistance value as 'measurement value') during the time that the measurement gas is injected. To obtain an output graph over time; Calculating an adsorption amount of a gas from the output time graph; And extracting the concentration of the gas using the adsorption amount calculated from calculating the adsorption amount of the gas. Gas concentration measuring apparatus, the gas sensor; A gas input device supplying a gas to the gas sensor; Odorless air input device for supplying odorless air to the gas sensor; And a gas amount measuring unit configured to calculate an amount of gas detached from the gas sensor from the measured value measured by the gas sensor. And a concentration calculating unit calculating a concentration of the gas from the gas amount calculated by the gas amount measuring unit. Thus, the gas concentration can be measured more accurately.

Gas sensor, odor measurement

Description

Gas concentration measuring method and gas concentration measuring apparatus used therein {Method for measuring concentriation of gas and device for the same}

The present invention relates to a gas concentration measuring method and a gas concentration measuring apparatus capable of measuring the concentration of malodorous gas.

In modern society, as environmental pollution sources are increased due to continuous industrialization and urbanization, continuous research on environmental technology and continuous investment in environmental industry market are being made. In this situation, various semiconductor gas sensors have been improved to cope with various factors in order to detect and prevent harmful gases which are environmental pollution sources in advance. In addition, a performance evaluation method for the developed gas sensor and a method for estimating the gas concentration (C) from the sensed output signal data have been presented.

The performance evaluation of a semiconductor gas sensor that is commonly used includes voltage (Vair) or resistance (Rair), which is an output value before gas is injected into the gas sensor, and output voltage (Vgas), resistance (Rgas), or resistance after gas is injected. As a proportional expression of change Rx, it consists of the following relationship.

S = Vair / Vgas, S = Vgas / Vair, S = Rair / Rgas, S = Rgas / Rair

S = (Vair-Vgas) / Vair, S = (Vair-Vgas) / Vgas, S = (Rair-Rgas) / Rair, S = (Rair-Rgas) / Rgas

S = Rgas / Rx

However, the conventional evaluation method generally evaluates the performance of the gas sensor by a simple proportional expression of the output values Vair and Rair before the gas is injected into the gas sensor and the output values Vgas, Rgas and Rx after the gas is injected. Due to the initial output value that varies with the measurement environment, the performance of the gas sensor could not be evaluated objectively. In addition, in the manufacturing process of the gas sensor, as all gas sensors do not have a constant resistance value, there was a problem that the output characteristics are different for each gas sensor. That is, the output value proportional expressions before and after gas injection were expressed with various values, and thus a unified performance evaluation method could not be applied. In addition, when the measurement gas is repeatedly injected at regular intervals, the output value of the gas sensor is expressed differently every moment, and thus there is a problem that the sensitivity reproducibility, which is a main requirement of the gas sensor, is significantly reduced.

The output characteristics of the semiconductor gas sensor are determined based on the initial resistance value (RS) of the gas sensor and the injected gas concentration (C) as main factors, but in the conventional method, the output characteristics are represented as the main factors (RS, C). It did not explain clearly. Since the initial resistance value RS is a value known at the manufacturing stage, the gas concentration C can be estimated by analyzing the electrical output signal of the gas sensor, but there is no clear definition of the output characteristic. Many difficulties have arisen in estimating (C).

The present invention has been made to solve the above problems, and an object thereof is to provide a gas concentration measuring method that can more accurately measure the gas concentration.

In order to solve the above problems, the present invention comprises the steps of putting a measurement gas into the gas sensor; Measuring the output voltage of both ends of the load resistance connected in series with the gas sensor or the internal resistance of the gas sensor (hereinafter, referred to as the output voltage and the internal resistance value as 'measurement value') during the time that the measurement gas is injected. To obtain an output graph over time; Calculating an adsorption amount of a gas from the output time graph; And extracting the concentration of the gas using the amount of adsorption calculated from the step of calculating the amount of adsorption of the gas.

Here, the odorless air injection step of injecting odorless air before injecting the measurement gas into the gas sensor, it is preferable to further include.

In the odorless air injection step, the time for injecting the odorless air is preferably longer than the time for injecting the measurement gas in the step of introducing the measurement gas.

And injecting odorless air into the gas sensor; Measuring the measured value of the gas sensor during the time that the odorless air is injected, and obtaining an output graph over time; Calculating a desorption amount of gas from the output time graph; And determining the state of the gas sensor by comparing the adsorption amount of the gas obtained in the step of calculating the adsorption amount of the gas with the desorption amount calculated from the step of calculating the desorption amount of the gas. effective.

The calculating of the adsorption amount of the gas may include calculating a rate of change of the measured value with respect to time; And calculating an area value obtained by integrating the area of the variation rate.

The calculating of the desorption amount of the gas may include calculating a variation ratio S of the measured value with respect to time; And obtaining an area value A in which the area of the variation rate S is integrated.

The extracting of the concentration of the gas may include extracting a concentration of the measurement gas from a characteristic relation between the adsorption amount and the concentration of the measurement gas, and the characteristic relation may include a plurality of measurement gas samples. The amount of adsorption is measured at, and obtained by a regression analysis method between the amount of adsorption and the concentration of the gas sample.

On the other hand, the present invention is a gas sensor; A gas input device supplying a gas to the gas sensor; Odorless air input device for supplying odorless air to the gas sensor; And a gas amount measuring unit which calculates an amount of gas detached from the gas sensor from the measured value measured by the gas sensor. It provides a gas concentration measuring apparatus comprising a; concentration calculation unit for calculating the concentration of the gas from the gas amount calculated by the gas amount measuring unit.

Here, the odorless air input device, it is preferable to include; activated carbon filter installed on the air flow path to deodorize the atmospheric air sucked.

The gas input device may further include a valve connected to the odorless air input device and the gas sensor to select air supplied to the gas sensor.

In addition, the gas input device, a dust filter for filtering dust from the gas; And a water removal device for filtering water from the gas.

The gas amount measuring unit calculates the rate of change of the measured value against time, and then calculates the amount of gas adsorbed and desorbed from the area value of the area of the rate of change.

The concentration calculating unit extracts the concentration of the measurement gas from the characteristic relational expression of the adsorption amount and the concentration of the measurement gas, and the characteristic relational formula measures the adsorption amount on a plurality of measurement gas samples, Obtained by the regression method between the concentrations of the gas samples.

According to the problem solving means of the present invention as described above it can be expected to include the following matters.

First, the method of estimating the gas concentration from the adsorption amount of the gas adsorbed on the sensor has the advantage of excellent reproducibility by showing the characteristics of the low relative standard deviation even if the concentration increases and the number of repetitions increases.

The present invention has the advantage that the gas attached to the sensor can be removed by performing the odorless air injection step of injecting odorless air before measuring gas injection. In addition, when injecting odorless air, the amount of gas falling from the surface of the sensor can be measured, and there is also an advantage that it is possible to invert the pollution degree of air in general.

In addition, there is an advantage that the performance of the gas sensor can be evaluated by comparing the adsorption and desorption amount.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the following description of the present invention, a detailed description of known functions and configurations will be omitted so as not to obscure the gist of the present invention.

1 is a block diagram briefly illustrating an internal structure of a gas concentration measuring apparatus according to an embodiment of the present invention.

The gas concentration measuring apparatus includes a gas sensor 130, a gas input device 100 for supplying gas to the gas sensor 130, and an odorless air input device 200 for supplying odorless air to the gas sensor 130. And a gas amount measuring unit 300 for calculating the amount of gas attached to and detached from the gas sensor from the measured value measured by the gas sensor, and the concentration of the gas from the gas amount calculated from the gas amount measuring unit 300. The concentration calculation unit 400 to calculate, the odorless air input device 200 and the gas input device 100 is selectively communicated with the gas sensor 130, the valve for injecting gas into the gas sensor 130 ( 103).

The odorless air input device 200 includes an activated carbon filter 210 installed on the air flow path 220 to deodorize the atmospheric air that is sucked in. Therefore, the smell of atmospheric air can be removed. In addition, the odorless air input device 200 may be configured as a separate tank to directly supply odorless air. However, in this case, there is a problem that the cost increases when used.

The gas injector 100 includes a dust filter 110 that filters dust from the gas and a water removal device 120 that filters moisture from the gas. The dust filter 110 includes a first dust filter 111 and a second dust filter 112 installed before and after the water removing device 120. The water treated by the water removing device 120 is discharged to the outside air by the solenoid valve.

The gas sensor 130 has a plurality of gas sensors 131 to 139 arranged in an array. The gas sensors 131 to 139 may be a semiconductor gas sensor, an electrochemical sensor, an optical sensor, or the like. As shown in FIG. 2, the gas sensor 130 is disposed at a point where the flow path 101 is bent so that the sensing surface 132a of the sensor is positioned perpendicular to the flow of the fluid. As shown in FIG. 3, the gas sensor 130 exhibits higher sensing efficiency when the gas sensor 130 is disposed perpendicular to the flow of the fluid, as shown in FIG. 2. This can be confirmed by the graphs of FIGS. 2 and 3.

The valve 103 is installed at a point where the uncontaminated air flows in with the flow path 102 and the contaminated air flows with the flow path 104, so that the air can be selectively injected. Therefore, after measuring the contaminated air, clean air is put in, thereby cleaning and stabilizing the sensor, maintaining the measurement accuracy of the sensor, and increasing the life of the sensor.

The flow rate meter 150 capable of measuring the flow rate is provided on the flow path 104 or the flow path 101 of the gas sensor 130 through which the polluted air flows.

The gas amount measuring unit 300 calculates the change rate S of the measured value with respect to time, and then calculates an area value A obtained by integrating the area of the change rate S, and calculates the amount of gas adsorbed and desorbed. . The detailed description thereof will be replaced with the description of the gas concentration measuring method to be described later.

The said concentration calculating part extracts the density | concentration of the said measurement gas from the characteristic relationship formula of the said adsorption amount and the density | concentration of the said measurement gas. The characteristic relation is obtained by a regression analysis method between the adsorption amount and the concentration of the gas sample by measuring the adsorption amount on a plurality of measured gas samples. Detailed description thereof will also be replaced with the description of the gas concentration measuring method described later.

Gas concentration measurement method, the step of injecting the measurement gas into the gas sensor 130, the output voltage (VL) of both ends of the load resistor 140 connected in series with the gas sensor 130 or the inside of the gas sensor Measuring a resistance (hereinafter, referred to as an output voltage and an internal resistance value as a 'measured value') during the time that the measurement gas is injected to obtain an output graph over time (FIG. 4); From the step of calculating the adsorption amount of the gas (FIGS. 5 and 6), and the step of extracting the concentration of the gas using the adsorption amount calculated from the step of calculating the adsorption amount of the gas.

The step of calculating the adsorption amount of the gas includes calculating a rate of change of the measured value with respect to time (FIG. 5), and calculating an area value obtained by integrating the area of the rate of change (FIG. 6).

The step of calculating the variation ratio of the output voltage with respect to time is to calculate the slope of the output voltage graph (Fig. 4) with respect to time, expressed as a graph with respect to time as shown in FIG.

The step of calculating the area value is a value obtained by integrating the area in the graph of FIG. 5. The method calculated as in FIG. 6 is called a sensor chromatogram area extraction method.

Tables below show the values of hydrogen sulfide (H ₂ S) of various concentrations measured by a conventional voltage comparison method and the value measured by the sensor chromatogram area extraction method of the present invention.

Target gas : H ₂ S  One ppm Sensor Model: MICS  5521 (manufacturer E2V , Swiss) Base (Vair) Max (Vgas) Vgas / Vair Sout area 1st 1.57 2.10 1.34 50.4 2nd 1.59 2.09 1.31 49.6 3rd 1.62 2.08 1.28 50.5 Average 1.59 2.09 1.31 50.17 Standard Deviation (S.D) 0.03 0.01 0.03 0.49 Relative standard deviation (% RSD) 1.58 0.48 2.05 0.98

In the table above, Vair is the sensor's output voltage when exposed to odorless air, Vgas is the sensor's output voltage when exposed to the target gas, and Sout_area is the value extracted by the sensor chromatogram area extraction method.

Target gas : H ₂ S  5 ppm Sensor Model: MICS  5521 (manufacturer E2V , Swiss) Base (Vair) Max (Vgas) Vgas / Vair Sout area 1st 1.53 2.69 1.76 103.9 2nd 1.60 2.55 1.59 106.7 3rd 1.65 2.41 1.46 103.0 Average 1.59 2.55 1.60 104.53 Standard Deviation (S.D) 0.06 0.14 0.15 1.93 Relative standard deviation (% RSD) 3.78 5.49 9.29 1.85

Target gas : H ₂ S  10 ppm Sensor Model: MICS  5521 (manufacturer E2V , Swiss) Base (Vair) Max (Vgas) Vgas / Vair Sout area 1st 1.54 2.81 1.82 133.8 2nd 1.67 2.71 1.62 129.8 3rd 1.76 2.67 1.52 129.4 Average 1.66 2.73 1.65 131.00 Standard Deviation (S.D) 0.11 0.07 0.16 2.43 Relative standard deviation (% RSD) 6.68 2.64 9.45 1.86

Target gas : H ₂ S  One ppm Sensor Model: TGS  2602 (Manufacturer Figaro Technology Research Institute, Japan) Base (Vair) Max (Vgas) Vgas / Vair Sout area 1st 1.42 2.19 1.54 65.2 2nd 1.44 2.10 1.46 68.4 3rd 1.44 2.07 1.44 64.1 Average 1.43 2.12 1.48 65.90 Standard Deviation (S.D) 0.01 0.06 0.06 2.23 Relative standard deviation (% RSD) 0.81 2.95 3.75 3.39

Target gas : H ₂ S  5 ppm Sensor Model: TGS2602 (Manufacturer Figaro Research Institute, Japan) Base (Vair) Max (Vgas) Vgas / Vair Sout area 1st 1.43 2.95 2.06 152.7 2nd 1.48 2.94 1.99 150.5 3rd 1.59 2.92 1.84 144.4 Average 1.50 2.94 1.96 149.20 Standard Deviation (S.D) 0.08 0.02 0.12 4.30 Relative standard deviation (% RSD) 5.46 0.52 5.87 2.88

Target gas : H ₂ S  10 ppm Sensor Model: TGS2602 (Manufacturer Figaro Research Institute, Japan) Base (Vair) Max (Vgas) Vgas / Vair Sout area 1st 1.55 3.48 2.25 206.9 2nd 1.65 3.55 2.15 204.6 3rd 1.76 3.40 1.93 201.7 Average 1.65 3.48 2.11 204.40 Standard Deviation (S.D) 0.11 0.08 0.16 2.61 Relative standard deviation (% RSD) 6.35 2.16 7.62 1.27

As can be seen from the results of Tables 1 to 6, the conventional voltage measurement method can be seen that the variation of the initial Vair value occurs as the number of measurements is repeated, and the occurrence of deviation increases as the concentration of the measurement gas increases. .

On the other hand, the sensor chromatogram area extraction method has the advantage of excellent reproducibility by showing the characteristics of the low relative standard deviation even if the concentration increases and the number of repetitions increases.

Extracting the concentration of the gas may include extracting the concentration of the measurement gas from the characteristic relational expression of the adsorption amount and the concentration of the measurement gas, wherein the characteristic relational expression includes the adsorption amount to a plurality of measurement gas samples. By measuring this, it can be obtained by a regression analysis method between the adsorption amount and the concentration of the gas sample. Since this method is a method that is frequently used statistically, detailed description thereof will be omitted.

Here, it is preferable to further include a odorless air injection step of injecting odorless air before injecting the measurement gas to the gas sensor. Conventionally, a small amount of gas is adsorbed on the surface of the sensor while the sensor is exposed to the atmosphere. In the case of injecting the measurement gas in such a state, there was a disadvantage in that it was difficult to obtain a desired characteristic graph because the sensitivity of the sensor was low. In contrast, the present invention has the advantage that the gas attached to the sensor can be removed by performing the odorless air injection step of injecting the odorless air before the measurement gas injection. In addition, when injecting odorless air, by extracting the sensor chromatogram, it is possible to measure the amount of gas falling from the surface of the sensor, which also has the advantage that it is possible to reverse the normal air pollution.

In the odorless air injection step, the time for injecting the odorless air is preferably longer than the time for injecting the measurement gas in the step of introducing the measurement gas.

That is, the time for injecting the odorless air is longer than the time for injecting the measurement gas, it is possible to increase the sensitivity of the sensor to the measurement air. In other words, when the measurement air is injected into the sensor for a long time, the amount of gas adhering to the sensor surface is increased, and the characteristics of the sensor are changed. Therefore, when the odorless air is injected for a long time and there is no increase or decrease in the amount of adhesion on the surface of the sensor, the measurement air is injected to obtain more accurate measured values.

On the other hand, the step of injecting the odorless air to the gas sensor (in Figure 4, the time indicated by the reference numeral 42) and the measurement value of the gas sensor during the time the odorless air is injected, the output graph over time Obtaining 42 (after 42 in FIG. 4), calculating a desorption amount of gas (112 in FIG. 5 and 117 in FIG. 6), and calculating an adsorption amount of the gas from the output graph versus time. Comparing the adsorption amount of the gas obtained in the step with the desorption amount calculated from the step of calculating the desorption amount of the gas, and determining the state of the gas sensor.

The step of calculating the desorption amount of the gas includes calculating a rate of change of the measured value with respect to time (112 in FIG. 5), and calculating an area value obtained by integrating the area of the rate of change (117 in FIG. 6). do.

That is, after inject | pouring a measurement gas, odorless air is inject | poured and the desorption amount of the gas adhering to a sensor is calculated | required.

In determining the state of the gas sensor, by comparing the adsorption and desorption amount, it is possible to evaluate the performance of the gas sensor. That is, when the difference in the adsorption and desorption amount on the surface of the gas sensor is managed within 3%, since the adsorption and desorption of the gas is reversibly made on the surface of the gas sensor, it can be seen that the gas sensor is in a good state. Is 3 ~ 5% or more, the gas is adsorbed on the gas sensor and it is not desorbed, so it is no longer used as an indicator that it is difficult to use as a sensor, or the filter is replaced and the inside of the odorless air supply unit. It can be used as an indicator of pipe contamination.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.

1 is a block diagram schematically illustrating the internal structure of a gas concentration measuring apparatus;

FIG. 2 is a detection sensor installed on the vertical flow path of FIG. 1 and a sensor chromatogram graph thereof

3 is a sensor sensor installed on the horizontal flow path of FIG. 1 and a sensor chromatogram graph thereof;

4 is a graph of output versus time of the sensor of FIG.

5 is a sensor chromatogram graph of FIG.

FIG. 6 is a graph illustrating integrating the sensor chromatogram graph of FIG. 4. FIG.

DESCRIPTION OF REFERENCE NUMERALS

130: gas sensor 140: load resistance

100: gas input device 200: odorless air input device

300: gas amount measurement unit 400: concentration calculation unit

210: activated carbon filter 103: valve

110: dust filter 120: moisture removal device

Claims (15)

Injecting a measurement gas into the gas sensor; Measuring the output voltage of both ends of the load resistance connected in series with the gas sensor or the internal resistance of the gas sensor (hereinafter, referred to as the output voltage and the internal resistance value as 'measurement value') during the time that the measurement gas is injected. To obtain an output graph over time; Calculating an adsorption amount of a gas from the output time graph; And Extracting a concentration of gas using the adsorption amount calculated from calculating the adsorption amount of the gas; Gas concentration measurement method comprising a. The method of claim 1, An odorless air injection step of injecting odorless air before injecting the measurement gas into the gas sensor; Gas concentration measurement method further comprising. The method of claim 2, In the odorless air injection step, the time for injecting the odorless air, the gas concentration measuring method, characterized in that longer than the time for injecting the measurement gas in the step of introducing the measurement gas. The method of claim 1, Injecting odorless air into the gas sensor; Measuring the measured value of the gas sensor during the time that the odorless air is injected, and obtaining an output graph over time; Calculating a desorption amount of gas from the output time graph; And Determining the state of the gas sensor by comparing the adsorption amount of the gas obtained in the step of calculating the adsorption amount of the gas with the desorption amount calculated from the step of calculating the desorption amount of the gas; Gas concentration measurement method comprising a further. The method according to any one of claims 1 to 4, Calculating the adsorption amount of the gas, Calculating a rate of change of the measured value against time; And Obtaining an area value obtained by integrating the area of the change rate; Gas concentration measurement method comprising a. The method of claim 4, wherein Calculating the desorption amount of the gas, Calculating a rate of change of the measured value against time; And Obtaining an area value obtained by integrating the area of the change rate; Gas concentration measurement method comprising a. The method according to any one of claims 1 to 4, Extracting the concentration of the gas, Extracting the concentration of the measurement gas from a characteristic relation between the adsorption amount and the concentration of the measurement gas; Gas concentration measurement method comprising a. The method of claim 7, wherein The characteristic relation is Measuring the adsorption amount on a plurality of measurement gas samples and obtaining the gas concentration by a regression analysis method between the adsorption amount and the concentration of the gas sample. Gas sensor; A gas input device supplying a gas to the gas sensor; Odorless air input device for supplying odorless air to the gas sensor; And A gas amount measuring unit configured to calculate an amount of gas detached from the gas sensor from the measured value measured by the gas sensor; A concentration calculating unit calculating a concentration of the gas from the gas amount calculated by the gas amount measuring unit; Gas concentration measuring apparatus comprising a. The method of claim 9, The odorless air input device, An activated carbon filter installed on the air passage to deodorize the atmospheric air to be sucked; Gas concentration measuring apparatus comprising a. The method of claim 9, The gas inlet device is connected to the odorless air inlet device and the gas sensor, the valve for selecting the air supplied to the gas sensor; Gas concentration measuring device further comprises. The method according to any one of claims 9 to 11, The gas injector, A dust filter for filtering dust from the gas; And A water removal device for filtering water from the gas; Gas concentration measuring apparatus comprising a. The method according to any one of claims 9 to 11, The gas amount measuring unit, After calculating the rate of change (S) of the measured value over time, A gas concentration measuring apparatus characterized by obtaining the amount of gas adsorbed and desorbed from the area value (A) in which the area of the change rate (S) is integrated. The method according to any one of claims 9 to 11, The concentration calculation unit, A gas concentration measuring apparatus, characterized by extracting the concentration of the measurement gas from the characteristic relation between the concentration of the measurement gas and the adsorption amount. The method of claim 14, The characteristic relation is A gas concentration measuring apparatus characterized by measuring the adsorption amount on a plurality of measurement gas samples and obtaining by a regression analysis method between the adsorption amount and the concentration of the gas sample.

Images