KR101984671B1 - Method of automatically calibrating sensor output characteristic of gas detector - Google Patents

Abstract

The present invention relates to a method for automatically calibrating the output characteristics of a gas detector according to the present invention, comprising the steps of injecting a standard gas having monotonically increasing test concentrations into a gas detector to obtain measured mean values corresponding to said test concentrations, Generating a first interpolation polynomial representing a relationship between measured averages, computing the first interpolation polynomial output values by substituting the test concentrations into the first interpolating polynomial, The interpolation polynomial equation comprising: extracting a correction object interval in which a correction object density having a maximum error occurs in accordance with an error of interpolation polynomial output values, Into the first interpolation polynomial to calculate a median value of the previous section, Calculating a median value of a subsequent interval by substituting the median density of a subsequent interval between the maximum density of the correction target interval and the first interpolation polynomial, A second interpolating polynomial generating step of generating a second interpolating polynomial expressing a relationship between input values including the intermediate density and output values including the measurement average values, the previous section intermediate value, and the subsequent section intermediate value, 2 interpolating the interpolation polynomial to produce a density output calibration function.
According to the present invention, a response characteristic of sensors used for detecting flammable or noxious gas can be expressed by an optimal approximation equation that can express the output voltage or current of a sensor corresponding to input gas by using a standard gas having various concentrations And a method of calculating an accurate concentration is provided.

Description

METHOD OF AUTOMATICALLY CALIBRATING SENSOR OUTPUT CHARACTERISTIC OF GAS DETECTOR [0002]

The present invention relates to a method for automatically calibrating the output characteristics of a gas detector.

Most of the gas sensors used in the conventional gas detectors have nonlinearity, and therefore, much efforts have been made to solve them.

However, it is not easy to numerically quantify physicochemical quantities in the natural world. Therefore, most gas detectors are made of standard specimens with 2 or 3 kinds of concentrations, and the input and output response characteristics of the sensor are tested to derive the first-order linear equation or the second-order equation, There is a problem that an error exists.

Korean Registered Patent No. 10-0831589 (Registered Date: May 16, 2008, Name: Method of Extracting Output Characteristics of Gas Sensor and Apparatus and Method for Measuring Gas Concentration Using It)

An object of the present invention is to provide an apparatus and method for measuring response characteristics of sensors used for detecting combustible or noxious gases by using a standard gas having various concentrations to obtain an optimal approximate equation expressing the output voltage or current of a sensor corresponding to input gas And to provide a method for calculating an accurate concentration.

In order to solve the above technical problems, the present invention provides a method for automatically calibrating the output characteristics of a gas detector, comprising the steps of: injecting a standard gas having test concentrations for monotonic increasing into a gas detector to obtain measurement average values corresponding to the test concentrations; A first interpolating polynomial generating step of generating a first interpolating polynomial expressing a relation between the test concentrations and the measured average values, a step of calculating the first interpolating polynomial output values by substituting the test concentrations into the first interpolating polynomial, A first interpolation polynomial expression output value calculation step of calculating a first interpolation polynomial expression output value corresponding to the first interpolation polynomial expression value and a second interpolation polynomial expression value corresponding to the first interpolation polynomial expression output value, An extraction step of extracting an object to be corrected, Wherein the intermediate concentration of the previous interval is calculated by substituting the intermediate concentration of the previous interval into the first interpolation polynomial to calculate the intermediate concentration of the interval between the correction target concentration and the maximum concentration of the correction target interval, An intermediate value calculation step of calculating an intermediate value of a subsequent interval by substituting the intermediate value of the previous interval and the intermediate value of the previous interval into the interpolation polynomial, A second interpolating polynomial generating a second interpolating polynomial expressing a relation between output values including an intermediate value and an intermediate value of the subsequent section, and a second interpolating polynomial generating a density output correcting function for inverting the second interpolating polynomial to generate a density output correcting function Generating step.

In the method of automatically calibrating the output characteristics of the gas detector according to the present invention, the measured average values obtained in the step of acquiring the measured average value by concentration are one of a current value, a voltage value and a power value.

The first interpolation polynomial generated in the first interpolating polynomial generating step may be a Lagrange interpolation polynomial or a Neville interpolation polynomial or a Newton interpolation polynomial, And is an interpolation polynomial (Newton interpolation polynomial).

In the method of automatically calibrating the output characteristics of a gas detector according to the present invention, in the second interpolation polynomial generation step, input values including the test concentrations, the intermediate concentration of the previous section, , Generating interpolation polynomials for each section to generate the second interpolation polynomial for each divided section, and connecting the interpolation polynomials for each section to generate the second interpolating polynomial.

The second interpolation polynomial generated in the second interpolating polynomial generating step may be a Lagrange interpolation polynomial or a Neville interpolation polynomial or a Newton interpolation polynomial, And is an interpolation polynomial (Newton interpolation polynomial).

In the method of automatically calibrating the output characteristics of the gas detector according to the present invention, in the step of generating the concentration output calibration function, the inverse interpolation polynomials are inversely transformed to generate the inverse inverse transform functions, Thereby generating a function.

According to the present invention, a response characteristic of sensors used for detecting flammable or noxious gas can be expressed by an optimal approximation equation that can express the output voltage or current of a sensor corresponding to input gas by using a standard gas having various concentrations And a method of calculating an accurate concentration is provided.

FIG. 1 is a view illustrating a method of automatically calibrating a gas sensor output characteristic according to an embodiment of the present invention,
FIG. 2 is a diagram illustrating an apparatus configuration in which an automatic gas sensor output characteristic correction method according to an embodiment of the present invention is performed,
FIG. 3 is a view for explaining a correction object section extraction step and an intermediate value calculation step in an embodiment of the present invention,
4 is a graph showing the concentration according to the sensor output voltage of the gas detector according to an embodiment of the present invention.

It is to be understood that the specific structural or functional description of embodiments of the present invention disclosed herein is for illustrative purposes only and is not intended to limit the scope of the inventive concept But may be embodied in many different forms and is not limited to the embodiments set forth herein.

The embodiments according to the concept of the present invention can make various changes and can take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It should be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms disclosed, but includes all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms may be named for the purpose of distinguishing one element from another, for example, without departing from the scope of the right according to the concept of the present invention, the first element may be referred to as a second element, The component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like are used to specify that there are features, numbers, steps, operations, elements, parts or combinations thereof described herein, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

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

FIG. 1 illustrates a method of automatically calibrating a gas sensor output characteristic according to an embodiment of the present invention. FIG. 2 illustrates an apparatus configuration in which an automatic gas sensor output characteristic correction method according to an embodiment of the present invention is performed. Fig.

Referring to FIGS. 1 and 2, a method of automatically calibrating gas sensor output characteristics according to an embodiment of the present invention includes a step of obtaining a measured average value by test concentration (S10), a first interpolating polynomial generating step (S20) An output value calculation step S30, a correction target section extraction step S40, an intermediate value calculation step S50, a second interpolation polynomial generation step S60 and a density output correction function generation step S70.

In the measurement average value acquiring step (S10), a process of injecting a standard gas having monotonously increasing test concentrations into the gas detector 10 and obtaining measurement average values corresponding to the test concentrations is performed.

One embodiment of the present invention allows a calibration process of obtaining optimal input / output response characteristic curves of various kinds of sensor units 12 applied to the gas detector 10 and a more accurate concentration calculation. To do this, first, a standard gas is prepared for each test concentration. For example, in the case of flammable gases, the standard gas can produce more than ten species so that the concentration between 0 (zero) and the explosion limit (100% LEL) is increased at a constant rate, that is, monotonously increased. In the case of toxic or noxious gases, it is possible to produce more than 10 kinds of threshold limit value (TLV) at 0 (zero).

For example, the detailed procedure of the measurement average value acquiring step (S10) for each test concentration may be configured as follows.

First, when standard gas having one kind of test concentration (for example, 0%) is injected into the sensor section 12 of the gas detector 10, the calculation / output section 14 of the gas detector 10 measures the measured value Output. An average of the voltage or current can be measured 10 times and recorded in a lookup table using an output meter 20 such as an oscilloscope or a precision voltage or current meter.

Next, an arithmetic average of the measured values of the voltage or current written in the above can be calculated and recorded.

As the above procedure, the test gas concentration of 9 standard gas (0.25%, 0.5%, 0.75%, 1.0%, 1.25%, 1.5%, 1.75%, 2.0%, 2.25% Are respectively injected into the gas detector 10, and the voltage and the current are measured 10 times each, and an average value is obtained.

For example, the measured average values obtained in the step of acquiring the measured average value by concentration may be one of a current value, a voltage value, and a power value.

In the first interpolation polynomial generating step S20, the sensor characteristic correcting apparatus 30 performs a process of generating a first interpolation polynomial expressing the relationship between the test concentrations and the measured average values.

For example, the test concentrations of 10 kinds of standard gases and the average values of the voltages measured by injecting them are 10 as shown in Table 1 below. The 10 average values of the ten measured voltages obtained by injecting 10 kinds of standard gases having 10 kinds of test concentrations (Xi, i = 0 to 9) into the sensor unit 12 are defined as Yi, i = 0 to 9 and Xi and Yi (P (x)). A polynomial is an approximate polynomial that can estimate the output to the input, which is termed a first interpolating polynomial.

Test concentration
(%, X) 0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 Print
(V, Y) 0.4235 0.5925 0.6245 0.724 0.8475 1.0355 1.125 1.1825 1.345 1.47

For example, the first interpolating polynomial generated in the first interpolating polynomial generating step S20 may be a Lagrange interpolation polynomial or a Neville interpolation polynomial or a Newton interpolation polynomial. .

In the first interpolation polynomial output value calculation step (S30), the sensor characteristic correction apparatus (30) performs the process of calculating the first interpolation polynomial output values by substituting the test concentrations into the first interpolation polynomial.

For example, by substituting X, i.e., test concentrations, into the first interpolation polynomial P (x) generated in the first interpolation polynomial generation step S20, 10 outputs are obtained and the result is shown on the 2-dimensional plane Although the error is smaller than that of the linear regression equation, it is still not perfectly matched with the output (Y) curve of the sensor unit 12 due to nonlinearity, and it can be confirmed that there is an error.

In the correction target section extracting step S40, the sensor characteristic correcting apparatus corrects the calibration target density in which the correction target density in which the maximum error occurs according to the measurement average values corresponding to the test concentrations and the error of the first interpolation polynomial output values, A process of extracting a section is performed.

For example, referring additionally to FIG. 3, the correction target density is X2, and the correction target section is a section from X1 to X3.

For example, the correction object section can be extracted in such a manner that the error between the output value of the sensor section 12 and the output of the first interpolation polynomial becomes ± 5% or more, or the section in which the gradient changes abruptly and the section in which the gradient changes abruptly are distinguished . However, the deviation can be arbitrarily changed by ± 3% ± 7%, ± 10%, etc. depending on the use of the sensor unit 12.

In the intermediate value calculation step (S50), the sensor characteristic correction apparatus calculates the intermediate value of the previous section by substituting the intermediate concentration of the previous section, which is a section between the concentration target concentration and the lowest concentration of the correction target section, into the first interpolation polynomial, The intermediate concentration of the subsequent section, which is a section between the correction target concentration and the maximum concentration of the correction target section, is substituted into the first interpolation polynomial, and then the intermediate value of the section is calculated.

For example, to reduce the error more, if the largest error is x2, find the intermediate concentration (x1.5) between x1 and x2, find the intermediate concentration (x2.5) between x2 and x3, (X1.5) which is an intermediate value of the previous section is substituted into the interpolation polynomial, and x2.5 is substituted into the first interpolation polynomial to calculate P (x1), P (x1.5), P (x2.5), and P (x3).

For example, it is possible to reduce the error by using the method of finding the intermediate value of the previous section and the intermediate value of the subsequent section and connecting them to each other, that is, by filtering the x2 point. If there is a section with a large error such as x2 in the other section, it can be processed in this manner.

In the second interpolating polynomial generating step S60, the sensor characteristic correcting apparatus 30 calculates the average values of the test concentration, the intermediate concentration of the previous section, the intermediate values of the following section and the measured average values, , And then generating a second interpolation polynomial expressing the relationship between output values including the intermediate value of the interval.

For example, in the second interpolation polynomial generation step (S60), the input values including the test concentrations, the intermediate concentration of the previous section, and the intermediate concentration of the following section are divided into a plurality of sections, A second interpolation polynomial can be generated by generating interpolation polynomials for each section to generate a polynomial and connecting interpolation polynomials for each section.

Since the computed data has been added through the intermediate value computation step (S50) described above, the data for interpolation polynomial creation, in other words, the number of points displayed on the graph has been increased from 10 to 12. Therefore, it is possible to make the eleventh order output correction function passing through 12 points. However, since the speed of the equation can be slowed down by the degree of the equation, In other words, the interpolation polynomial of each section is obtained by numerical analysis.

For example, the second interpolating polynomial generated in the second interpolating polynomial generating step S60 may be a Lagrange interpolation polynomial or a Neville interpolation polynomial or a Newton interpolation polynomial. .

In the density output calibration function generating step S70, the sensor characteristic correcting device 30 performs a process of inverting the second interpolation polynomial to generate the density output calibration function.

For example, in the step of generating the density output calibration function (S70), it is possible to generate the density output calibration function by inverting the interpolation polynomials of each section to generate the inverse inverse transform functions and connecting the inverse inverse transform functions to each other.

By connecting all of the inverse transformed polynomials, that is, the inverse transform functions of each interval, it is possible to derive the optimal concentration output calibration curve, in other words, the density output correction function.

When the unknown concentration is injected into the gas detector 10 through the process of steps S80 and S90, the calculation / output unit 14 of the gas detector 10 outputs the corresponding sensor output And the unknown concentration can be finally determined by assigning it to the second interpolation polynomial.

  In conclusion, the above procedure is summarized as follows. First, no matter how various sensors exist, the error range is defined first, and the output value of each sensor is measured to make a lookup table. After obtaining the interpolation polynomials, the interpolation polynomials are obtained for each zone, and the inverse transformed polynomials are connected to the inversely transformed polynomials to obtain a calibration curve for measuring the gas concentration .

FIG. 4 shows the correlation between the sensor output voltage of the gas detector and the concentration of methane gas. This shows that the interpolation polynomial applied to each section is synthesized so as to express the entire section.

As described in detail above, according to the present invention, it is possible to express the response characteristic of the sensors used for detecting flammable or noxious gas by using the standard gas having various concentrations to express the output voltage or current of the sensor corresponding to the input gas There is an effect that a method of calculating an accurate approximate equation by calculating an optimal approximate equation is provided.

10: Gas detector
12:
14: Arithmetic /
20: Output Meter
30: Sensor characteristic correcting device
S10: Measurement value acquisition step by test concentration
S20: First interpolation polynomial generation step
S30: First interpolation polynomial output value calculation step
S40: Extraction step of the region to be corrected
S50: intermediate value calculation step
S60: Second interpolation polynomial generation step
S70: Step of generating density output calibration function

Claims (6)

Obtaining a measured average value for each test concentration by injecting a standard gas having monotonic increasing test concentrations into a gas detector to obtain measurement average values corresponding to the test concentrations;
A first interpolating polynomial generating step of generating a first interpolating polynomial expressing a relationship between the test concentrations and the measured average values;
A first interpolating polynomial output value calculating step of calculating first interpolation polynomial output values by substituting the test concentrations into the first interpolating polynomial;
A correction object interval extracting step of extracting a correction object interval in which a correction object density in which a maximum error occurs in the middle is in the middle of the measurement average values corresponding to the test concentrations and the error of the first interpolation polynomial output values;
Calculating a median value of the previous section by substituting the intermediate concentration of the previous section, which is a section between the correction target concentration and the lowest concentration of the correction target section, into the first interpolation polynomial, An intermediate value calculation step of calculating an intermediate value of the interval by substituting the intermediate density of the interval between the first and second intervals into the first interpolation polynomial;
Wherein the test results include input values including the test concentrations, the intermediate concentration of the previous interval, and the intermediate concentration of the following interval, and output values including the measured average values, the previous interval interval, A second interpolating polynomial generating step of generating a second interpolating polynomial; And
And a density output calibration function generation step of generating a density output calibration function by inversely converting the second interpolation polynomial,
In the second interpolating polynomial generation step, the input values including the test concentrations, the intermediate density of the previous section, and the intermediate density of the following section are divided into a plurality of sections, and the second interpolation polynomial is divided And generating the second interpolation polynomial by concatenating the interpolation polynomials of each section,
Wherein the density output calibration function generation step generates the density output calibration function by inverting the interpolation polynomials of each section to generate the inverse inverse transform functions and connecting the inverse inverse transform functions to each other to generate the density output correction function. The method according to claim 1,
Wherein the measurement average values obtained in the measurement average value acquisition step for each test concentration are one of a current value, a voltage value, and a power value. The method according to claim 1,
Wherein the first interpolating polynomial generated in the first interpolating polynomial generating step is a Lagrange interpolation polynomial or a Neville interpolation polynomial or a Newton interpolation polynomial. How to calibrate the output characteristics of the probe. delete The method according to claim 1,
Wherein the second interpolating polynomial generated in the second interpolating polynomial generating step is a Lagrange interpolation polynomial or a Neville interpolation polynomial or a Newton interpolation polynomial. How to calibrate the output characteristics of the probe.
delete

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