KR20130094106A - Portable analyzer for hydronic nutrients - Google Patents

Abstract

PURPOSE: A portable nutrient solution analysis device is provided to analyze a nutrient solution by being carried conveniently in a field, and to improve an accuracy of an analysis, a use convenience, and a size and portability. CONSTITUTION: A portable nutrient solution analysis device comprises a measuring terminal (100), a control unit (240), and an analysis device main body (200). The measuring terminal reacts to an ion of a different component included in a nutrient solution. The measuring terminal comprises multiple selectivity measuring electrodes which generate an electric signal, and a standard electrode as one gathered form. The control unit is connected with the measurement terminal either with or without wire. The control unit transmits and analyzes the electric signal obtained from the measuring electrodes. A density value of each component is calculated. The analysis device main body comprises a display unit (250) indicating a content analyzed in the control unit. [Reference numerals] (100) Measuring terminal; (210) Input and output interface unit; (220) Amplification unit; (230) Signal conversion unit; (240) Control unit; (250) Display unit; (260) Power supply unit

Description

Portable Analyzer for Hydronic nutrients

The present invention relates to a nutrient solution analyzer, and more particularly, to a portable nutrient solution analyzer that improves the accuracy of analysis in addition to size, mobility, and ease of use so that the nutrient solution can be easily carried on site.

In recent years, the plant-based nutrient solution cultivation method which can cope with the high demand for safe and high-quality agricultural products and is attracting attention as an automated crop cultivation method, is based on a circulating cultivation technique in which the nutrient solution once used is reused. In such a circulating culture technique, it is important to measure the concentration of nutrients present in the used nutrient solution in real time and add a concentrated culture solution to meet the reference concentration to adjust the balance of the overall culture concentration.

In this regard, current-based (EC) -based concentration control, which is currently being used, is not able to detect the concentration of individual ions in the nutrient solution and may cause unbalance of individual ion concentration, It is almost impossible to efficiently manage the replenishment of deficient components and the elimination of excess components. Therefore, it is necessary to develop a sensor technology that can easily and quickly measure various nutrient concentrations required for crop growth such as nitrate nitrogen (NO ₃ -N), potassium (K), calcium (Ca), and magnesium (Mg) .

However, the quantitative analyzer developed to date is small enough to be easily carried in the field and there is no product with convenience at the same time.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the related art as described above, and an object of the present invention is to provide a portable liquid nutrient solution which can be easily carried on site to analyze nutrient solution, And to provide an analysis apparatus.

In order to achieve the above object, the portable nutrient solution analyzing apparatus according to the technical idea of the present invention includes a plurality of selective measuring electrodes for generating electrical signals in response to ions of different components contained in a nutrient solution, A measuring terminal provided in an aggregated form; A control unit connected to the measurement terminal by wires or wirelessly for receiving an electric signal obtained from the measurement electrodes and analyzing the electric signal to calculate a concentration value of each component; and a display unit for displaying contents analyzed by the control unit And an analysis apparatus main body.

Here, the plurality of measurement electrodes may be arranged at equal intervals while drawing a circle around the reference electrode.

The measuring electrode may include an electrode body filled with a reaction liquid to induce an electromotive force while reacting with one component of ions contained in the nutrient solution, And an ion selective membrane which selectively permeates only ions of one component contained in the nutrient solution while preventing leakage of the ionic selective membrane to the electrode body, wherein the ion selective membrane is bonded to the tip of the electrode body without a separate component have.

In addition, the electrode body may have a recessed groove formed at the tip of the electrode body so that the ion-selective membrane is recessed.

In addition, a protruding plug of a copper material is provided at a rear end of the measuring electrode to transmit the generated electrical signal to the outside of the measuring electrode. And a plurality of sockets for holding the plugs are provided.

In addition, the casing of the measuring terminal may include a main body having a through hole through which the reference electrode penetrates in the center, and a plurality of sockets arranged at equal intervals in a circle around the through hole, A cable having a connection terminal for connecting an external cable and internal cables which are installed on the rear side of the main body and which hold the rear end of the reference electrode and receive an electric signal from the measurement electrode and the reference electrode, And a cover in which the distal end portion of the measurement electrode and the reference electrode protrudes to the outside and the distal end portion of the cable box is screwed to the rear end opening portion, . ≪ / RTI >

In addition, the main body of the analyzer may further include an amplifying unit for buffering the electrical signal transmitted from the measuring electrode and applying a filter to remove noise.

Also, the amplifying unit buffers the electric signals generated by the measuring electrodes using an operational amplifier to amplify the nA-level microcurrent to a mA level.

The two-point normalization method calculates a concentration value of each component by using a two-point normalization method. The two-point normalization method is a method of calibrating a two-point normalization method by inputting a concentration value of a low- Calculating an electromotive force value (Y _1n , Y _2n ) as a reference of the reference voltage; Measuring an electromotive force value (Y ₁₀ , Y ₂₀ ) of the low-concentration and high-concentration solution already known in concentration to obtain the characteristics of the measurement electrode; Calculating a correction coefficient through Y _1n , Y _2n , Y ₁₀ , and Y ₂₀ values obtained in the previous step; Measuring each component of the nutrient solution for which the actual concentration is to be determined by the measurement electrode; Correcting an electromotive force value measured from each component of the nutrient solution by the measuring electrode based on the correction coefficient; And a step of substituting the corrected value into the calibration equation to predict and calculate each component concentration value of the nutrient solution.

Also, the controller calculates concentration values of the respective components by a three-point calibration method in parallel with the two-point normalization method, and the three-point calibration method includes a concentration band of each component of the nutrient solution to be measured Measuring a concentration value (X _n) and an electromotive force value (Y _n ) of three or more calibration solutions; Calculating a regression equation by the concentration value (X _n) and the electromotive force value (Y _n ) of the three or more calibration solutions; Measuring each component of the nutrient solution for which the actual concentration is to be determined by the measurement electrode; And estimating and calculating each component concentration value of the nutrient solution by inversely substituting the calculated electromotive force value measured from each component of the nutrient solution by the measuring electrode into the calculated regression equation.

The portable nutrient solution analyzing apparatus according to the present invention can be greatly reduced in size by a radial arrangement method of electrodes and a simple joining method of an ion selective membrane which does not use a separate component, Can be implemented.

In addition, the present invention provides a new two-point normalization method capable of effectively compensating an error that is caused by continuous use of an electrode while ensuring that the gap between the electrodes is as wide as possible, It is possible to obtain a more accurate result value.

In addition, the present invention can easily mount the measurement electrode and the reference electrode by a socket method.

In addition, according to the present invention, the main body, the cable box, and the cover, each of which serves as a casing, constitute the three parts, so that the product can be easily assembled.

1 is a perspective view for explaining a measuring terminal and a main body of a portable nutrient solution analyzer according to an embodiment of the present invention;
2 is a cross-sectional view of a measurement terminal according to an embodiment of the present invention.
3 is a side view showing a front end portion of a measuring terminal according to an embodiment of the present invention.
4 is an exploded cross-sectional view illustrating a configuration of a measurement terminal according to an embodiment of the present invention.
5 is a sectional view for explaining a configuration of a measuring electrode according to an embodiment of the present invention.
FIG. 6 is an overall configuration view of a portable nutritive analysis apparatus according to an embodiment of the present invention. FIG.
7 to 9 are a series of circuit diagrams for explaining an amplification unit of an analyzer main body according to an embodiment of the present invention.
10 is a flowchart illustrating a two-point normalization method of a control unit according to an embodiment of the present invention.
11 is a flowchart for explaining a three-point calibration method of a control unit according to an embodiment of the present invention.

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

The portable nutrient solution analyzing apparatus according to the embodiment of the present invention is improved in size, mobility and ease of use so as to easily carry it in the field and analyze the nutrient solution, and the accuracy of the analysis is further improved.

To this end, the portable nutrient solution analyzing apparatus according to the embodiment of the present invention is a portable nutrient solution analyzing apparatus according to an embodiment of the present invention, in which a measuring electrode and a reference electrode are separately used, It is configured to implement one product. Further, the newly developed two-point normalization method is applied in parallel with the three-point calibration method, so that a more accurate concentration value can be calculated.

Hereinafter, the configuration of a portable nutrient solution analyzing apparatus according to an embodiment of the present invention will be described.

1 is a perspective view illustrating a measuring terminal and a main body of a portable nutrient solution analyzer according to an embodiment of the present invention.

As shown in the figure, in the embodiment of the present invention, the portable nutrient solution analyzing apparatus is largely composed of the measuring terminal 100 and the analyzer main body 200, all of which are compact in size so that they can be easily carried in the field. In particular, in the case of the measuring terminal 100, an original placement technique of the electrodes 120 and 130 and a new installation technique of the ion selective membrane 124 are applied so as to minimize the size of the measuring terminal 100 to a hand type. That is, as can be seen from the figure, the measurement electrodes 120 are arranged at equally spaced intervals around the reference electrode 130 so as to measure the electromotive force generated in response to the different components of the nutrient solution. And the gap between the electrodes is maximized relative to the area while forming the aggregated shape. Furthermore, the problem of increasing the thickness of the measuring electrode 120 due to the ion-selective membrane 124 is remarkably improved, so that the ion-selective membrane 124 can be attached to the tip of the electrode bodies 121 and 122 without any additional parts It is a technical point that it is directly bonded.

Hereinafter, the detailed configuration of the measuring terminal 100 and the analyzer body 200 will be described. However, for convenience of explanation, the configuration of the measuring terminal 100 will be described first, and then the configuration of the analyzer main body 200 will be described.

FIG. 2 is a sectional view of a measuring terminal according to an embodiment of the present invention, FIG. 3 is a side view showing a front end of a measuring terminal according to an embodiment of the present invention, FIG. 4 is a view showing a configuration of a measuring terminal according to an embodiment of the present invention Fig. And FIG. 5 is a cross-sectional view illustrating a configuration of a measurement electrode according to an embodiment of the present invention.

As shown in the drawing, the measuring terminal 100 according to the embodiment of the present invention is extremely simplified as a casing 110, a plurality of measuring electrodes 120, and a reference electrode 130.

First, the casing 110 is composed of three parts, that is, a main body 110a, a cable box 110b, and a cover 110c, which support and support a plurality of measurement electrodes 120 and a reference electrode 130, And serves to receive the internal cables 113a for transmitting the electric signals generated by the measurement electrode 120 and the reference national 130. [

The main body 110a of the casing 110 has a cylindrical shape and a through hole 118 through which the reference electrode 130 passes is formed at the center of the main body 110a. A plurality of sockets 111 are formed on the front surface of the main body 110a. The sockets 111 are formed at equal intervals while forming a circle around the through holes 118. The plurality of sockets 111 are fitted to the plugs 126 provided at the rear end of each of the measurement electrodes 120 in a forced fit manner. As a result, the plurality of measurement electrodes 120 can be easily fitted. In the drawing, five sockets 111 are shown to support five measuring electrodes 120. However, the number of the sockets 111 may vary depending on the number of components to be measured.

The cable box 110b of the casing 110 is provided with a connection terminal 115 connected to the external cable 113b so as to transmit an electric signal to the main body 200 of the analyzer. The connection terminal 115 is provided with a plurality of internal cables 113a connected to the measurement electrode 120 through the socket 111 of the main body 110a. The cable box 110b of the casing 110 is provided with a reference electrode socket 111 so that the rear end of the reference electrode 130 can be inserted and supported. Thus, the reference electrode 130 can be simply fitted.

The cover 110c of the casing 110 is formed in a cylindrical shape having a wide internal space and accommodates the main body 110a of the casing 110 in its internal space. The tip of the reference electrode 130 mounted on the measurement electrode 120 and the cable box 110b mounted on the main body 110a is inserted into the opening 116a formed in the tip of the cover 110c of the casing 110 And can be immersed in the nutrient solution. The front end of the cable box 110b of the casing 110 is screwed to the rear end of the cover 110c of the casing 110. [ As a result, the opening 116b at the rear end of the cover 110c is blocked.

The measuring electrode 120 measures an electromotive force, which is a potential difference based on the reference electrode 130, and generates an electric signal therefrom. As shown in FIG. 3, Are arranged at equal intervals while drawing a circle around the center 130. According to such a unique radial arrangement method, all the measurement electrodes 120 maintain the same gap with respect to the reference electrode 130, so that they can receive the same influence by the reference electrode 130, It is possible to minimize the error and the deviation thereof due to mutual interference. In addition, the radial arrangement method can maximize the distance between the electrodes, thereby minimizing the inter-electrode interference and enabling a compact product.

The measurement electrode 120 may include an electrode body 121 having an inner chamber 121a, an ion selective membrane 124, a platinum electrode body 125, a fitting plug 126).

Here, the electrode bodies 121 and 122 are formed in such a manner that two objects, that is, the head part 121 and the connection part 122, are screwed in order to facilitate the installation of the reaction liquid 123, the platinum electrode body 125, And an O-ring 127 is provided between the head part 121 and the connection part 122 to prevent the leakage of the reaction solution 123. The inner chamber 121a of the electrode bodies 121 and 122 is filled with a reaction solution 123 that induces electromotive force while reacting with ions of one component contained in the nutrient solution. At the front end of the electrode bodies 121 and 122, a seating groove 121b recessed to seat the ion selective membrane 124 is formed. In this embodiment, it is illustrated that five measuring electrodes 120 are provided to detect nitric acid (NO ₃ ), potassium (K), calcium (Ca), magnesium (Mg) the measurement electrodes 120 are each concentration of 0.01M NaNO ₃ + concentration of 0.01M NaCl, 0.01M concentration of KCl, the reaction solution 123 is injected into a MgCl ₂ solution of CaCl _2, 0.01 M concentration of 0.01M concentration . In the case of the measuring electrode 120 for detecting phosphorus (P) ions, the reaction liquid 123 can also be provided in the same manner.

The ion permeable membrane 124 of the measuring electrode 120 may prevent the reaction liquid 123 from flowing out from the tip of the electrode bodies 121 and 122 to the outside of the chamber 121a, And selectively permeates only ions of the component.

It is noted that the ion permeable membrane 124 has a simple connection structure in which THF (tetrahydrofuran) is applied with an adhesive without using a separate part while being seated in a seating groove 121b formed at the tip of the electrode bodies 121 and 122 . Although this configuration is simple, it is possible to drastically reduce the width of the measurement electrode 120 that can be enlarged due to the installation of the ion-permeable membrane 124. For reference, a method of fixing the membrane 124 by separately providing a cylindrical cap surrounding the outer edge of the electrode according to the prior art has been applied. The traditional way of using this separate part, the cap, has raised the problem of increasing the electrode width by at least 5% to 15%.

The ion permeable membrane 124 is formed of a polymer membrane (PVC) as a matrix membrane to detect nitric acid (NO ₃ ), potassium (K), calcium (Ca), and magnesium (Mg) In the case of phosphorus (P), the type of ion-selective membrane with satisfactory performance has not been reported yet, but it is reported that cobalt (Co) is a substance capable of detecting phosphorus (Kim et al., 2007 ) A cobalt material having a purity of 99.95% may be used as the phosphorus sensing material.

The platinum electrode body 125 of the measuring electrode 120 is provided over the entire chamber 121a of the electrode bodies 121 and 122 filled with the reaction liquid 123 in the form of a needle. The platinum electrode assembly 125 collects and stably transmits an electric signal generated by the electromotive force generated from the reaction liquid 123.

The plug 126 of the measuring electrode 120 is electrically connected to the copper electrode body 125 so as to be inserted into the socket 111 of the casing 110 while being smoothly transmitted with electric signals collected from the platinum electrode body 125, ). The tip end of the plug 126 is fitted in a state that the rear end of the chamber 121a of the electrode bodies 121 and 122 is sealed like a cap. In this state, the fitting groove 126a formed at the tip end of the plug body 126, And the rear end is engaged. The rear end of the plug 126 is formed in a protrusion shape and is fitted in a socket 111 provided in the casing 110. When the plug 126 is provided on the measuring electrode 120, the measuring electrode 120 can be easily connected to the casing 110 by the socket 111 while continuing to transmit the electric signal transmitted from the platinum electrode body 125. [ So that it can be mounted.

As described above, the measuring terminal 100 according to the embodiment of the present invention includes the measuring electrode 120 and the reference electrode 130 in one aggregate form, So that the widths of the electrodes can be maintained without using any additional parts due to the installation of the ion selective membrane 124. In addition, Accordingly, the measurement terminal 100 can be realized as a miniature hand type product that can be used with one hand.

Next, the analysis apparatus main body 200 of the portable nutritive analysis apparatus according to the embodiment of the present invention will be described.

FIG. 6 is an overall configuration diagram of a portable nutrient solution analyzing apparatus according to an embodiment of the present invention, and FIGS. 7 to 9 are a series of circuit configuration diagrams for explaining an amplifying unit of the analyzer main body according to an embodiment of the present invention.

The main body 200 of the analyzer according to the embodiment of the present invention includes an input / output interface unit 210, an amplification unit 220, a signal conversion unit 230, a control unit 240, a display unit 250, Referring to FIG. 1, the external appearance of the apparatus is shown in a compact form so that the apparatus can be easily connected to the measurement terminal 100 after being carried in a bag.

The input / output interface unit 210 includes a connection port 251 to which an external cable 113b is connected so as to be connected to the measurement terminal 100 so as to exchange electric signals. In addition, A USB port 252, and a LAN port 253 for communication via a network.

The amplification unit 220 buffers an electrical signal transmitted from the measurement electrode 120 and applies a filter to remove noise. To this end, the amplification unit 220 buffers the electric signals generated by the measurement electrodes 120 using an operational amplifier (OP AMP) to amplify the minute current of the nA level to the mA level.

Specifically, the potential difference generated in the electrode has a very small energy (several pW to several hundreds pW). Therefore, since it is easy to be affected by ambient noise, a technique of amplifying the signal with a level of energy capable of signal processing is required, and a technology for effectively eliminating the accompanying noise is also needed. The amplification unit 220 buffers an electrical signal collected using an operational amplifier and applies a filter to remove noise. At this time, the voltage follower circuit removes the influence of the load through the configuration shown in FIG. 7, so that the input impedance per channel allocated to each measurement electrode 120 becomes 10 ¹² or more. This circuit has no input resistance or feedback resistance, and the output is directly connected to the inverting input terminal. Since the input resistance of this circuit is the same as the high input resistance of the operational amplifier and the output resistance is very small, the input impedance is close to ∞ and the output impedance is low enough to be zero. In order to collect a plurality of electrical signals, an operational amplifier is used to buffer (amplify and amplify) a signal for each channel assigned to each measurement electrode 120 as shown in FIG. 8, So that the current can be supplied to about mA. This enables smooth measurements without signal attenuation. The output value of each channel is related to the reference electrode 130, and the electromotive force value at that time is collected and transmitted to the signal converting unit 230. Also, as shown in FIG. 9, a second active salley-key filter is applied so as to eliminate the easily exposed 60 Hz power source noise and to minimize the influence of the raw signal.

The signal converting unit 230 converts an electric signal transmitted from the measuring electrode 120 from an analog signal to a digital signal.

The controller 240 analyzes the electric signal transmitted from the measuring electrode 120 and calculates the concentration value of each component contained in the nutrient solution. In this process, the two-point normalization method is applied in parallel with the three-point calibration method, which enables more accurate analysis by correcting accumulated errors due to continuous use of the electrodes.

Here, the two-point normalization method is a method in which a calibration equation already learned in a laboratory is directly applied to an electrode newly mounted on the field, and a slope and a slice obtained by remeasuring the two samples, Is a method of correcting the change value of the value. The two-point normalization method is performed through the following steps according to the flow shown in FIG.

First, the concentration values of the low-concentration and high-concentration solutions that already know the concentration are input in the calibration formula, and the electromotive force values (Y _1n , Y _2n ) serving as the reference of the correction are calculated.

Then, in order to know the characteristics of the measuring electrode 120, the electromotive force values (Y ₁₀ , Y ₂₀ ) of the low concentration and high concentration solutions already known in concentration are measured by the measuring electrode 120.

Then, the correction coefficient is calculated through the values Y _1n , Y _2n , Y ₁₀ , and Y ₂₀ obtained in the previous step.

Then, each component of the nutrient solution to be actually measured by the measuring electrode 120 is measured.

Thereafter, the electromotive force value measured from each component of the nutrient solution by the measuring electrode 120 is corrected based on the correction coefficient.

Finally, the calibrated value is substituted into the calibration equation, and the concentration value of each component of the nutrient solution is predicted and calculated.

This two-point normalization method can more accurately analyze the increase of the error due to the memory effect when the measurement electrode 120 and the reference electrode 130 are continuously used.

Meanwhile, the three-point calibration method applied in parallel with the two-point normalization method is a method in which a regression equation is measured in real time by measuring a standard sample of three or more customary samples used in a pH meter, to be. The three-point calibration method is performed through the following steps according to the flow shown in FIG.

First, the concentration value (X _n) and the electromotive force value (Y _n ) of three or more calibration solutions including the concentration band of each component of the nutrient solution to be measured are measured.

Then, a regression equation is calculated based on the concentration value (X _n) and the electromotive force value (Y _n ) of the three or more calibration solutions.

Then, each component of the nutrient solution to be actually measured by the measuring electrode 120 is measured.

Finally, the concentration values of the respective components of the nutrient solution are predicted and calculated by inversely substituting the calculated electromotive force values measured from the respective components of the nutrient solution by the measurement electrode 120 into the calculated regression equation.

The display unit 250 is provided with a touch panel of about 7 inches, and is configured to set or display calibration, measurement, and electrode configuration, as well as a basic function of displaying various result values calculated by the controller .

The power supply unit 260 provides power to the measurement terminal 100 and the analyzer body 200 and includes a power switch 261 and a rechargeable battery suitable for portable use. And has a DC power terminal for directly using external power or for charging the battery.

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 exemplary embodiments. It is clear that the present invention can be suitably modified and applied in the same manner. Therefore, the above description does not limit the scope of the present invention, which is defined by the limitations of the following claims.

100: measuring terminal 110: casing
111: socket 121b: seat groove
124: ion selective membrane 120: measuring electrode
130: reference electrode 200: analyzing apparatus main body
210: input / output interface unit 220:
230: signal conversion unit 240:
250: display part 260: power part

Claims (10)

A measurement terminal having a plurality of selective measurement electrodes for generating an electrical signal in response to ions of different components included in the nutrient solution, together with a reference electrode in one aggregated form;
Is connected to the measurement terminal in a wired or wireless manner, the control unit for receiving the electrical signal obtained from the measuring electrodes and analyzing it to calculate the concentration value of each component, and a display unit for displaying the content analyzed by the control unit Portable nutrient solution analysis device comprising an analysis device body. The method of claim 1,
And the plurality of measuring electrodes are disposed at equal intervals while drawing a circle around the reference electrode. The method of claim 1,
The measuring electrode includes an electrode body in which a reaction solution filled with an ionic liquid induces electromotive force while reacting with ions of one component contained in the nutrient solution, and the reaction solution flows from the chamber to the outside at the tip of the electrode body. It is provided with an ion selective membrane for selectively permeating only one component of ions contained in the nutrient solution while blocking the
The ion-selective membrane is a portable nutrient solution analyzer, characterized in that bonded to the tip of the electrode body without a separate component. The method of claim 3,
Portable nutrient solution analysis device, characterized in that the recessed groove is formed in the front end of the electrode body to seat the ion-selective membrane. The method of claim 1,
A protruding plug made of copper material is installed at the rear end of the measuring electrode to transfer the generated electrical signal to the outside of the measuring electrode, and the plug of each measuring electrode is provided at a casing of the measuring terminal. Portable nutrient solution analysis device characterized in that a plurality of sockets to be fitted. The method of claim 5,
The casing of the measurement terminal, the casing, the main body having a through hole through which the reference electrode penetrates in the center and a plurality of sockets disposed at equal intervals while drawing a circle around the through hole in the front; A cable box installed at a rear side of the main body and spaced apart from each other to support a rear end of the reference electrode, and having a connection terminal for connecting internal cables and external cables to receive electrical signals from the measurement electrode and the reference electrode; And a cylindrical shape to accommodate the main body in an inner space, the front end of the measuring electrode and the reference electrode protruding to the outside, and the rear end of the cable box to the front end of the cable box. Portable nutrient solution analyzer. The method of claim 1,
Wherein the analyzing apparatus main body further comprises an amplifying unit for buffering an electric signal transmitted from the measuring electrode and applying a filter to remove noise. The method of claim 7, wherein
Wherein the amplifying unit buffers the electric signals generated by the measuring electrodes using an operational amplifier to amplify the nA-level microcurrent to the mA level. The method of claim 1,
The control unit calculates the concentration value of each component by a two-point normalization method, the two-point normalization method,
Calculating an electromotive force value (Y _1n , Y _2n ) as a reference for correction by inputting concentration values of a low concentration and a high concentration solution having a known concentration in a calibration equation;
Measuring an electromotive force value (Y ₁₀ , Y ₂₀ ) of the low-concentration and high-concentration solution already known in concentration to obtain the characteristics of the measurement electrode;
Calculating a correction coefficient through Y _1n , Y _2n , Y ₁₀ , and Y ₂₀ values obtained in the previous step;
Measuring each component of the nutrient solution for which the actual concentration is to be determined by the measurement electrode;
Correcting an electromotive force value measured from each component of the nutrient solution by the measuring electrode based on the correction coefficient;
And a step of estimating each component concentration value of the nutrient solution by substituting the corrected value into the calibration equation. 10. The method of claim 9,
The control unit calculates the concentration value of each component by a three-point calibration method in parallel with the two-point normalization method, wherein the three-point calibration method,
Measuring concentration values (X _n) and electromotive force values (Y _n ) of three or more calibration solutions including concentration bands of each component of the nutrient solution to be measured;
Calculating a regression equation by the concentration value (X _n) and the electromotive force value (Y _n ) of the three or more calibration solutions;
Measuring each component of the nutrient solution for which the actual concentration is to be determined by the measurement electrode;
And estimating and calculating each component concentration value of the nutrient solution by inversely substituting the calculated electromotive force value measured from each component of the nutrient solution by the measuring electrode into the calculated regression equation, Device.

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