JP2008203129A - Salinity concentration meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a salinity concentration meter capable of reducing dependency on a kind of a sample, while allowing simple measurement, and capable of dispensing with dilution of the sample. <P>SOLUTION: This salinity concentration meter of the present invention includes a refractive index detecting means for detecting a refractive index of the sample, an electric conductivity detecting means for detecting an electric conductivity of the sample, a data storage means for storing a data indicating a relation between the refractive index and the electric conductivity, and a salinity concentration and a salinity concentration determination means for determining the salinity concentration of the sample, based on the detected refractive index and electric conductivity of the sample, and the data of the data storage means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a salinity meter that simply measures the salinity of a sample.

  Many salinity meters used to measure the salinity concentration of miso soup, soy sauce, sauce, etc. at restaurants and homes measure the salinity concentration based on electrical conductivity (see, for example, Patent Document 1). If titration with silver nitrate is performed, more accurate measurement is possible, but it requires a reagent and is not simple. In addition to the method of measuring the salinity concentration by conductivity, a method of measuring by the refractive index is also known.

  FIG. 13 is a diagram showing an example of the relationship between the salinity concentration and the conductivity. In this example, measurement is performed on saline and 10 types of food. Samples other than saline are low-salt soy sauce, saikoshi soy sauce, tamari soy sauce, koikuchi soy sauce, white soy sauce, light soy sauce, thick sauce, Worcester sauce, tomato juice, and tomato puree. If the salinity is sufficiently low, a linear relationship can be found between the salinity and the conductivity. In this case, the linear relationship does not vary greatly depending on, for example, the type of soy sauce. By preparing one approximate line in advance, the salinity concentration can be obtained from the conductivity for a plurality of types of soy sauce.

FIG. 14 is a diagram showing an example of the relationship between the salinity concentration and the refractive index. In this example as well, measurement is performed on the above-described 11 types of samples. A relatively linear relationship is maintained between the salinity concentration and the refractive index even when the salinity concentration increases.
JP 2002-22525 A

  When the salinity concentration is measured by the electrical conductivity, if the salinity concentration is increased, the linear relationship between the salinity concentration and the electrical conductivity cannot be maintained. In particular, since various foods other than saline contain ionic components other than salt, the salt concentration and electrical conductivity as shown in FIG. 13 due to the fact that the interaction with the ionic components differs depending on the concentration. The relationship between and the food is greatly different. For example, even in soy sauce, in regions where the salt concentration is high, the conductivity varies greatly depending on the type. For this reason, when a sample having a high salt concentration is measured by the conductivity, it is necessary to dilute the sample.

  Further, when the salinity concentration is measured by the refractive index, the linear relationship between the salinity concentration and the refractive index can be obtained in a wide concentration range, so there is no need to dilute the sample, but the linear relationship greatly differs depending on the type of the sample. For this reason, in order to obtain the salinity concentration accurately from the refractive index, it is necessary to prepare an approximate line for each sample in advance. However, in order to select an approximate line that matches the sample, the type of sample must be specified during measurement. For example, even if there is no hindrance in selecting whether the sample is soy sauce or processed tomato products, if the type of soy sauce is not selected and accurate measurement cannot be performed, there will be a large inconvenience in terms of measurement and practical use.

  Therefore, there is a demand for a salinity meter that is simple measurement but has little dependence on the type of sample and does not require dilution of the sample.

  The salinity meter provided by the present invention shows a refractive index detection means for detecting the refractive index of a sample, a conductivity detection means for detecting the conductivity of the sample, and the relationship between the refractive index, the conductivity, and the salinity concentration. Data storage means for storing data; and salinity concentration determination means for determining the salinity concentration of the sample based on the detected refractive index and conductivity of the sample and data in the data storage means.

  In the salinity meter, the refractive index detection means may have a prism on which the sample is placed, and the conductivity detection means may have an electrode formed on the sample placement portion on the prism.

  By adopting the above configuration, using the data showing the relationship between the refractive index and conductivity and the salinity concentration, the salinity concentration is determined from the detected values of both. It is possible to provide a salinity meter that does not require dilution of the sample and that does not require dilution.

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

  FIG. 1 is a diagram showing an example of a schematic configuration of a salinity meter in the present embodiment. The salinity meter 101 includes a prism 102 for measuring the refractive index of a liquid sample such as soy sauce by a total reflection method. The casing 103 of the salinity concentration meter 101 is provided with an opening for exposing the sample mounting surface 104 of the prism 102, and the sample 105 is dropped onto the sample mounting surface 104 through the opening.

  Light from the light source 106 is incident on the sample mounting surface 104 that is an interface between the sample 105 and the prism 102, and the light receiving sensor 107 receives the light reflected by the sample mounting surface 104. The light source 106 and the light receiving sensor 107 are connected to the processing circuit 108. The processing circuit 108 controls the light source 106 and obtains the refractive index of the sample 105 based on the detection value of the light receiving sensor 107.

  Further, in the salinity concentration meter 101, a pair of electrodes 109 are formed on the sample mounting surface 104 of the prism 102. The electrode 109 is connected to the signal detection circuit 110, and a conductivity sensor including the electrode 109 and the signal detection circuit 110 detects the conductivity of the sample 105 and outputs the detected value to the processing circuit 108.

  In the processing circuit 108, an MPU 112, interface circuits 113 and 114, and a memory 115 are connected via a bus 111. The interface circuit 113 is used to connect the light source 106, the light receiving sensor 107, and the signal detection circuit 110 to the processing circuit 108. The MPU 112 performs input / output with respect to the light source 106, the light receiving sensor 107, and the signal detection circuit 110 via the interface 113. The interface circuit 114 connects the operation panel 116 to the processing circuit 108. The operation panel 116 is provided with a display device such as a liquid crystal display and an input device such as a measurement start button. The MPU 112 receives an instruction from the user via the operation panel 116 via the interface circuit 114, and outputs a measurement result or a message to the user to a display device or the like.

  The memory 115 stores the code of the control program 117 and the like. The MPU 112 implements the function of the salinity meter 101 by inputting / outputting a circuit connected to the bus 111 in accordance with an instruction of the control program 117.

  Furthermore, in this embodiment, the memory 115 also stores a reference table 118. The reference table 118 has data indicating the relationship between the refractive index and conductivity, and the salinity concentration. When the MPU 112 detects the refractive index and conductivity of the sample 105, the MPU 112 determines the salinity concentration of the sample 105 based on the detected refractive index and conductivity and data of the reference table 118.

  FIG. 2 is a diagram illustrating an example of the approximate surface for a plurality of types of samples, and FIGS. 3 and 4 are diagrams illustrating an example of data used to obtain the approximate surface. The look-up table has such approximate surface data indicating the relationship between the refractive index and conductivity and the salinity concentration. This approximate surface data is obtained from a plurality of types of soy sauce samples. The types of soy sauce used as samples are low-salt soy sauce, saiko soy sauce, tamari soy sauce, koikuchi soy sauce, white soy sauce, and light soy sauce. The salt concentration of these soy sauce stocks is 8.7% for low-salt soy sauce, 14.3% for soy sauce soy sauce, 14.8% for tamari soy sauce, and 17.0% for koikuchi soy sauce. Yes, white soy sauce was 17.7%, and light soy sauce was 18.5%. Data is obtained using samples obtained by serially diluting these stock solutions. Saline is used for calibration.

  The black circles in FIG. 2 indicate the salt concentration values of the samples (various soy sauces and saline solutions) shown in FIGS. In order to obtain a curved surface with little approximation error from these samples, the method for measuring the composition of a ternary solution disclosed in Japanese Patent No. 2804417 by the present inventor can be used. Soy sauce can be divided into three components in the form of water, salt and other components. The concentration of one of these components, that is, the salinity, can be obtained by using a refractive index sensor and a conductivity sensor that are independent of each other.

In this embodiment, the concentration function F with respect to the refractive index X and the conductivity Y is given by the following equation.

ここで、a_i，b_i，c_i，d_i，y0は係数である。図２の例は、この関数Ｆをサンプルにフィッティングし、屈折率Ｚを表す近似面を得たものである。参照テーブルに、その近似面の方程式のデータ（係数などを表すデータ）を予め格納しておけば、導電率および屈折率の検出値をその方程式に代入する演算を処理回路のＭＰＵが実行することにより、試料の塩分濃度を決定することができる。

Here, a _i , b _i , c _i , d _i and y0 are coefficients. In the example of FIG. 2, this function F is fitted to a sample to obtain an approximate surface representing the refractive index Z. If the data of the equation of the approximate surface (data representing the coefficient, etc.) is stored in advance in the reference table, the MPU of the processing circuit executes an operation for substituting the detected values of conductivity and refractive index into the equation. Thus, the salinity of the sample can be determined.

  As for the conductivity of the sample, the effect by the ionic component mainly composed of salt is dominant, and as for the refractive index, the effect by the non-ionic component is dominant. For this reason, components other than water and salt are composed of multiple components, and even if the nonionic component fluctuates somewhat, by using both detected values of conductivity and refractive index, the type of soy sauce in one approximate plane It is possible to obtain relatively high accuracy regardless of the density.

  FIG. 5 is a graph showing measurement errors when the salt concentration of soy sauce is measured only by conductivity. In this figure, the horizontal axis represents the salinity obtained by titration with silver nitrate, and the vertical axis represents the measurement error of the salinity. The kind of soy sauce used as a sample is the same as the examples of soy sauce so far, and saline is used for calibration.

  As shown in this figure, when the salinity concentration is 2% or more, the non-linearity increases and the measurement error increases for any kind of soy sauce. Furthermore, when the salinity is 4% or more, measurement errors vary depending on the type of soy sauce. For a saline solution containing only sodium chloride as an ionic component, the salinity concentration can be determined by measuring only the conductivity. However, when an ionic component other than salt is included as in soy sauce, the relationship between the electrical conductivity and the salinity concentration changes, and an accurate salinity concentration cannot be obtained.

  FIG. 6 is a graph showing measurement errors when the salt concentration of soy sauce is measured by both conductivity and refractive index. Also in this figure, the horizontal axis represents the salinity concentration obtained by titration with silver nitrate, and the vertical axis represents the measurement error of the salinity concentration. These data are collected using the approximate surface of FIG. 2 for the same sample as the example of FIG.

  As shown in this figure, the measurement error for all types of soy sauce is greatly reduced compared to the measurement using only the conductivity, and the salinity changes between 0% and 18%. Shows good results. When both detected values of conductivity and refractive index are used, the measurement error is about 1% even when the salinity concentration is increased to about the salinity concentration of the stock solution. On the other hand, in the measurement using only the conductivity, as shown in FIG. 5, since the measurement error has already reached 1% when the salinity concentration is around 4%, the detection values of both the conductivity and the refractive index are used. The measurement error is remarkably suppressed over a wide density range. That is, it becomes possible to measure the salt concentration of many soy sauces without diluting them.

  Furthermore, the point that the measurement error is slight does not change even if the type of soy sauce is different. In the example of FIG. 14 in which the salt concentration is obtained only by the refractive index, if the soy sauce type is different, the relationship between the refractive index and the salt concentration is greatly different. Therefore, if the soy sauce type is not properly determined, the measurement error increases. There was a fear. There was a similar fear for the measurement based only on the conductivity when the salt concentration was not sufficiently low. When compared with those, if both detected values of conductivity and refractive index are used, a highly accurate measurement value can be obtained by one approximate surface regardless of the type of soy sauce.

  Therefore, for example, if the soy sauce is dropped on the sample mounting surface of the prism on which the electrode of the conductivity sensor is formed without selecting the type of soy sauce, the salt concentration can be accurately adjusted without diluting the soy sauce. It becomes possible to measure.

  When the basic components are not similar as in soy sauce and processed tomato products, different approximate surfaces may be used for one sample group and another sample group, or the same approximate surface may be used. In the case of using different approximate surfaces, it is necessary to select the approximate surface to be used by selecting a sample at the time of measurement. However, even if there is a problem in selecting the type of soy sauce, the difference between the soy sauce and the processed tomato product is obvious at a glance, and the user can easily select these types from the operation panel. Therefore, if measurement is performed using both refractive index and conductivity, there is practically no inconvenience.

  FIG. 7 is a diagram showing another example of the approximate surface for a plurality of types of samples, and FIG. 8 is a diagram showing an example of processed tomato product data used to obtain the approximate surface. The reference table can have a plurality of approximate surface data as shown in FIGS. 2 and 7 for each sample having different basic components. This approximate surface data was obtained for samples of processed tomato products such as tomato juice and tomato puree. The salt concentration of the stock solution of tomato juice is 0.31%, and the salt concentration of the stock solution of tomato puree is 0.19%. Data is obtained using samples obtained by serially diluting these stock solutions. Saline is used for calibration. The black circles in this example indicate the salt concentration of each sample (various processed tomato products and saline) shown in FIGS.

  The user can specify whether to use an approximate surface suitable for soy sauce or an approximate surface suitable for processed tomato products from the operation panel. The MPU reads data from the lookup table according to the designation, and obtains the salinity concentration from the detected refractive index and conductivity.

  FIG. 9 is a graph showing a measurement error when the salt concentration of the processed tomato product is measured only by conductivity. Also in this figure, the horizontal axis represents the salinity concentration obtained by titration with silver nitrate, and the vertical axis represents the measurement error of the salinity concentration. The processed tomato products used as samples are tomato juice and tomato puree, as in the example of FIG. Saline is used for calibration. In processed tomato products, although the salt concentration of the stock solution is lower than that of soy sauce, the measurement error tends to increase from a considerably low concentration. For this reason, it is difficult to accurately measure the salinity concentration of processed tomato products based only on the conductivity.

  FIG. 10 is a graph showing a measurement error when the salt concentration of the processed tomato product is measured by both the conductivity and the refractive index. Also in this figure, the horizontal axis represents the salinity concentration obtained by titration with silver nitrate, and the vertical axis represents the measurement error of the salinity concentration. These data are collected using the approximate surface of FIG. 7 for the same sample as the example of FIG.

  As shown in this figure, the measurement error is greatly reduced in both the tomato juice and tomato puree compared to the measurement using only the conductivity. Similar to the example of soy sauce, the salt concentration of the processed tomato product is accurately measured by one approximate surface regardless of the type of processed tomato product.

  FIG. 11 is a diagram showing still another example of the approximate surface for a plurality of types of samples. This approximate surface data is obtained for the various soy sauces and various processed tomato products described above. The black circles in FIG. 11 indicate the salt concentration values of the samples (various soy sauces, various processed tomato products, and saline) shown in FIG. 3, FIG. 4 and FIG. Even if the basic components are not similar as in these samples, the same approximate surface can be used. In this case, it is not necessary to select an approximate surface according to the measurement target.

  FIG. 12 is a graph showing measurement errors when the salinity concentrations of various soy sauces and processed tomato products are measured by both conductivity and refractive index. These data are obtained by using the approximate surface of FIG. 11 for the same sample as the example of FIGS.

  As shown in this figure, the measurement error is greatly reduced compared to the measurement using only the electrical conductivity for various types of soy sauce such as salt reduction, sashimi, and tamari, tomato juice, and tomato puree. Even when the same approximate surface is used for samples whose basic components are not similar, the salinity concentration of these samples is accurately measured.

  As described above, in the salinity meter according to the present embodiment, the salinity concentration is measured with high accuracy regardless of the type of the sample or the salinity concentration by measuring the salinity concentration using both the detected values of the conductivity and the refractive index. It becomes possible to do.

  Further, in the salinity meter in this embodiment, an approximate surface is obtained by a function including a multiplication term of a refractive index and a conductivity as shown in Equation 1. Even when data is obtained from a plurality of independent measurement systems of refractive index and conductivity, an approximate surface suitable for obtaining the salinity concentration can be obtained.

  Furthermore, in the salinity meter in the present embodiment, electrodes are formed on the sample mounting surface of the prism, and in the measurement of conductivity and refractive index, the amount and style of the measurement sample are similar, so the same It is possible to measure the refractive index and the conductivity of the sample in parallel. Since both have an open sensor structure, it is easy to replace the sample and clean the sensor.

  In addition, the salinity meter may further include a temperature compensation circuit that performs temperature compensation on the detection value of the sensor.

  In the above example, six kinds of soy sauce and salt water data are used to obtain an approximate surface suitable for soy sauce, but the present invention is not limited to this. An approximate surface may be generated using a sample of less soy sauce, and the data of the approximate surface may be stored in the reference table in advance. Since the salinity concentration is measured using the detected refractive index and conductivity and the approximate surface, high accuracy can be obtained even when measuring a type of sample that is not used to obtain the approximate surface. Furthermore, using salt water data to obtain approximate surface data is useful and practical for checking accuracy and calibrating, but the approximate surface may be obtained without using salt water data. .

  In addition, when the operation panel receives the designation that the sample is diluted, the processing circuit calculates the salinity concentration based only on the conductivity. If there is no designation, the processing circuit calculates both the refractive index and the conductivity. You may make it measure salt concentration.

  The embodiments described above do not limit the technical scope of the present invention, and various modifications and applications other than those already described are possible within the scope of the present invention. For example, in the above-described embodiment, an example of measuring the salt concentration of soy sauce or processed tomato products has been described. However, the present invention is a salinity meter that easily measures the salt concentration of other foods such as miso soup and sauces, dishes, and seasonings. The invention can also be applied.

  Although the salinity meter according to the present invention is a simple measurement, the dependence on the type of sample is small, there is no need to dilute the sample, and the measurement is highly accurate, soy sauce, processed tomato products, sauce It is useful for measuring the salinity of various samples such as miso soup at restaurants and homes.

It is a figure which shows an example of schematic structure of the salt concentration meter in this Embodiment. It is a figure which shows an example of the approximate surface with respect to a some sample. It is a figure which shows the data of the soy sauce used for obtaining an approximate surface. It is a figure which shows the data of the salt solution used for obtaining an approximate surface. It is a figure which shows the measurement error at the time of measuring the salt concentration of soy sauce only by electrical conductivity. It is a figure which shows the measurement error at the time of measuring when measuring the salt concentration of soy sauce by both electrical conductivity and refractive index. It is a figure which shows the other example of the approximate surface with respect to multiple types of sample. It is a figure which shows the data of the tomato used for obtaining an approximate surface. It is a figure which shows the measurement error at the time of measuring the salt concentration of a processed tomato product only by electrical conductivity. It is a figure which shows the measurement error at the time of measuring the salt concentration of processed tomato products by both electrical conductivity and refractive index. It is a figure which shows the further another example of the approximate surface with respect to multiple types of sample. It is a figure which shows the measurement error at the time of measuring the salt concentration of soy sauce and a tomato processed product by both electrical conductivity and refractive index. It is a figure which shows the example of the relationship between salt concentration and electrical conductivity. It is a figure which shows the example of the relationship between salt concentration and a refractive index.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Salinity meter 102 Prism 103 Case 104 Sample mounting surface 105 Sample 106 Light source 107 Light receiving sensor 108 Processing circuit 109 Electrode of conductivity sensor 110 Signal detection circuit of conductivity sensor 117 Control program 118 Reference table

Claims (2)

A refractive index detection means for detecting the refractive index of the sample;
Conductivity detecting means for detecting the conductivity of the sample;
Data storage means for storing data indicating the relationship between refractive index and electrical conductivity and salinity;
A salinity meter comprising: a salinity concentration determining unit that determines a salinity concentration of the sample based on the detected refractive index and conductivity of the sample and data of the data storage unit. The refractive index detection means has a prism on which the sample is placed,
The salinity meter according to claim 1, wherein the conductivity detecting unit has an electrode formed on a sample mounting portion on the prism.

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