JPH08159946A - Method and device for measuring solution concentration - Google Patents

Abstract

PURPOSE: To accurately measure the concentration of a solution without being affected by the change in ultrasonic propagation distance and the measurement error by obtaining the concentration of a solution to be measured from the relational expression on the ultrasonic propagation time of a plurality of solutions with a known concentration and a reference liquid. CONSTITUTION: A reference liquid (a solution with a concentration of 0 to 100%, for example, ultra-pure water) and a plurality of solutions with a known concentration CN are successively guided to a detector, propagation times ts and tN of the reference liquid and solutions with a known concentration corresponding to several temperatures Ts including the upper and lower limits in an operating range are measured, and an expression I : ts =F(Ts ), an expression II : CN=F(Rs , Ts ) [Rs : ratio of propagation time], and an expression III : CN=(Dts , Ts ) [Dts : propagation time difference |ts -TN|] are obtained and stored in an operation circuit. Then, when measuring the concentration of a liquid with an unknown concentration, a temperature Tx and a propagation time tx of the liquid to be measured are measured by the detector, a value equivalent to the propagation time ts of a reference liquid at the same temperature tx is obtained by the expression I, then a propagation time ratio Rs =tx /ts or propagation time difference Dts =|ts -tx | is calculated, and then the concentration of liquid to be measured is obtained by either the expression II or III.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a solution concentration using ultrasonic waves and a solution concentration measuring device (ultrasonic densitometer).

[0002]

2. Description of the Related Art A method for measuring the concentration of a solution from the ultrasonic wave propagation time of the solution is generally performed in a chemical device or the like,
Various proposals have been made in measurement methods and devices. For example, in Japanese Examined Patent Publication No. 62-35063, the solution to be measured is generated by irradiating an ultrasonic wave to the solution to be measured, measuring the acoustic wave velocity in the solution to be measured or its reciprocal, and generating it by an electronic circuit. There is described a method of measuring the solution concentration by correcting it with an acoustic parameter corresponding to a reference liquid having a temperature equal to and the temperature information of the solution to be measured. Japanese Patent Publication No. 4-8746 discloses an apparatus for measuring the concentration of a solution to be measured by a function formula of ultrasonic wave propagation velocity and temperature.

[0003]

The method of measuring the concentration of a solution using an ultrasonic wave propagation time measuring circuit has a fast response time and can be easily used for computer control and the like using an electronic circuit. , Has been widely used recently. The concentration measuring method of the prior art is to measure the acoustic parameter which is the ultrasonic wave propagation velocity or its inverse from the ultrasonic wave propagation time and the ultrasonic wave propagation path distance in the detector of the solution to be measured,
The concentration is measured by ultrasonic wave propagation velocity or acoustic parameter corresponding to the reference liquid and temperature information.

The method using such ultrasonic wave propagation velocity is premised on that the ultrasonic wave propagation path distance of the solution to be measured is accurately measured in order to improve the measurement accuracy of the ultrasonic wave propagation velocity. However, the ultrasonic propagation path distance is substantially the reciprocal length of this ultrasonic wave, the processing accuracy such as the perpendicularity of the reflecting surface, the mounting angle of the ultrasonic receiving and emitting element, the expansion of the cell in use, and the reciprocal length due to the contamination of the cell. It is difficult to constantly measure and grasp the propagation path length of the detector due to a change in the environment, which is a major cause of hindering the improvement of the measurement accuracy of the ultrasonic propagation velocity.

That is, the ultrasonic wave propagation time is usually measured in the detector cell by measuring the ultrasonic wave propagation time in the liquid before the ultrasonic wave is reflected from the ultrasonic wave emitting element to the opposite surface and returned to the ultrasonic wave receiving element. The sound wave propagation path distance is twice the liquid distance from the ultrasonic wave transmitting / receiving element in the detector cell to the facing surface (reciprocating length). It is extremely difficult to accurately measure the ultrasonic wave propagation path distance of each detector during manufacture or during use. A) There is a limit to the manufacturing processing accuracy such as the detector length, the perpendicularity of the emitting surface / reflecting surface, and the mounting angle of the ultrasonic receiving / emitting element, and the absolute value of the ultrasonic propagation path distance that combines these is measured. There is an error in some cases. B) As a change in propagation path distance over time during use, ultrasonic wave receiving and emitting surfaces and reflective surfaces are scraped with slurry, etc. There are also changes in the dimensions of the detector, and especially when the detector material is plastic, the changes in dimensions due to temperature changes are large, and the swelling / contraction of the detector material due to the influence of the liquid to be measured can be mentioned.

The measuring instruments having an electronic circuit are as follows: A) power supply voltage, ambient temperature, humidity, vibration, aging of parts,
Due to factors such as deterioration, drift of measured values (stability,
Periodic fluctuations, movements in a certain direction, etc.) B) Errors (steady-state errors) occur in the detector, converter, reference voltage generator, reference frequency generator and correction calculator of the components of the measuring instrument. In general, it is always included, and it is a major factor that affects the measurement accuracy.

In order to improve the accuracy of the concentration measurement value, the acoustic parameters of the solution to be measured and the standard solution are used in Japanese Patent Publication No. 62-35063, which is disclosed in Japanese Examined Patent Publication No. 4-874.
In No. 6, a function formula of ultrasonic wave propagation velocity and temperature is used, but since all of these methods only perform temperature correction on the ultrasonic wave propagation velocity, the ultrasonic wave propagation velocity is measured as described above. The value includes an error in the propagation path length, and the above drift and steady-state error in the measurement circuit cannot be avoided, and the measurement accuracy is limited.

That is, in the conventional method, only the temperature correction is focused in this way, and the error in the measured value of the ultrasonic wave propagation velocity, the drift and the steady error in the electronic circuit remain. An object of the present invention is to solve the above problems in a concentration measuring device using an ultrasonic wave propagation time measuring circuit, and to provide a method and a device for measuring a solution concentration with high accuracy.

[0009]

Means for Solving the Problems As a result of intensive studies on the above problems in a concentration measuring apparatus using an ultrasonic propagation time measuring circuit, the inventor has found that an ultrasonic wave propagation time detector for a solution (referred to as a detector) By measuring the ultrasonic propagation time of a solution of several known concentrations and reference solution,
It is possible to obtain the concentration of the liquid to be measured from these relational expressions without using the ultrasonic wave propagation velocity, thereby eliminating the error in the propagation path length and improving the measurement accuracy. When using multiple ultrasonic detectors, if an electronic circuit after the ultrasonic circuit is commonly used for each detector, the drift and steady-state error in the electronic circuit can be substantially significantly reduced, at fixed time intervals, or at a specific time. By incorporating a mechanism to calculate and store the above-mentioned ultrasonic propagation path time correction coefficient by command, the error due to the change in propagation distance over time during use is corrected, and high measurement accuracy can always be obtained. , As a result of these, it is possible to obtain a highly accurate concentration measurement value comparable to that of a titration analyzer, and also the ultrasonic propagation time and temperature of the reference liquid, from the initial measurement value and the measurement value after use, The degree of fluctuation of the measuring instrument can be grasped concretely, and moreover, by using multiple detectors for the reference liquid and the detector for the measured liquid, and processing information with a common electronic circuit for them, one analyzer can be used. The present invention has been accomplished by finding that it is possible to perform multi-point analysis and becomes an economically excellent analyzer.

That is, according to the present invention, the ultrasonic wave propagation time detector measures the ultrasonic wave propagation time of a plurality of solutions having a known concentration and a reference solution, or further measures the temperature to prepare a relational expression to determine the ultrasonic wave propagation velocity. A method of measuring a solution concentration, which is characterized by obtaining the concentration of a liquid to be measured from the relational expression without using a method, a method of using a common ultrasonic circuit when performing a method using a plurality of detectors, A method of correcting the relational expression by measuring the ultrasonic propagation time by passing a solution having a known concentration through a detector at a specific time or a specific command,
, Or a solution concentration measuring device having the function of, and measuring the ultrasonic wave propagation time and temperature of the reference solution or solution of known concentration to create a relational expression, and calculate the ultrasonic wave propagation time of the reference solution or solution of known concentration. It is a solution concentration measuring device having means for monitoring the deviation of the measuring device from the measurement information and the ultrasonic wave propagation time from the relational expression.

The method of measuring the ultrasonic wave propagation times of a plurality of solutions having a known concentration and the reference solution in the present invention and obtaining the concentration of the liquid to be measured from these relational expressions without using the ultrasonic wave propagation velocity is particularly limited. However, there may be one detector or a plurality of detectors, for example, various methods such as a method of obtaining from a relational expression of a propagation time ratio or a time difference between a plurality of known concentrations and a solution of a reference solution at a constant temperature can be mentioned. . A specific example will be described below. Note that the following explanation is a relational expression in which a temperature factor is added to the ultrasonic wave propagation time of a plurality of solutions of known concentration and reference solution, but the solution to be measured is always kept at a specific temperature using a thermostat or the like to determine the concentration. When the measurement is performed, the matters relating to the temperature correction are unnecessary, and the precise concentration measurement can be performed with a simpler relational expression.

In the following description, the known concentration liquid and the liquid to be measured are aqueous solutions of the same substance, and pure water is used as the reference liquid. One of the solutions of known concentration in the method of the present invention is
A liquid with a concentration equal to or extremely close to the maximum scale of the densitometer is desirable, and a 0% or 100% concentration solution is generally selected as the reference liquid. When measuring an aqueous solution, it is used as the reference liquid. Ultrapure water or the like is used.

(Measurement Method When One Detector is Used) A reference liquid and a plurality of solutions of known concentration (C _N ) are sequentially introduced to a detector S serving as a reference, and the upper limit and the lower limit within the use range are included. The propagation time t _S of the reference liquid and the propagation time t _N of the known concentration liquid corresponding to several temperature levels (T _S ) are measured. The following relational expressions of C _N , T _S , t _S , and t _N are obtained and stored in the measuring device. A) Relational expression between the propagation time and temperature of the reference liquid of the detector t _S = F (T _S ) (1-1) b) Relational expression between R _S , T _S and C _N C _N = F (R _S , T _S ) (1-2) C) Relational expression between Dt _S , T _S and C _N C _N = F (Dt _S , T _S ) (1-3) where propagation time ratio R _S = t _N / t _S (1-2) 'Propagation time difference Dt _S = | t _S -t _N | (1-3)' For concentration measurement, along with equation (1-1), the time ratio method of equation (1-2), ( It can also be obtained from any of the relational expressions of the time difference method of equation 1-3). To measure the concentration of an unknown concentration liquid, the measured liquid is introduced into a detector, the temperature T _X and the propagation time t _X are measured, and the value corresponding to the propagation time t _S of the reference liquid at the same temperature is calculated as (1-1 ), Then calculate R _S = t _X / t _S or Dt _S = | t _S -t _X |, and calculate the time ratio method of the equation (1-2) or the time difference method of the equation (1-3). Obtain the concentration of the solution to be measured from the formula. Both the time ratio method using R _S and the time difference method using Dt _S can perform highly accurate concentration measurement without the need to measure the propagation path length.

In the above calculation method, if the detectors having the same reference liquid temperature but different ultrasonic wave propagation path lengths are used (1-
The equation (1) changes, and even in the case of the solution to be measured having the same concentration and temperature, the value of Dt _S changes due to the different propagation time t _N.
That is, since the basic part of the relational expression is different every time the propagation path length is different, a relational expression for each detector is required. However, by introducing a correction coefficient related to the propagation distance as shown below, Will be resolved.

In the case of the time ratio method of the formula (1-2) based on the propagation time ratio R _S , the propagation time t _S of the liquid having an arbitrary concentration at a certain temperature, which is measured by the temporary reference detector _S , When the propagation time measured by the detector X whose path length is K times that of the detector S is t _X , if K is calculated from K = t _X / t _S , the detector whose propagation path length is K times that of the detector S is obtained. If the same measurement as in X is performed, the propagation times are all K times. R _S = by the detector S of the formula (1-2) '
The time ratio of the detector X corresponding to t _N / t _S is (K * t _N )
Since / (K * t _S ) = t _N / t _S , the value of R _S is a factor specific to the type of solution that is not affected by the length of the propagation path. Also, R _S = (K * t _N ) / (K * t _S ) =
In (1 / K) * (K * t _N / t _S ), [K *
t _N ] is the same as the direct measurement value of the detector X, and t _S is
Focusing on the fact that it is derived from the equation (1-1), R _S can be obtained from the measurement data of the detector X, and the concentration can be measured. That is, when measuring the unknown concentration solution with the detector X,
First, the temperature T _X and the propagation time t _X of the solution are measured, and (1-1)
The reference liquid propagation time t _S at the temperature T _X of the detector _S is calculated by substituting T _{X in} the temperature term of the equation, and the corrected propagation time ratio R _S =
Calculate (1 / K) * t _X / t _S , then R _{S in} equation (1-2)
The concentration is obtained by substituting the numerical value for the temperature term.

In the case of the time difference method of the equation (1-3) based on Dt _S , K is obtained in the same manner as in the time ratio method of the equation (1-2),
When the same measurement is performed by the detector X whose propagation path length is K times that of the detector S, the propagation time becomes K times. Therefore, the time difference of the detector X corresponding to Dt _S = | t _S −t _N | by the detector _S is | K * t _S −Kt _N | = K * | t _S −t _N | = K * Dt
_S , which is a multiple of the propagation path length, and Dt _S = | t
_S −t _N | = | t _S − (1 / K) * K * t _N |.
Here, (K * t _N ) is the same as the direct measurement value of the detector X, and t _S is derived from the equation (1-1).
It is possible to obtain Dt _S from the data of (1), and it becomes possible to measure the concentration, that is, when measuring a solution of unknown concentration with the detector X, the temperature T _{X of the} solution and the propagation time t _X are measured, and (1-1 )
The reference liquid propagation time t _S at the temperature T _X of the detector _S is calculated by substituting T _X into the temperature term of the equation, and the corrected propagation time difference Dt _S is calculated.
= | T _S − (1 / K) * t _X | and obtain Dt of equation (1-3)
_The concentration is obtained by substituting the numerical values for the _S and temperature terms.

As described above, in any method based on the propagation time difference or the propagation time ratio between the reference solution and the solution to be measured, no matter how the propagation path length of the detector changes, the correction coefficient K is obtained.
With the introduction of, it becomes unnecessary to obtain a separate relational expression for each detector. When measuring with only one detector, the ultrasonic wave propagation time measuring circuit, the arithmetic circuit, and the like are common to the liquid to be measured and the reference liquid, and the influence of drift and steady-state error in the electronic circuit on data collection is small.

(Measurement method in the case of a plurality of detectors) Switching the reference solution with the same detector is considerably complicated because it is necessary to completely wash the detectors and it takes time, and therefore, the following plural detectors are used. A method using a single detector is generally performed. Leads to a plurality of known concentration (C _N) solution successively measured solution detector to X, measuring several propagation time t _'N corresponding to the temperature level (T _S) comprising upper and lower limits of the range of use Then
If the detector S is used as a reference, the propagation time t of the reference liquid is increased for each T _S.
Measure _S.

The detector propagation path length of X is in the case of identical special detector S t _'N a t _N, R' _S a R _S, Dt _'S a Dt
When _S, relation of _{R S, Dt S, C N} , T S, t S, t N , the detector is exactly the same as the one. That is, a) the relational expression of the propagation time of the reference liquid of the detector and the temperature t _S = F (T _S ) (1-1) b) the relational expression of R _S , T _S and C _N C _N = F (R _S , T _S ) (1-2) C) Relational expression between Dt _S , T _S, and C _N C _N = F (Dt _S , T _S ) (1-3) However, propagation time ratio R _S = t _N / T _S (1-2) ′ Propagation time difference Dt _S = | t _S −t _N | (1-3) ′ R ′ _S : Propagation time of known concentration liquid at detector X / detector S at the same temperature Reference liquid propagation time at Dt ' _S : | Reference liquid propagation time at detector S-Propagation time of known concentration liquid at detector X at the same temperature |

In the general case where the propagation path length of the measured detector X is not equal to the propagation path length of the reference liquid detector S,
The ratio K of the propagation path lengths of the detectors is obtained, and a correction coefficient for the propagation distance is introduced. That is, let t _{S be} the propagation time measured by the detector S for a liquid of arbitrary concentration at a certain temperature, and let t _{X be} the propagation time measured by the detector X whose propagation path length is K times that of the detector S, and K = t _X Find K from / t _S and use equation (1-2) or (1-
By applying it to the equation (3), it can be expanded as follows. _{R S = t N / t S} = (1 / K) * K * t N / t S = (1 / K) * t 'N / t S Dt S = | t S -t N | = | t S over (1 / K) * K * t _N | = | t _S − (1 / K) * t ′ _N | Therefore, from the measured values t ′ _N and K of the detector X, the corrected propagation time ratio R _S = (1 / _{K) * t 'N / t} S or corrected propagation time difference _{Dt S = | t S - (} 1 / K) * t' N | can be obtained, it is possible to density measurement.

To measure the concentration of the unknown concentration liquid, the temperature _{X of the} liquid to be measured and the propagation time t _X are measured by the detector X, and the value corresponding to the propagation time t _S of the reference liquid at the same temperature is given by ( 1-1), then R _S = (1 / K) * (t _X / t _S ) or Dt _S = | t _S- (1 / K) * t _X | 2)
Obtain the concentration of the solution to be measured from the time ratio method of formula or the time difference method of formula (1-3). Thus, even if the propagation path lengths of the detectors X are different, by using K, it is possible to obtain exactly the same values of R _S and Dt _S as when two detectors S of the same size are used. Equation (1-2) or equation (1-3) can be used in exactly the same way.

In the above measuring method, the equation (1-2) 'based on the time difference, R _S = t _N / t _S = (1 / K) * K *
Instead of t ′ _N / t _S , the normalized corrected propagation time ratio DR _S = ±
It is possible to obtain the concentration by setting (1−R _S ), and obtaining C _N = F (DR _S , T _S ). In this case (1-
The sign before R _S ) is chosen such that DR _S increases with increasing concentration. If the measured liquid is selected pure water as a reference solution with an aqueous solution, since this method calibration curve DR _S and concentration by performing passes through the origin, be very to understand easily simple, yet when processing data No special ingenuity is required.

(Correction method after the start of use) In the densitometer of the type that obtains the concentration from the ultrasonic wave propagation velocity, changes in the propagation path length of the detector during long-term use, long-term drift of the electronic circuit of the measuring instrument, and It is difficult for general users to understand the error due to aging, and it is difficult to correct it. For such a problem, when the number of detectors is one, the procedure is the same as that when detectors having different ultrasonic wave propagation path lengths are used, and the correction is extremely simple. That is, the propagation time measured by introducing a liquid of known concentration (which may be the reference liquid) at the temperature T _{S to} the detector X after long-term use is t _X , and the measured propagation time of the solution under the same conditions in the detector S at the beginning. If it is t _S , K = t _X / t _S is calculated, and by updating K before that, the subsequent measurement is normally performed. The degree of change in K is a standard indicating the stability of the entire measuring device including the detector, and by monitoring K, the necessity of maintenance and inspection can be determined. As a means of monitoring the deviation of the solution concentration measuring device, the degree of change in K is also a standard for indicating the stability of the entire measuring device including the detector, and maintenance and adjustment are required when the change exceeds a certain value. It is preferable to add an alarm mechanism that operates.

However, if the number of detectors is one, the correction by the above method involves the removal of the detector if the detector is directly attached to the piping of the chemical plant, etc. Since it takes a certain amount of time to completely replace the liquid to be measured and the like, it is difficult to carry out frequently. In the method using a plurality of detectors that divide the detector into one for reference liquid and one for measured liquid, the following correction method is performed,
Such a problem is solved.

That is, when the concentration meter after use is corrected by a method using a plurality of detectors, the reference liquid detector S is stored and the propagation path length of the measured liquid detector X is corrected. When performing the accuracy check and calibration of the entire densitometer, which also serves as the densitometer, fill the detector S and the detector X with a solution of the same temperature and concentration (the liquid under measurement may be the measurement target) and propagate from the measurement propagation time at that time. By calculating the road length ratio K and updating K before that, correct measurement is always possible.

(Correction method when electronic circuit after ultrasonic circuit is commonly used for a plurality of detectors) In the above method, errors due to drift or deterioration of the measuring circuit shorter than the update time of K can be completely eliminated. Although this is not the case, this drawback is eliminated by using a common electronic circuit in a method using a plurality of detectors and by carrying out the following. That is, the electronic circuit after the ultrasonic circuit is commonly used for a plurality of detectors, the signals of the plurality of detectors are switched at a high speed by a switching device, and the ultrasonic circuit common to each detector is used for the ratio measurement solution and the reference solution. If the temperature of each solution is constantly measured by a temperature measuring device and the concentration is measured by a relational expression, the propagation time will show steady errors in the measurement circuit and errors due to short-term and long-term drifts, etc., appearing approximately in each propagation time information. By the information processing based on the time ratio, those errors can be almost eliminated.

The expansion of the equation in this case is basically the same as that described above, and the following method is performed. The detector X for the liquid to be measured and the detector S for the reference liquid are installed in a constant temperature bath or the like in which the respective internal temperatures are always the same, and the internal solution temperature between the detectors is maintained to be the same. A plurality of solutions of known concentration (C _N ) are sequentially introduced to the detector X, the propagation time t ′ _N corresponding to several temperature levels (T _S ) including the upper limit and the lower limit within the use range is measured, and the detector is detected. At S, the propagation time t _S of the reference liquid is measured for each T _S. This time,
By switching the ultrasonic signal between the ultrasonic circuit and each detector with the switch and using a common electronic circuit after the ultrasonic circuit, the influence of drift is eliminated and more precise measurement can be performed.

The following relational expression is obtained and stored in the same procedure as described above. In the special case where the propagation path length of the detector X is exactly the same as that of the detector S, t ′ _N is t _N , R ′ _S is R _S , and Dt ′ _S is D.
where t _S , R _S , Dt _S , C _N , T _S , t _S , t _N
The relational expression of A is a relational expression of R _S , T _S , and C _N C _N = F (R _S , T _S ) (1-2) a) The relational expression of Dt _S , T _S , and C _N C _N = F (Dt _S , T _S ) (1-3) R _S = t _N / t _S (1-2) 'Dt _S = | t _S -t _N | (1-3)' where R _'S : detection Propagation time of known concentration in detector X / reference liquid transit time in detector S at the same temperature Dt ' _S : | Reference liquid transit time in detector S-known in detector X at the same temperature Concentration liquid propagation time | In a general case where the propagation path length of the measured detector X is not equal to the propagation path length of the reference liquid detector S, the ratio K of the propagation path lengths is calculated, and the correction coefficient for the propagation distance is calculated. To introduce. _{R S = t N / t S} = (1 / K) * K * t N / t S = (1 / K) * t 'N / t S Dt S = | t S -t N | = | t S - (1 / K) * K * t _N | = | t _S − (1 / K) * t ′ _N | Therefore, from the measured values t ′ _N and K of the detector X, R _S or D
Since t _s can be obtained, the concentration can be measured.

Detector X for measured liquid and detector S for reference liquid
The liquid to be measured and the reference liquid are respectively guided to each detector, the detector and the ultrasonic circuit are switched at high speed by the switch, the propagation time and the temperature are measured, and the concentration is calculated from the relational expression. Ie detector X
In unknown concentration temperature T _X and the propagation time t _X solution, the propagation time t _S of reference liquid in at detector S in the temperature is measured, R _S
= (1 / K) * (t _X / t _S ) or Dt _S = | t _S
The concentration is obtained by calculating − (1 / K) * t _X | and inserting the numerical value into the above formula (1-2) or formula (1-3).

When the internal temperature of each detector is not the same, the following method is performed. The reference liquid detector S measures the propagation time t _S of the reference liquid for each appropriate temperature level (T _S ), and the relational expression t _S = F (T _S ) [(1-1) [Formula] is created and stored. When the measured temperature T _{1 of the} solution to be measured and the measured temperature T _{2 of the} reference solution are not equal, t when determining R _S or Dt _S
S is (1-1) instead of the measurement propagation time at the detector for reference liquid
Using the numerical value obtained by substituting T ₁ for the temperature term of the equation, (1-
Obtain the concentration using formula (2) or formula (1-2). If the measuring device is normal, the measurement ultrasonic wave propagation time of the reference liquid and t _S = F
The difference from the value obtained by substituting T ₂ for (T _s ) should be zero, and as a means for monitoring the deviation of the solution concentration measuring device, this difference or the change in K became a certain value or more. In some cases, it is preferable to add an alarm mechanism requesting maintenance and adjustment.

When a plurality of ultrasonic wave detectors are used in this way, the common ultrasonic wave circuit can significantly reduce the drift and steady-state error in the electronic circuit. Further, if the correction coefficient of the ultrasonic wave propagation path time is automatically calculated at regular time intervals or by a specific command, highly accurate measurement can be continuously performed. Furthermore, by using multiple detectors for the reference liquid and detectors for the measured liquid, and processing information with an electronic circuit common to them, it is possible to perform multipoint analysis with one analyzer, which is economically superior. It becomes an analyzer.

In order to measure the concentration by the above method, the following device is used. (a) When there is one detector, a detector having an ultrasonic wave emitting element for emitting ultrasonic waves and an ultrasonic wave receiving element, a temperature measuring device for the substance in the detecting device, an ultrasonic wave propagation time measuring circuit, an ultrasonic wave for the reference liquid. Solution concentration measuring device characterized by having a means for calculating the concentration of the liquid to be measured from the ultrasonic wave propagation time and the ultrasonic wave propagation time of the liquid to be measured without using the ultrasonic wave propagation velocity (b) Multiple detection In the case of a detector, a detector for liquid to be measured and a detector for reference liquid having an ultrasonic wave emitting element for emitting ultrasonic waves and an ultrasonic wave receiving element, a temperature measuring device for each detector, and a common detector for each detector Solution characterized by having an ultrasonic wave propagation time measuring circuit, means for calculating the concentration of the solution to be measured from the ultrasonic wave propagation time of the standard solution and the ultrasonic wave propagation time of the solution to be measured without using the ultrasonic wave propagation velocity. Concentration measuring device In order to be continued
To the devices (a) and (b), a means for correcting the relational expression by adding a solution having a known concentration to a detector for measuring the liquid to be measured at a specific time, measuring the ultrasonic wave propagation time, is added.

The apparatus for measuring the solution concentration using ultrasonic waves of the present invention (ultrasonic densitometer) is used for many purposes such as concentration measurement of acid, alkali, specific metal salt, sugar, organic solvent, alcohol solution. To be Since the ultrasonic wave propagation time in the solution largely depends on the solution temperature, when measuring without temperature compensation, the temperature of the solution inside the detector should be accurately measured and kept constant in order to improve the measurement accuracy of the solution concentration. Need to control. To measure the temperature of each detector for this purpose, a resistance thermometer, a thermocouple thermometer, a thermistor thermometer, etc. are usually used.

In the method of the present invention, the relational expression for concentration measurement can be simplified by keeping the ultrasonic wave propagation time detector at a constant temperature as described above, and in the case of using a plurality of detectors. It is possible to perform measurement with higher measurement accuracy. A constant temperature bath is usually used to keep the temperature of the detector constant. The shape of this constant temperature bath is not particularly limited, and for example, the detector can be installed in a pipe that is always kept at a constant temperature. If there is only one detector, heat exchange is introduced into the detector by switching between the measured solution and the standard solution in the constant temperature bath in order to keep the measured solution and the standard solution at the same temperature. Can be used.

The ultrasonic wave propagation time is measured using an ultrasonic wave emitting element for emitting ultrasonic waves and a detector provided with an ultrasonic wave receiving element. The detector that measures the ultrasonic transit time,
Usually, an ultrasonic wave emitting element having a frequency of about 1 to 10 MHz is used. The signal of the detector is an ultrasonic wave propagation time measurement circuit
(Hereinafter referred to as the ultrasonic circuit). A sing-around method is usually used for this ultrasonic circuit.
The electrical signal from the ultrasonic circuit and the temperature measurement signal of each detector are sent to the calculator, and the concentration of the target substance in the liquid to be measured is calculated by the relational expression stored in the calculator, and the concentration indicator is displayed if necessary. Displayed or recorded on.

When a plurality of detectors are used, one of them is used as a detector for the reference liquid, and the number of detectors for the liquid to be measured is determined by the number of flow paths of the concentration measuring device used. It It is more accurate to keep these detectors at the same temperature and the calculation is simple, so they are often installed in a common constant temperature bath. The signal from each detector communicates with the ultrasonic circuit and the ultrasonic propagation time is measured and sent to the computing unit.If an ultrasonic circuit is installed for each detector, the drift and steady-state error of each electronic circuit Since the measurement accuracy will decrease due to the influence, it is desirable to use a common ultrasonic circuit by using a switch. That is, since this ultrasonic circuit is an electronic circuit, drifts and steady errors are unavoidable as described above, and such drifts and steady errors differ depending on each circuit. The signals of the ultrasonic circuit of each detector of the reference liquid and the liquid to be measured are switched in a short time by using a switch and the ultrasonic circuit and subsequent circuits are processed by a common electronic circuit, so that drift and steady state after the ultrasonic circuit can be prevented. Since the error appears in the ultrasonic wave propagation time and the like to the same extent, the influence of drift and steady error is eliminated by performing relative processing with the information of each detector, and the accuracy of concentration measurement is significantly improved. The signal from the detector of the reference liquid and the signal from the detector of the liquid to be measured in the switch can be switched at a specific time by a timer, or by a specific command such as synchronization with the ultrasonic circuit. You can also

In the method of using a plurality of detectors, the method of significantly reducing the influence of temperature is to take measures so as not to make a difference in the internal temperature of each detector, and to make the reference solution close to the concentration usually measured. A liquid is used, and data is processed by an electronic circuit common to each detector using a switching device. As a result, in the measurement of the concentration close to that of the reference liquid, the effect that the temperature correction is substantially unnecessary is obtained by both the method based on the propagation time ratio and the method based on the propagation time difference as will be described in the following examples. Therefore, when the measured concentration is almost constant, it is preferable to select a liquid having an approximate concentration as the reference liquid. As mentioned above, if the temperature of the sample solution and standard solution are kept at the same temperature using a constant temperature bath, etc., a highly accurate concentration can be obtained with a relatively simple formula, but it can be detected by the influence of the temperature of the sample solution or the ambient temperature. It is often difficult to keep the temperature of the vessel constant. Since the ultrasonic wave propagation time in a solution largely depends on the solution temperature, even when using a constant temperature bath, it is possible to improve the measurement accuracy of the solution concentration by adding a temperature factor to the relational expression between the propagation time ratio and the concentration. it can.

It has been explained above that the slightest difference in the propagation length of the detector is corrected by using the correction coefficient K in order to improve the accuracy of the densitometer. It also serves as a zero adjustment. To calibrate the correction coefficient, switch the designated sample valve with a correction command, introduce a solution of the same concentration and temperature (reference solution or measured solution) into the detector, and after a certain period of time, close the sample valve and propagate each detector. Memorizes the time measurement value, calculates the ratio of the measured values of the measured liquid detector and the reference liquid detector, replaces it with the previous correction coefficient, switches the specified sample valve to the original state, and returns to the measurement state. Done by. This correction command may be corrected periodically by pressing a specific command switch or by a sequencer interval timer or the like.

Next, the device of the present invention will be described with reference to the drawings. FIG. 1 is a device configuration diagram of a solution concentration measuring device of the present invention when one detector is used. In FIG. 1, the reference liquid (pure water) or the liquid to be measured (alkaline liquid) is introduced into the detector through the heat exchanger. Switching between the reference liquid and the liquid to be measured is performed by a solenoid valve installed in each flow path. The detector has an ultrasonic wave emitting / receiving element and a temperature sensing element, and ultrasonic signals are communicated between the ultrasonic wave receiving / emitting element and the ultrasonic circuit. The heat exchanger and the detector are incorporated in a constant temperature bath (bath unit), and are kept at a constant temperature by a temperature controller incorporated in the constant temperature bath. The ultrasonic propagation time measurement signal from the ultrasonic circuit and the temperature signal from the detector temperature converter are sent to the arithmetic circuit. The storage device of this arithmetic circuit stores an arithmetic expression and a correction coefficient K necessary for the concentration measurement based on the data as shown in the embodiment, and the propagation time information from the ultrasonic circuit and the detector temperature converter are stored. Input the temperature information of, calculate the concentration based on the stored calculation formula, display the concentration on the display, and until the next calculation result is obtained,
Density measurement is performed by a program that repeatedly holds the density value. The functions such as input, storage, calculation and concentration display are all executed by one sequencer.

FIG. 2 is a device configuration diagram of the solution concentration measuring apparatus of the present invention when a plurality of (three) detectors are used. In FIG. 2, a detector for a standard liquid (pure water) and two detectors for a solution to be measured (alkaline liquid) are installed in the same constant temperature bath (bath unit). The ultrasonic receiving and emitting elements of each detector are connected to a common ultrasonic circuit via a switch. The switch has a manual position and an automatic position. When the basic data of the concentration and the propagation time is collected, the switch is set to the manual position, and when the concentration is measured, the switch is sequentially switched by the command of the sequencer as the automatic position. Concentration measurement is performed almost in the same way as in FIG. 1 above, and functions such as input, storage, calculation, and concentration display are all performed by one sequencer, but switching of each detector is also performed by one sequencer even when measuring two flow paths. The density data can be updated at a very high speed of about 3 seconds, about 3 seconds. Therefore, in the device as shown in FIG. 2, since the propagation time measurement signal of each detector is commonly processed by the electronic circuit after the ultrasonic circuit via the switch, each measurement signal may have drift or steady error of the electronic circuit. Will be included to the same extent,
By using the concentration measurement method based on the propagation time difference and the propagation time ratio that relatively process the measurement signals from each detector, the above error is substantially eliminated, and high-precision measurement is maintained for a long time. Will be.

[0041]

【Example】

Example 1 In the concentration measuring device shown in FIG. 2, pure water was used as a reference liquid for the detector I and a solution of known concentration was used for the detector II.2.
Fill the detectors with 5wt%, 5.0wt%, 7.5wt% and 10.0wt% alkaline solution, set the constant temperature bath to 20 ℃, 30 ℃ and 40 ℃, emit ultrasonic waves to each detector, and the propagation time Was measured. The ultrasonic propagation distance of the detector is approximately 140.5 mm, and the ultrasonic circuit is a sing-around method. At the time of data collection, the ultrasonic circuit and each detector were switched manually. Table 1 shows the measurement results of the ultrasonic wave propagation time at each temperature. This display is a direct reading value (μs) from the measurement circuit of the sing-around method, and since the number of repetitions is 4, it is four times the actual ultrasonic wave propagation time. The temperature difference between the internal solutions of Detector I and Detector II during the experiment is within ± 0.02 ℃.

[0042]

[Table 1] 20 ℃ test 30 ℃ test 40 ℃ test Concentration detector I detector II detector I detector II detector I detector II 0.0 379.03 379.24 372.37 372.58 367.61 367.82 2.5 379.03 369.63 372.37 364.02 367.60 360.06 5.0 379.03 360.18 372.37 355.58 367.60 352.38 7.5 379.03 350.88 372.37 347.23 367.61 344.77 10.0 379.03 341.77 372.36 338.99 367.61 337.22

The results of the following calculations based on the above measured values are shown in Tables 2 to 4 and FIGS. 1) Ultrasonic propagation velocity V (m / s) The ultrasonic propagation velocity V (m / s) was calculated from the measurement time of the detector II and the approximate propagation distance (140.5 mm). The relationship between the alkali concentration at each temperature and the propagation speed is shown in FIG. 3a. Thus, the method of obtaining the solution concentration from the ultrasonic wave propagation velocity is a conventional method.

2) Propagation time difference (DTa = t _s -t _N ) Propagation time difference (DTa) between the measured propagation time t ₀ when the reference liquid is pure water in the detector II and the measured propagation time t _{N at} each concentration. = t _s -t _N ), and the relationship between alkali concentration and propagation time difference at each temperature is shown in FIG. 3b. This is a case where the solution concentration is obtained from the propagation time difference in one detector by the method of the present invention, and the solution concentration is uniquely determined from the propagation time difference and the temperature as described above, and this method causes a measurement error of the propagation distance. Since the influence is eliminated, highly accurate measurement is performed.

3) Corrected Propagation Time Difference Percentage The propagation time ratio of each detector when both the detector II and the detector I are filled with the reference liquid is defined as a propagation distance correction coefficient K, and
Propagation time difference obtained by subtracting the value obtained by multiplying the measured propagation time t _N for each concentration of the detector II by 1 / K from the measurement time t _{s of} I [DTb = t
_s- (1 / K) * t _N ] is calculated, and DTb at 20 ° C, 10.0% is 100%.
3c shows the relationship between the alkali concentration at each temperature and the percentage of the corrected propagation time difference. This relational diagram is used when detectors with different ultrasonic wave propagation lengths are used or for correction of the detectors after the start of use, and the relational diagram can be commonly used by obtaining K of the detector to be corrected. .

4) Propagation time ratio (Ra = t _N / t _s ) The measured propagation time t _s of the reference liquid concentration (pure water 100.0 wt%) in the detector II and the measured propagation time t _{N at} each concentration The propagation time ratio (Ra = t _N / t _s ) was calculated. The relationship between the alkali concentration and the propagation time ratio at each temperature is shown in FIG. 4a. This is a relational diagram when the solution concentration is calculated from the propagation time ratio in one detector, and the solution concentration is uniquely determined from the propagation time ratio and temperature in this way, and the influence of the measurement error of the propagation distance is eliminated. Therefore, highly accurate measurement is performed.

5) Propagation time ratio (Rb = t _N / t _s ) Measured propagation time t _{N at} each concentration in detector II and measured propagation time t _s of reference liquid concentration (deionized water 100.0 wt%) in detector I And the propagation time ratio (Rb = t _N / t _s ) of
The relationship between the alkali concentration at each temperature and the propagation time ratio is shown in FIG. 4b. This is a case where the solution concentration is calculated from the propagation time ratio with multiple detectors, and it is easy to correct the detectors after using them with multiple detectors, and the ultrasonic circuit and subsequent ones can be shared by using a switching device. Highly accurate measurement can be easily performed.

6) Normalized corrected propagation time ratio [DRs = 1- (1 /
K) * (t _N / t _s )]] Calculate the propagation time ratio of the measured propagation time t _{N at} each concentration in the detector II and the measured propagation time t _s of the reference liquid concentration (deionized water 100.0 wt%) in the detector I. Then, the normalized corrected propagation time ratio [DRs = 1- (1 /
K) * (t _N / t _s )], and the relationship between the alkali concentration and the normalized correction propagation time ratio at each temperature is shown in FIG. 4c. This is the case where the solution concentration is calculated from the normalized corrected propagation time ratio for multiple detectors.This relationship diagram is for the case of using detectors with different ultrasonic wave propagation lengths and for correcting the detectors after the start of use. The relationship diagram can be used in common by obtaining the K of the detector to be corrected, and by performing this method, the DRs and concentration calibration curves pass through the origin, so it is very easy to understand and simple. In addition, no special device is required when further processing the data.

[0049]

(Table 2) (Example 1, 20 ° C. test) Concentration Propagation velocity V Time difference DTa DTb DT% Time ratio Ra Rb DRs 0.0 1481.9 0.00 0.00 0.00 1.00000 1.00055 0.00000 2.5 1520.4 9.61 9.60 25.63 0.97466 0.97520 0.02534 5.0 1560.3 19.06 19.05 50.87 0.94974 0.95027 0.05026 7.5 1601.7 28.36 28.34 75.67 0.92522 0.92573 0.07478 10.0 1644.4 37.47 37.45 100.0 0.90120 0.90170 0.09880

[0050]

(Table 3) (Example 1, 30 ° C test) Concentration Propagation velocity V Time difference DTa DTb DT% Time ratio Ra Rb DRs 0.0 1508.4 0.00 0.00 0.00 1.00000 1.00056 0.00000 2.5 1543.9 8.56 8.56 22.86 0.97703 0.97758 0.02297 5.0 1580.5 17.00 16.99 45.37 0.95437 0.95491 0.04563 7.5 1618.5 25.35 25.34 67.66 0.93196 0.93249 0.06804 10.0 1657.9 33.59 33.56 89.61 0.90984 0.91038 0.09013

[0051]

(Table 4) (Example 1, 40 ° C. test) Concentration Propagation velocity V Time difference DTa DTb DT% Time ratio Ra Rb DRs 0.0 1527.9 0.00 0.00 0.00 1.00000 1.00057 0.00000 2.5 1560.9 7.76 7.75 20.03 0.97890 0.97949 0.02107 5.0 1594.9 15.44 15.42 41.17 0.95802 0.95860 0.04195 7.5 1630.1 23.05 23.04 61.52 0.93733 0.93787 0.06267 10.0 1666.6 30.60 30.58 81.66 0.91681 0.91733 0.08319

An example of the relational expression including the term of temperature correction created based on the above experimental data is shown below. C _N = F (DRs, T) = 75.7477 * DRs + 1.14268 * DRs * T-2.2576
7 * 10 ^-3 * DRs * T ² + 33.4798 * DRs ² + 0.155824 * DRs ² * T-8.62
56 * 10 ^-3 * DRs ² * T ² Table 5 shows the relationship between the concentration obtained by substituting DRs and T in this equation (calculated concentration) and the concentration used in the experiment (experimental concentration).
Shown in It can be seen that a highly accurate relational expression is obtained from this.

[0053]

[Table 5] Experimental concentration (20 ℃ test) (30 ℃ test) (30 ℃ test) (wt%) DRs calculated concentration DRs calculated concentration DRs calculated concentration 0.0 0.00000 0.00 0.00000 0.00 0.00000 0.00 2.5 0.02534 2.50 0.02297 2.50 0.02107 2.49 5.0 0.05026 4.99 0.04563 4.99 0.04195 4.99 7.5 0.07478 7.49 0.06804 7.49 0.06267 7.49 10.0 0.09880 9.98 0.09013 9.98 0.08319 9.98

Example 2 In the same concentration measuring apparatus as in Example 1, the detector I was used as a solution having a known concentration of 0.0 wt%, 1.0 wt%, 2.0 wt% and 2.38 wt%.
, 3.00wt%, 4.0wt% and 5.0wt% alkaline solution is filled in the detector, and detector III is always filled with 2.38wt% alkaline solution as the standard solution, and the thermostat is kept at 10 ℃, 20 ℃, 35 ℃.
And 50 ° C., ultrasonic waves were emitted to each detector and the propagation time was measured. This time is a direct reading value (μs) from the measurement circuit of the sing-around method, and since the number of repetitions is 4, it is four times the actual ultrasonic wave propagation time. Further, the following calculation was performed, and the results are shown in Tables 6-9.

[0055] 1) correction propagation time difference _{[DTb = t s - (1 /} K) * t
_N ] The detection time ratio of each detector when both the detector I and the detector III are filled with the reference liquid (concentration 2.38 wt%) is set as the propagation distance correction coefficient K, and detected from the measurement time t _s of the detector III. instrumental propagation time difference of a difference obtained by subtracting the numerical value obtained by multiplying the K to the measured time t _N for each concentration of I - a _{[DTb = t s (1 / K} ) * t N ] were calculated. The relationship between the alkali concentration at each temperature and the corrected propagation time difference is shown in FIG. 5a. This is a case in which a solution with a concentration similar to that of the measured liquid is used as the reference liquid with multiple detectors, and the solution concentration is obtained from the corrected propagation time difference. Very few and highly accurate concentration measurements are made.

2) Propagation time ratio (Rb = t _N / t _s ) Measurement time t _{N at} each concentration in the detector I and the detector
The propagation time ratio of the reference liquid concentration (concentration 2.38 wt%) in III to the measurement time t _s was calculated. This is a case where a solution with a concentration similar to the measured solution is used as the standard solution with multiple detectors, and the solution concentration is obtained from the propagation time ratio. High-accuracy measurement can be easily carried out, and particularly in the case of the liquid to be measured having a concentration close to that of the reference liquid, very high-precision concentration measurement is performed.

3) Corrected propagation time ratio [Rc = (1 / K) * (t _N /
t _s )] Measurement time t _{N at} each concentration in detector I and detector
The propagation time ratio of the reference solution concentration (concentration 2.38 wt%) in III to the measurement time t _s was calculated and corrected with the propagation distance correction coefficient K [Rc = (1 / K) * (t _N / t _s )]. . The relationship between the alkali concentration at each temperature and the corrected propagation time ratio is shown in FIG. 5b. This is a case where a solution with a concentration similar to the solution to be measured is used as the standard solution with multiple detectors, and the solution concentration is determined from the corrected propagation time ratio.This relationship diagram uses detectors with different ultrasonic wave propagation lengths. In the case or after the start of use, it is used for the correction of the detector, and the relationship diagram can be commonly used by obtaining the K of the detector to be corrected.

3) Normalized corrected propagation time ratio (DRs = 1.0-Rc
) Figure 5C shows the relationship between the alkali concentration and DRs at each temperature. If K is calculated for each detector and DRs is calculated, it is possible to obtain the solution concentration with high accuracy by making this relationship diagram common.

[0059]

[Table 6] (Example 2, 10 ° C test) Concentration Propagation time I Propagation time III Time difference DTb Time ratio Rb Time ratio Rc DRs 0.0 382.77 374.26 -10.43 1.02274 1.02787 -0.02787 1.0 378.36 374.27 -5.99 1.01093 1.01600 -0.01600 2.0 374.04 374.28 -1.64 0.99936 1.00438 -0.00438 2.38 372.45 374.32 0.00 0.99500 1.00000 0.00000 3.0 369.80 374.37 2.71 0.98779 0.99275 0.00725 4.0 365.61 374.46 7.01 0.97637 0.98127 0.01873 5.0 361.27 374.32 11.24 0.96514 0.96998 0.03002

[0060]

(Table 7) (Example 2, 20 ° C test) Concentration Propagation time I Propagation time III Time difference DTb Time ratio Rb Time ratio Rc DRs 0.0 373.70 366.51 -9.06 1.01962 1.02473 -0.02473 1.0 369.97 366.61 -5.22 1.00917 1.01423 -0.01423 2.0 366.18 366.60 -1.42 0.99885 1.00387 -0.00387 2.38 364.78 366.61 0.00 0.99501 1.00000 0.00000 3.0 362.41 366.61 2.38 0.98854 0.99350 0.00650 4.0 358.71 366.61 6.10 0.97845 0.98336 0.01664 5.0 355.02 366.65 9.85 0.96828 0.97314 0.02686

[0061]

[Table 8] (Example 2, 35 ° C test) Concentration Propagation time I Propagation time III Time difference DTb Time ratio Rb Time ratio Rc DRs 0.0 364.78 358.92 -7.69 1.01633 1.02142 -0.02142 1.0 361.52 358.90 -4.43 1.00730 1.01235 -0.01235 2.0 358.34 358.92 -1.22 0.99838 1.00339 -0.00339 2.38 357.13 358.92 0.00 0.99501 1.00000 0.00000 3.0 355.17 358.96 2.01 0.98944 0.99440 0.00560 4.0 352.01 358.98 5.21 0.98058 0.98550 0.01450 5.0 348.89 359.03 8.39 0.97176 0.97663 0.02337

[0062]

(Table 9) (Example 2, 50 ° C test) Concentration Propagation time I Propagation time III Time difference DTb Time ratio Rb Time ratio Rc DRs 0.0 359.40 354.45 -6.75 1.01397 1.01905 -0.01905 1.0 356.55 354.44 -3.90 1.00595 1.01100 -0.01100 2.0 353.73 354.44 -1.07 0.99800 1.00301 -0.00301 2.38 352.67 354.44 0.00 0.99501 1.00000 0.00000 3.0 350.92 354.44 1.76 0.99007 0.99504 0.00496 4.0 348.12 354.44 4.57 0.98217 0.98710 0.01290 5.0 345.32 354.44 7.39 0.97427 0.97916 0.02084

An example of the relational expression including the term of temperature correction created based on the above experimental data is shown below. C _N = F (DRs, T) = 76.5041 * DRs + 1.02363 * DRs * T-0.0008
97496 * DRs * T ² -7.71778 * DRs ² -1.04891 * DRs ² * T + 0.0175
716 * DRs ² * T ² +2.38 Table 1 shows the relationship between the concentration obtained by substituting DRs and T in this equation (calculated concentration) and the concentration used in the experiment (experimental concentration).
0 is shown. It can be seen that a highly accurate relational expression is also obtained in this example.

[0064]

[Table 10] Experimental concentration (20 ° C test) (35 ° C test) (50 ° C test) (wt%) DRs calculated concentration DRs calculated concentration DRs calculated concentration 0.0 -0.02473 -0.02 -0.02142 -0.01 -0.01905 -0.02 1.0 -0.01423 1.00 -0.01235 1.00 -0.01100 1.00 2.0 -0.00387 2.01 -0.03393 2.00 -0.00301 2.00 2.38 0.00000 2.38 0.00000 2.38 0.00000 2.38 3.0 0.00650 3.01 0.00560 3.00 0.00496 3.00 4.0 0.01664 3.98 0.01450 3.99 0.01290 4.00 5.0 0.02686 4.96 0.02337 4.97 0.02084 4.99

[0065]

In the solution concentration measuring method and apparatus according to the present invention, the propagation time is measured without using the ultrasonic velocity, so that the influence of the change of the ultrasonic propagation distance and the measurement error thereof can be eliminated. And very accurate concentration can be obtained. Also, when the detectors for standard solution and measured solution are separately installed, the ultrasonic circuit and the subsequent circuits can be shared by a switch, so that drift and steady-state error in the electronic circuit can be shared and highly accurate concentration measurement can be performed. Is done. Thus, the present invention provides highly accurate concentration measurements comparable to conventional titration analyzers. Furthermore, the solution concentration measuring device according to the present invention is constituted by a commercially available general electronic circuit or the like, and is extremely advantageously used in an automatic control device or the like, and the industrial significance of the present invention is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a device configuration of a concentration measuring device when a solution to be measured and a standard solution are commonly used in one ultrasonic detector according to the present invention.

FIG. 2 is a diagram showing a device configuration of a concentration measuring device in the case of two detectors for a liquid to be measured and a detector for a standard liquid according to the present invention.

FIG. 3 shows the ultrasonic wave propagation velocity from the data in Example 1,
Propagation time difference (DTa = t _s -t _N ) and corrected propagation time difference (
DTb = t _s - a (1 / K) * t _N] and the drawings showing the relationship between the alkali concentration.

FIG. 4 is a propagation time ratio (Ra = t _N / t _s ) and a normalized correction propagation time ratio [DRs = 1- (1 / K) * (t _N / t _s )] and the alkali concentration.

FIG. 5: Corrected propagation time difference [DTb = (t _s
-(1 / K) * t _N )], corrected propagation time ratio [Rc = (1 / K) * (t _N
/ t _s )] and the normalized corrected propagation time ratio (DRs = 1.0 −R
It is a drawing which shows the relationship between c) and alkali concentration.

Claims (13)

[Claims] 1. A solution ultrasonic wave propagation time detector measures ultrasonic wave propagation times of a plurality of solutions having a known concentration and a reference solution to prepare a relational expression, and the relational expression is used without using the ultrasonic wave propagation velocity. Solution concentration measuring method characterized in that the concentration of the liquid to be measured is obtained from the formula 2. The solution according to claim 1, wherein ultrasonic wave propagation times and temperatures of a plurality of solutions having a known concentration and a reference solution are measured to create a relational expression, and the concentration of the liquid to be measured is determined from the relational expression. How to measure concentration. 3. The solution concentration measurement according to claim 2, wherein temperature compensation is performed on ultrasonic wave propagation time information of a solution having a known concentration and a reference solution, and the time ratio of the information or the corrected time ratio is used in a relational expression. Method. 4. The method for measuring a solution concentration according to claim 2, wherein temperature compensation is performed on ultrasonic wave propagation time information of a solution having a known concentration and a reference solution, and the time difference of the information or the corrected time difference is used in a relational expression. 5. The ultrasonic wave propagation time of a plurality of solutions having known concentrations and a reference solution is measured by one detector, and the concentration of the solution to be measured is determined by the relational expression. The method for measuring the solution concentration according to. 6. An ultrasonic wave propagation time of a plurality of solutions having known concentrations is measured by a detector for a liquid to be measured, using a plurality of detectors.
The method for measuring the solution concentration according to any one of claims 1 to 4, wherein the ultrasonic wave propagation time of the reference solution is measured by a reference solution detector, and the concentration of the solution to be measured is determined by the relational expression. 7. The method for measuring a solution concentration according to claim 6, wherein a common ultrasonic circuit is used for a plurality of detectors. 8. The method according to claim 1, wherein a solution having a known concentration is passed through a detector at a specific time or a specific command to measure an ultrasonic wave propagation time, and the relational expression is corrected. Solution concentration measurement method. 9. A detector having an ultrasonic wave emitting element for emitting an ultrasonic wave and an ultrasonic wave receiving element, a temperature measuring device for the substance in the detector, an ultrasonic wave propagation time measuring circuit, a plurality of solutions of known concentration and a reference. The ultrasonic wave propagation time of the liquid is measured to create a relational expression, and the concentration of the liquid to be measured is calculated from the ultrasonic wave propagation time of the reference liquid and the ultrasonic wave propagation time of the liquid to be measured without using the ultrasonic wave propagation velocity. An apparatus for measuring a solution concentration, which comprises means. 10. A detector for liquid to be measured and a detector for reference liquid having an ultrasonic wave emitting element for emitting an ultrasonic wave and an ultrasonic wave receiving element, a temperature measuring device for each detector, and a common detector for each detector. Ultrasonic wave propagation time measurement circuit, measuring the ultrasonic wave propagation time of multiple solutions of known concentration and reference solution, and creating a relational expression, from the ultrasonic wave propagation time of the reference solution and the measured solution. A solution concentration measuring device comprising means for calculating the concentration of a liquid to be measured without using ultrasonic wave propagation velocity. 11. The method according to claim 9, further comprising means for filling a detector for measuring the liquid to be measured with a solution having a known concentration at a specific time, measuring the ultrasonic wave propagation time and temperature, and correcting the relational expression. 10. The solution concentration measuring device according to 10. 12. An ultrasonic wave propagation time of the reference liquid is measured to create a relational expression, and from the difference or ratio between the ultrasonic wave propagation time obtained from the temperature information of the reference liquid and the time obtained by measurement,
The solution concentration measuring device according to any one of claims 9 to 11, further comprising means for monitoring a deviation of the solution concentration measuring device. 13. An ultrasonic wave propagation time of a solution having a known concentration is measured to create a relational expression, and the deviation of the solution concentration measuring device is monitored from the time course of ultrasonic wave propagation time information and temperature information of the solution. The solution concentration measuring apparatus according to claim 11, further comprising: