JP3182539B2 - Liquid weighing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid measuring method for measuring a fixed amount of liquid using a liquid level detecting means utilizing electric resistance, light and the like.

[0002]

2. Description of the Related Art Generally, in order to absorb various components in a gas into an absorbing solution for measurement, it is necessary to accurately measure a predetermined amount of the absorbing solution for absorbing a sample gas. In order to measure the absorbing liquid, the measuring container is provided with a function of measuring the amount of the liquid, and the measuring container itself measures the amount.

Conventionally, there has been a gas concentration measuring apparatus having a measuring container having a function of measuring a liquid as shown in FIG. To weigh the absorption liquid in the gas concentration measuring device shown in this figure, first, the level electrode 32 provided vertically movably to the impinger 31, the volume V _a of the bottom tip of the level electrode 32 is to weigh Adjust so that the liquid volume is attained. Then, the pump 33 is operated and the electromagnetic valve 34 is opened to introduce the absorbing liquid 35 from the storage tank 36 into the impinger 31. When the absorption liquid 35 introduced into the impinger 31 gradually rises and the liquid level reaches the level electrode 32, the resistance between the level electrode 32 and the conductivity and level measurement counter electrode 37 changes. The control unit 38 detects the change in the resistance, and the control unit 38 that has detected the change in the resistance stops the solenoid valve 34. Therefore, since the absorbing liquid 35 stops in a state where the liquid level coincides with the tip surface of the level electrode 32, the impinging liquid 31 is filled with the desired amount of the absorbing liquid 35,
The liquid measurement is completed.

Then, a sample gas is introduced into the impinger 31 through the introduction pipe 41 by sucking from the exhaust pipe 40, and the conductivity and level measurement counter electrode 37 and the conductivity measurement electrode 42 are used to measure the conductivity. The change is detected, and the control unit 38
Calculates the concentration of the specific component in the sample gas.

[0005]

However, in the above-mentioned conventional liquid measuring method, the preparation work for measuring is extremely complicated and inefficient.

That is, since the lower end of the level electrode must be accurately positioned, the level electrode must be raised and lowered many times in order to adjust the lower end of the level electrode to a predetermined position. . In addition, since one level electrode is required to measure one type of liquid volume, when continuously measuring multiple liquid volumes, prepare multiple level electrodes of different lengths corresponding to multiple liquid volumes. I had to. Furthermore, when changing the amount of liquid to be measured,
The lower end of the level electrode had to be reset each time it was changed.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a liquid measuring method capable of accurately measuring a liquid amount with extremely simple work.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and a liquid measuring method according to the present invention comprises introducing a liquid into a container having a liquid level detecting means, and supplying a predetermined amount of the liquid. In the method of measuring the liquid, the time from the start of introduction of the liquid until the liquid level is detected by the liquid level detection means is set as a reference time, and the time when the liquid level is detected by the liquid level detection means is introduced into the container. Determine the correlation of the time until the amount of the liquid reaches the amount to be measured with respect to the reference time, measure the reference time when introducing the liquid to be measured into the container, and from the time when the reference time is reached, When the time obtained from the correlation with reference to the actually measured value has elapsed, the introduction of the liquid to be measured is stopped.

According to the liquid measuring method of the present invention, as a preparation operation to start an actual measuring operation, a time (t _s ) from the start of introduction of the liquid into the container to the detection of the liquid level by the liquid level detecting means,
The time from when the liquid level is detected by the liquid level detection means until the amount of liquid introduced into the container reaches the amount to be measured
Find the correlation with (t _x ). This correlation, for example, according to the mode of the flow rate of introducing the liquid to be measured into the measuring container,
_{t x = αt s, t x} = α (t s -β), t x = αt s 2 + βt s +
Any suitable relational expression such as γ can be used. In these relational expressions, α, β, and γ are predetermined coefficients.

The principle by which the liquid amount can be accurately measured by using the above correlation will be described with reference to FIG. In this figure, reference numeral 21 denotes a container, and reference numeral 22 denotes a liquid level detecting means using electric resistance, light, ultrasonic waves, or the like.If a detection signal is obtained by contact with the liquid surface, it is provided inside the container as shown. However, when a signal can be obtained in a non-contact manner using light or the like, the signal may be provided outside the container. Reference numeral a denotes a liquid level detected by the liquid level detecting means, reference numeral b denotes a liquid level of a liquid amount to be measured, and liquid level a is set at an arbitrary position below the liquid level b. In such a state, the following settings are made. t _s : time until the liquid level is detected by the liquid level detecting means (reference time) t _x : the liquid level reaches the liquid level of the liquid amount to be measured from the liquid level detected by the liquid level detecting means time to V _s: the amount of liquid to the liquid surface to be detected by the liquid level detection unit (constant) V _x: liquid volume tries to weighing v: introduced is the flow rate of the liquid

In FIG. 2, the flow rate V at which the liquid is introduced is
Assuming a constant, the liquid volume V up to the liquid level a _sIs V_s= Vt_s
And the liquid volume V up to the liquid level b_xIs V_x= Vt_x+ V_sso
is there.

At this time, _if the correlation between t _s and t _x is t _x = α _x t _s ... (Α _x is a coefficient), V _x = v · t _x + V _s = v _{· α x · t s + V} s = V s (1 + α x) .................. formula becomes, V _x and alpha _x is uniquely determined. Therefore,
If seeking alpha _x corresponding to V _x of a desired value, by measuring the t _s, it is possible to obtain the t _x from equation, reach the liquid surface a liquid level is detected by the liquid level detecting means T
By introducing the weighing liquid between _x time can be accurately introduce V _x to be weighed into the container.

The coefficient α _x varies depending on the position of the liquid level a, but can be obtained as follows.

First, in the equation, α _{x is set} to an appropriate initial value α ₀ ,
Liquid volume the balance when performing metering in this condition, is measured in a graduated cylinder or the like, when the liquid amount to V _0, the relational expression to V ₀ and alpha _{0 is, V 0 = V s (1} + α 0) ……………… Expression Therefore, V _s is eliminated from the equation and α _x
In summary, α _x = (1 + α ₀ ) V _x / V ₀ -1...

In the formula, α ₀ is an arbitrarily set value, and V ₀ is an actual measured value. Therefore, _if a desired liquid amount to be measured is given to V _x , the desired liquid amount is obtained. Α _x can be determined.

As described above, the actual weighing operation is started after the correlation between t _S and t _x has been determined.

First, the liquid to be measured is introduced into the container, and a reference time from the start of the introduction to the detection of the liquid level by the liquid level detecting means is measured.

The liquid to be measured is introduced when the time obtained from the correlation has elapsed with reference to the actually measured time, starting from the time when the liquid level was detected by the liquid level detecting means. Close the valve and stop the introduction. As a result, the liquid to be measured is accurately filled in the container by a desired amount.

The liquid measuring method of the present invention is not affected by the shape of the container and the presence of a member which is immersed in the liquid to be measured, for example, an electrode for measuring conductivity. Therefore, the container used in the present invention can be applied to a dedicated measuring container for measuring a liquid or a measuring container provided with various members inside the container.

In the present invention, when the liquid amount to be measured is changed, α _x is calculated again without changing the position of the liquid level a, and the correlation between the new t _S and t _x is simply obtained. Is good.

Further, when a plurality of liquid amounts are continuously measured, it is only necessary to obtain a plurality of relational expressions without providing a plurality of liquid level detecting means.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the liquid measuring method according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a gas concentration measuring device for performing a liquid measuring method. In FIG.
Is an impinger as a container in which measurement is performed. An opening 2 for an electrode is formed in an upper part, a liquid inlet 3 for filling a liquid is formed in a lower part, and an exhaust pipe 4 is formed in an intermediate part. ing. A level electrode 6 as a liquid level detecting means is fixed to the electrode opening 2 via a fixing member 5, and the tip is set at an arbitrary position. A temperature sensor 7 is provided inside the level electrode 6. The temperature sensor 7 is for measuring the temperature of the liquid. However, the level electrode 6 is immersed in the liquid when the measurement of the liquid is completed.

An electrode 8 for measuring conductivity and a counter electrode 9 for measuring conductivity and level are provided inside the lower portion of the impinger 1, and a gas inlet pipe 10 is provided above these electrodes 8 and 9. Is provided.

Then, the level electrode 6, the temperature sensor 7,
The conductivity measuring electrode 8 and the counter electrode 9 are electrically connected to the control unit 11. The liquid inlet 3 is provided with a solenoid valve 12.
A liquid supply tank 15 filled with an absorption liquid 14 as a liquid to be measured is connected via a pump 13 and the electromagnetic valve 12
Is electrically connected to the control unit 11.

[0026] The control unit 11, wherein t _x = t _{s [(1 + α 0) V x} / V 0 -1 ] .................. expression is registered. This equation is given by α _x
Is deleted and summarized. In the formula, t _x : time required for the liquid level to reach the liquid level of the liquid volume to be measured from the level electrode tip t _s : actual measured value of the time required for the liquid level to reach the level electrode tip V _x : attempt to measure Fluid volume α ₀ : arbitrarily set coefficient V ₀ : Measured liquid volume when the coefficient is α ₀ . Further, the control unit 11 detects a change in the resistance between the level electrode 6 and the counter electrode 9 for conductivity and level measurement, measures the time t _s until the liquid surface reaches the tip of the level electrode, and also measures the time t _x was calculated from the formula, further, it is set to close the solenoid valve 12 from then on after t _x time. Further, the concentration of the predetermined component in the gas is calculated based on the input from the conductivity measuring electrode 8 and the input from the counter electrode 9 and the input from the temperature sensor 7.

A method for measuring the amount of liquid in the above apparatus will be described. Weigh 20 ml of liquid. That is, V _x = 20 ml. Also, suppose that t _s = 3
Let us assume that seconds, t _x = 1 second and V _s = 15 ml. In addition,
T _s = 3 seconds is a value actually obtained by measurement,
t _x = 1 second and V _s = 15 ml are necessary values for the following description, and are unknown values at the time of measurement.

First, α ₀ and V ₀ are determined. First, α
₀ = 1/4 and set, by counting the absorbing liquid 14 from the time when the liquid level reaches the level electrode 6, and stopping the introduction of the absorbing liquid 14 when the elapsed t ₀ = α ₀ · t _s time, in pin The amount of liquid V ₀ filled in the jar 1 is measured with a measuring cylinder. As a result, V ₀
= 75/4 ml (Since V _s = 15 ml, V ₀ = 15 + ／ · 15 = 75/4 from the formula, and the measured value is appropriate).

Then, the above α ₀ = 1/4, V ₀ = 75/4 and V _x = 20 are input to the control unit 11 to specify the equation. Then, expression, t _x = t _s · [(1 + 1/4) 20 / (75/4) -1] .................. formula, and the only t _s is the expression of the variable. Thus, the preparation work for measuring the liquid is completed, and then the actual measurement work is started.

First, the pump 13 is operated and the electromagnetic valve 12 is opened to introduce the absorbent 14 into the impinger 1. When the introduced absorbing liquid 14 gradually rises and the liquid level reaches the level electrode 6, the control unit 11 measures the required time t _s = 3 seconds, and from the measurement result t _s = 3, t _{x in the} formula. And t _x = 3 · [(1 + 1/4) 20/75 / 4-1] = 1
(This value matches the condition set at the beginning.)

The control unit 11 closes the solenoid valve 12 when one second elapses from the time when the liquid level reaches the level electrode 6, and stops the introduction of the absorbing liquid 14. As a result, the impinger 1 is accurately filled with V _x = 20 ml, which is the amount of liquid to be measured.

After the absorption liquid 14 is measured as described above, the concentration of a predetermined component of the sample gas is measured as in the conventional case.

Next, FIG. 4 shows the test results of the liquid measuring method of the present invention. The liquid was weighed by the method described above, and the average value of the five weighing results was shown as デ ー タ in the figure as one data. From this result, it was confirmed that the measurement was accurate with a small error.

[0034]

According to the present invention, the position of the liquid level detecting means does not need to be adjusted, the measurement and the calculation based on the result need only be performed once, and when the liquid amount to be measured is changed,
It is not necessary to change the setting of the liquid level detecting means every time the liquid amount is changed, and only the measurement and the calculation based on the result need to be performed once at first, so that the liquid can be measured very easily. Furthermore, when continuously measuring multiple liquid volumes,
It is not necessary to prepare a plurality of corresponding liquid level detecting means, and only one liquid level detecting means is required, so that the apparatus can be simplified, and as a result, maintenance such as cleaning becomes easy.

In the case where a liquid level detecting means such as a level electrode which can obtain a detection signal by contacting the liquid surface is used, the liquid level detecting means is immersed in the liquid to be measured when the measurement is completed. As a result, the temperature sensor can be integrated with the liquid level detecting means, and the measuring container can be made simple.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a gas concentration measuring device for performing a liquid measuring method according to the present invention.

FIG. 2 is a schematic diagram illustrating the principle of a liquid measuring method according to the present invention.

FIG. 3 is a schematic diagram of a gas concentration measuring device for performing a conventional liquid measuring method.

FIG. 4 is a graph showing a test result of the liquid measuring method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Impinger (container) 6 Level electrode (liquid level detection means) 7 Temperature sensor 8 Conductivity measurement electrode 9 Conductivity and level measurement counter electrode 11 Control unit 12 Solenoid valve 14 Absorbing liquid (liquid to be measured)

Claims (1)

(57) [Claims] 1. A method for measuring a fixed amount of liquid by introducing a liquid into a container having a liquid level detecting means, wherein a time from the start of introduction of the liquid until the liquid level is detected by the liquid level detecting means is set as a reference time. From the time when the liquid level is detected by the liquid level detecting means, the correlation between the time until the amount of the liquid introduced into the container reaches the amount to be measured is determined with respect to the reference time, and the liquid to be measured is stored in the container. A liquid measuring method for measuring the reference time when introduced into the liquid measuring method and stopping the introduction of the liquid to be measured when the time obtained from the correlation with reference to the actually measured value has elapsed since the reference time was reached.