JP3099362B2 - Measurement method of sensor response time of pH meter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pH meter for measuring the pH of a liquid to be measured, and more particularly, to measuring the response time of a pH sensor. PH can be measured automatically by simply putting the first calibration solution into the second calibration solution
The present invention relates to a method for measuring sensor response time of a pH meter and a pH meter.

<Conventional technology> Conventionally, to measure the response time of a pH sensor, for example, a measurement value from a pH sensor to be measured is connected to a recorder or the like through a conversion circuit and the output value is connected in such a state. Immerse the pH sensor in the first calibration solution (for example, pH 4 reference solution)
After confirming (identifying) that the measured pH value of the first calibration solution is stable, the pH measurement start button of the conversion circuit is pressed for measurement, and at the same time, the pH sensor is connected to the second calibration solution (for example, a pH7 reference solution). ). Then, the measurement state until the pH measurement value was stabilized was measured on a chart display, and the response time of the pH sensor at that time was determined.

FIG. 4 is a diagram provided for explanation of a conventional technique. In FIG. 4, the horizontal axis represents time, and the vertical axis represents pH output value.

PH Introduction to the pH sensor immersed in the first calibration solution time t ₀
Presses the pH measurement start button when is at P ₀ , and ideally, at the same time t ₀ , the pH sensor should be moved from the first calibration solution to the second calibration solution. the second calibration liquid the pH sensor time difference tau ₁ of, for example, 5 to 10 seconds until the dipped to always occur after pressing the start button. When the time for immersing the pH sensor in the second calibration liquid and t _1, the time difference between time t ₀ ~t ₁ (the error of the time) pH value between tau ₁ is as shown in FIG. 4 In addition, the stable state (P ₀ ) of the first calibration liquid slightly rises (or falls), and the state is unstable. Then, in the at a time t ₁ after the pH sensor is immersed in the second calibration solution, constant response to pH values (referred to as Pn) in subsequent measurement of the pH sensor is the second calibration solution Calms down with characteristics. Second calibration solution pH value (Pn) and made up to the from the response characteristic of the pH value P ₂ of the example, 90% of the positions of the time
apparent response time of the pH sensor (response time including tau ₁₎
It can be.

In general, the response time of 63% is used in the control system, but the chemical reaction of the measurement solution in the chemical process is relatively fast, and the response of the pH meter used for the control is used as a measure of the response. Is used as a value of 90%. Therefore, in this specification, the response time to be measured is described as, for example, 90%.

<Problem to be Solved by the Invention> Such a conventional technique has the following problems.

(A) in order to transfer the pH sensor after pressing the start button at time t ₀ in a state immersed in a first calibration liquid to the second calibration solution, 90% response time so during this time the time difference tau ₁ has the ( τ ₂ ) Accurate response measurement time cannot be measured because it is included as an error time in measurement.

(A) The operation involved in pressing the start button and transferring the pH sensor to another calibration solution is complicated and difficult to perform alone.

The present invention has been made in view of the above-mentioned problems of the related art, and an object of the present invention is to reduce the measurement error as much as possible and easily measure the sensor response time. It is an object of the present invention to provide a pH meter and a method of measuring a sensor response time of the pH meter.

<Means for Solving the Problems> In order to achieve the above object, the present invention relates to a pH meter that performs calibration using two types of calibration solutions having different pH values. After the indicated value is stabilized, the first memory for storing the time and measured value when a constant value (P ₁ ... ΔpH) is reached when immersed in the second calibration liquid, and the indicated value is determined from this time. And a second memory for storing the time until the value (P ₂ ) and the measured value, and storing one or more times and the measured value between the time and the measured value stored in the first and second memories. A third memory, and a calculating means for calculating a response time until the predetermined value (P ₂ ) is reached based on the time and measured value stored in the first to third memories and the pH value of the second calibration liquid. Is provided.

In the pH meter for performing calibration using two kinds of calibration liquids having different pH values, the present invention is characterized in that, after stabilization of the indicated value in the first calibration liquid, a certain value ( P ₁ ... ΔpH), a first memory for storing the time and the measured value, and a second memory for storing the time and the measured value from this time until the indicated value reaches a predetermined value (P ₂ ). And calculating means for calculating a response time until the predetermined value (P ₂ ) is reached based on the time and measurement value stored in the first and second memories and the pH value of the second calibration liquid. It is characterized by the following.

4. The process according to claim 3, wherein the pH meter is calibrated using two types of calibration solutions having different pH values.

After confirming the stability of the measured value with one of these calibration solutions, a step of replacing the pH sensor with the other calibration solution and updating the measured value.

And a step of storing, in the first memory, a time when the measured value change becomes equal to or more than a fixed value (P ₁ ... ΔpH) from the initial value (P ₀ ) when the measured value is updated.

Successively storing the time and the measured value at one or more points in the three memories sequentially and storing the time and the measured value when the pH measured value reaches a predetermined value (P ₂ ) in the second memory;

Calculating a response time at the predetermined measurement value (P ₂ ) from the data stored in the first to third memories.

It is characterized by including.

5. The method according to claim 4, wherein the calibration is performed using two types of calibration solutions having different pH values.

After confirming the stability of the measured value with one of these calibration solutions, a step of replacing the pH sensor with the other calibration solution and updating the measured value.

A step of storing, in the first memory, the time when the measured value change becomes equal to or more than a predetermined value (P ₁ ... ΔpH) from the initial value (P ₀ ) when updating the measured value.

A step of successively storing the time and measured value when the value reaches a predetermined value (P ₂ ) in the second memory;

Calculating a response time until the predetermined value (P ₂ ) is reached based on the data stored in the first and second memories and the pH value of the second calibration liquid.

It is characterized by including.

<Example> An example will be described with reference to the drawings.

In the following drawings, parts that are the same as in FIG. 4 are given the same reference numerals, and descriptions thereof are omitted.

FIG. 1 is a diagram showing a specific embodiment of the present invention, FIG. 2 is a flowchart showing the operation of FIG. 1, and FIG. 3 is a sensor response time characteristic diagram used for explaining FIGS. 1 and 2. .

In FIG. 1, 1 is a pH sensor to be measured, 2
Is a preamplifier, 3 is an A / D (analog-to-digital converter) which converts a signal from the preamplifier into a digital signal and outputs it.
Is composed of a storage element (RAM 4a ₁ , ROM 4a ₂ ) 4a for storing an input value and a method of operation processing in advance, a microprocessor for performing a predetermined operation while exchanging information with the storage element, and the like. Calculation means (CPU) 4b and external equipment /
PH calculation means consisting of an I / O (input / output interface) 4c for transmitting and receiving signals to and from the circuit, 5 is for manually inputting start signals and inputting data setting values, etc. to the pH calculation means And a driver 6 for driving the display unit 7 based on information from the pH calculating means.

2 and 3 based on such a configuration, when measuring the response time of the pH sensor of the present invention, the measurement of the response time is ideally started and a predetermined value (for example, 90 %) Will be described.

The outline of the measurement is that while performing a series of operations of immersing in the first calibration solution, immersing in the second calibration solution after indicating the stability, the response time excluding the error time as in the related art can be seen. This is done in the following manner.

(I). First, calibration between the pH sensor and the pH calculating means is performed using the first and second calibration liquids (standard solutions). At this time, the first
The measured value when the pH reference value of the calibration solution is K ₁ is P ₀ (first
Here, the calibration solution is referred to as “K ₁ pH solution”, and the measured value when the pH reference value of the second calibration solution is K ₂ is Pn (here, the second calibration solution is “K ₂ pH solution”). ).

(B). Such after completion of the calibration of the pH sensor standard solution with, the after confirming the stability of the instruction at K ₁ pH solution
Replace the pH sensor with K ₂ pH solution and update the measured value.

(C) Replace with .K ₂ pH solution t after time t ₀₀ (P ₀ ) in FIG.
If a pH sensor measurement P ₁ of ₁₀ (When changed to a value more than △ pH from P _0), to verify that became the P ₁ at pH calculating means 4, automatic response time measurement is started (or may be input a start signal using the external input means 5), the measurement data P _1, the time t ₁₀ in this case RAM4
a Memorize in ₁ .

(D). Here, the method of the memory, the method of data processing, there are two cases corresponding to the storage capacity of the RAM 4a _1.

Here, an area for storing a time at which a value becomes equal to or more than a certain value (P ₁ ... ΔpH) from an initial value (P ₀ ) and a measured value is stored in a first memory.
The area for storing the time and the measured value when the pH measured value reaches a predetermined value (P ₂ ) is stored in the second memory, and the time and the area for storing the measured time from P ₁ to P ₂ is stored in the second memory. Think of it as three memories.

<< Case 1 >>: When the storage capacity of the RAM 4a ₁ is abundant, the RAM 4a ₁ stores the elapsed time (t ₁₀ , t ₁₁ ,..., T ₂₀ ,
.. Tn) and the measured value change values (P ₁ ,... P ₂ ,..., Pn) of the pH sensor are stored in the first to third storage areas, and when the measured value change values become stable (K ₂ pH in measurements stable value Pn) of the liquid, the calculating means 4 calculates the time tau ₃ according to the first 90% response from the elapsed time及Pi measured value change which is stored until then.

(E). Next, FIG. 3 calculates the elapsed time (error time) δ for the pH, that is, the calculating means 4 approximates the pH response to a temporarily delayed response, and calculates t from the values of ΔpH and P ₀ and P _{2. 00} to t ₁₀
Calculate the time until. Then, this time is added to τ ₃ to calculate a correction value.

(F). Thus, by calculating δ and adding it to τ ₃ , the response time measurement of the pH sensor can be performed accurately and simply.

<< Case 2 >>: When the memory capacity is limited (for example, there are only two memory capacities), the RAM4a ₁ stores the measurement stable value (Pn: known value) and the measurement start value (initial value) P of the K ₂ pH solution. The measured value of ₁ and the time (t ₁₀ ) are stored in the first memory. Then a predetermined value on the basis of the initial value P ₁ value (P ₂₎ which is (90% in this case) is calculated by the following equation.

P ₂ = (Pn−P ₁ ) × 0.9 + P ₁ And the time t ₂₀ when the measured value P ₂ of 90% obtained by the above equation is passed is stored in the second memory. Next, (t ₂₀ −t ₁₀ ) is calculated, and this time is set as a 90% response time.

In this case, as described above, the time required to reach ΔpH has a time that changes from the initial value P ₀ to a certain value or more, but since this time is very short with respect to the 90% response time, it should be ignored. I do.

Although the embodiment of the present invention has been described focusing on the 90% response time, the sensor response time of the present invention can be arbitrarily set without being limited to 90%.

<Effects of the Invention> Since the present invention has been described above, the response time can be reduced simply by transferring from the first calibration solution to the second calibration solution without considering the error time as in the related art. Measurement becomes possible. That is, in the second aspect, the measurement can be performed simply and accurately, and in the third aspect, the measurement can be easily performed although the accuracy is lower than that of the method of the second aspect.

[Brief description of the drawings]

FIG. 1 is a diagram showing a specific embodiment of the present invention, and FIG.
FIG. 3 is a flow chart showing the operation of the figure, FIG. 3 is a sensor response time characteristic diagram used for explaining FIGS. 1 and 2, and FIG. 4 is a diagram used for explaining a conventional technique. 1 pH sensor 4 pH calculating means 7 Display unit

Claims (4)

(57) [Claims] In a pH meter for performing calibration using two kinds of calibration solutions having different pH values, after the indicated value of the first calibration solution is stabilized,
A first memory for storing a time and a measured value when a constant value (P ₁ ... ΔpH) is reached when immersed in the second calibration liquid, and the indicated value becomes a predetermined value (P ₂ ) from this time. A second memory for storing the time and the measured value up to, a third memory for storing one or more times between the time and the measured value stored in the first and second memories and the measured value, Calculating means for calculating a response time until the predetermined value (P ₂ ) is reached, based on the time and measured value stored in the third memory and the pH value of the second calibration liquid. pH meter. 2. A pH meter for performing calibration using two types of calibration solutions having different pH values, wherein after the indicated value is stabilized by the first calibration solution,
A first memory for storing a time and a measured value when a constant value (P ₁ ... ΔpH) is reached when immersed in the second calibration liquid, and the indicated value becomes a predetermined value (P ₂ ) from this time. And a second memory for storing the measured time and the measured value, and the predetermined value (P ₂ ) based on the measured time, the measured value and the pH value of the second calibration liquid stored in the first and second memories. A pH meter provided with a calculating means for calculating a response time until the pH becomes zero. 3. Using two types of calibration solutions having different pH values.
The process of calibrating the pH meter. After confirming the stability of the measured value with one of these calibration solutions, a step of replacing the pH sensor with the other calibration solution and updating the measured value. And a step of storing, in the first memory, a time when the measured value change becomes equal to or more than a fixed value (P ₁ ... ΔpH) from the initial value (P ₀ ) when the measured value is updated. Successively storing the time and the measured value at one or more points in the three memories sequentially and storing the time and the measured value when the pH measured value reaches a predetermined value (P ₂ ) in the second memory; Calculating a response time at the predetermined measurement value (P ₂ ) from the data stored in the first to third memories. A method for measuring response time of a pH meter sensor, comprising: 4. A step of performing calibration using two kinds of calibration solutions having different pH values. After confirming the stability of the measured value with one of these calibration solutions, a step of replacing the pH sensor with the other calibration solution and updating the measured value. And a step of storing, in the first memory, a time when the measured value change becomes equal to or more than a fixed value (P ₁ ... ΔpH) from the initial value (P ₀ ) when the measured value is updated. A step of successively storing the time and measured value when the value reaches a predetermined value (P ₂ ) in the second memory; Calculating a response time until the predetermined value (P ₂ ) is reached based on the data stored in the first and second memories and the pH value of the second calibration liquid. A method for measuring the response time of a PH meter sensor, comprising: