JPH0321065B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an improvement of a densitometer having an automatic calibration function, and more particularly to a densitometer having an abnormality determination function added to prevent automatic calibration to an abnormal value. <Prior art> An example of this type of concentration meter is a PH with automatic calibration function.
The meter is one with an electronic servo mechanism that automates the standard value calibration and sensitivity calibration instead of manual one, or one that calculates two-point coordinates from two calibration fluids and set values and stores a function that passes through them. There is. However, with these PH meters, a necessary and sufficient range for automatic calibration is established by using a volume or setting upper and lower limits for the coefficients of the function, and calibration is disabled when the range is exceeded. As a result, automatic calibration is forced for abnormalities within the range that can be automatically calibrated, such as electrode deterioration, deterioration, and dirt, and as a result, sample measurement accuracy deteriorates without realizing it. This causes such inconvenience. <Effects of the Invention> In view of the above, the present invention aims to eliminate the above-mentioned disadvantages of the conventional device by checking whether or not the calibration is for an abnormal value from the viewpoint of the required measurement accuracy. It is something. <Structure of the Invention> In order to achieve the above object, the densitometer with an abnormality judgment function according to the present invention includes a detector that emits an electric signal according to the concentration of a sample and a calibration substance, and a detection signal of the calibration substance. a calculation section that performs calculations to calculate the concentration based on the detection signal of the sample, a storage section that stores the measured values from the previous calibration, and a comparison section that compares the measured values from the previous and current calibration. and a control setting section that sets control values according to the required measurement accuracy, and at the time of periodic calibration, compares the measured value at the previous calibration with the current measured value, The gist of the system is that if the comparison result exceeds a control value, it is determined to be abnormal. <Example> FIG. 1 shows the basic configuration of the present invention, and 1 is a detector that emits an electric signal according to the concentration of a sample and a calibration substance. In the case of a PH meter, as a detector
A PH measurement electrode and a temperature detector are used. In this case, two calibration solutions are used as calibration substances. 2
is a calculation section that performs automatic calibration using the detection signal a of the calibration substance and calculates the concentration using the detection signal b of the sample. The sample concentration determined by the calculation section 2 is displayed on the display section 3. Reference numeral 4 denotes a storage unit that stores measured values from the previous calibration. 5
is a comparison section that compares the measured values from the previous and current calibration. Reference numeral 6 denotes a management setting section, in which a limit value required from the viewpoint of measurement accuracy is set as the difference between the measured values at the time of the previous calibration and the time of the current calibration. Reference numeral 7 denotes a determination unit that monitors whether the comparison output of the comparison unit 5 is larger than the control value of the management setting unit 6, and if larger, issues a judgment output indicating that there is an abnormality. This judgment output is used to activate an alarm,
Alternatively, it can be used in addition to other controllers to cancel the current automatic calibration. According to this configuration, since abnormality can be determined during calibration, there are advantages such as improved reliability of the meter. In the above configuration, it goes without saying that the calculation section 2, storage section 4, comparison section 5, management setting section 6, and determination section 7 can be replaced by one microcomputer. Next, FIG. 2 shows a measuring instrument configured to measure the pH of an electroplating solution according to a specific example of the present invention, in which 11 is a plating tank, and 12 is an electrode chamber provided separately from the plating tank 11. be. A sample (plating liquid) in the plating tank 11 is introduced into the electrode chamber 12 by the sampling pump 14 when the plating liquid introduction valve 13 is in an open state, and is subjected to measurement. On the other hand, the sample after the measurement is returned to the plating tank 11 through the return pipe 15. 16 is a cleaning liquid tank, 1
7 is a first calibration liquid tank, 18 is a second calibration liquid tank, and the liquid in each tank is supplied by opening the introduction valves 19, 20, 21 provided in the piping of each tank and operating the introduction pump 22. It can be introduced into the electrode chamber 12. Reference numeral 23 denotes a pressure air introduction valve, and when each liquid is introduced into the electrode chamber 12, this valve is also opened for a certain period of time to effect bubbling with the pressure air. 24 is a discharge valve;
25 is a pH measuring electrode provided in the electrode chamber 12, and 26 is a temperature detector. If the PH measuring electrode itself has a built-in temperature sensor, that can be used, and there is no need to provide a separate temperature sensor. 27 is a tank storing Kcl to be introduced into the reference electrode in the PH measurement electrode 25; 28 is a sensor for detecting the temperature of the sample in the plating tank 11; 29 is a temperature signal from this sensor 28 and the PH measurement electrode 2;
5 and the detection signal from the temperature detector 26. Note that if the plating tank 11 is kept at a constant temperature, the temperature sensor 28 is not necessary. In that case, a signal indicating a constant temperature may be generated using a resistor or the like and input to the calculation unit 29. 30 is a program controller that operates the above-mentioned valves and pumps in a fixed order to perform automatic cleaning, introduction of calibration liquid, and sampling operations. Next, the automatic cleaning, introduction of calibration liquid, and sampling operations performed by the program controller 30 and the processing in the calculation section will be described. Automatic cleaning and introduction of calibration liquid () After opening the discharge valve 24 and discharging the liquid in the electrode chamber 12, the introduction valve 19 is opened and the introduction pump 22 is activated. As a result, the cleaning liquid is introduced into the electrode chamber 12 . At the same time, the pressure air introduction valve 23 is also opened to bubble the cleaning liquid within the electrode chamber 12 to enhance the cleaning effect. () When cleaning is completed, open the discharge valve 24,
The cleaning liquid is drained and the inlet valve 20 is then opened, thereby introducing the first calibration liquid into the electrode chamber 12 . In this case as well, the pressure air introduction valve 2
3, and bubble the first calibration solution. After bubbling for a sufficient time to eliminate the influence of the preliquid, the discharge valve 24 is opened and discharged. After the discharge is completed, the introduction valve 20 is opened again and the first calibration liquid is introduced into the electrode chamber 12.
The temperature of the liquid inside the electrode chamber at this time is
_TA and electrode potential _EA are detected, and the detection signals TA _{and EA} are input to the calculation section. () When the detection is finished, open the discharge valve 24, discharge the first calibration liquid, and then open the introduction valve 21.
A second calibration solution is introduced into the electrode chamber 12 . In this case as well, as in the case of the first calibration solution in (), the solution is introduced twice. The first time is to remove the influence of the previous solution, and the second time is to adjust the temperature T _B and electrode potential E _B
This is for the detection of The detection signals T _B and E _A detected by the second introduction are input to the calculation section 29 . Sampling operation When the above operation is completed, the discharge valve 24 is opened and the second calibration liquid is discharged, and then the sampling pump 14 is operated and the liquid introduction valve 13 is opened.
A sample is taken into electrode chamber 12 . At this time, the electrode potential E _X and the liquid temperature in the electrode chamber
T _X is detected and input to the calculation section along with a temperature signal indicating the temperature T _t in the plating tank 11 . Processing in the arithmetic unit When each of the detection signals and the temperature signal _Tt described above is input, the arithmetic unit performs the following processing. () Calculation of PH value of calibration solution Temperature detection values of first and second calibration solutions T _A , T _B
The PH value of the calibration solution is determined based on the following formula: PH=a/T+b+cT+dT ² (1) where T is the absolute temperature of the calibration solution. In the above formula, a, b, c, and d are constants specific to the liquid. As an example, the values of a, b, c, and d for oxalate and phthalate are shown in the following table.

[Table] () Calculation of electrode sensitivity A and inert potential B Calculate electrode sensitivity A based on the following formula. A=E _A −E _B P/a {T _A (PH _A −7) − T _B (PH _B −7)}…
...(2) Also, calculate the inactive potential B based on the following formula. B=E _B・T _A (PH _A −7)−E _A・T _B (PH _B −7)/T _A (PH _A
-7) -T _B (PH _B -7) ...(3) Here, PH _A is the PH value of the first calibration solution, and PH _B is the PH value of the second calibration solution, which are the subordinates of equation (1). It is required. a is the temperature correction coefficient of the glass electrode (1/27
3.15). Automatic calibration is completed by calculating these A and B. () Calculation of PH value inside the electrode chamber The PH value (PH _X ) inside the electrode chamber is calculated by the following formula. PH _X = _{E X} -B/A・_a・_T Calculation of the PH _value of When _PH Can be done. PH _t =PH _X -k(T _{t -T} This k differs depending on the type of plating liquid. The value of k can be determined by analyzing the plating solution. For example, in the case of Zn-Fe plating liquid, k is given by k=0.013-0.07 ^W Fe ³⁺ (6). However, ^W Fe ³⁺ is
Fe ³⁺ concentration (w/v%). If the value of k changes depending on the ion concentration as in equation (6) above, store equation (6) in the calculation section and input the ion concentration each time a measurement is made to calculate k. If you calculate it by hand, even if the k of the liquid changes every moment, the pH will be adjusted accordingly.
It is convenient because t can be determined without error. The PH _t determined as described above is outputted from the calculation section 29 as a transmission output and displayed on a display section not shown. In addition, during the calibration, the first
When switching from the calibration solution to the second calibration solution, the electrode potential changes from E _A to E _B. Measure the time to reach 90% of the total change, or measure the amount of potential change per unit time. By calculating the response speed of the electrode, it is possible to objectively judge the lifespan of the electrode. Next, FIG. 3 shows a circuit for determining abnormality of the measuring instrument using the output signal of the calculation section 29.
1, a comparing section 32, a management setting section 33, and a determining section 34. The storage unit 31 stores the measured values from the previous calibration. The comparison unit 32 compares the measurement value output from the storage unit 31 during the previous calibration with the measurement value output from the calculation unit 29 during the current calibration. Normally, this comparison value should be within a certain small range, but between the previous calibration and the current calibration, for example, there may be damage, dirt, or deterioration in the response membrane of the glass electrode, dirt on the reference electrode, or inner electrode. If an abnormality such as a chemical change occurs, the value will exceed the above range. In the management setting section 33, a maximum allowable value is set as the comparison value. This value is determined from the measurement accuracy required for the instrument. The determining unit 34 checks whether the comparison value exceeds the set value of the management setting unit 33, and if it does, issues an abnormal signal. By detecting abnormal operation in this way, it is possible to manage the accuracy of the instrument during measurements between calibrations, and
This method has the advantage that the calibration period can be made as long as possible within the range of required measurement accuracy, and that expensive calibration solutions can be used effectively. In addition, in the present invention, the difference between the measured values at the time of the previous calibration and the time of the current calibration is determined, and if the difference exceeds the control value, it is determined to be abnormal. Abnormalities can also be determined from the side. The circuit shown in FIG. 4 adopts the latter of these, and is designed not only to judge abnormalities but also to control the length of the calibration cycle depending on the magnitude of the calibration amount. Management accuracy setting section 36
, a second comparing section 37 , and a period determining section 38 . The first comparison unit 35 determines the difference between the measured values of the calibration solution before and after calibration. Here, the measured value of the calibration solution before calibration refers to the measured value of the calibration solution measured before adjusting the inert potential and electrode sensitivity, and the measured value of the calibration solution after calibration refers to the measured value of the calibration solution measured before making adjustments to the inert potential and electrode sensitivity. This refers to the measured value of the calibration solution after performing In the management accuracy setting section 36, a limit value that is allowable in terms of measurement accuracy is set as the difference between the calibration solution measurement values before and after calibration. The second comparison section 37 compares the comparison value with the setting value of the management accuracy setting section 36. The period determining section 38 determines the calibration period from the comparison result of the second comparing section 37. That is, the first comparison section 3
If the comparison value of No. 5 exceeds the setting value of the management accuracy setting unit 36, the calibration period is shortened, and conversely, if the comparison value does not exceed the setting value, the calibration period is lengthened. As a method of lengthening or shortening the calibration cycle, for example, a method of lengthening or shortening the calibration cycle by unit time may be used. The calibration cycle determined by the cycle determining unit 38 is input to the program controller 30, and the length of the calibration cycle set in the controller 30 is controlled. 39 in the figure is the first
The alarm is activated when the comparison value of the first comparison section 35 exceeds the set value of the management accuracy setting section 36. 40
is the second alarm, and the calibration cycle is the minimum cycle setting section 41.
It is activated when the minimum calibration period is shorter than the minimum calibration period set in . 42 is a comparator. <Effects of the Invention> Since the densitometer with an abnormality determination function according to the present invention is configured as described above, it has the following effects. The accuracy of the instrument is kept within a certain range during measurements during periodic automatic calibration, making stable measurements possible. Abnormal calibration operations can be detected immediately, allowing prompt response. The calibration cycle can be extended to the limit of the required control accuracy, making effective use of expensive calibration substances, and reducing running costs.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of the densitometer of the present invention, and Figs. 2 and 3 show the electroplating solution.
Diagram 4 showing an example of applying the present invention to a PH measuring device
The figure shows a circuit that adjusts the calibration cycle. 1, 25...detector, 7, 29...computing section,
4, 31... Storage section, 5, 32... Comparison section, 6,
33... Management setting section.

Claims (1)

[Claims] 1. A detector that emits an electrical signal according to the concentration of the sample and the calibration substance, a calculation unit that performs automatic calibration based on the detection signal of the calibration substance, and calculates the concentration based on the detection signal of the sample, and It has a storage section that stores the measured values at the time of calibration, a comparison section that compares the measured values at the previous and current calibration, and a management setting section that sets the control values according to the required measurement accuracy. , at the time of periodic calibration, the measured value at the previous calibration is compared with the current measured value, and if the comparison result exceeds the control value, it is determined to be abnormal. Concentration meter with abnormality judgment function.