JP2000298052A - Storage device and storage level detection method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a storage device and a storage level detection method capable of detecting a storage level simply by filling a container with a storage object. A detection electrode is formed from a lower electrode and an upper electrode, and when a storage object is put into a container, a change in a measured value of an electrical characteristic when the lower electrode is buried in the storage object is determined, and the measurement is performed. By comparing the change in the value with the measured value of the electrical property of the storage material obtained from the upper electrode, the storage level of the storage material placed in the container is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage device for measuring a storage level of a liquid substance or a powdery substance stored in a container and a method of detecting the storage level.

[0002]

2. Description of the Related Art As a method of detecting the amount of stored material stored in a container, that is, a storage level, there are a contact method in which a detection unit such as an electrode is brought into contact with a stored material and a non-contact method in which measurement is performed without contact. There is. FIG. 11 is a schematic diagram of a storage device for detecting a storage level by a contact method. In such a storage device, a liquid 19 is stored in a container 1 made of a grounded metal. An electrode 20 is inserted into the liquid 19 in a substantially vertical direction as a detection unit. The electrode 20 is connected to a detection circuit 21, and the detection circuit
Electrical characteristics such as electric resistance, capacitance, and impedance between the electrode 20 and the container 1 are detected. Then, based on the detected change in the electrical characteristics, the storage level of the storage object is detected, and control is performed so that the storage object does not overflow from the container 1.

[0003]

In the storage device, it is necessary to detect the storage level by bringing the electrode 20 into contact with the storage object and prevent the storage object from overflowing from the container 1. Therefore, it is necessary to calibrate the relationship between the measured value detected by the electrode 20 and the storage level in advance for each stored object because the physical property value detected by the electrode 20 differs. Specifically, in FIG. 11, when storing the liquid 19 in the container 1, before actually storing the liquid 19, the electrical characteristics between the electrode 20 and the container 1 are measured with the container 1 being empty. Then, the measured values are stored (hereinafter, referred to as “zero setting”), and the electrical characteristics are measured while the container 1 is filled with the liquid 19 up to the maximum level.
The measured value is stored (hereinafter referred to as “span setting”),
It is essential to calibrate based on such set values,
In addition, since the set value changes when the type of the liquid 19 is different, it is necessary to repeat the calibration each time. Also,
When the composition of the stored material changed over time, the level could not be measured. Furthermore, since contamination of the electrode surface, which causes an error in level measurement, cannot be electrically detected, an error may occur in level measurement. Therefore, the present invention allows the container to be filled with storage in advance, without calibrating the relationship between the measured value and the storage level, the storage level can be detected only by filling the container with storage, and furthermore, different types are used. It is an object of the present invention to provide a storage device and a storage level detection method capable of accurately detecting a storage level even when a storage object is replaced.

[0004]

Therefore, as a result of earnest research, the inventor has formed a detection electrode from a lower electrode and an upper electrode,
When the storage is filled in the container, the change in the measured value of the electrical property when the lower electrode is buried in the storage is determined, and the change in the measured value and the electrical property of the storage obtained from the upper electrode are determined. By comparing the measured value with the measured value, it was found that the storage level of the storage material filled in the container could be detected, and the present invention was completed.

That is, the present invention relates to a storage device for detecting a storage level of a stored product in a container, comprising: a conductive container for storing the stored product; A detection electrode, which is connected to the detection electrode, measuring means for measuring the electrical characteristics of the storage, and processing means for processing the measured value obtained by the measuring means, the detection electrode, At least a lower electrode and an upper electrode that are electrically separated from each other, and when a storage object is loaded into the container, a change in a measured value of an electrical property when the lower electrode is buried in the storage object is measured. It is measured by the measuring means, and the change of the measured value is compared with the measured value of the electrical property of the storage material obtained from the upper electrode by the processing means, and the charged substance is put into the container and comes into contact with the upper electrode Storage device characterized by detecting the storage level of a stored item It is. By using such a storage device, it is possible to detect the storage level while actually putting in the storage item without filling the storage container in advance and measuring the capacitance as in the conventional method. In addition, since such storage level detection is performed every time a storage object is discharged and charged, it is possible to accurately detect the storage level even when the type of storage object changes. In addition, the detection electrode can be composed of three or more electrodes.

[0006] The measuring means may measure an electrostatic capacitance between the container and the detection electrode.

[0007] The measuring means may measure an electric resistance between the container and the detection electrode.

In the present invention, the measuring means may further include a detecting means for measuring an electrical characteristic of the lower electrode buried in the storage material and detecting a change with time in the physical property value of the storage material. Since the entire lower electrode is buried in the storage, by monitoring the electrical characteristics of the storage with the lower electrode,
It is possible to detect a temporal change in the physical property value of the stored material, and it is also possible to detect the occurrence of contamination of the electrode and the like in addition to the detection of the change in the concentration of the stored material.

It is preferable that the detection electrode has a plurality of guard electrodes provided between the electrodes constituting the detection electrode, above and below, and connected to a guard potential. With such a structure, when the electrical characteristics are measured using the lower electrode or the upper electrode, an unnecessary measurement value can be obtained without generating unnecessary stray capacitance.

Further, the present invention may further comprise switching means for selecting one of the electrodes constituting the detection electrode, connecting the selected electrode to the measuring means, and connecting the remaining electrodes to the guard potential. As described above, by setting the other electrode not used for the measurement to the guard potential, a stray capacitance generated in such an electrode can be eliminated, and accurate measurement can be performed.

Further, it is preferable that a display means for displaying a result detected by the detection electrode is provided. This is for visually confirming a change in the storage material level and the physical property value of the storage material.

The present invention also relates to a storage level detecting method for detecting a storage level of a stored product in a container, comprising: a conductive container for storing the stored product;
Prepare a detection electrode including a lower electrode and an upper electrode of substantially the same shape that comes into contact with the storage object, and measure the electrical characteristics using the lower electrode and the upper electrode without storing the storage object in the container. Then, the values are stored as zero-point set values C _LZ and C _HZ , a storage object is charged into the container, and the measured value of the lower electrode at the time when the measured value of the upper electrode starts to change is set as a span set value C. _It is stored as _LS , and the electrical property of the storage object in contact with the upper electrode is measured using the upper electrode to obtain a measured value C _{H, which} is obtained from the zero point set value C _LZ and the span set value C _LS. Comparing the rate of change with the amount of change between the zero point set value C _HZ and the measured value C _H to determine the storage level of the storage object in contact with the upper electrode. Is a detection method. By using such a detection method, it is possible to detect the storage level while actually putting in the storage item without filling the storage container in advance and measuring the capacitance as in the conventional method. In addition, when the storage is replaced with another type of storage, the above-described method is repeated to update the zero point set value and the like, and it is possible to accurately detect the storage level and the like of the replaced storage. Become.

Furthermore, the span setting the measurement value when the above-mentioned upper electrode with measuring the electrical characteristic of the reservoir in contact with the upper electrode, measured value is equal to the span setting value C _LS The value may be stored as the value C _HS , and the span set value C _HS may be used as the upper limit of the storage level of the storage material. By determining the upper limit of the storage level in this way, it is possible to prevent the stored product from overflowing from the container.

The present invention further relates to a method of measuring the electrical characteristics of a storage object using the lower electrode in a state where the lower electrode is buried in the storage object, and detecting the physical property value of the storage object. . Accordingly, it is possible to detect a change in the concentration of the stored material and the like, and it is also possible to detect occurrence of contamination and the like of the electrode.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 will be described with reference to FIG. FIG. 1 shows a system configuration of a level sensor with an automatic level correction function according to the present invention. In FIG. 1, reference numeral 1 denotes a conductive container for storing a storage object, which is grounded to a ground potential. A detection electrode is provided in the container 1 in a substantially vertical direction. The detection electrode includes a lower electrode 2 and an upper electrode 3 which are electrically separated from each other. 4 is an upper electrode 2 and a lower electrode 3
This is a detection electrode switching means for switching an electrode used for measurement between the detection electrodes consisting of: Reference numeral 5 denotes capacitance measuring means for measuring the capacitance between the detection electrode and the container 1. The measuring means is provided with a guard output (see reference numeral 14 in FIG. 3) for eliminating the generation of stray capacitance. Reference numeral 6 denotes control means for selecting a detection electrode, storing a measurement result, and calculating a storage level based on the measurement result. Reference numeral 7 denotes level display means for displaying the storage level calculated by the control means 6, and the like.

FIG. 2 shows a circuit configuration used for capacitance measurement according to the first embodiment, and shows the principle of a method of outputting a guard output and a method of eliminating stray capacitance. Here, the entire circuit is a lumped constant with respect to the impedance Zx (Zx is a complex impedance, which is omitted in the specification and the dot is attached to Zx in the specification, the same applies hereinafter) of the storage object 19 as the element to be measured. A sine wave AC voltage having a wavelength within a range that can be handled as a circuit is applied. The voltage measuring means indicated by reference numeral 9 measures the voltage V, and the current measuring means indicated by reference numeral 10 measures the current I. From the measurement results, the equation: Zx = V
/ I is used to determine the impedance Zx. Here, since the imaginary component of the impedance Zx is considered to substantially correspond to the capacitance C, the capacitance can be calculated based on the measurement result of the impedance Zx. Further, in the circuit of FIG. 2, the voltage at the position indicated by the reference numeral 11 is output as a guard output around the measured element Zx. By applying the guard output in this manner, the AC voltage source indicated by reference numeral 8 is an ideal AC voltage source having an output impedance of zero, and the current measuring means indicated by reference numeral 10 is an ideal AC voltage source having an impedance of zero. In the case of the current measuring means, the measured applied voltage indicated by the reference numeral 12 and the guard output indicated by the reference numeral 11 have the same potential, there is no leakage current, and no stray capacitance is added to the measurement result. In an actual measurement, it is considered that such a state close to the ideal state is obtained by using the guard output, the stray capacitance is not added to the measurement result, and almost accurate capacitance is measured. The frequency of the sine wave AC voltage used for the measurement is determined from the phase resolution of these capacitance measuring means, the size of the electrodes, the system cost, and the like, and 10 kHz to 1 MHz is practically used.

FIG. 3 is a side view of the detection electrode used in FIG. The detection electrode includes a lower electrode 2 and an upper electrode 3 which are electrically separated from each other. A guard potential is provided below the lower electrode 2, between the lower electrode 2 and the upper electrode 3, and above the upper electrode 3. And a guard electrode 14 connected to the gate electrode. The lower electrode 2 and the upper electrode 3 are connected to the switching means 4 by conducting wires, and the guard electrode 14 is also connected to the guard output by conducting wires. In addition, it is also possible to make only the length of the upper electrode 3 longer than the lower electrode 2. Even in such a case, the storage level of the storage object in contact with the upper electrode 3 can be detected based on the measurement value using the lower electrode 2.

FIG. 4 shows the electrode switching means 4 used in FIG.
FIG. 3 is a diagram showing details of the first embodiment, and includes an electrode switching circuit 15, a capacitance measurement circuit 16 connected thereto, and a control circuit 17. Reference numeral 18 denotes a signal switching device such as a relay or an analog switch. The periphery of the electrode switching circuit 15 is guarded by a guard output. In the electrode switching circuit, when either the lower electrode 2 or the upper electrode 3 is selected by the control circuit 17, the other electrode is connected to the guard output, and the stray capacitance of the other electrode becomes the measured value. They are not added.

Next, a method of detecting a storage level using the storage device according to the present invention will be described with reference to FIGS. FIG. 5 is a cross-sectional view of the empty state storage device before storage is put. In the container 1, the above-described detection electrodes (see FIG. 3) are arranged in a substantially vertical direction. The upper ends of the electrodes are respectively connected to the terminals on the right end in FIG. 4 and are connected to the capacitance measuring circuit. The container 1 is made of a conductive metal and is grounded to the ground potential. Further, the guard electrodes 14 are respectively connected to the guard outputs of FIG. Lower electrode 2
And the upper electrode 3 have substantially the same shape.

In the detection method according to the present embodiment, as shown in the flowchart of FIG. 9, the electrodes are scanned by the electrode selection output in the control circuit of FIG. , Lower electrode 2 and container 1
And the capacitance between the upper electrode 3 and the container 1 are measured. The shapes of the lower electrode 2 and the upper electrode 3 are substantially the same, and the lower electrode 2 is measured in such an empty state.
The electrostatic capacitance C _LZ, the capacitance C _HZ of the upper electrode 3 becomes equal (Step 91). Subsequently, as shown in step 92, the capacitance C _HZ and the capacitance C _LZ are stored as zero point values in a control circuit connected to the capacitance measurement circuit (zero point setting).

Subsequently, as shown in FIG. 6, the storage 19 is loaded, and the control circuit scans the electrodes.
Here, the storage 19 is a liquid, but may be a powder, a granular material, a pellet, or the like other than the liquid. When the storage level of the storage object 19 comes into contact with the lower end of the lower electrode 2 by charging the storage object 19, the value of the capacitance gradually increases, and this is proportional to the input amount of the storage object 19. However, at this time, since data for level conversion cannot be obtained, the storage level cannot be detected and displayed.

Subsequently, as shown in FIG. 7, when the storage level of the storage item 19 increases and reaches the lower end of the upper electrode 3, the value of the capacitance measured at the upper electrode 3 starts to increase. By detecting such an increase in the capacitance of the upper electrode 3 as shown in step 93 of FIG. 9, it is determined that all of the lower electrodes 2 have come into contact with the storage material 19 and at this time, as shown in step 94. The capacitance C _LS measured by the lower electrode 2 is stored (span setting 1).

Subsequently, the storage 19 is further loaded, and as shown in step 95, a point in time when the capacitance measured at the lower electrode 2 and the capacitance measured at the upper electrode 3 become the same is detected. I do. As described above, since the shape of the lower electrode 2 and the shape of the upper electrode 3 are substantially the same, this point in time, that is, FIG.
As shown in (2), it is detected that the upper end of the storage reaches the upper end of the upper electrode 2. Therefore, the upper electrode 3
If the upper end of the container is previously set to a position that is the upper end of the storage level, unlike the conventional method, the storage object 19 is not filled up to the upper limit of the container in advance and the capacitance is not measured at that time. It is possible to detect the upper limit of the storage level while charging the storage 19, and to stop charging the storage 19.

Finally, as shown in step 96, when the capacitances measured at the lower electrode 2 and the upper electrode 3 become equal, the capacitance C _HS of the upper electrode is stored (span setting 2). .

Through the above steps, the initial setting is completed, and as shown in step 97, the level conversion is started. That is, the capacitance detected by the lower electrode 2 and the upper electrode 3 and
Since the storage level of the storage item 19 is proportional, the storage level of the storage item 19 can be detected by comparing the measured value with the value of the zero point setting and the values of the span settings 1 and 2.

Steps 98 to 102 are flow charts showing a series of operations for level measurement after completion of the initial setting.

First, as shown in step 98, when the capacitances measured at the upper and lower electrodes are different, the storage level is lower than the upper limit. Is displayed.

On the other hand, if the capacitances measured at the upper and lower electrodes are the same, it is determined whether the measured value is lower (smaller) than the initial set values C _Hs and C _Ls (step 99). Then, if it is determined to be lower, it is determined whether it is lower than the zero point set values C _HZ and C _LZ (step 10).
0). Further, when it is determined that the temperature is low, it is considered that the container 1 is empty, and neither the lower electrode 2 nor the upper electrode 3 is in contact with the storage 19, so that the zero point setting value is corrected to correct the zero point setting value. Update the values C _HZ and C _LZ .

In step 99, the measured value is the span value C.
If the measured values are not lower than _Hs and C _Ls , and if the measured values are not lower than the default zero point set values C _HZ and C _LZ in step 100, the span values C _Hs and C are changed because the concentration of the stock 19 has changed. _Since it is considered that _Ls has changed, in step 101, the span set values C _Hs and C _Ls of both the upper and lower electrodes are updated. This makes it possible to detect the storage level accurately even when the concentration or the like of the storage material 19 changes during storage.

As described above, by using the storage device according to the present embodiment, unlike the conventional method, the storage device is actually filled without previously filling the storage container with the container and measuring the capacitance. The storage level can be detected while supplying the water. Further, even when the capacitance changes due to a change in the concentration of the stored material, fine adjustment of the set value is automatically performed in response to the change, so that the level measurement can be performed without causing a measurement error. .

When the storage level is maintained at or above the upper end of the lower electrode 2, the capacitance measured at the lower electrode 2 is monitored to measure abnormal measurement conditions, electrode contamination, and the like. Can also be detected.

Further, for example, when the storage 19 is discharged from the lower part of the container 1, when the capacitance of the lower electrode 2 begins to decrease before the capacitance of the upper electrode 3 decreases by a certain value or more. Can be recognized as having a deposit on the electrode.

Embodiment 2 FIG. In the present embodiment, a level detection device that measures impedance and also serves as a device for detecting a change in the physical properties of the storage object 19 will be described.
That is, in the first embodiment, the level of the storage object 19 is detected by measuring the capacitance. In the present embodiment, the electric resistance is simultaneously measured in addition to this. In other words, by separately measuring the real component (electric resistance) and the imaginary component (capacitance) of the impedance, it is possible to grasp the change in the physical properties of the measured object.

For example, it is possible to measure the level of a tank for temporarily storing waste liquid generated by a wet etching apparatus or the like in the course of semiconductor manufacturing, and at the same time, control the degree of contamination of the tank. In the case of the conventional method, FIG.
As shown in FIG. 1, since the electrode 20 is one and is not separated into two as in the present embodiment, the impedance changes each time the storage level changes, and it is impossible to detect only the degree of contamination. It was possible. On the other hand, in the present embodiment, since the lower electrode 2 can be in a state of being immersed in the storage solution 19 regardless of a change in the storage level, the electric resistance value is measured using the lower electrode 2. As a result, a change in the physical properties of the storage solution 19 can be detected.

Further, by using the storage device according to the present embodiment, it is possible to control the water content of the storage 19.
For example, the alternative CFC detergent is a mixture of a detergent having a relative dielectric constant of about 2 and water having a relative dielectric constant of about 80.
By measuring the capacitance using the lower electrode 2, it is possible to detect a change with time of the moisture contained in the cleaning agent. Further, by measuring the electric resistance value, the degree of contamination of the solution can be measured. In addition, it goes without saying that the automatic adjustment function of the storage level described in the first embodiment can be used in addition to the detection of the change in the physical property of the storage object 19 in the second embodiment.

Embodiment 3 In the first embodiment, as shown in FIG. 3, the storage level is measured by using two separate electrodes, the lower electrode 2 and the upper electrode 3, as the detection electrodes. It is also possible to measure electrical characteristics using each electrode as a separate electrode.

As an application example using such an electrode, for example, detection of an interface of a liquid such as water and oil which is separated when left unmixed and detection of a layer can be considered. In this case, it is possible to simultaneously grasp the emulsion state, the emulsified state, and the like immediately after the supply of the storage liquid 19 or when the storage liquid 19 is mixed. Further, when a plurality of separated electrodes are used, even if an abnormality occurs in a part other than the uppermost electrode, if the uppermost electrode is operating normally, the upper limit of the storage 19 can be detected, and The thing 19 can be prevented from overflowing from the container 1.

[0038]

As is clear from the above description, by using the storage device according to the present invention, the container is filled with the storage material in advance and the capacitance, electric resistance,
Alternatively, the storage level can be detected without actually measuring the impedance while the storage object is being charged.

Further, by monitoring the electrical characteristics measured by the lower electrode, it is possible to detect a change in the characteristics of the stored material, contamination of the electrodes, and the like.

Further, even when the storage object is exchanged for another type of storage object, the set value is updated, so that the storage level of the storage object can be accurately detected.

Further, by forming the detection electrode from three or more separated electrodes, the state of the mixed solution such as the emulsion state can be detected.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a level sensor with an automatic level correction function according to an embodiment;

FIG. 2 is a circuit configuration of a capacitance measuring circuit according to the present embodiment.

FIG. 3 is a side view of the detection electrode according to the embodiment.

FIG. 4 is a circuit configuration of an electrode switching unit according to the present embodiment.

FIG. 5 is a process diagram of storage level detection according to the present embodiment.

FIG. 6 is a process chart of storage level detection according to the present embodiment.

FIG. 7 is a process diagram of storage level detection according to the present embodiment.

FIG. 8 is a process diagram of storage level detection according to the present embodiment.

FIG. 9 is a flowchart of an initial setting according to the embodiment.

FIG. 10 is a flowchart of level measurement according to the present embodiment.

FIG. 11 is a sectional view of a storage device according to a conventional method.

[Explanation of symbols]

1 storage container, 2 lower electrode, 3 upper electrode, 4 electrostatic electrode switching means, 5 capacitance measuring means, 6 control means,
7 display means, 8 AC voltage source, 9 voltage measurement means, 1
0 current measuring means, 11 guard output, 12 applied voltage, 14 guard electrode, 15 electrode switching means, 16
Capacitance measurement circuit, 17 control circuit, 18 signal switching device, 19 storage, 20 electrodes, 21 detection circuit.

Claims (10)

[Claims] 1. A storage device for detecting a storage level of a storage item in a container, comprising: a conductive container for storing the storage item; and a detection device disposed substantially vertically in the container and brought into contact with the storage item. An electrode, a measuring means connected to the detecting electrode, for measuring an electrical property of the storage object, and a processing means for processing a measurement value obtained by the measuring means, wherein the detecting electrodes are electrically connected to each other. A measuring device that includes at least a separated lower electrode and an upper electrode and measures a change in a measured value of an electrical property when the lower electrode is buried in the storage when the storage is inserted into the container; Then, the change in the measured value is compared with the measured value of the electric property of the storage material obtained from the upper electrode by the processing means, and the storage of the storage material that is put into the container and comes into contact with the upper electrode is stored. A storage device for detecting a level. 2. The storage device according to claim 1, wherein the measuring means measures a capacitance between the container and the detection electrode. 3. The storage device according to claim 1, wherein the measuring means measures an electric resistance between the container and the detection electrode. 4. The apparatus according to claim 1, wherein said measuring means includes a detecting means for measuring an electrical characteristic of said lower electrode buried in the storage material and detecting a change with time in the physical property value of the storage material. The storage device according to claim 1. 5. The detection electrode according to claim 1, wherein the detection electrode includes a plurality of guard electrodes provided at an upper portion and a lower portion between the respective electrodes constituting the detection electrode and connected to a guard potential. Storage device. 6. The apparatus according to claim 1, further comprising switching means for selecting one of the electrodes constituting the detection electrode, connecting the selected electrode to a measuring means, and connecting the remaining electrodes to a guard potential.
A storage device according to claim 1. 7. The storage device according to claim 1, further comprising display means for displaying a result detected by said detection electrode. 8. A method for detecting a storage level of a storage item in a container, comprising: a conductive container for storing the storage item; and a substantially container that is placed substantially vertically in the container and contacts the storage item. A detection electrode including a lower electrode and an upper electrode having the same shape is prepared, and electrical characteristics are measured using the lower electrode and the upper electrode in a state where no storage is placed in the container, and the value is set to zero. _Storing the point set values C _LZ and C _HZ , storing the contents in the container, and storing the measured value of the lower electrode at the time when the measured value of the upper electrode starts to change as a span set value C _LS ; Using the upper electrode, the electrical property of the storage object in contact with the upper electrode is measured to obtain a measured value C _H , a rate of change obtained from the zero point set value C _LZ and the span set value C _LS , by comparing the amount of change between the zero point setting value C _HZ and the measured value C _H, top electrode Storage level detection method and obtains the storage level of the reservoir in contact. 9. Further, the electrical characteristics of the reservoir in contact with the upper electrode by using the upper electrode is measured, the measured value when the measured value is equal to the span setting value C _LS detection method according to claim 8 which stores the span setting value C _HS, characterized in that the upper limit of the storage level of the reservoir the span setting value C _HS. 10. The method according to claim 1, wherein the lower electrode is buried in a storage object, wherein the lower electrode is used to measure an electrical property of the storage object and detect a physical property value of the storage object. 10. The detection method according to 8 or 9.