JPH07128114A - Level measuring method and level measuring instrument - Google Patents

Abstract

PURPOSE:To provide a level meter which can easily, accurately and effectively measure a level. CONSTITUTION:A switching means SW20 which receives an capacitance detection signal from a controller 35 controls switches to detect the capacitance between opposed measuring electrode TE1 and a ground electrode GE10 before storing an object to be detected. The detected initial value (capacitance) between the electrodes is stored in a storage circuit 30, an initial mean value is obtained by averaging initial values, and a difference between the initial value means and initial value is used as a correction value. When a level of the object after the storage is measured, an actually measured value (capacitance) is corrected by the correction value. Since the level is measured by using the capacitance between the opposed measuring and ground electrodes, the level can be effectively measured without influence of other factor, and since the actually measured value is corrected after the initial value is detected, an effectively and accurate level can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a level measuring method and a level measuring instrument, and more particularly to ensuring and accurate measurement.

[0002]

2. Description of the Related Art There are various measuring instruments for measuring the level of liquid stored in a tank, and one of them is a capacitance type level meter. The electrostatic capacitance type level meter is an instrument for measuring the electrostatic capacity to obtain the upper surface level of the liquid in the tank.

FIG. 21A is a schematic diagram showing the electrical connection relationship between the capacitance level meter, the liquid 33 and the tank when the level of the stored liquid is measured. This capacitance type level meter has an electrode group 1 in which a plurality of electrodes 50 are connected in a vertical direction to a liquid 33 stored in a tank 40.
0, a power source 2 connected to the electrode group 10, and a control portion (not shown).

Such a capacitance type level meter has a power source 2
Power is sequentially supplied to the tank 40 and each electrode 50 of the electrode group 10, and the electrostatic capacitance between the tank 40 and the electrode 50 is detected. That is, the electrostatic capacitance between the tank 40 and the electrode 50 that electrically plays the role of a capacitor is detected. Here, when the electrode 50 is immersed in the liquid 33, the liquid 33 comes into contact with the electrode 50, so that the capacitance is high. On the other hand, the electrode 5
When 0 is not immersed in the liquid 33, the liquid 33 does not come into contact with the electrode 50, so that the capacitance is low.

FIG. 20A shows the relationship between the capacitance thus detected and the liquid surface. Here, the step portion (center portion LS) on the horizontal axis of FIG. 20A is detected as the liquid surface.

Another capacitance type level meter will be described. Here again, description will be given based on the schematic diagram of the electrical connection relationship between the capacitance level meter, the liquid 33, and the tank when measuring the level of the stored liquid shown in FIG. 21B. This capacitance type level meter includes a measurement (long) electrode 50 provided in the tank 40, a reference (short) electrode 51 provided at the bottom of the tank 40, and a power supply 2 connected to both electrodes.
And a control part (not shown).

Unlike the level meter described above, this capacitance type level meter does not detect the capacitance between each electrode and the tank, but measures the liquid 33 to the entire measurement (long) electrode 50. The capacitance is directly detected, and the liquid level in the tank 40 is directly measured from the measured value. The dielectric constant changes depending on the type of the liquid 33, which causes a difference in the detected capacitance. Therefore, in order to correctly detect the level of different types of liquid, the tank 40
A reference (short) electrode 51 is provided at the bottom of the liquid crystal to measure the reference capacitance, and the reference capacitance of each liquid is measured.

Further, the capacitance of each liquid as a whole is corrected based on the capacitance at the reference electrode. FIG. 20B illustrates the relationship between the measured capacitance and the liquid surface. Here, the end point of the horizontal axis of FIG. 20B is detected as the liquid surface. As described above, it is possible to reliably measure the level of the liquid surface by using any of the capacitance type level meters.

[0009]

However, the conventional capacitance type level meter has the following problems. In the discontinuous capacitance level meter shown in FIG. 21A,
The capacitance between the tank 40 and each electrode 50 was detected to measure the liquid level. Therefore, there is a problem that the capacitance is affected by other elements between the tank 40 and each electrode (other than the tank 40 and the electrodes), and accurate level measurement cannot be performed.

Further, in the continuous capacitance level meter shown in FIG. 21B, the capacitance correction of the entire liquid 33 in the tank 40 is performed at one point of the reference (short) electrode 51 provided at the bottom of the tank 40. It was It should be noted that even if the liquids stored in the tank 40 are of the same type, their dielectric constants differ depending on the temperature of the liquid 33. Therefore, the tank 4
When there is a temperature difference in the liquid 33 above and below 0, the standard (short)
The one-point correction by the electrode 51 has a problem that the electrostatic capacitance cannot be accurately detected and the level cannot be measured reliably. In addition, there is a problem that depending on the type of the object to be detected, it is affected by changes in water content and gas concentration in the gas above the tank.

Further, the liquid 3 stored in the tank 40
When oil etc. is mixed in 3 and adheres to the measurement (long) electrode 50,
The measured capacitance changes, causing an error. Therefore, there is a problem that an accurate level measurement cannot be performed. Even in the discontinuous capacitance type level meter, there is a problem that the capacitance is affected by other elements between the liquid 33 and the measurement (long) electrode 50, and accurate level measurement cannot be performed. .

Therefore, an object of the present invention is to provide a level meter capable of performing accurate and reliable measurement.

[0013]

A level measuring instrument according to claim 1 is partially inserted into an object to be detected, and a plurality of measuring electrodes are provided on the interface of the object to be detected so as to face the ground electrode. In contrast to the electrode group provided in the vertical direction, a measurement circuit for sequentially measuring the capacitance between the measurement electrode and the ground electrode of the electrode group, the change in the capacitance between the measurement electrode and the ground electrode measured by the measurement circuit And a level detection circuit for detecting the level of the detection target based on the detection target.

A level measuring instrument according to a second aspect is characterized in that, in the level measuring instrument according to the first aspect, the ground electrode is continuously provided in a direction perpendicular to an interface of an object to be detected.

According to a third aspect of the level measuring device of the first aspect, in the level measuring device according to the first aspect, the level detecting circuit stores a capacitance measured by the measuring circuit, and a static circuit stored in the storing circuit. It is characterized in that it is composed of a determination circuit that determines the portion of the capacitance having the largest change as the level of the detection target.

According to a fourth aspect of the level measuring instrument of the present invention, in the level measuring instrument according to the first aspect, the capacitance between each of the measuring electrodes and the ground electrode is sequentially measured in a state where the electrode group is not inserted in the object to be detected. The level detection circuit corrects the capacitance value between each of the measurement electrodes and the ground electrode in a state where a part of the electrode group is inserted into the detection target by using the initial value to detect the detection target. It is characterized by detecting the level of an object.

According to a fifth aspect of the level measuring device, in the level measuring device according to the first aspect, the measuring circuit sequentially measures the electrostatic capacitance between each measuring electrode and the ground electrode, and the level detecting circuit measures the electrostatic capacitance between each electrode. When the capacitance is sequentially viewed from the upper end, the electrode combination having the capacitance that initially exceeds the initial value is set as the target counter electrode, and the level of the detection target is detected in more detail based on the capacitance of the target counter electrode. It is characterized by

According to a sixth aspect of the level measuring device of the fifth aspect, the level detecting circuit calculates the distance to the upper end of the measuring electrode directly below the target counter electrode as the burial distance, and at the same time measuring directly below the electrode. The interface distance XL from the upper end of the electrode to the interface of the detection target is calculated based on the following formula,
The interface distance XL is added to the burial distance to detect the level of the object to be detected. Here, the interface distance XL is calculated based on the following formula: XL = LL · Cx / C, where , C = Ca-Cb, Cx
= Cr-Cb, where Ca is the capacitance between the measurement electrode and the ground electrode that is completely buried by the detection target, and Cb is the capacitance between the measurement electrode and the ground electrode that is not buried by the detection target. Capacitance, Cr is the actual capacitance between the target counter electrodes, and LL is the length from the upper end of the measuring electrode immediately below the target counter electrode to the lower end of the measuring electrode immediately above.

A level measuring device according to a seventh aspect is the level measuring device according to the sixth aspect, wherein the Ca is most adjacent to the interface of the object to be detected, and both are completely buried by the object to be detected. Cb is the capacitance between the ground electrodes, and Cb is closest to the interface of the detection target,
In addition, both are capacitances of the capacitance between the measurement electrode and the ground electrode that are not buried by the detection target.

The level measuring device according to claim 8 is the level measuring device according to claim 6, wherein the Ca is completely buried by the object to be detected and the average value of the capacitance between all the measuring electrodes and the ground electrode and The Cb is an average value of the electrostatic capacitances between all the measurement electrodes and the ground electrodes which are not buried by the detection object.

The level measuring instrument according to claim 9 is a claim 1, claim 2, claim 3, claim 4 and claim 5 or claim 6.
In the level measuring device according to (1), the electrode group is characterized by being formed as a pattern on a flexible substrate formed in a cylindrical shape.

According to a tenth aspect of the present invention, in the level measuring instrument according to the ninth aspect, the lower end of the cylindrical flexible substrate is open so that the object to be detected can be introduced. .

The level measuring device of claim 11 is the same as that of claim 10.
In the level measuring device according to (1), the electrode group is provided outside the side wall of the container that stores the detection target.

A level measuring device according to claim 12 is the level measuring device according to claim 1,
In the level measuring device according to claim 2, claim 3, claim 4 or claim 5 or claim 6, a rapid change in capacitance between the measurement electrode and the ground electrode in the initial value measurement is detected. In addition, a warning instruction signal output circuit for outputting a warning instruction signal is provided.

The level measuring instrument of claim 13 is the level measuring instrument of claim 1,
At the time of measurement for detecting the interface of the detection target in the level measuring device according to claim 2, claim 3, claim 4 and claim 5 or claim 6, the capacitance between the measurement electrode and the ground electrode. The change in the positive or negative direction is the interface of the detection target, and the change in the positive and negative directions is not the interface of the detection target.

The level measuring instrument according to claim 14 is the level measuring instrument according to claim 1,
Each measurement measured by storing the average value of the initial value of the capacitance between each measurement electrode and the ground electrode in the level measuring device according to claim 2, claim 3, claim 4 or claim 5 or claim 6. A warning instruction signal output circuit that outputs a warning instruction signal when the difference between the electrostatic capacitance between the electrode and the ground electrode and the average value of the initial values is equal to or larger than a predetermined value is provided.

In the level measuring method of the fifteenth aspect, a ground electrode and a plurality of measuring electrodes facing the ground electrode, and a part of an electrode group provided in a direction perpendicular to the interface of the object to be detected are used as the object to be detected. It is characterized in that it is inserted, the capacitance between the measurement electrode and the ground electrode is sequentially measured, and the level of the detection target is detected based on the change in the measured capacitance between the measurement electrode and the ground electrode.

[0028]

In the level measuring device and the level measuring method according to the first and the fifteenth aspects, the ground electrode and a plurality of measuring electrodes facing the ground electrode are provided in the electrode group provided in the direction perpendicular to the interface of the object to be detected. It is inserted into a part of the object to be detected, and the capacitance between the measurement electrode and the ground electrode is sequentially measured. Further, the level of the detection target is detected based on the change in the measured capacitance between the measurement electrode and the ground electrode. Therefore, regardless of the object to be detected, it is possible to reduce the influence of the container or the like and detect the level of the object to be detected even if oil or the like is attached.

A level measuring device according to a second aspect is the first aspect.
In the level measuring device according to (1), the ground electrode is continuously provided in the direction perpendicular to the interface of the object to be detected. Therefore, the structure of the electrode group can be simplified.

A level measuring device according to a third aspect of the present invention is the level measuring instrument of the first aspect.
In the level measuring device according to the above, the level detection circuit stores the capacitance measured by the measurement circuit as a storage circuit, and the portion with the largest change in the capacitance stored in the storage circuit is used as the level of the detection target. It is composed of a judgment circuit for judgment. Therefore, it becomes possible to perform accurate level measurement.

A level measuring device according to a fourth aspect is the first aspect.
In the level measuring instrument according to the above, the capacitance between each of the measurement electrodes and the ground electrode is sequentially measured as an initial value in a state where the electrode group is not inserted into the detection target, and the level detection circuit causes the electrode group to be detected. The value of the capacitance between each of the measurement electrodes and the ground electrode in the state where a part of the above is inserted is corrected using the initial value to detect the level of the detection target. Therefore,
It is possible to eliminate the influence of the container and the like.

The level measuring instrument according to claim 5 is the level measuring instrument according to claim 1.
In the level measuring device according to the above, the measurement circuit sequentially measures the capacitance between each measurement electrode and the ground electrode from the measurement electrode at the upper end or the lower end of the electrode group-the ground electrode, and the measurement electrode located at the interface of the detection target- The ground electrode is the counter electrode of interest. In addition, the level detection circuit detects the level of the detection target in more detail based on the capacitance between the counter electrode of interest and the measurement electrode-ground electrode completely buried in the detection target. Therefore, it is possible to perform detailed level detection of the detection target.

According to a sixth aspect of the present invention, in the level measuring instrument according to the fifth aspect, the level detection circuit has a measurement electrode located at the uppermost position of the electrodes completely buried in the object to be detected from the measured capacitance. -Detecting the ground electrode and calculating the burial distance from the lower end of the electrode group to both electrodes,
The interface distance from the upper end of the counter electrode of interest to the interface of the detection target is calculated, and the interface distance is added to the burial distance to detect the level of the detection target. Therefore, not only the burial distance but also the interface distance from the lower end of the target counter electrode to the surface of the detection target can be calculated.

The level measuring device according to claim 7 and claim 8 is the level measuring device according to claim 6, wherein the Ca is most adjacent to the interface of the object to be detected, and both are completely buried by the object to be detected. Is the capacitance between the measurement electrode and the ground electrode, wherein Cb is the closest to the interface of the detection target, and both are not buried by the detection target-the ground electrode. It is the capacitance of the capacitance between. Further, Ca is an average value of capacitances between all measurement electrodes and ground electrodes completely buried by the detection target, and Cb is between all measurement electrodes and ground electrodes not buried by the detection target. Is the average value of the electrostatic capacitance. Therefore, the capacitance measured at the counter electrode of interest is the average of the capacitance between the measurement electrode closest to the counter electrode of interest and the ground electrode or between the measurement electrode and the ground electrode that are buried or not buried by the object to be detected. The value can be used to correct.

The level measuring instrument according to claim 9 is the level measuring instrument according to claim 1, claim 2, claim 3, claim 4 or claim 5 or claim 6, wherein the electrode group is formed in a cylindrical shape. It is formed as a pattern on a flexible substrate. Therefore, the electrode formation is easy, and it is not necessary to adjust the electrode for each measurement.

A level measuring device according to a tenth aspect is the level measuring device according to the ninth aspect, wherein the lower end of the cylindrical flexible substrate is open, and the object to be detected can be introduced. Therefore, since the detection target can be introduced not only on the outside of the flexible substrate but also on the inside thereof, the capacitance detected when the detection target is present only on the outside of the flexible substrate and the outside and inside of the flexible substrate. The difference in capacitance detected when there is an object to be detected on both sides is large.

A level measuring instrument according to an eleventh aspect is the level measuring instrument according to the tenth aspect, wherein the electrode group is provided outside a side wall of a container for storing an object to be detected. Therefore, the object to be detected does not adhere to the electrodes.

The level measuring instrument according to claim 12 and claim 13 is the level measuring instrument according to claim 1, claim 2, claim 3, claim 4 and claim 5 or claim 6 in the initial value measurement. A rapid change in the capacitance between the measurement electrode and the ground electrode in the positive and negative directions is detected, and a warning instruction signal is output. Further, the warning instruction signal output circuit stores the average value of the initial value of the capacitance between each measurement electrode and the ground electrode, and the measured capacitance between each measurement electrode and the ground electrode and the average value of the initial value. If the difference between and is greater than or equal to a predetermined value, a warning instruction signal is output.
Therefore, it is possible to know in advance the case where accurate level measurement cannot be performed.

A level measuring device according to a fourteenth aspect detects an interface of a detection object in the level measuring device according to any one of the first, second, third, fourth and fifth or sixth aspects. Therefore, it is assumed that the change in the capacitance between the measurement electrode and the ground electrode in the positive or negative direction at the time of measurement is the interface of the detection target, and the change in both the positive and negative directions is not the interface of the detection target. Therefore, changes in both the positive and negative capacitances due to adhesion to the electrodes are not detected as the interface of the object to be detected.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the level measuring device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the level measuring device 500 of this embodiment. The level measuring device 500 is composed of a sensor unit 10 which is an electrode group, a switching unit SW20, a receiving circuit 25, a storage circuit 30, and a control circuit 35 which is a determination circuit and also a warning instruction signal output circuit.

The sensor unit 10 has n values from TE1 to TEn.
One measurement electrode is provided vertically, and the ground electrode GE100 is provided so as to face the measurement electrode and continuously in a direction perpendicular to the interface of the detection target. Measuring electrode TE1
Each measurement electrode from to TEn is connected to the switching means SW20, and the ground electrode GE100 is grounded.

The switching means SW20 is for selecting which measuring electrode is connected to the receiving circuit 25. The switching means SW20 is connected to the control circuit 35 via the control signal line 9. The receiving circuit 25 is composed of an inductor 17, an oscillator 18, a diode 19, a capacitor 16, an operational amplifier 11, a plurality of resistors and an A / D converter 13. Although the control signal line 9 is shown as a single line for convenience of description, it is actually made up of a plurality of lines.

FIG. 2A shows the outer shape of the sensor unit 10 of this embodiment. The sensor portion 10 has measurement electrodes TE1, TE2, TE.
3 ... TEn and the ground electrode GE100 face each other, and the ground electrodes are continuously arranged. Both electrodes are formed as a pattern on the flexible substrate 60, the flexible substrate 60 is formed in a cylindrical shape, and the outside is covered with an insulating tube ZT. Such a flexible substrate 6
Fig. 3 shows the detailed development of No. 0. FIG. 3A shows the relationship between both electrodes on the flexible substrate 60 and the signal line and the ground line. The measurement electrodes TE1, TE2, TE3 ... TEn are arranged at predetermined intervals, and the ground electrode GE100 is integrally arranged as a pattern on the flexible substrate 60.

Measuring electrodes TE1, TE2, TE3 ... TEn
A signal line SL is drawn out from each of the
A ground line GL is drawn from 00.

FIG. 3B is a plan view of the flexible substrate shown in FIG. 3A. The flexible substrate 60 is composed of a polyimide insulating sheet PS having a two-layer structure, and is provided with a measurement electrode and a ground electrode, a signal line SL and a ground line GL. The signal line SL of the flexible substrate 60
Is provided with a signal terminal ST and is connected to the switching means SW20, and the ground line GL is provided with a ground terminal GT and is grounded.

FIG. 2B shows a sectional view taken along the line CC ′ of the sensor section 10 shown in FIG. 2A. A cylindrical electrode core material TM1 is formed in the center of the sensor unit 10, a flexible substrate 60 is formed in a cylindrical shape on the outer side, and an insulating tube ZT is provided on the outer periphery thereof. Since both the measurement electrode and the ground electrode are provided as a pattern on the flexible substrate 60, the electrodes can be easily formed. Moreover, since the insulating tube ZT is provided on the outer periphery of the flexible substrate 60, oil or the like does not directly adhere to the electrodes. Therefore, it is not necessary to adjust the electrodes each time measurement is performed, and easy measurement is possible.

The operation of the level measuring instrument 500 will be described below. Here, it is assumed that the sensor unit 10 is provided in the tank 40. First, the initial value is detected before the object to be detected is stored in the tank 40. In order to detect the initial value, the control circuit 35 outputs a capacitance detection signal to the switching means SW20 through the control signal line 9 (see FIG. 1). The electrostatic capacitance detection signal is a signal that enables the electrostatic capacitance between the opposing measurement electrode and ground electrode to be detected by switching the switch provided in the switching means SW20.

The switching means SW20 receives the electrostatic capacitance detection signal from the control circuit 35, and sequentially switches the switches so that the electrostatic capacitance between the measurement electrode and the ground electrode can be detected at the timing shown in FIG.

Next, the switching operation of the switch in the switching means SW20 at the time of detecting the initial value will be described with reference to FIGS. 4 and 5. FIG. 4 shows a part of the sensor unit 10 (from the measurement electrode TE1 to the measurement electrode TE4) and the ground electrode GE1.
00 and a part of the switching means SW20.

In the switching means SW20, two switches (switch S10 to switch S17) are provided for each measuring electrode. Also, switching means SW2
The switches in 0 (measurement electrodes S10, S12, S14 and S16) are connected to the measurement signal line 7, and the switching means SW
Other switches in 20 (switches S11, S13 and S
15) is grounded. In addition, here, the ground electrode GE1
00 is grounded.

Next, the actual measurement of the initial value will be described. For example, consider a case where an initial value (capacitance) between the measurement electrode TE1 and the ground electrode GE100 is detected. The switching means SW20 measures the measuring electrode TE based on the electrostatic capacitance detection signal given from the control circuit 35 via the control signal line 9.
The control for closing the switch S10 connected to 1 is performed. Further, the switching means SW20, under the control of the control circuit 35, controls the switches S13, S15 and S17 to be closed at substantially the same time as the above control, and grounds the measurement electrodes TE2, TE3 and TE4.

As is apparent from FIG. 5, the measuring electrode TE1
And initial value between ground GE100 (timing T
Measurement electrode TE2 not used for detection at M1)
Therefore, TE4 is grounded. Further, only the measuring electrode TE1 is connected to the receiving circuit 25.

In the receiving circuit 25, the impedance of the input measurement signal is converted into electrostatic capacitance (analog measurement signal) by the operational amplifier 11, and the measurement electrode TE1 and the ground electrode G are converted.
The electrostatic capacitance (initial value) between E100 is detected. The detected capacitance is converted into a digital measurement signal by the A / D converter 13 and then output to the storage circuit 30. The memory circuit 30 stores this digital measurement signal.

In the storage device 30, the combination of the measurement electrode and the ground electrode used for the detection and the capacitance value are stored in association with each other. For example, the measurement electrode TE1 and the ground electrode GE
The combination between 100 is P1, and the initial value between the measurement electrode TE1 and the ground electrode GE100 (combination P1) is 50.
It is assumed that 0 [F] is detected. The detection result shows that the initial value of the combination P1 is 500 in the storage device 30.
It is stored as [F]. FIG. 6 shows a storage state of the storage device 30.

When the storage of the combination P1 is completed in the storage circuit 30, the storage circuit 30 outputs a storage end signal to the control circuit 35. The control circuit 35 that has received the storage end signal outputs a capacitance detection signal for detecting the capacitance (initial value) between the measurement electrode TE2 and the ground electrode GE100 to the switching means SW20. Next, the switching means SW20, based on this electrostatic capacitance detection signal,
The switch control as described above is performed at the timing TM2 in. Thereby, the initial value between both electrodes is detected and stored in the storage device 30 as the combination P2.
The same operation is sequentially performed up to the electrode TEn to obtain the initial value, and the combination is stored in the storage device 30 (FIG. 6).
The initial value between both electrodes thus obtained is graphed and shown in FIG. 7A.

Here, the control circuit 35 compares the initial values of the adjacent electrode combinations stored in the memory circuit 30 with each other, and makes a difference of a predetermined value or more (for example, the initial values of the adjacent electrode combinations). 10% or more), a warning instruction signal is output. For example, assume that the initial value of the electrode combination P1 is 500 [F] and the initial value of the combination P2 is 580 [F]. It can be seen that the initial value 580 for the electrode combination P2 is 10% or more of the initial value 500 [F] for the electrode combination P1.

When it is detected that there is a predetermined value or more difference between the initial values, a warning instruction signal is issued from the control circuit 35, and a display device or an alarm transmitter (not shown) is issued based on the warning instruction signal. Displays a warning signal indicating that measurement is impossible (sending)
To do. That is, the capacitance of the electrode abruptly rises due to corrosion of the electrode itself or oil or the like attached to the insulating tube ZT of the electrode portion.
A warning signal is displayed (transmitted) when accurate measurement cannot be performed. By displaying (transmitting) such a warning signal, it is possible to easily know in advance such cases, and it is possible to take necessary measures such as electrode replacement and removal of oil adhering to the insulating tube, so perform reliable level measurement. Is possible.

In the above, the initial values between the adjacent measurement electrode-ground electrode combinations stored in the storage circuit 30 are compared with each other, and if there is a difference of a predetermined value or more, a warning instruction signal is output. However, another method may be used as long as it can reliably detect an abnormality in each adjacent measurement electrode-ground electrode combination. For example, the average of the initial values stored in the storage circuit 30 may be calculated, and the warning instruction signal may be output when the difference between the capacitance between the electrode combinations and the average of the initial values is equal to or greater than a predetermined value. Good. Also in this case, since the abnormality between the adjacent electrode combinations can be easily known in advance, the necessary measures can be taken as described above, and the reliable level measurement can be performed. After comparing the initial values, the initial values shown in FIG. 6 are corrected. Here, the correction of the initial value means that the initial values stored in the storage circuit 30 are averaged to obtain an average initial value, and the difference between the initial value and the initial average value between the electrode combinations is calculated as a correction value. (See Figure 6).

For example, assuming that the initial value average in each measurement electrode-ground electrode combination is 505 [F],
A difference obtained by subtracting the initial value from the initial value average is stored as a correction value. That is, for example, +5 obtained by subtracting the initial value 500 [F] of the combination P1 from the initial value average 505 [F] is stored as the correction value for the combination P1. Similarly, the difference obtained by subtracting the initial value from the average of the initial values of all the combinations is stored as a correction value for each electrode combination (FIG. 6). The initial value is corrected here to reduce the measurement error of the electrode itself during actual measurement, the adhesion of oil, etc., and the influence of the shape of the tank and the devices in the tank. Therefore, the influence of the above conditions is reduced, and reliable and stable operation can be performed.

Next, the level measuring operation of the level measuring device 500 when measuring the object to be detected will be described. The measurement of the level of the detection target object is performed in the tank 40.
Perform with 3 stored. Also in this case, similarly to the initial value detection, the electrostatic capacitance between the opposing measurement electrode and ground electrode is detected, and the level is measured based on the electrostatic capacitance. Here again, as shown in FIG. 8, the level measuring instrument 500 of this embodiment is used.
Consider the case of measuring the level of the detection object 33 stored in the tank 40 using.

Here again, the control circuit 35 uses the switching means S.
The capacitance detection signal is output to W20, and the switching means SW20 performs the switch control as described above. That is, the switching means SW20 connects only the measurement electrode for detecting the capacitance to the receiving circuit 25 (FIG. 4, FIG.
(See FIG. 5). By this control, the measured actual value (electrostatic capacity) is stored in the memory circuit 30 together with the combination of electrodes (combination Q) (see FIG. 6). The control circuit 35 recognizes that all the initial value measurements have been completed,
Control is performed to store the measured actual value in another location in the storage circuit 30.

When the storage in the storage circuit 30 is completed, the control circuit 35 outputs to the changeover switch SW20 a capacitance detection signal for detecting the capacitance in the next combination between the measurement electrode and the ground electrode. . Switching means SW20 receiving the electrostatic capacitance detection signal from the control signal 35
Switches the switch by the same operation as described above.
The same operation as above is performed for all combinations of the measurement electrodes (n pieces) and the ground electrode, and the capacitance of each combination (electrode combination Q1) is stored (FIG. 6). In addition,
Here, the control circuit 35 compares the actual measurement values stored in the storage circuit 30 between the facing electrode combinations, and the adjacent actual measurement values have a change in both positive and negative directions. When it is detected that the value is equal to or more than the predetermined value, the warning instruction signal is output. For example, the actual measurement value of the combination Q1 shown in FIG. 6 is 500 [F], the actual measurement value of the combination Q2 is 460 [F], and the actual measurement value of the combination Q3 is 51 [F].
It is assumed that it is 0 [F]. The measured values of the combination Q2 and the combination Q3 change in both positive and negative directions with respect to the measured values of the adjacent combination Q1. Also, this positive
Assuming that the predetermined value of the change in the measured value in the negative bidirectional direction is 10% of the measured value of the adjacent combination Q1, the difference between the combination Q1 and the combination Q2 is 40 [F], which is less than the predetermined value. The difference between the combination Q1 and the combination Q3 is 50 [F], which corresponds to 10% of the combination Q1. Therefore, in this case, the control circuit 35 issues a warning instruction signal.

Based on this warning instruction signal, the display device or the warning transmitter (neither is shown) displays (transmits) a warning signal indicating that measurement is impossible. That is, a warning signal is displayed (transmitted) when an abnormality occurs in the electrode during measurement and accurate measurement cannot be performed, and the display of this warning signal (transmission) causes abnormality in the electrode (attached to the insulating tube). Since it is possible to take necessary measures for removing oil, etc.), it is possible to perform reliable level measurement.

In the above, the measured values are compared between the adjacent electrode combinations stored in the memory circuit 30,
A warning instruction signal was output when a change in a predetermined value anomaly in both positive and negative directions was detected between measured values between adjacent electrode combinations. However, any other method may be used as long as it is possible to reliably detect an abnormality between adjacent electrode combinations.For example, the average of all stored actual measurement values is calculated, and the actual measurement values between all electrode combinations and all actual measurement values are calculated. A warning instruction signal may be output when a change in a predetermined value anomaly in both the positive and negative directions is detected between the average value and the average value. Also in this case, since the abnormality between the adjacent electrode combinations can be easily known in advance, the level can be surely measured. Next, the actual measurement value is corrected based on the correction value (see FIG. 6). The actual measurement value obtained above is corrected using the correction value (calculated) corresponding to it. For example, the measured value 502 [F] of the electrode combination Q1
Are corrected using the corresponding correction value +5 (FIG. 6). That is, the correction value +5 is added to the measured value 502 [F]. As a result, the corrected actual measurement value 507 [F] is calculated. Similarly, the actual measurement value 506 of the electrode combination Q2 is
[F] is corrected using the correction value -3 corresponding thereto. That is, the correction value -3 is subtracted from the measured value 506 [F]. As a result, the corrected actual measurement value 503 [F] is calculated. In this way, all the measured values are corrected, and the corrected measured values are obtained and stored in the storage circuit 30 (FIG. 6).

FIG. 7B shows a graph of the actually measured values after correction.
Shown in. Here, of the electrostatic capacitances stored in the storage circuit 30 by the control circuit 35, the part LS2 having the largest change.
Is determined as the level of the detection target 33 in the tank 40. That is, the electrode combination P10 in FIG.
Between P1 and P11 is the largest change, and between measurement electrode TE10 and ground electrode GE100 and between measurement electrode TE11 and ground electrode GE100 in FIG. 8 is detected as the level of the detection target. In this way, the portion with the largest change in capacitance is determined as the level of the detection target, so that reliable level measurement can be performed. The level of the detection object 33 thus measured is output to the outside of the level measuring device 500 and used for controlling a liquid supply pump or the like (not shown).

As described above, in this embodiment, the capacitance between the opposing measurement electrode and ground electrode is detected to measure the level of the detection object 33. Therefore, even if the detection target is water 63 and oil 62 as shown in FIG. 9A, for example, the interface SF1 can be reliably measured. Here, the interface SF1 (liquid level) between water and oil
Is detected as a portion LS3 that changes in two steps in the capacitance value shown in FIG. 7C. Therefore, oil 6
Even when only 2 is desired to be removed, the reliable removal can be performed based on the measured interface.

Further, as shown in FIG. 9B, water 63 and oil 6
Even if the interface SF2 with 2 is in an emulsion state (an air layer is partially formed in an emulsion state), it is possible to reliably detect the interface by detecting the width of change in capacitance. Become. Here, the interface in the liquid emulsion state is represented by the capacitance width WD2 in FIG. 7B. Therefore, even if the liquid is in an emulsion state, it is possible to reliably measure the interface.

In the above example, the average value of all the initial values (initial value average) was calculated, and the difference between the initial value and the initial average value for each electrode combination was calculated as the correction value corresponding to each combination. Furthermore, the corrected actual measurement value is calculated by correcting the actual measurement value in each combination using the calculated correction values. However, another method may be used as long as it can accurately measure the level. For example, after obtaining the initial value, the actual measurement value may be obtained without calculating the correction value, the difference between the initial value and the actual measurement value may be calculated as the change value, and the level measurement may be performed based on this change value. FIG. 10A shows the storage state of each value (electrostatic capacitance) in the storage circuit 30 here.
A graph of the change values is shown in FIG. 10B. The liquid level in FIG. 10B is the portion LS4 in which the change value is the largest.

As described above, in the electrostatic capacity type level meter 500 of this embodiment, the level of the object to be detected is detected based on the electrostatic capacity between each opposing measurement electrode and ground electrode. Therefore, it is possible to perform reliable level measurement without being affected by the container (tank 40) between the tank 40 and each electrode. That is, the detection target 3
Even if there is a temperature difference above and below 3, it is possible to perform accurate level measurement without being affected by the difference in dielectric constant due to the temperature difference.

Next, another embodiment of the level measurement according to the present invention will be described. In the above example, the distance between the measurement electrode and the ground electrode at the interface of the detection target was detected by using the capacitance between the opposing measurement electrode and ground electrode (FIG. 7).
B, see FIG. 8). However, in this embodiment, not the distance to the electrode where the interface of the detection target is located, but the interface itself of the detection target is measured. Therefore, more accurate level measurement is possible.

The level measuring device 500 is also used in this embodiment.
Although the level is calculated using (FIG. 1), it differs from the above embodiment in that the electrode group 90 is used as the sensor unit. Figure 11
The electrode group 90 is shown in FIG. Electrode group 90
The seven electrodes from the measurement electrode TE10 to the measurement electrode TE70 and the ground electrode GE100 are formed in this. In addition,
A large number of measurement electrodes are provided in the electrode group used for actual level measurement, but here, for convenience of description, the capacitance is detected by using seven measurement electrodes and level measurement is performed.

The level measuring device 500 using the electrode group 90 as described above measures the level of the detection object 33 stored in the tank 40. For example, consider level measurement when the detection object 33 is stored in the tank 40 at the level L20 (FIG. 12).

Here, the lower end of the flexible substrate 60 forming the electrode group 90 is open. Therefore, when the electrode group 90 is inserted into the detection target 33, the detection target 33 stored in the tank 40 is also introduced inside the flexible substrate 60. That is, in the electrode group 90 of this embodiment,
Unlike the sensor unit 10 of the above-described embodiment, the detection target 33 is present both outside and inside the electrode group 90 (FIG. 12). From this fact, the capacitance detected when the detection target is present only outside the electrode group 90 and the electrode group 90.
The difference from the capacitance detected when there is an object to be detected both outside and inside is large. Therefore, it is possible to perform reliable and accurate level measurement.

The level measurement in this embodiment will be described below. Here, it is assumed that the initial value measurement and the like have already been completed. Also in this embodiment, the switching means SW2
The switching operation of each switch at 0 is the same as in the above embodiment. That is, for example, the measurement electrode-ground electrode (measurement electrode TE10-ground electrode GE100) at the lower end of the electrode group 90.
From the (interval) to the upper end, the capacitance is sequentially measured and stored.

Here, the control circuit 35 recognizes, as the target counter electrode, the electrode combination having the electrostatic capacitance which exceeds the initial value when the electrostatic capacitance between the electrode combinations is sequentially viewed from the upper end of the electrode group 90. Further, the control circuit 35 controls the detection target 33
Capacitances between the measurement electrode and the ground electrode that are completely buried in and between the measurement electrode and the ground electrode that are not buried in the object to be detected are detected and stored.

FIG. 13 is a graph showing changes in the capacitance between the measurement electrode and the ground electrode when the detected substance 33 is stored in the tank 40 at the level L20. As described above, the control circuit 35 recognizes, as the target counter electrode, the electrode combination having the electrostatic capacitance that initially exceeds the initial value when the electrostatic capacitance between the electrode combinations is sequentially viewed from the upper end of the electrode group 90. That is, first, the measurement electrode TE40-ground electrode GE100 having a capacitance exceeding the initial value is recognized as the target counter electrode.

Further, the control circuit 35 calculates the distance from the target counter electrode (measurement electrode TE40-ground electrode GE100) to the upper end of the measurement electrode as the buried distance. Therefore, the distance to the upper end of the measurement electrode TE30 is calculated as the burial distance. That is, the control circuit 35 calculates the distance from the lower end of the electrode group 90 to the upper end of the measurement electrode (measurement electrode TE30) as the burial distance. For example, the structural distance from the lower end of the electrode group 90 to the upper end of the measurement electrode TE30 is 70c.
If it is m, the burial distance is calculated to be 70 cm.

After calculating the burial distance, the control circuit 35 calculates the distance (interface distance) from the upper end of the measurement electrode immediately below the target counter electrode (measurement electrode TE40-ground electrode GE100) to the interface of the object to be detected. The interface distance thus calculated is added to the already calculated buried distance to measure the level of the detection object 33 up to the interface itself.

The calculation of the interface distance will be described below.
In FIG. 14A, the detection target 33 is level L2 in the tank 40.
The following is a graph showing the relationship between the electrode combination and the object to be detected when stored at 0, and the capacitance between the electrode combinations.

At the left end of FIG. 14A is shown the tank 40 in which the detection object 33 is stored at the level L20, and on the right side thereof are the measuring electrodes TE10 to TE70, the tank 4
The ground electrode GE100 is shown on the left side with 0 in between.

Here, CH10 shown on the right side of the measuring electrode
Is the measurement electrode TE40- in the case where the detection target object 33 stored in the tank 40 is a high dielectric constant material (for example, water).
It is a graph which shows the electrostatic capacitance between the ground electrodes GE100.
In addition, the measurement electrodes TE20 to TE7 are provided on the right side of CH10.
CH20 is a graph in which electrostatic capacities between electrode combinations between 0 and the ground electrode GE100 are combined.

In CH20 of FIG. 14A, 20 to G1
00 is 30 between the measurement electrode TE20 and the ground electrode GE100,
To G100 are between the measurement electrode TE30 and the ground electrode GE100, and 40 to G100 are between the measurement electrode TE40 and the ground electrode GE.
Between 100, 50-G100 is between the measurement electrode TE50 and the ground electrode GE100, and 60-G100 is between the measurement electrode TE6.
0 to the ground electrode GE100, 70 to G100 indicate the capacitance between the measurement electrode TE70 and the ground electrode GE100.

In FIG. 14A, the capacitance between the electrode combinations completely buried in the detection object 33 is represented by Ca, and the capacitance between the electrode combinations not buried by the detection object is represented by Cb. Be done. Further, Cr is the actual capacitance between the target counter electrode (measurement electrode TE40-ground electrode GE100), and LL is from the upper end of the measurement electrode immediately below the target counter electrode to the lower end of the measurement electrode immediately above the target counter electrode. Is the length of.

In FIG. 14B, the detection object 33 is set to level L20.
4 shows the storage state of the electrostatic capacitance between each electrode combination when stored in the tank 40. Here, the control circuit 35 sequentially searches the stored capacitances between the electrode combinations that are not in the Cb state from the capacitances between the electrode combinations on the upper side of the electrode group 90. From this search, measurement electrode T
E70-ground electrode GE100, measurement electrode TE60-ground electrode GE100 and measurement electrode TE50-ground electrode GE1
It is determined that all the capacitances at 00 are in the Cb state.

First, the control circuit 35 first detects a difference between the electrode combinations (measuring electrode TE4) having a capacitance exceeding the initial value (Cb).
The interface distance is calculated based on the capacitance (Cr) of the 0-ground electrode GE100). In addition, here, the measuring electrode TE10
Since the capacitance from the ground electrode GE100 to the measurement electrode TE30-ground electrode GE100 is Ca or Cf, it can be seen that the capacitance is completely buried in the detection target 33 (see FIG. 14A).

Next, the control circuit 35 is in the Cr state between the electrode combinations (measurement electrode TE40-ground electrode GE100).
The interfacial distance is calculated from the capacitance of. The interface distance XL here is a length proportional to Cr, and the interface distance XL is expressed by the following equation.

XL = LL · Cx / C (formula 1), where C = Ca-Cb and CX = Cr-Cb, and C
a is the capacitance between the measurement electrode and the ground electrode that is completely buried by the detection target, Cb is the capacitance between the measurement electrode and the ground electrode that is not buried by the detection target, and Cr is the target counter electrode. The actual capacitance, LL, is the length from the upper end of the measurement electrode immediately below the counter electrode of interest to the lower end of the measurement electrode immediately above (see FIG. 14A).

That is, the interface distance XL is calculated by multiplying Cx shown in FIG. 14A by C and the length LL from the upper end of the measurement electrode immediately below the target counter electrode to the lower end of the measurement electrode immediately above. . As is clear from the above equation, C is obtained by subtracting the electrostatic capacitance Cb between the electrodes not buried by the detection target object from the electrostatic capacitance Ca between the electrodes completely buried by the detection target object 33. And Cx is obtained by subtracting the Cb from the actual capacitance (Cr) between the target counter electrodes. The interface distance when the detection object 33 is stored at the level L20 is calculated by substituting a specific numerical value in the above equation.

Next, the control circuit 35 adds the calculated burial distance (structural distance from the lower end of the electrode group 90 to the measuring electrode TE30-upper end of the ground electrode GE100) to the interface distance calculated as described above. . Even if the detection target 33 is stored at another level, the level of the detection target can be measured by the same method as described above.

As described above, by performing the method described in this embodiment using the level measuring device 500 (see FIGS. 1 and 11) using the electrode group 90, the level of the interface itself of the object to be detected can be surely obtained. Can be measured. Therefore, more accurate level measurement can be performed.

In the capacitance graphs CH10 and CH20 shown in FIG. 14A, since the object to be detected is a high dielectric constant, the interval S10 when the capacitance changes from the Cb state to the Ca state (FIG. 14A) substantially matches the electrode pitch L. However, when the object to be detected is a low dielectric constant material (for example, kerosene, resin pellets, etc.), the interval S10
Does not always match the electrode pitch L. In this case, the value of LL in the above equation (Equation 1) (page 23) is not the distance from the upper end of the measurement electrode immediately below the target counter electrode to the lower end of the measurement electrode immediately above, but between the target counter electrodes. An accurate interface distance can be calculated by substituting the value of the interval when the capacitance of changes from the Cb state to the Ca state.

By the way, in the present embodiment, the measuring electrode TE1 located at the lower end of the electrode group 90 when the burial distance is calculated.
Capacitance was sequentially detected from 0-ground electrode GE100 to measurement electrode TE20-ground electrode GE100. However, if the capacitance can be detected reliably and accurately, the measurement electrode TE70-located at the upper end of the electrode group 90-
From between the ground electrode GE100, between the measurement electrode TE60 and the ground electrode GE100, between the measurement electrode TE50 and the ground electrode GE10.
Capacitance may be detected from 0 to. Further, the capacitance is not sequentially detected from either the upper electrode combination or the lower electrode combination of the electrode group 90, and the upper electrode and the lower electrode combination are sequentially and simultaneously (measurement electrode T
Between E70 and ground electrode GE100, between measurement electrode TE60 and ground electrode GE100, and between between measurement electrode TE10 and ground electrode GE100, measurement electrode TE20 and ground electrode GE10.
The capacitance may be detected in the order of 0 ... (See FIG. 12).

Further, in this embodiment, the electrode group 90 was inserted into the tank 40, and the detection object 33 was introduced inside to measure the level. However, as shown in FIG. 15, the level may be measured by providing the electrode group 90 on the outside of the side wall of the non-conductive tank 40 and detecting the capacitance between the electrodes. In this way, the electrode group 90 is provided on the outer side wall of the tank 40.
With the provision of, the object to be detected or the like does not come into direct contact with each electrode. Therefore, adhesion of oil or the like does not occur on the electrode surface, and accurate level measurement is possible even after years of use.

Further, in the above embodiment, when calculating the interface distance XL, C is the electrostatic capacitance (Ca) between the electrodes completely buried by the object to be detected and the electrostatic capacitance between the electrodes not buried by the object to be detected. What reduced the capacity (Cb) was used (refer FIG. 13). However, as long as an accurate interface distance XL can be calculated, another one may be used, for example, instead of Ca, an electrode combination completely buried in the detection object (measurement electrode TE10-ground electrode GE100 to measurement electrode TE).
30-up to ground electrode GE100), using an average value of capacitance, between electrode combinations not buried in the object to be detected instead of Cb (from measurement electrode TE50-ground electrode GE100 to measurement electrode TE70-ground electrode GE100). The interface distance XL may be calculated by substituting it into the above equation using the average value of the electrostatic capacitances.

In the above, when the interface distance XL was calculated, the average value of the electrostatic capacitances between the electrode combinations completely buried in the detection object and between the electrodes not completely buried in the object was used.
However, another one may be used, for example, instead of Ca, the capacitance between the electrode combinations that are closest to the interface of the detection target and are completely buried by the detection target (see FIG. 13). KB1), and instead of Cb, the capacitance (HB1 in FIG. 13) between the electrode combinations that are closest to the interface of the detection target and are not buried by the detection target may be used.

Further, in this embodiment, when the control circuit 35 sequentially detects the capacitance between the measurement electrode and the ground electrode, the change in the capacitance in the positive and negative directions is not at the interface of the detection object 33. To determine. That is, for example, as shown in FIG. 16, it is assumed that the capacitance between the measurement electrode TE10 and the ground electrode GE100 is changed between the measurement electrode TE30 and the ground electrode GE100 in both positive and negative directions. At this time, the control circuit 35 determines that the change PN2 of the capacitance in both positive and negative directions is not the interface of the detection object 33. That is, the control circuit 35
Recognizes only the change in the capacitance from the positive electrode to the negative electrode, such as between the measurement electrode TE30-ground electrode GE100 and the measurement electrode TE40-ground electrode GE100, as the interface of the detection target 33. As a result, even if the electrostatic capacitance may change both positively and negatively due to the adhesion of oil or the like to the electrode, the change is not detected as the interface of the object to be detected. Therefore, it becomes possible to perform accurate level measurement.

Further, the change of Cx in this embodiment is linear as shown in FIG. 13, and the interface distance XL with these changes.
FIG. 17A shows the relationship between and. But,
The change in Cx is not necessarily linear, and a curved change may occur as shown in FIG. 17B. In such a case, the relationship between Cx and the interface distance XL is obtained in advance, and the interface distance XL is calculated in consideration of the relationship, whereby accurate level measurement can be performed.

Next, another embodiment according to the present invention will be described below. In the above-described embodiment, the level measurement is performed by detecting the capacitance between the electrodes of the sensor unit 10 or the electrode group 90 of the level measuring device 500 shown in FIG.

However, the electrostatic capacitance detected between the electrodes of the sensor unit 10 or the electrode group 90 was input to the receiving circuit 25 via the switching means SW20 and the receiving signal line 8. Therefore, stray capacitance is generated in the wiring from the electrode to the receiving circuit 25, and the detected electrostatic capacitance value cannot be directly input to the receiving circuit 25. Therefore, it is difficult to perform precise level measurement.

Therefore, as shown in FIG. 18, a dedicated receiving circuit 26 (excluding the A / D converter 13) is provided for each electrode combination to shorten the distance from each electrode combination to the receiving circuit 26. As a result, no stray capacitance is generated, and the capacitance value detected in the electrode combination is directly input to the receiving circuit 26. Therefore, it is possible to perform precise level measurement of an object to be detected having a very low dielectric constant. The operation of the receiving circuit 26 is performed by switching ON / OFF of an oscillator (not shown) in each receiving circuit 26 by the operation switching means SW40. That is, the operation of the receiving circuit 26 is controlled by controlling the oscillation of the oscillator.

The capacitance value (detection signal) detected by the receiving circuit 26 is input to the A / D converter 13 through the common signal line 18 (FIG. 18). The A / D converter 13 outputs the detection signal converted into a digital signal to the control circuit 35 and a storage circuit (not shown).

In all of the above embodiments, the initial value (electrostatic capacity) between the electrode combinations is detected in advance before the object to be detected is stored in the tank 40, and the initial value is corrected and corrected. The value was calculated. Further, the measured value (capacitance) detected after storing the detection target is corrected using this correction value to obtain the corrected actual measurement value, and the level of the detection target is measured based on the corrected actual measurement value. That is, the initial value is corrected.

However, even if each electrode combination is inserted into a homogeneous object to be detected, the capacitances (after initial value correction) between the electrode combinations are not equal. That is, the detection capabilities of the electrode combinations are not equal. This is the sensor unit 1
It is considered that this is due to the processing accuracy of each electrode combination in the electrode group 0 or the electrode group 90, the gap between the electrodes, and the like. Therefore, accurate level measurement cannot always be performed.

Therefore, a correction coefficient is obtained in order to make the detection capabilities of the respective electrode combinations match, and the actual measurement value is corrected based on the correction coefficient. As a result, it becomes possible to perform accurate level measurement in consideration of the processing accuracy of each electrode combination, the gap between the electrode intervals, and the like. The details of calculating the correction coefficient will be described below. First, the initial value between each electrode combination is detected by the same method as in the above-described embodiment. Next, all the electrode combinations of the sensor unit 10 or the electrode group 90 are inserted into the detection object with uniform component / temperature (uniform capacitance), and provisional measurement values (capacitance) between each electrode combination. Is detected and stored. Here, the span capacitance value between each electrode combination is calculated by subtracting the initial value from the detected provisional measurement value. Further, after detecting the calculated span capacitance value across all electrode combinations, the average of all span capacitance values is calculated and used as a temporary average value. Next, the correction coefficient between each electrode combination is calculated by dividing the temporary measurement value between each electrode combination by the temporary average value.

For example, the initial value between certain electrode combinations is 52
It is assumed that the value is 0 [F] and the provisional measurement value is 900 [F]. Here, from the provisional measurement value 900 [F] to the initial value 52
380 [F] obtained by subtracting 0 [F] corresponds to the span capacity value. The provisional average value is obtained by detecting this span capacitance value over all electrode combinations and calculating the average of all span capacitance values. For example, if the temporary average value is 400 [F], the correction coefficient is about 0.95 obtained by dividing the span capacity value of 380 [F] by the temporary average value of 400 [F].

The correction error calculated in this way is used to correct the measurement error between each electrode combination. That is, the value of the capacitance between the electrode combinations after the error correction is calculated. The value of the capacitance between the electrode combinations here is obtained by multiplying the temporary measurement value minus the initial value by 1 / correction coefficient.
That is, 380 obtained by subtracting 520 [F] from 900 [F]
Multiply [F] by 1 / 0.95. Calculate this 4
00 [F] is calculated as the value of the electrostatic capacitance between the main electrode combinations. By thus calculating the value of the electrostatic capacitance between the electrode combinations using the correction coefficient, it becomes possible to perform more accurate level measurement. The correction coefficient is calculated as described above between other electrode combinations to correct the actual measured value.

In the above, after inserting all the electrode combinations into a homogeneous object to be detected, the provisional measurement value (electrostatic capacity) between each electrode combination is detected and stored. But,
When the sensor unit 10 or the electrode group 90 itself is long, the work itself of inserting all the electrode combinations into a homogeneous detection target takes time. Therefore, as shown in FIG. 19A, the pseudo detection object GK2 is moved in the direction of the arrow 150 at a position separated from the sensor unit 10 (or the electrode group 90) by the distance DS2, and is positioned between the electrode combinations so that the temporary measurement value Detection). As a result, it is not necessary to actually insert all the electrode combinations of the sensor unit 10 or the electrode group 90 into a homogeneous object to be detected, and it is possible to easily and accurately detect a provisional measurement value (electrostatic capacitance). .

Further, the pseudo detection product GK2 shown in FIG. 19A is used.
FIG. 19B shows a case in which is formed as the cylindrical shape pseudo detection object FR2. By moving this cylindrical pseudo detection object FR2 in the direction of arrow 170 by operating a rope or the like and positioning it between electrode combinations, it is possible to detect a provisional measurement value (capacitance). This makes it possible to easily and accurately detect a provisional measurement value (capacitance) without actually inserting all the electrode combinations into a homogeneous detection target at a place where the sensor 10 or the like is installed. .

On the other hand, there are cases where this cylindrical pseudo detection object FR2 is used to detect the actual measurement value. For example, the detection target 3
When 3 is a liquid or the like having a very low dielectric constant, the cylindrical pseudo detection object FR2 is floated on the liquid or the like as the detection object,
An actual measurement value (electrostatic capacity) between the electrode and the cylindrical shape pseudo detection object FR2 is measured. This makes it possible to perform reliable level measurement even with a liquid having a low dielectric constant.

As described above, by using the level measuring device and the level measuring method according to the present invention, it is possible to perform reliable and accurate level measurement of the object to be detected.

[0111]

The level measuring device and the level measuring method according to the first and the fifteenth aspects of the present invention include an electrode in which a ground electrode and a plurality of measuring electrodes facing the ground electrode are provided in a direction perpendicular to the interface of the object to be detected. The group is inserted into a part of the object to be detected, and the capacitance between the measurement electrode and the ground electrode is sequentially measured. Further, the level of the detection target is detected based on the change in the measured capacitance between the measurement electrode and the ground electrode. That is, regardless of the object to be detected, it is possible to reduce the influence of the container or the like and to detect the level of the object to be detected even if oil or the like is attached to the electrodes. Therefore, it is possible to perform accurate and reliable level measurement.

The level measuring device according to claim 2 is the level measuring device according to claim 1.
In the level measuring device according to (1), the ground electrode is continuously provided in the direction perpendicular to the interface of the detection target. That is, the structure of the electrode group can be simplified. Therefore, it becomes possible to perform accurate level measurement.

The level measuring instrument according to claim 3 is the level measuring instrument according to claim 1.
In the level measuring device according to the above, the level detection circuit stores the capacitance measured by the measurement circuit as a storage circuit, and the portion with the largest change in the capacitance stored in the storage circuit is used as the level of the detection target. It is composed of a judgment circuit for judgment. Therefore, it becomes possible to perform accurate level measurement.

The level measuring instrument according to claim 4 is the level measuring instrument according to claim 1.
In the level measuring instrument according to the above, the capacitance between each of the measurement electrodes and the ground electrode is sequentially measured as an initial value in a state where the electrode group is not inserted into the detection target, and the level detection circuit causes the electrode group to be detected. The value of the capacitance between each of the measurement electrodes and the ground electrode in the state where a part of the above is inserted is corrected using the initial value to detect the level of the detection target. That is, the influence of the container or the like can be eliminated. Therefore, it is possible to perform reliable and accurate level measurement.

A level measuring device according to a fifth aspect is the level measuring instrument according to the first aspect.
In the level measuring device according to the above, the measurement circuit sequentially measures the capacitance between each measurement electrode and the ground electrode from the measurement electrode at the upper end or the lower end of the electrode group-the ground electrode, and the measurement electrode located at the interface of the detection target- The ground electrode is the counter electrode of interest. In addition, the level detection circuit detects the level of the detection target in more detail based on the capacitance between the counter electrode of interest and the measurement electrode-ground electrode completely buried in the detection target. That is, not only the buried distance but also the interface distance from the lower end of the electrode of interest to the surface of the detection target can be calculated. Therefore, it becomes possible to perform accurate level measurement.

According to a sixth aspect of the level measuring device of the fifth aspect, in the level measuring device according to the fifth aspect, the level detecting circuit is located at the uppermost position of the electrodes completely buried in the object to be detected from the measured capacitance. -Detecting the ground electrode and calculating the burial distance from the lower end of the electrode group to both electrodes,
The interface distance from the upper end of the counter electrode of interest to the interface of the detection target is calculated, and the interface distance is added to the burial distance to detect the level of the detection target.

That is, not only the buried distance but also the interface distance from the lower end of the target counter electrode to the surface of the object to be detected can be calculated. Therefore, it is possible to perform accurate and reliable level measurement.

The level measuring device according to claim 7 and claim 8 is the level measuring device according to claim 6, wherein the Ca is closest to the interface of the object to be detected, and both are completely buried by the object to be detected. Is the capacitance between the measurement electrode and the ground electrode, wherein Cb is the closest to the interface of the detection target, and both are not buried by the detection target-the ground electrode. It is the capacitance of the capacitance between. Further, Ca is an average value of capacitances between all measurement electrodes and ground electrodes completely buried by the detection target, and Cb is between all measurement electrodes and ground electrodes not buried by the detection target. Is the average value of the electrostatic capacitance. That is, the capacitance measured at the target counter electrode is the average of the capacitance between the measurement electrode closest to the target counter electrode and the ground electrode or between the measurement electrode and the ground electrode that are buried or not buried by the detection target. The value can be used to correct. Therefore, it becomes possible to perform accurate level measurement.

The level measuring instrument according to claim 9 is the level measuring instrument according to claim 1, claim 2, claim 3, claim 4 or claim 5 or claim 6, wherein the electrode group is formed in a cylindrical shape. It is formed as a pattern on a flexible substrate. That is, the electrode formation is ready, and it is not necessary to adjust the electrode for each measurement. Therefore, it becomes possible to easily and accurately measure the level.

According to a tenth aspect of the level measuring instrument of the ninth aspect, the lower end of the cylindrical flexible substrate is open, and the object to be detected can be introduced. That is, the detection target can be introduced not only on the outside of the flexible substrate but also on the inside.
The difference between the electrostatic capacitance detected when the detection target is present only outside the flexible substrate and the electrostatic capacitance detected when the detection target is present both inside and outside the flexible substrate is large. Therefore, it is possible to perform reliable and accurate level measurement.

According to the eleventh aspect of the level measuring instrument of the tenth aspect, the electrode group is provided outside the side wall of the container for storing the object to be detected. That is, the object to be detected does not adhere to the electrodes. Therefore, accurate level measurement is possible.

The level measuring instrument according to claim 12 and claim 13 is the level measuring instrument according to claim 1, claim 2, claim 3, claim 4 and claim 5 or claim 6 in the initial value measurement. A rapid change in the capacitance between the measurement electrode and the ground electrode in the positive and negative directions is detected, and a warning instruction signal is output. Further, the warning instruction signal output circuit stores the average value of the initial value of the capacitance between each measurement electrode and the ground electrode, and the measured capacitance between each measurement electrode and the ground electrode and the average value of the initial value. If the difference between and is greater than or equal to a predetermined value, a warning instruction signal is output.
That is, it is possible to know in advance that accurate level measurement cannot be performed. Therefore, it becomes possible to perform reliable level measurement.

The level measuring instrument according to claim 14 detects the interface of the object to be detected in the level measuring instrument according to claim 1, claim 2, claim 3, claim 4 and claim 5 or claim 6. Therefore, it is assumed that the change in the capacitance between the measurement electrode and the ground electrode in the positive or negative direction at the time of measurement is the interface of the detection target, and the change in both the positive and negative directions is not the interface of the detection target. In other words, changes in both positive and negative capacitances due to adhesion to electrodes are not detected as the interface of the detected object. Therefore, it becomes possible to perform accurate level measurement.

[Brief description of drawings]

FIG. 1 is a block diagram showing a structure of a level measuring device according to the present invention.

FIG. 2 is a diagram showing an outer shape of a sensor unit and a cross section thereof.

FIG. 3 is a detailed view showing an electrode and a structure of a flexible substrate.

FIG. 4 is a diagram for explaining an operation of a switch connected to an electrode.

5 is a timing chart showing the opening / closing timing of each switch shown in FIG.

FIG. 6 is a diagram showing a storage state of capacitance in a storage device.

FIG. 7 is a graph of detected capacitance values.

FIG. 8 is a side view when the level of the liquid stored in the tank is measured using the level measuring device shown in FIG.

FIG. 9 is a cross-sectional view showing a state in which an object to be detected is water and oil, and an emulsion is formed at the interface thereof.

FIG. 10 is a diagram showing a storage state of each value (electrostatic capacity) in a storage circuit according to another embodiment.

FIG. 11 is a diagram showing an electrode group used in another example according to the present invention.

12 is a side view of the case where the level of an object to be detected stored in a tank at level L20 is measured using the electrode group shown in FIG.

FIG. 13 is a diagram showing a change in capacitance between electrodes when a detection target is stored at a level L20 in a tank.

FIG. 14 is a graph showing a relationship between a detection object stored in a tank and each ground electrode-measurement electrode, showing a change in capacitance between the ground electrode-measurement electrode.

FIG. 15 is a side view showing a state in which the electrode group shown in FIG. 11 is provided on the outer side of only a side wall.

FIG. 16 is a diagram showing changes in capacitance between electrodes in both positive and negative directions.

FIG. 17 is a diagram showing the relationship between the change in capacitance and the interfacial distance.

FIG. 18 is a block diagram showing another embodiment of the level measuring device shown in FIG. 1.

FIG. 19: A method of measuring a provisional measurement value and an actual measurement value by using a pseudo detection object and a cylindrical pseudo detection object.

FIG. 20 is a diagram showing the relationship between the capacitance and the liquid level measured using a conventional capacitance level meter.

FIG. 21 is a schematic view showing an electrical connection relationship between a liquid and a tank in a conventional capacitance level meter.

[Explanation of symbols]

 30 ... Memory circuit 35 ... Control circuit SW20 ... Switching means GE100 ... Ground electrode TE1 ... Measuring electrode

Claims (15)

[Claims] 1. An electrode group, a part of which is inserted into an object to be detected, wherein a plurality of measuring electrodes are provided so as to face the ground electrode and the electrode is provided in a direction perpendicular to the interface of the object to be detected. Measuring circuit for sequentially measuring the capacitance between the measurement electrode and the ground electrode, and a level detection circuit for detecting the level of the detection target based on the change in the capacitance between the measurement electrode and the ground electrode measured by the measurement circuit A level measuring instrument comprising: 2. The level measuring device according to claim 1, wherein the ground electrode is continuously provided in a direction perpendicular to an interface of an object to be detected. 3. The level measuring device according to claim 1, wherein the level detecting circuit stores a capacitance measured by the measuring circuit, a storage circuit for storing the capacitance, and a capacitance of the capacitance stored in the storage circuit. A level measuring instrument comprising: a determination circuit that determines the largest portion as the level of the detection target. 4. The level measuring device according to claim 1, wherein the capacitance between each of the measuring electrodes and the ground electrode is sequentially measured as an initial value in a state where the electrode group is not inserted in the detection target, and the level is set. The detection circuit detects the level of the detection target by correcting the value of the capacitance between each of the measurement electrodes and the ground electrode in the state where a part of the electrode group is inserted in the detection target by using the initial value. A level measuring instrument characterized by: 5. The level measuring device according to claim 1, wherein the measuring circuit sequentially measures the capacitance between each measuring electrode and the ground electrode, and the level detecting circuit comprises the electrostatic capacitance between each measuring electrode and the ground electrode. When the capacity is sequentially viewed from the upper end, the electrode combination having the electrostatic capacity that exceeds the initial value is the target counter electrode, and the level of the detection target is detected in more detail based on the electrostatic capacity of the target counter electrode. A level measuring instrument characterized by. 6. The level measuring device according to claim 5, wherein the level detecting circuit calculates the distance to the upper end of the measuring electrode immediately below the target counter electrode as the burial distance, and detects from the upper end of the measuring electrode immediately below the level An interface distance XL to the interface of the object is calculated based on the following formula, and the interface distance XL is added to the burial distance to detect the level of the object to be detected. XL is calculated based on the following formula: XL = LL · Cx / C, where C = Ca−Cb, Cx
= Cr-Cb, where Ca is the capacitance between the measurement electrode and the ground electrode that is completely buried by the detection target, and Cb is the capacitance between the measurement electrode and the ground electrode that is not buried by the detection target. Capacitance, Cr is the actual capacitance between the target counter electrodes, and LL is the length from the upper end of the measuring electrode immediately below the target counter electrode to the lower end of the measuring electrode immediately above. 7. The level measuring device according to claim 6, wherein the Ca is closest to the interface of the object to be detected, and both of them are completely buried by the object to be detected. The capacitance Cb is the capacitance between the capacitances, and Cb is the capacitance of the capacitance between the measurement electrode and the ground electrode that is closest to the interface of the detection target and both are not buried by the detection target. A level measuring instrument characterized by: 8. The level measuring device according to claim 6, wherein the Ca is the average value of the electrostatic capacitances between all the measurement electrodes and the ground electrodes which are completely buried by the object to be detected, and the C.
b is the average value of the electrostatic capacitances between all the measurement electrodes and the ground electrode that are not buried by the object to be detected. 9. Claim 1, claim 2, claim 3, claim 4
The level measuring device according to claim 5 or 6, wherein the electrode group is formed as a pattern on a flexible substrate formed in a cylindrical shape. 10. The level measuring device according to claim 10, wherein the lower end of the cylindrical flexible substrate is open so that the object to be detected can be introduced. 11. The level measuring device according to claim 11, wherein the electrode group is provided outside a side wall of a container that stores an object to be detected. 12. The level measuring device according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6, wherein the capacitance between the measurement electrode and the ground electrode in the initial value measurement. A level measuring instrument, comprising: a warning instruction signal output circuit that detects a sudden change in the positive and negative directions and outputs a warning instruction signal. 13. A level measuring instrument according to claim 1, claim 2, claim 3, claim 4 and claim 5 or claim 6, wherein a measurement is performed at the time of measurement for detecting an interface of a detection target. A level characterized in that the change in the capacitance between the electrode and the ground electrode in the positive or negative direction is the interface of the detection target, and the change in both the positive and negative directions is not the interface of the detection target. Measuring instrument. 14. The level measuring device according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6, wherein the initial value of the capacitance between each measurement electrode and the ground electrode is A warning instruction signal output circuit that stores the average value and outputs a warning instruction signal when the difference between the measured capacitance between the measurement electrode and the ground electrode and the average value of the initial value is a predetermined value or more, A level measuring instrument characterized by being provided. 15. A ground electrode and a plurality of measurement electrodes facing the ground electrode, and a part of an electrode group provided in a direction perpendicular to an interface of the detection target is inserted into the detection target, and the measurement electrode-grounding is performed. A level measuring method comprising: successively measuring the capacitance between the electrodes, and detecting the level of the detection target based on the measured change in the capacitance between the measurement electrode and the ground electrode.