JP5044336B2 - Level gauge sensor - Google Patents

Description

  The present invention relates to a level gauge sensor that detects a storage level of a substance stored in an insulating container.

  In a general industrial plant, various liquids suitable for each process are used in a manufacturing process, an inspection process, and the like. For example, in various manufacturing processes such as a chemical manufacturing process and a semiconductor manufacturing process, various liquids are used in each step. Such liquids include strongly acidic substances such as sulfuric acid and nitric acid. These liquids are indispensable in each manufacturing process, but are hardly preferred for the human body. Therefore, every time the liquid is used, it is troublesome for an operator to measure and use the liquid, and should be avoided when considering the influence of the human body.

  For this reason, regardless of the dangerous substances such as strongly acidic chemicals, the plants that use liquids are automated in their weighing and use. Since such a liquid is frequently used in the plant, it is stored in a tank in the plant. Moreover, since a large amount of liquid is used in each process as described above, the facility manager needs to know the amount of liquid stored in the tank from the viewpoint of manufacturing and management. As a measuring instrument for measuring the amount of liquid stored in such a tank, there is a capacitance sensor (for example, Patent Document 1).

  In the capacitance sensor described in Patent Document 1, an anode used as a shape surrounding a tubular body and an electrode used as a cathode are arranged at a predetermined interval on the outer surface of the tubular body included in a tank for storing liquid. This electrode is formed in a ring shape or a spiral shape. By forming the electrode in such a shape, an electric field is formed between the anode and cathode electrodes, the electric field distribution changes according to the liquid level in the tube, and the capacitance between the electrodes changes. Arise. Based on this change in capacitance, the liquid level and the like are detected in comparison with the reference value. However, in the capacitance sensor according to Patent Document 1, since the electrode has a ring shape or a spiral shape as described above, the tube body is removed from the tank and attached to the tube body when the electrode is attached to the tube body. In addition, it is necessary to produce an electrode or perform winding, which is very time-consuming.

JP-A-6-194212 (paragraph numbers 0004, 0005, etc.)

  In view of the above problems, an object of the present invention is to provide a level gauge sensor that can be easily attached to an insulating container or an insulating gauge tube disposed in the container.

In order to achieve the above object, the level gauge sensor according to the present invention is characterized in that the level gauge sensor is stored in an insulating container and detects a storage level of a substance based on a displacement of capacitance, the container Or, the insulating gauge tube attached to the container for monitoring the storage level of the substance is arranged along the increasing / decreasing direction of the storage level of the substance, and can hold the container or the gauge pipe provided with a pair of elongated sensor support, Ri Oh provided planar electrode having conductivity on the sensor support, with said sensor support and hinge and fittings, the container, or the gauge It surrounds over the tube in circumferential direction, and the sensor support and the hinge and the fixture lies in that is configured to be respectively separated.

  Thus, a planar electrode is provided on an insulating container or an elongated sensor support that is attached to the container and can be placed on an insulating gauge tube that monitors the storage level of the substance. Therefore, the contact area between the container or the gauge tube and the electrode can be increased, and the contact surface can be made uniform. Therefore, it is possible to accurately detect even a very small capacitance displacement. In addition, since the electrodes are provided on a pair of long sensor supports capable of sandwiching the container or the gauge tube, the attachment of the electrode to the container or the gauge tube regardless of whether the container is newly installed or existing, Since it can be carried out by sandwiching it with the sensor support, simple attachment is possible.

  In the level gauge sensor, it is preferable that the planar electrode has a mesh configuration.

  With such a configuration, since the planar electrode is a mesh-like conductive material, the adhesion between the container or gauge tube and the electrode can be improved. In addition, if it is a mesh-like conductive material and has a shape that can be bent easily, even if the diameter of the gauge tube is slightly increased or decreased, it can be flexibly accommodated and can be easily attached. it can. Furthermore, since the planar electrode has a mesh shape, air between the container or gauge tube and the electrode can be removed, so that measurement can be performed with high accuracy.

  In the level gauge sensor, it is preferable that a backup member having insulation and elasticity is provided between the planar electrode and the sensor support.

  With such a configuration, the side where the planar electrode does not come into contact with the gauge tube is pressed by a backup member having insulation and elasticity, so that the adhesion between the planar electrode and the container or the gauge tube is further improved. Can be improved. Further, since the backup member has an elastic characteristic, the planar electrode is not excessively pressed against the container or the gauge tube, so that there is no problem that the container or the gauge tube is damaged. .

  In the level gauge sensor, it is preferable that the sensor support is electrically grounded.

  With such a configuration, the sensor support that is electrically grounded can be used as a shield member capable of removing noise from the outside. Therefore, the noise resistance of the level gauge sensor can be improved. Therefore, since it is not necessary to arrange a shield member having noise resistance again, the attachment can be easily performed.

[First embodiment of the present invention]
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing a tank 1 used as a container for storing a liquid. Such a tank 1 is provided in a plant, and a liquid used in the plant is stored. The tank 1 includes a storage unit 2 that stores liquid, and a gauge tube 3 that is provided so that the storage level of the liquid stored in the storage unit 2 can be viewed. The liquid stored in the tank 1 is sent to each device (not shown) in the plant via the discharge port 4. When liquid is used in each device, the amount of liquid stored in the tank 1 also decreases. However, by visually checking the position of the liquid surface of the gauge tube 3, the administrator or operator of the tank 1 Can recognize the storage level stored in the tank 1.

  FIG. 2 is a schematic diagram showing the configuration of the level gauge sensor 10 of the present invention. The level gauge sensor 10 includes a detection unit 11, a control unit 12, a connection cable 13, and the like. The detection unit 11 detects the storage level of the liquid stored in the tank 1, and the detected detection signal is transmitted to the control unit 12 via the connection cable 13. The control unit 12 performs signal processing based on the detection signal detected by the detection unit 11 and calculates a storage level.

  The control unit 12 includes a signal amplification amplifier (not shown) for amplifying the detection signal acquired by the detection unit 11. A plurality of buttons 12 a are arranged on the front surface of the housing of the control unit 12. An administrator or operator of the tank 1 can set the offset of the signal amplification amplifier and perform calibration within the measurement range by pressing a predetermined button 12a. In addition, a connection cable terminal 12b for connecting the connection cable 13 is provided on the side surface, and a power supply terminal 12c is also provided. The voltage applied via the power supply terminal 12c is used as the power supply voltage of the signal amplification amplifier. Furthermore, an output terminal 12d for outputting the detected sensor signal is provided on the other side surface. It is also possible to perform computer management by connecting the output terminal 12d and a computer (not shown) with a cable and taking out the liquid storage level obtained by the level gauge sensor 10 as an electrical signal to the computer.

  The level gauge sensor 10 is a level gauge sensor that detects the storage level of the liquid stored in the tank 1 based on the displacement of the capacitance C. The level gauge sensor 10 is disposed outside the gauge tube 3 (see FIG. 1) provided in the tank 1 so that the positive electrode 11a and the negative electrode 11b sandwich the gauge tube along the increasing / decreasing direction of the substance storage level. . This clamping is performed by a long sensor support 14. By disposing the level gauge sensor 10 in the gauge tube 3 in this way, the change in the capacitance C generated between the positive electrode 11a and the negative electrode 11b according to the change in the storage level inside the gauge tube 3. Accordingly, the storage level in the gauge tube can be detected. Therefore, it is possible to measure the storage level that continuously changes in the gauge tube 3 by calculating using the change in the capacitance C as a detection signal. Note that the connection cable 13 is preferably a coaxial cable, for example. When a coaxial cable is used as the connection cable 13, the wiring cable can be easily routed. When a coaxial cable is used, although not shown, it is preferable to connect the inner conductor to the positive electrode 11a and the outer conductor to the negative electrode 11b. With such a connection, it is possible to protect changes in the capacitance C, which is a minute signal, from external noise. Alternatively, the outer conductor can be connected to the positive electrode 11a and the inner conductor can be connected to the negative electrode 11b.

  The positive electrode 11a and the negative electrode 11b are preferably planar electrodes having conductivity so as to cover the gauge tube 3. By making the positive electrode 11a and the negative electrode 11b into such planar electrodes, the contact area between the positive electrode 11a and the negative electrode 11b and the gauge tube 3 can be increased. It becomes possible to detect with high accuracy. The planar electrode is preferably made of a mesh-like conductive material such as a conductive cloth tape in order to improve contact.

  The level gauge sensor 10 measures a minute change in the capacitance C. Therefore, it is necessary to prevent the detection unit 11 from being affected by external noise or the like. Therefore, the sensor support 14 is made of a conductive material, and is used as a shield member by electrically grounding the sensor support 14. If the negative electrode 11b is used as a ground electrode, it is preferable to connect the negative electrode 11b and the sensor support 14 on the negative electrode 11b side and also ground the sensor support 14 on the positive electrode 11a side. With such a configuration, the positive electrode 11a can be largely covered with the sensor support 14 serving as a shield member, functioning as a guard, and noise resistance is improved.

  However, since a voltage is applied to the positive electrode 11a from the control unit 12, the positive electrode 11a and the sensor support 14 need to be insulated and separated. Therefore, a backup member 15 having insulation and elasticity is disposed between the positive electrode 11 a and the sensor support 14. The backup member 15 is preferably formed of a sponge-like material having elastic force. Further, the backup member 15 is arranged not only between the positive electrode 11a and the sensor support 14, but also between the negative electrode 11b and the sensor support 14 as shown in FIG. good. Thus, by arranging the backup member 15 between the planar electrode made up of the positive electrode 11a and the negative electrode 11b and the sensor support 14, the adhesion between the planar electrode and the gauge tube 3 can be improved. it can. Further, since the backup member 15 has an elastic force, it can be easily attached while preventing an excessive force from being applied particularly during the attachment.

  Each sensor support 14 provided with the positive electrode 11a and the negative electrode 11b is provided with a hinge 16 on one side surface in the longitudinal direction, and is connected so as to be movable within a predetermined range. The number of hinges 16 is not particularly limited as long as the positive electrode 11 a and the negative electrode 11 b can be extended and fixed in the longitudinal direction of the gauge tube 3. The sensor support 14 on the positive electrode 11 a side, the sensor support 14 on the negative electrode 11 b side, and the negative electrode 11 b are preferably electrically grounded via the hinge 16. When such electrical grounding is performed, wiring for connecting them again becomes unnecessary. Of course, when the hinge 16 made of an insulating material is used, each sensor support 14 can be set to the same potential by connecting each sensor support 14 with wiring.

The level gauge sensor 10 is used by attaching a positive electrode 11a and a negative electrode 11b so as to sandwich a gauge tube 3 provided in the tank 1. Accordingly, the fixture 17 is disposed on the other side surface of the sensor support 14 on which the hinge 16 in the longitudinal direction is provided. The positive electrode 11a and the negative electrode 11b are fixed to the gauge tube 3 by sandwiching the gauge tube 3 with the fixture 17 and locking it with bolts 17a and wing nuts 17b. Similarly this fixture 17 also hinge 16, and the positive electrode 11a and negative electrode 11b is equal to or can be attached extending in the longitudinal direction of the gauge pipe 3, not particularly those quantities are limited . Further, when the conductive fixture 17 is used, the sensor support 14 on the positive electrode 11a side and the sensor support 14 on the negative electrode 11b side can be set to the same potential.

  FIG. 3 is a top perspective view when the level gauge sensor 10 is attached to the gauge tube 3. As shown in FIG. 3, the sensor support 14 can be arranged so as to sandwich the gauge tube 3 by a hinge 16 and a fixture 17.

  A cross-sectional view when the level gauge sensor 10 is fixed to the gauge tube 3 is shown in FIG. As shown in FIG. 4, the positive electrode 11a and the negative electrode 11b are pressed by the gauge tube 3 by locking the fixture 17, and the backup member 15 is compressed. Therefore, the positive electrode 11a, the negative electrode 11b, and the gauge tube 3 receive an appropriate pressing force by the backup member 15 and are fixedly fixed.

  Next, the detection principle of the level gauge sensor 10 will be described. FIG. 5 is a circuit diagram for illustrating the detection principle. As described above, the level gauge sensor 10 is configured to change the storage level in the gauge tube 3 by the change in the capacitance C between the positive electrode 11a and the negative electrode 11b according to the change in the storage level in the gauge tube 3. Detection is in progress. The positive electrode 11 a and the negative electrode 11 b form a capacitor in FIG. 5, and the dielectric constant ε of the capacitor is determined by the liquid stored in the tank 1. The control unit 12 applies a pulse signal as shown in FIG. 6 to the capacitor via the positive electrode 11a, and sets the time constant τ until the charging current flowing into the capacitor at that time reaches a predetermined value (for example, 10%). Based on this, the capacitance C of the capacitor is calculated.

ここで、I（ｔ）：充電電流、Ｖ：パルス信号の電圧値であり、時定数τはＲ×Ｃである。
したがって、抵抗Ｒは液体の貯留レベルに拘らず一定であるため、パルス信号を印加した際の時定数τを測定することにより、静電容量Ｃを演算することができる。 Specifically, the charging current of the capacitor in the electric circuit shown in FIG. 5 can be obtained by equation (1).

Here, I (t): charging current, V: voltage value of the pulse signal, and time constant τ is R × C.
Therefore, since the resistance R is constant regardless of the liquid storage level, the capacitance C can be calculated by measuring the time constant τ when a pulse signal is applied.

  FIG. 7 is a charge current characteristic diagram when the capacitor is charged with the pulse signal shown in FIG. 6 in the electric circuit shown in FIG. As shown in FIG. 7, the charging current has a characteristic that it becomes difficult to flow as time passes. This is nothing but the characteristic that the capacitor stops flowing current in response to charging. The characteristic as shown in FIG. 7 is expressed by the above-described equation (1).

  FIG. 8 shows the test results when the level gauge sensor 10 is attached to the gauge tube 3 and “tap water” is used as the liquid. The “tap water” stored in the tank 1 is gradually increased, the change in the capacitance C is calculated from the time constant τ, and the storage level is calculated based on the calculation result. As is clear from FIG. 7, the water level (storage level) can be obtained based on the capacitance C by using the level gauge sensor 10.

  The level gauge sensor 10 is used by being attached to the gauge tube 3 as described above. A cross-sectional top view when attached to the gauge tube 3 is shown in FIG. In FIG. 4, the positive electrode 11a and the negative electrode 11b are illustrated as being substantially parallel in a state where the gauge tube 3 is sandwiched, but the positive electrode 11a and the negative electrode 11b of the level gauge sensor 10 are It is not essential to be parallel. As shown in FIG. 9, even when the diameter of the gauge tube 3 is larger than the width of the detector 11, the positive electrode 11a and the negative electrode 11b are in contact with the gauge tube 3 and the fixture 17 can be locked. If there is, the capacitance C can be detected. Furthermore, in such a case, it is possible to easily attach to the gauge tube 3 having a large diameter by replacing the fixture 17 with a larger size if necessary. Even in this case, the level gauge sensor 10 can detect the storage level of the liquid stored in the tank 1.

  If the single level gauge sensor 10 is too long and the gauge tube 3 is too long to continuously measure from a state where there is no liquid in the gauge tube 3 (small state) to a full state, as shown in FIG. It is also possible to connect the level gauge sensor 10 in a plurality of stages in the longitudinal direction. FIG. 10 shows an example in which the level gauge sensor 10 is used in three stages. In this way, when used in a plurality of stages, the level gauge sensors 10 need only be integrated in a connected state. Therefore, each positive electrode 11a is connected by a positive electrode connection line 18 to support each sensor. The body 14 is connected by a sensor support connecting line 19. Even the integrated level gauge sensor 10 formed in this way can be easily attached to the gauge tube 3 with the fixture 17, and the storage level can be measured.

[Second embodiment of the present invention]
In the first embodiment, since the capacitance C of the capacitor is very small, the detection signal acquired by the detection unit 11 is amplified by the signal amplification amplifier of the control unit 12. In the present level gauge sensor 10, the positive electrode 11a and the negative electrode 11b are covered with a sensor support 14 that is electrically grounded, and therefore has excellent noise resistance. Therefore, the electrostatic capacity C can be calculated from the time constant τ of the charging current as shown in the first embodiment, and the storage level can be accurately detected based on the electrostatic capacity C, but further accuracy is required. In some cases, such as when the sensor support 14 is not used, measurement can be performed using a high-precision amplifier based on another principle. Further, for example, the capacitance C can be measured by using a known technique disclosed in JP-A-2002-195867.

[Other Embodiments]
In the said embodiment, although demonstrated as the positive electrode 11a and the negative electrode 11b being a planar electrode, it does not restrict to this. If either one is a planar electrode, it is possible to detect the storage level with high accuracy and easy attachment.

  In the said embodiment, although the liquid used by the measurement result of the level gauge sensor 10 demonstrated as tap water, it is not restricted to this. In this level gauge sensor 10, for example, even a liquid such as sulfuric acid, hydrochloric acid, or hydrofluoric acid can naturally detect the storage level, or even a powder such as ferric oxide. Detection is possible. If the dielectric constant of such a liquid or powder is constant, it is possible to detect the storage level with this level gauge sensor 10. The gauge tube 3 for fixing the level gauge sensor 10 is a glass gauge tube, for example, when the liquid for detecting the storage level is a substance that is erosive to glass such as hydrofluoric acid. Instead of 3, it is also possible to use a gauge tube 3 made of plastic such as fluororesin or acrylic. Thus, even if the material of the gauge tube 3 is different, the storage level can be detected if the material is insulating.

ここで、Ｖ（ｔ）：コンデンサの両端にかかる電位差であり、Ｅ：入力電圧として印加する電圧である。また、時定数τはＲ×Ｃである。電位差Ｖ（t）は、時間と共に電圧Ｅに飽和するような特性となるため、例えば、電位差が０〔Ｖ〕から電圧Ｅの９０％に達するまでの時間を時定数τとして使用すると、静電容量Ｃを容易に演算することができる。 In the first embodiment, the time constant τ used for the calculation of the storage level has been described as being obtained based on the charging current of the capacitor. However, the present invention is not limited to this. Of course, it is possible to obtain the time constant τ based on the voltage applied to both ends of the capacitor. When obtaining the time constant τ from the voltage, the following equation (2) should be used.

Here, V (t) is a potential difference applied to both ends of the capacitor, and E is a voltage applied as an input voltage. The time constant τ is R × C. Since the potential difference V (t) is saturated with the voltage E over time, for example, if the time until the potential difference reaches 0% from 0 [V] to 90% of the voltage E is used as the time constant τ, The capacity C can be easily calculated.

  In the above embodiment, the level gauge sensor 10 has been described as being locked and fixed by the fixture 17 when the level gauge sensor 10 is attached to the gauge tube 3, but this is not a limitation. The positive electrode 11a and the negative electrode 11b are covered with an insulating elastic member such as a rubber tube, air is introduced into the rubber tube, and the positive electrode 11a and the negative electrode 11b are pressed against the gauge tube 3 by the pressure of the air. Of course, it is also possible to configure it to be fixed. Even with such a configuration, the contact of the positive electrode 11a and the negative electrode 11b with the gauge tube 3 can be improved.

  In the said embodiment, when attaching the fixture 17 to the gauge pipe 3, it demonstrated as locking by using the volt | bolt 17a and the wing nut 17b, but it does not restrict to this. As shown in FIG. 11, a plate spring 20 may be provided between the sensor supports 14, and the gauge tube 3 may be sandwiched and fixed by the sensor support 14 by the urging force of the plate spring 20. Or although not shown in figure, it is also possible to fix a pair of sensor support body 14 provided with the positive electrode 11a and the negative electrode 11b with respect to the gauge tube 3 with a belt or a string. Further, for example, a buckle used for a seat belt of a car or a buckle used for a wristwatch may be provided on the sensor support 14 and fixed to the gauge tube 3 using the buckle.

  In the above embodiment, the positive electrode 11a and the negative electrode 11b are described as being disposed in the gauge tube 3, but the present invention is not limited to this. The storage level may be measured by directly attaching the positive electrode 11a and the negative electrode 11b to the storage part 2 for storing the liquid. The storage part 2 is disposed so as to be sandwiched directly by the sensor support 14 and stored. The level may be measured.

  In the above embodiment, the level gauge sensor 10 is disposed in the tank 1 (container) or the insulating gauge tube 3 that monitors the storage level of the substance attached to the tank (container) and measures the storage level. As explained. However, the scope of application of the present invention is not limited to this. For example, the tank 1 (container) includes insulating tubes, pipes, hoses, and the like, and it is naturally possible to measure the storage level by directly attaching the level gauge sensor 10 to these.

  According to the level gauge sensor 10, it is not necessary to remove the gauge tube 3 and prepare and install the positive electrode 11 a and the negative electrode 11 b according to the gauge tube 3. Disappears. Therefore, even when liquid is contained in the tank 1, the level gauge sensor 10 can be easily attached.

Diagram showing the outline of the tank Side view of level gauge sensor Top perspective view of level gauge sensor Sectional view when the level gauge sensor is fixed to the gauge tube Circuit diagram showing measurement principle Diagram showing the pulse signal to be applied Diagram showing changes in current when a pulse signal is applied Diagram showing the relationship between measured capacitance and water level The figure which shows the example of arrangement when a positive electrode and a negative electrode are not in a parallel state The figure which shows the example at the time of connecting a level gauge sensor to a longitudinal direction The figure which shows the example of the fixture using a leaf | plate spring

Explanation of symbols

3: Gauge tube 10: Level gauge sensor 11: Detection unit 11a: Positive electrode 11b: Negative electrode 12: Control unit 12a: Button 12b: Connection cable terminal 12c: Power supply terminal 12d: Output terminal 13: Connection cable 14: Sensor support 15: Backup member 16: Hinge 17: Fixture 17a: Bolt 17b: Wing nut

Claims (4)

A level gauge sensor that detects a storage level of a substance stored in an insulating container based on displacement of capacitance,
The insulating gauge tube attached to the container or the container and monitoring the storage level of the substance is disposed along the increasing / decreasing direction of the storage level of the substance, and holds the container or the gauge pipe With a possible pair of elongated sensor supports,
Oh Ri provided planar electrode having conductivity on the sensor support,
Between the sensor support and the hinge and fittings, the container, or, surrounds over the gauge tube in the circumferential direction, and the sensor support and the hinge and the fixture has been configured to be respectively separated Level gauge sensor.   The level gauge sensor according to claim 1, wherein the planar electrode has a mesh configuration.   The level gauge sensor according to claim 1 or 2, wherein a backup member having insulation and elasticity is provided between the planar electrode and the sensor support.   The level gauge sensor according to any one of claims 1 to 3, wherein the sensor support is electrically grounded.

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