JP6320655B1 - Sensor - Google Patents

Abstract

The sensor sets a value larger than the detected value of the capacitance at the time of arrangement as the first threshold value, and when the detected value exceeds the first threshold value, sets a value smaller than the detected value as the second threshold value. . After the setting of the second threshold, when the detected value exceeds the first threshold, the second threshold is updated to a value smaller than the detected value, and when the detected value is equal to or lower than the second threshold, One threshold is updated to a value larger than the detected value. The output unit outputs a detection result indicating whether or not a substance is present based on the first threshold value and the second threshold value.

Description

  The present invention relates to a sensor that detects the presence or absence of a substance based on capacitance.

  Conventionally, a capacitance type sensor that detects a storage level of a substance such as a liquid or a granular material stored in a container or detects a substance flowing through a pipe has been used. Examples of such capacitance type sensors include the following.

  The conventional capacitance type sensor takes in the capacitance between the measurement electrodes (between the detection electrode and the ground electrode insulated from each other) into the circuit, and captures the change in the capacitance between the measurement electrodes. Detects the presence or absence of substances present in That is, whether a substance has reached a predetermined amount by attaching a sensor to a container, piping, etc., and detecting the difference between the empty capacitance value and the capacitance value of the substance. (Whether or not there is between measurement electrodes). However, in order to determine whether or not the substance has reached a predetermined amount, it is necessary to manually set a capacitance threshold value beforehand in the capacitance type sensor.

  Here, in general, in a capacitance type sensor, there is no substance in the container or piping in advance, so-called empty value and the capacitance value when the substance is filled. The threshold value is set with reference to a value between the capacitance values (for example, an intermediate value). In the following description, a substance such as a liquid or a granular material to be measured will be simply referred to as a “measurement object”. When the measured capacitance value is large with respect to this threshold, it is determined that the object to be measured exists (has reached a predetermined amount), and when the measured capacitance value is small It is determined that the object to be measured does not exist (has not reached the predetermined amount). Such a threshold value is manually set and adjusted using a variable resistor or the like.

In the prior art described above, it is necessary to set a threshold value corresponding to the object to be measured in advance, and setting such a threshold value is troublesome for the user. This is because the setting width (difference between the capacitance value when empty and the capacitance value when full) is different between the low and high measured objects, and the dielectric constants are different. This is because it is necessary to set a threshold according to the object to be measured.
Also, if the type of object to be measured changes during measurement, or the dielectric constant of the object to be measured changes, the conventional capacitive sensor cannot make a correct determination, and resets the threshold each time. There was a need.
In addition, when the object to be measured adheres to the measurement electrode when the object to be measured reaches a predetermined amount, even if the object to be measured has been reduced from the predetermined amount, the measurement electrode Since the adhesion residue remains, it may be erroneously determined that the predetermined amount has been reached. Also in this case, it was necessary to reset the threshold value in consideration of the attached matter.

  Therefore, there is a need for a sensor that automates the above-described threshold setting, which has been a conventional problem.

  A characteristic configuration of the sensor according to the present invention is a sensor that detects the presence or absence of a substance based on capacitance, and has a detection electrode and a grounding part that are insulated from each other, and extends between the detection electrode and the grounding part. A detection unit that detects the electrostatic capacitance according to the dielectric constant of the substance present, and a capacitance value detected by the detection unit when the detection unit is disposed at a predetermined detection position. A first threshold value setting unit that sets a large value as a first threshold value; and a capacitance value detected by the detection unit when a capacitance value detected by the detection unit exceeds the first threshold value. A second threshold value setting unit that sets a value smaller than the second threshold value as a second threshold value, and a capacitance value detected by the detection unit after the setting of the second threshold value exceeds the first threshold value, Smaller than the capacitance value detected by the detection unit A second threshold value updating unit that updates the second threshold value and a capacitance value detected by the detection unit when the capacitance value detected by the detection unit is equal to or less than the second threshold value. A first threshold value updating unit that updates the first threshold value to a value greater than the value; and a capacitance value detected by the detection unit exceeds the first threshold value, the substance is detected at the detection position. A detection result indicating that the substance is not present at the detection position when the capacitance value detected by the detection unit is equal to or less than the second threshold value. And an output unit for outputting.

  With such a characteristic configuration, the first threshold value used when determining that the substance to be detected exists at the detection position and the second threshold value used when determining that the substance to be detected does not exist are provided. It can be automatically set according to the object to be measured. Therefore, it is possible to automatically set the threshold value without manually adjusting the threshold value.

  In addition, the sensor includes a peak value storage unit that stores a peak value among capacitance values detected by the detection unit, and the second threshold update unit is configured to update the peak value when the peak value is updated. It is preferable to update the second threshold value.

  With such a configuration, it is possible to increase a margin when determining that the substance to be detected does not exist. Therefore, for example, when the level of the substance to be detected is lower than the detection position where the detection unit is arranged, if the substance remains attached to the detection unit or due to disturbance or secular change, the detection target It is possible to prevent erroneous determination such that it is determined that the substance to be detected is present even though the substance is not present.

  In addition, the second threshold value updating unit has a second width that is set in advance from the capacitance value detected by the detection unit when the peak value stored in the peak value storage unit is updated. It is preferable to update the second threshold value to a smaller value between a small value and a value of a preset ratio of the capacitance value detected by the detection unit.

  With such a configuration, it is possible to increase a margin when determining that the substance to be detected does not exist. Therefore, it is possible to prevent an erroneous determination such that it is determined that the substance to be detected does not exist due to the capacitance change due to the change in dielectric constant or the like, even though the substance to be detected exists.

It is the figure which showed the example at the time of arrange | positioning a sensor to a container. It is the figure which showed the structure of the sensor typically. It is the figure which showed the 1st threshold value and 2nd threshold value which are set according to the change of the value of an electrostatic capacitance.

  The sensor according to the present invention is configured such that a threshold value used when detecting the presence or absence of a predetermined substance to be detected can be automatically set based on the capacitance. In other words, according to this sensor, even in a situation where it has been necessary to reset the threshold value in the past, it is easily determined whether or not a substance to be detected exists based on the automatic setting of the threshold value and the measured capacitance. Is possible. Hereinafter, the sensor 1 of the present embodiment will be described. In the following description, in order to facilitate understanding, the substance to be detected (measurement object) is assumed to be “oil” having a predetermined dielectric constant.

  FIG. 1 shows an example in which it is determined whether or not oil is stored in the container 2 using the sensor 1. In the present embodiment, the sensor 1 is provided on the side surface 5 of the container 2. Of course, it may be provided on the bottom 3 side or the top 4 side, or may be appropriately provided in a place where it is desired to detect.

  Here, the sensor 1 is a so-called capacitance type level switch. Since this type of capacitance type level switch is well-known, detailed description is omitted, but a detection electrode 11A described later and a ground electrode 11C as an example of a “ground portion” (when the container 2 is a metal container) The capacitance value between the ground electrode 11C and the wall 2 or the bottom of the container 2 connected to the ground electrode 11C is determined when oil is stored up to the position where the sensor 1 is provided in the container 2 and when the oil is stored. (Corresponding to when the container 2 is filled with “air”). The sensor 1 detects whether or not the substance to be detected has reached the position of the sensor 1 based on such a change in the capacitance value.

  FIG. 2 is a block diagram schematically showing the configuration of the sensor 1. As shown in FIG. 2, the sensor 1 includes a detection unit 11, a first threshold setting unit 12, a threshold storage unit 13, a peak value storage unit 14, a determination unit 15, a second threshold setting unit 16, and a second threshold update unit. 17, a first threshold update unit 18, and an output unit 19. These functional units can be appropriately constructed by hardware and / or software.

  The detection unit 11 is inserted into the container 2 as shown in FIG. 1 and detects a substance at the inserted position. In the present embodiment, the detection unit 11 includes a detection electrode 11A and a ground electrode 11C that are configured in a rod shape as shown in FIG. 1 and are insulated from each other. The detection electrode 11A and the ground electrode 11C are insulated by the insulating portion 11B. In this embodiment, the detection part 11 is arrange | positioned in order of the detection electrode 11A, the insulation part 11B, and the ground electrode 11C from the said rod-shaped front end side. When the inner wall portion of the container 2 is made of metal, the ground electrode 11C may be connected to the inner wall portion.

  The detection unit 11 detects a capacitance according to the dielectric constant of a substance existing across the detection electrode 11A and the ground electrode 11C. The sensor 1 detects whether or not the oil storage level has reached the position of the detection unit 11 in the container 2 based on the change in the dielectric constant of the substance between the detection electrode 11A and the ground electrode 11C.

  Here, the upper part of FIG. 3 shows the value of the capacitance detected by the detection unit 11 (shown by a solid line in FIG. 3), and a first threshold value and a second threshold value which will be described later. Shows a detection result by the sensor 1. Hereinafter, description will be given with reference to FIG. 3 together with FIG.

  The first threshold value setting unit 12 sets a value larger than the capacitance value detected by the detection unit 11 as the first threshold value when the detection unit 11 is arranged at a predetermined detection position. “When the detection unit 11 is arranged at a predetermined detection position” is when the detection unit 11 is arranged in the container 2. Here, generally, the detection unit 11 is arranged in a state where the container 2 is empty. For this reason, when the detection unit 11 is arranged at a predetermined detection position, the detection result of the detection unit 11 includes the detection electrode 11A and the ground electrode 11C in a state where no substance to be detected exists at the detection position. The value of the capacitance in between is acquired. In FIG. 3, the capacitance value at this time (t = t0) is shown as C0.

  The first threshold value setting unit 12 sets a value larger than the capacitance value C0 at this time as the first threshold value (# 01). The “value larger than the capacitance value C0” is preferably a value that is larger than the capacitance value C0 by a preset first width, for example. The “first width set in advance” is, for example, a capacitance that allows the determination unit 15 described later to determine that the object to be measured exists even for a substance having the lowest dielectric constant among the objects to be measured. It is preferable to set based on the increase width. In the present embodiment, the first width is described as “0.1 pF”. Therefore, when the detection unit 11 is disposed at a predetermined detection position, the first threshold setting unit 12 sets a value that is 0.1 pF larger than the capacitance value at this time as the first threshold. Note that “0.1 pF” is an example, and other values may be used.

  The threshold storage unit 13 stores each threshold used by the sensor 1. The “each threshold value used by the sensor 1” is a threshold value used when the sensor 1 determines whether or not a substance to be detected exists. Specifically, the first threshold described above corresponds to a second threshold described later.

  The peak value storage unit 14 stores a peak value among the capacitance values detected by the detection unit 11. As described above, after the first threshold value is stored in the threshold value storage unit 13, the substance (oil) to be detected is introduced into the container 2 and the remaining amount level increases. As the remaining amount level of the substance (oil) increases, the capacitance value between the detection electrode 11A and the ground electrode 11C increases as shown in FIG. The peak value storage unit 14 sequentially receives detection results from the detection unit 11 and holds the peak value. The storage of the peak value by the peak value storage unit 14 is continuously performed while the sensor 1 determines the presence / absence of the substance to be detected, and the capacitance value larger than the currently stored peak value. Is detected, the peak value stored so far is updated with the capacitance value.

  The determination unit 15 determines whether or not the capacitance value detected by the detection unit 11 exceeds the first threshold value. Specifically, the detection result is sequentially transmitted from the detection unit 11 to the determination unit 15. When the detection result is transmitted to the determination unit 15, the first threshold value currently stored in the threshold storage unit 13 is referred to. Then, it is determined whether or not the capacitance value related to the transmitted detection result is larger than the first threshold value.

  The second threshold value setting unit 16 sets a value smaller than the capacitance value detected by the detection unit 11 to the second threshold value when the capacitance value detected by the detection unit 11 exceeds the first threshold value. Set as. Whether or not the capacitance value detected by the detection unit 11 exceeds the first threshold value is determined by the determination unit 15 and the determination result is transmitted. When such a determination result is transmitted from the determination unit 15 (t = t1), the second threshold setting unit 16 sets a value smaller than the capacitance value detected by the detection unit 11 as the second threshold. (# 02). For this reason, it is preferable to transmit the value of the electrostatic capacitance detected by the detection unit 11 resulting from the determination result to the second threshold setting unit 16 from the determination unit 15 together with the determination result described above. Of course, it is also possible to configure such that the detection unit 11 directly transmits to the second threshold setting unit 16. The second threshold set by the second threshold setting unit 16 is stored in the threshold storage unit 13 described above.

  The “value smaller than the value of the capacitance detected by the detection unit 11” is preferably set to a value smaller than the value of the capacitance by a preset second width, for example. The “predetermined second width” may be the same value as the first width or a different value. Further, the second width is based on a reduction width of the capacitance that can be determined by the determination unit 15 described later even if a substance having the lowest dielectric constant among the objects to be measured does not exist. Is preferable. In the present embodiment, when the capacitance value detected by the detection unit 11 exceeds the first threshold value, the second threshold setting unit 16 sets a value smaller by 0.1 pF than the capacitance value at this time. Set as the second threshold. Note that “0.1 pF” is an example, and other values may be used.

  The second threshold update unit 17 is detected by the detection unit 11 when the capacitance value detected by the detection unit 11 exceeds the first threshold after setting the second threshold by the second threshold setting unit 16. The second threshold value is updated to a value smaller than the value of the capacitance that has been set. In particular, in the present embodiment, the second threshold update unit 17 detects the static value detected by the detection unit 11 when the value of the capacitance detected by the detection unit 11 exceeds the first threshold and the peak value is updated. The second threshold value is updated to a value smaller than the value of the electric capacity. As described above, the second threshold value is set by the second threshold value setting unit 16. In addition, the determination unit 15 determines whether or not the capacitance value detected by the detection unit 11 has exceeded the first threshold value stored in the threshold value storage unit 13. Further, when a capacitance value larger than the currently stored peak value is transmitted to the peak value storage unit 14, the peak value stored so far is updated with the capacitance value. The The second threshold value updating unit 17 is configured when the detected capacitance value exceeds the first threshold value and the peak value stored in the peak value storage unit 14 is updated after setting the second threshold value. (T = t2), the second threshold value stored in the threshold value storage unit 13 is updated to a value smaller than the capacitance value corresponding to the updated peak value (# 03). Note that the second threshold value is updated by the second threshold value updating unit 17 until the capacitance value becomes smaller than the second threshold value again (t = t3). When it becomes larger, it is continuously performed (# 03 to # 05).

  When the capacitance value detected by the detection unit 11 is equal to or less than the second threshold value, the first threshold update unit 18 sets the first threshold update unit 18 to a value larger than the capacitance value detected by the detection unit 11. 1 Threshold value is updated. Whether or not the capacitance value detected by the detection unit 11 is equal to or smaller than the second threshold value is stored in the threshold value storage unit 13 when the determination unit 15 receives the detection result from the detection unit 11. The determination is made with reference to the second threshold. The first threshold update unit 18 is stored in the threshold storage unit 13 when the determination unit 15 determines that the capacitance value detected by the detection unit 11 is equal to or less than the second threshold (t = t3). The first threshold value is updated to a value larger than the capacitance value at this time. At this time, as described above, it is preferable to update to a value larger by the first width than the capacitance value, that is, a value larger by 0.1 pF than the capacitance value at this time (# 06). The updating of the first threshold value by the first threshold value updating unit 18 is such that once the capacitance value detected by the detection unit 11 becomes equal to or smaller than the second threshold value (t = t3), Until the value becomes larger than the first threshold value again (t = t4), the process is continuously performed when the value becomes smaller than the previously acquired value (# 07). When the first threshold is updated by the first threshold update unit 18, the peak value stored in the peak value storage unit 14 is once reset, and for example, a zero value is stored in the peak value storage unit 14. Alternatively, the peak value stored in the peak value storage unit 14 is not reset, and the capacitance value detected by the detection unit 11 is overwritten in the peak value storage unit 14. It may be configured.

  The output unit 19 indicates that the substance is present at the detection position when the value of the capacitance detected by the detection unit 11 is larger than the first threshold, and the capacitance detected by the detection unit 11 When the value of is less than or equal to the second threshold, a detection result indicating that no substance is present at the detection position is output. When the detection result is transmitted from the detection unit 11, the determination unit 15 determines whether the capacitance value detected by the detection unit 11 is larger than the first threshold value stored in the threshold value storage unit 13. Further, it is determined whether or not the capacitance value detected by the detection unit 11 is equal to or less than the second threshold value stored in the threshold value storage unit 13. Such a determination result of the determination unit 15 is transmitted to the output unit 19.

  In the present embodiment, when the output unit 19 determines that the capacitance value detected by the detection unit 11 is larger than the first threshold value stored in the threshold value storage unit 13 by the determination unit 15, 3 (between t = t1 and t = t3, after t = t4), the detection ON signal is output, and the capacitance value detected by the detection unit 11 by the determination unit 15 is the threshold storage unit. When it is determined that the value is equal to or smaller than the second threshold value stored in FIG. 13, the detection on signal output is stopped or the detection is turned off as shown in FIG. 3 (between t = t3 and t = t4). Output a signal. Thereby, it is possible to specify whether or not the “measurement object” exists. Of course, when the determination unit 15 determines that the value of the capacitance detected by the detection unit 11 is larger than the first threshold value, a detection off signal is output, and the determination unit 15 detects the static value detected by the detection unit 11. When it is determined that the capacitance value is equal to or less than the second threshold value, it is possible to configure using a different determination method such as stopping output of the detection off signal or outputting a detection on signal. is there.

In the present sensor 1, the first threshold value and the second threshold value can be automatically set as described above, and the presence or absence of the substance to be detected is appropriately determined based on the first threshold value and the second threshold value thus set. Can be determined.
In addition, setting thresholds according to the object to be measured, resetting the threshold when the type of object to be measured changes during measurement, or the dielectric constant of the object changes, measurement electrodes It is not necessary to reset the threshold value when the adhering residue remains.

[Other Embodiments]
In the above embodiment, the substance to be detected (measurement object) is “oil”, and when empty, the container 2 is filled with “air”. However, the substance to be detected is “ It may be a substance other than “oil”, such as a liquid, a granular material, a solid, or a gas, or may be other than “air” when no substance to be detected exists.

  In the above embodiment, an example in which the sensor 1 detects the storage level of oil stored in the container 2 has been described. However, a substance that circulates or stores something other than a container such as a pipe by the sensor 1 is a detection target. It can also be used to determine whether or not the substance is a certain substance. In addition, the sensor 1 is provided at an arbitrary place different from the container, piping, etc., and is used to determine whether or not the substance to be detected exists around the sensor 1 (within a preset range from the sensor 1). Is also possible.

  In the above embodiment, the detection unit 11 is described as being configured in a rod shape, but the detection unit 11 may be configured in a circular shape or a flat shape. Of course, other shapes can be used. Further, the whole or a part of the detection unit 11 may be covered with a resin or the like. In any case, the detection electrode 11A and the ground electrode 11C may be configured to be insulated.

  In the above embodiment, the first threshold value and the second threshold value are set in the sensor 1. However, the first threshold value and the second threshold value may be set individually, or may be set as one common threshold value. May be. In particular, when setting as one threshold value, the threshold value storage unit 13 has one threshold value, and the determination unit 15 determines whether the capacitance value exceeds the threshold value stored in the threshold value storage unit 13. It may be configured to determine whether or not the capacitance value is equal to or less than a threshold value stored in the threshold value storage unit 13. In addition, when setting it as one threshold value in this way, a "1st threshold value setting part" and a "2nd threshold value setting part" shall be one "threshold value setting part", and a "1st threshold value update part" and "2nd The “threshold update unit” may be one “threshold update unit”. Further, when one threshold is used, the storage capacity of the threshold storage unit 13 can be reduced.

  In the above embodiment, the second threshold update unit 17 updates the second threshold to a value smaller than the capacitance value detected by the detection unit 11. Specifically, the second threshold update unit 17 is a detection unit. When the capacitance value detected by 11 exceeds the first threshold value and the peak value is updated, the second threshold value is updated to a value smaller than the capacitance value detected by the detection unit 11. explained. However, the second threshold update unit 17 sets the first threshold value to a value smaller than the capacitance value detected by the detection unit 11 regardless of whether or not the peak value stored in the peak value storage unit 14 has been updated. It is also possible to configure to update the two threshold values.

  In addition, the second threshold update unit 17 has a second width that is set in advance from the value of the capacitance detected by the detection unit 11 when the peak value stored in the peak value storage unit 14 is updated. It is also possible to configure the second threshold value to be updated to a smaller value between the small value and the value of the preset ratio of the capacitance value detected by the detection unit 11. That is, when the peak value stored in the peak value storage unit 14 is updated, the second threshold update unit 17 has a value that is smaller than the current capacitance value by a second width (for example, 0.1 pF), It is possible to configure the second threshold value to be updated to a smaller value out of a predetermined ratio value (for example, a value of 95%) of the current capacitance value. In addition, it is possible to add a function that can freely change at least one of the first width and the second width according to the measurement situation.

  Furthermore, the second threshold update unit 17 sets the capacitance value detected by the detection unit 11 in advance regardless of whether or not the peak value stored in the peak value storage unit 14 has been updated. It is possible to configure the second threshold value to be updated to a ratio value (for example, a value of 95%), and the second threshold value updating unit 17 updates the peak value stored in the peak value storage unit 14. In such a case, the second threshold value may be updated to a preset ratio value (for example, a value of 95%) of the capacitance value detected by the detection unit 11.

  In the above embodiment, the sensor 1 includes the peak value storage unit 14 that stores the peak value among the capacitance values detected by the detection unit 11, and the second threshold update unit 17 updates the peak value. However, the sensor 1 may not be provided with the peak value storage unit 14 depending on the measurement and environmental conditions. In this case, the second threshold value updating unit 17 sets the second threshold value when the capacitance value detected by the detection unit 11 exceeds the current first threshold value (the currently set first threshold value). It can be configured to update.

  In the above embodiment, the first threshold value setting unit 12 sets a value that is larger than the detected capacitance value by the first width as the first threshold value, and the first threshold value updating unit 18 sets the detected capacitance value. Although it has been described that the first threshold value is updated to a value that is larger than the value by the first width, the first width can be changed as appropriate, and the first width itself need not be provided.

  In the above embodiment, the second threshold value setting unit 16 sets a value that is smaller than the detected capacitance value by the second width as the second threshold value, and the second threshold value updating unit 17 sets the detected capacitance value. Although it has been described that the second threshold value is updated to a value smaller than the value by the second width, the second width can be changed as appropriate, and the second width itself does not have to be provided.

  The present invention can be used for a sensor that detects the presence or absence of a substance based on capacitance.

1: sensor 11: detection unit 11A: detection electrode 11C: ground electrode 12: first threshold value setting unit 14: peak value storage unit 16: second threshold value setting unit 17: second threshold value updating unit 18: first threshold value updating unit 19 : Output section

Claims (3)

A sensor that detects the presence or absence of a substance based on capacitance,
A detection unit that includes a detection electrode and a grounding part that are insulated from each other, and that detects the capacitance according to a dielectric constant of the substance existing between the detection electrode and the grounding part;
A first threshold setting unit configured to set a value larger than the value of the capacitance detected by the detection unit as the first threshold when the detection unit is disposed at a predetermined detection position;
A second threshold value setting that sets a value smaller than the capacitance value detected by the detection unit as the second threshold value when the capacitance value detected by the detection unit exceeds the first threshold value. And
After the setting of the second threshold value, when the capacitance value detected by the detection unit exceeds the first threshold value, the first value is smaller than the capacitance value detected by the detection unit. A second threshold update unit that updates two thresholds;
When the value of the capacitance detected by the detection unit becomes equal to or less than the second threshold value, the first threshold value is updated to a value larger than the value of the capacitance detected by the detection unit. A threshold update unit;
If the value of the capacitance detected by the detection unit exceeds the first threshold, it indicates that the substance is present at the detection position, and the capacitance detected by the detection unit An output unit that outputs a detection result indicating that the substance is not present at the detection position when the value is equal to or less than the second threshold;
Comprising a sensor. Among the capacitance values detected by the detection unit, a peak value storage unit that stores a peak value,
The sensor according to claim 1, wherein the second threshold update unit updates the second threshold when the peak value is updated.   The second threshold value updating unit is a value that is smaller by a preset second width than the capacitance value detected by the detection unit when the peak value stored in the peak value storage unit is updated. 3. The sensor according to claim 2, wherein the second threshold value is updated to a smaller value between a predetermined value of the capacitance value detected by the detection unit.

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