Sensor and liquid level meter for determining position of interface

Abstract

The present invention is provided with: a ground conductor (40) extending in a liquid level detection direction; a sensor unit (30) that is provided with a plurality of electrodes (31) that are arranged in the liquid level detection direction and that form capacitance between the ground conductor (40) and the electrodes (31); an adjustment unit (70); a switching unit (80); a determination unit (90); and a liquid level determination means (100) in which the electrodes (31) are divided into n groups, the i-th group (i = 1, 2,..., n) comprises the electrodes (31) at the (2i-1)-(2k-1)-th (k is a natural number of 1 to 2n-i) positions from the lowermost position in the liquid level detection direction, the electrodes belonging to the same group among the electrodes (31) are connected in parallel and are connected to the switching means (80), and for i = 1, 2,..., n-1, n is a natural number of 1 to 2n-i. A determination means (100) determines the magnitude of the capacitance between the i-th group and the group obtained by combining the i + 1-th group to the n-th group, and determines the magnitude of the capacitance between the n-th group and the adjustment unit (70), and in order to enable determination, a switching means (80) sequentially switches the connections between the groups and the determination means (90), and determines the liquid level on the basis of the determination by the determination means (90).

Description

Technical Field

[0001] The present disclosure relates to a sensor for determining the position of an interface between two substances (hereinafter, referred to as an interface sensor) and a liquid level meter including the interface sensor. Background Art

[0002] Figure 1 Patent Document 1 Figure 1 The conventional water level sensor measures the water level from a predetermined reference position (e.g., the bottom of the water tank) in the water tank 1 to the liquid level L. The reference line 10 is an imaginary line, and Z observation points Q are pre-set on the reference line 10. z (z=1, 2, ..., Z). Figure 1 In the example shown, Z=7, and seven observation points Q1 to Q7 are shown.

[0003] The electrode pairs P1 to P7 are arranged one-to-one on the horizontal plane (level) of the observation points Q1 to Q7. The determination units 11 to 17 are connected one-to-one to the electrode pairs P1 to P7. Each of the determination units 11 to 17 has a function of determining whether the electrostatic capacitance value of the corresponding electrode pair in the electrode pairs P1 to P7 exceeds a prescribed reference value. For example, when the determination unit 13 determines that the electrostatic capacitance value of the electrode pair P3 arranged on the horizontal plane of the observation point Q3 exceeds the prescribed reference value, there is liquid on the horizontal plane of the observation point Q3. When the determination unit 13 determines that the electrostatic capacitance value of the electrode pair P3 arranged on the horizontal plane of the observation point Q3 does not exceed the prescribed reference value, there is no liquid on the horizontal plane of the observation point Q3.

[0004] When i determination units from the first to the i-th (i∈{1, 2, ..., Z}) among the Z determination units output a determination result indicating that the reference value is exceeded, the water level output unit 20 outputs information indicating the water level at the i-th observation point. Figure 1 In the example shown, the determination units 11 to 14 corresponding to the electrode pairs P1 to P4 below the liquid level L (i.e., immersed in the liquid) output determination results indicating that the reference value is exceeded, and the determination units 15 to 17 corresponding to the electrode pairs P5 to P7 above the liquid level L (i.e., not immersed in the liquid) output determination results indicating that the reference value is not exceeded, so the water level output unit 20 outputs information indicating the horizontal plane of the fourth observation point Q4.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 11-311562 Summary of the invention

[0008] Problems to be solved by the invention

[0009] The water level sensor of the prior art described above determines the water level by determining the presence or absence of liquid on the horizontal plane of each of the two or more observation points set in the direction of water level change (hereinafter referred to as the horizontal plane change direction) based on the electrostatic capacitance value of each of the two or more electrode pairs arranged one-to-one on the horizontal plane of the two or more observation points. The water level sensor of the prior art described above approximately determines the water level based on discrete values. Therefore, if the water level sensor of the prior art described above is used to determine the water level with a high resolution, a plurality of electrode pairs are required, and as a result, a plurality of wires are also required corresponding to the plurality of electrode pairs.

[0010] For example, in order to determine the water level with high resolution, Z observation points are set in the direction of the horizontal plane change, and the above-mentioned prior art water level sensor requires not only Z electrode pairs but also Z+1 wires. This is because the electrodes of one side of the Z electrode pairs are connected to a common wire, and the electrodes of the other side of the Z electrode pairs are connected one-to-one to Z different wires.

[0011] In view of the above background technology, an interface sensor having a structure capable of making the total number L of wires led out from the interface sensor less than Z+1 (where Z is the total number of observation points), and a liquid level meter including the interface sensor are disclosed.

[0012] Means for solving problems

[0013] The technical matters described herein are not provided for the purpose of explicitly or implicitly limiting the invention described in the claims, nor are they provided for the purpose of enabling persons other than the beneficiaries of the present invention (e.g., the applicant and the patentee) to limit the invention described in the claims, but are simply provided for the purpose of facilitating the understanding of the gist of the present invention. The overview of other aspects of the present invention can be understood, for example, based on the claims of the patent application.

[0014] The sensor disclosed in the present invention is a sensor for determining the position of the interface of two substances (i.e., a first substance and a second substance that are different from each other). The sensor includes a first electrical conductor, E second electrical conductors, L wires, and a wire selector. With respect to E and L, the following equations hold. In these equations, K is a predetermined integer satisfying 2≤K, for each j∈{x∈N:1≤x≤K}, n(j) is a predetermined integer satisfying 2≤n(j), and N is a set of all positive integers.

[0015] [Mathematical formula 1]

[0016]

[0017] The E second electric conductors are located on E planes that are not aligned with each other and are parallel to each other in an order that follows the magnitude relationship of the elements of the set {x∈N:1≤x≤E}.

[0018] For each p∈{x∈N:1≤x≤E-1}, the pth second electrical conductor among the E second electrical conductors is connected to the s(p)th conducting wire among the L conducting wires. With respect to s(p), the following equation holds: n(0)=1 in this equation.

[0019] [Mathematical formula 2]

[0020]

[0021] In the above formula, r is determined by p∈W(r). For each k∈{x∈N:1≤x≤K}, the kth set W(k) is represented by the following formula. In this formula, the K+1th set W(K+1) is an empty set.

[0022] [Mathematical formula 3]

[0023]

[0024] An Eth second electrical conductor among the E second electrical conductors is connected to an Lth conducting wire among the L conducting wires.

[0025] The wire selector can select any one of the L wires.

[0026] Or, for each k∈{x∈N:1≤x≤K}, the wire selector

[0027] 1) When k≠K and n(k)≠2,

[0028] For each y∈{x∈N:1≤x≤n(k)-2}, select two wires from the L wires determined by the elements belonging to the set Y(y), where

[0029] [Formula 4]

[0030]

[0031] For y=n(k)-1, select (2+Σ j＝k+1 K (n(j)-1)) conductors, where

[0032] [Mathematical formula 5]

[0033]

[0034] 2) When k≠K and n(k)=2,

[0035] Select the L wires, determined by the elements belonging to the set Y (2 + Σ j＝k+1 K (n(j)-1)) conductors, where

[0036] [Mathematical formula 6]

[0037]

[0038] 3) In the case of k = K,

[0039] For each y∈{x∈N:1≤x≤n(k)-1}, select two wires from the L wires determined by the elements belonging to the set Y(y), where

[0040] [Formula 7]

[0041]

[0042] Effects of the Invention

[0043] According to the present invention, the total number L of wires led out from the interface sensor can be made less than Z+1 (where Z is the total number of observation points). BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a diagram showing a configuration example of a conventional water level sensor.

[0045] Figure 2 It is a diagram for explaining the structure of Example 1 of the water level gauge according to the present invention.

[0046] Figure 3 (a) is used to illustrate Figure 2 The diagram of the water level gauge shown in FIG. (b) is used to illustrate the operation of the water level gauge. Figure 2 The diagram shows the operation of the water level gauge.

[0047] Figure 4 It is shown based on Figure 2 Flow chart of the process of water level measurement by the water level gauge shown.

[0048] Figure 5 It is shown based on Figure 2 Table showing the operation of switches in water level measurement of a water level gauge.

[0049] Figure 6 It is a diagram for explaining the structure of Example 2 of the water level gauge based on the present invention.

[0050] Figure 7 It is shown based on Figure 6 Flow chart of the process of water level measurement by the water level gauge shown.

[0051] Figure 8 It is shown based on Figure 6 Table showing the operation of switches in water level measurement of a water level gauge.

[0052] Fig. 9 It is a diagram for explaining the structure of Example 3 of the water level gauge based on the present invention.

[0053] Fig.10 (a) is used to illustrate Fig. 9 The diagram of the water level gauge shown in FIG. (b) is used to illustrate the operation of the water level gauge. Fig. 9 The diagram shows the operation of the water level gauge.

[0054] Fig.11 It is shown based on Fig. 9 Table showing the operation of switches in water level measurement of a water level gauge.

[0055] Fig.12 It is a diagram for explaining the structure of Example 4 of the water level gauge based on the present invention.

[0056] Fig.13 Is based on Fig.12 Table showing the operation of switches in water level measurement of a water level gauge.

[0057] Fig.14 It is a diagram for explaining the structure of Example 5 of the water level gauge based on the present invention.

[0058] Fig.15 This is a structural example of an interface sensor that is related to the interface sensor of the present disclosure but is not protected by the claims of the present application.

[0059] Fig.16 This is a structural example of the interface sensor disclosed in the present invention.

[0060] Fig.17 This is a structural example of the interface sensor disclosed in the present invention. DETAILED DESCRIPTION

[0061] The liquid level meter according to the embodiment of the present invention will be described by way of example with reference to the accompanying drawings. Figures 2 to 14 In the related description, water is used as an example of liquid.

[0062] Example 1

[0063] Figure 2 This is a diagram showing the structure of Example 1 of a water level meter based on the present invention, wherein the water level meter includes a sensor unit 30, a grounding conductor 40, a carrier generating circuit 50, two resistors 61, 62, an adjustment unit 70, a switching unit 80, a determination unit 90, a water level determination unit 100 and a control unit 110.

[0064] The sensor unit 30 includes a plurality of (15 in this example) electrodes 31 arranged in the water level detection direction, and the electrodes 31 form an electrostatic capacitance with a ground conductor 40 extending in the water level detection direction. Although the substrate is not shown in the figure, these electrodes 31 are arranged in a pattern on the substrate, and a waterproof coating is applied to the pattern. The ground conductor 40 is, for example, a metal tube surrounding the sensor unit 30, and the metal tube is, for example, made of stainless steel. In addition, for the 15 electrodes 31, as shown in FIG. Figure 2 As shown, the symbols C1 to C15 are given in order from the electrode located at the bottom.

[0065] The 15 electrodes 31 are divided into 4 groups. Here, the number of groups is n, and the n groups are referred to as the first to nth groups. The electrodes 31 constituting the i-th group (i=1, 2, ..., n) are located at the second position from the bottom in the water level detection direction. i-1 (2k-1) (k is 1 to 2 n-i In this example, if C1 to C15 are used to represent the electrodes 31 of each group composed of n=4, the following is obtained.

[0066] Group 1…C1, C3, C5, C7, C9, C11, C13, C15

[0067] Group 2…C2, C6, C10, C14

[0068] Group 3…C4, C12

[0069] Group 4…C8

[0070] With regard to all the electrodes 31 , the electrodes 31 belonging to the same group are connected in parallel to each other and to the switching unit 80 .

[0071] As indicated by the symbols S1 to S7, the switching unit 80 in this example includes seven switches 81, and is structured so as to switch paths according to the on / off state of these switches 81, thereby being able to input (connect) the detection values ​​(electrostatic capacitance of each group) obtained by each group of the sensor unit 30 to either of the two inputs a and b of the determination unit 90.

[0072] The carrier generation circuit 50 is connected to two wirings from the switching unit 80 to the two inputs a and b of the determination unit 90 via resistors 61 and 62. The carrier generation circuit 50 generates and outputs a carrier.

[0073] The adjustment unit 70 is formed as a capacitor having an electrostatic capacitance as described later, one end of which is connected to a wiring from the switching unit 80 to the input b of the determination unit 90 , and the other end of which is grounded.

[0074] The determination unit 90 determines the magnitude relationship between the electrostatic capacitances connected to the inputs a and b. Here, the electrostatic capacitance connected to the input a is C a , let the electrostatic capacitance connected to input b be C b When, refer to Figure 3 The timing diagram shown is for distinguishing C a and C b The circuit operation of the determination unit 90 for determining the magnitude relationship will be described.

[0075] C a >C b When it becomes Figure 3 (a) is a timing chart. The carrier generation circuit 50, the resistance of the resistor 61 and the electrostatic capacitance C a Since the CR delay circuit is formed, the waveform at point a is a waveform that is delayed relative to the carrier wave (rectangular wave) output by the carrier wave generating circuit 50. The waveform at point b is also a waveform that is delayed, but due to the C a >C b , so the delay of one side of the waveform at point b is smaller. In this example, the discrimination unit 90 includes a circuit for binarizing each waveform using the voltage s as a threshold, and a logic circuit that sets the rising edge of the binarized waveform at point a to Hi and the rising edge of the binarized waveform at point b to Lo. The waveform of the discrimination process (the output waveform of the logic circuit) becomes as follows: Figure 3 (a) as shown. a >C b , the waveform of the discrimination processing becomes Hi for a period exceeding half a cycle, so the Hi time becomes longer than the Lo time.

[0076] C a <C b When it becomes Figure 3 (b) is a timing diagram. In this case, the waveform at point a has a smaller delay, and the waveform of the discrimination process becomes as follows through the above circuit structure. Figure 3 As shown in (b), the Lo state is reached when the time exceeds half a cycle, so the Lo state is longer than the Hi state. Therefore, by comparing the Hi state and the Lo state of the judgment processing waveform, C can be determined. a and C b The size of the discriminant unit 90 is C a >C b Output 1 at C a <C b Output 0 when

[0077] The water level determination unit 100 determines the water level based on the determination of the determination unit 90 operating in this way and outputs it to the outside. In addition, the on / off of the seven switches 81 of the switching unit 80 is controlled by a control signal from the control unit 110, and a signal synchronized with the control is also input from the control unit 110 to the water level determination unit 100.

[0078] Next, refer to Figure 4 The flowchart shown in FIG. 1 illustrates the process until the water level output based on the water level gauge having such a structure. Figure 4 In G, the number of groups is set to n, i represents the i-th group, G i+1 , G i+2 , G n They represent the i+1th group, the i+2th group, and the nth group respectively.

[0079] First, i=1 (step M1), and all switches 81 of the switching unit 80 are turned OFF (step M2). Then, the input a of the connection determination unit 90 and the input G are turned ON. i The switch 81 further turns on the input b of the determination unit 90 and the input G i+1 , G i+2 , …, G n The switch 81 is turned on (steps M3 and M4). The determination unit 90 determines the magnitude relationship of the inputs a and b (step M5). If a>b, 1 is output to the water level determination unit 100. If a<b, 0 is output to the water level determination unit 100. The water level determination unit 100 stores it as 2 i-1 The value of the bit (steps M6, M7).

[0080] Next, i=i+1 is set (step M8), and it is determined whether i=n (step M9). If i=n is not, the process returns to step M2, and steps M2 to M9 are repeated until i=n.

[0081] If i=n, ​​after all switches 81 of the switching unit 80 are turned OFF (step M10), the inputs a and G of the connection determination unit 90 are turned ON (step M20). n The switch 81 is turned on (step M11). The determination unit 90 determines the magnitude relationship of the inputs a and b (step M12). If a>b, 1 is output to the water level determination unit 100. If a<b, 0 is output to the water level determination unit 100. The water level determination unit 100 stores it as 2 n-1 The water level determination unit 100 refers to the memory and calculates the value of the 2 bits obtained in this way (steps M13 and M14). 0 Position ~2 n-1The bit value, that is, the binary number is converted into a water level and output (step M15).

[0082] Like this, in this example, for i=1, 2, ..., n-1, the determination unit 90 respectively determines the magnitude relationship between the detection value obtained by the i-th group and the detection value obtained by merging the i+1-th group to the n-th group, and further, the water level is measured by determining the magnitude relationship between the detection value obtained by the n-th group and the detection value obtained by the adjustment unit 70. In order to enable such a determination based on the determination unit 90, the switching unit 80 sequentially switches the connection between the groups of the sensor unit 30 and the determination unit 90.

[0083] Figure 5 Table 1 shows the Figure 2 The number n of the water level gauges, i.e., the sensor units 30, is 4. Figure 4 In the water level gauge where i is 1 to 4 in the flowchart shown, the seven switches 81, i.e., S1 to S7, of the switching unit 80 are turned on / off when i=1 to 4. Figure 2 In the water level gauge shown, if the first to fourth groups are represented by G1 to G4, the connection of the two input groups a and b to the determination unit 90 becomes as follows when i=1 to 4.

[0084]

[0085]

[0086] Below, the water level W is located at Figure 2 The electrostatic capacitance connected to the inputs a and b of the determination unit 90 will be specifically described by taking the case where the ninth electrode C9 from the bottom is immersed in water as the position indicated by the double-dashed line in FIG.

[0087] The electrostatic capacitance when the electrode 31 is in the air is represented by C air , let the electrostatic capacitance when in water be C water The capacitor of the adjustment unit 70 is denoted as C99 below, and the electrostatic capacitance is assumed to be 0.5C. water The relative dielectric constant of water is 80 at 20°C, which is C water =80C air In the case of i=1 to 4, the electrostatic capacitance connected to the inputs a and b is as follows.

[0088] <i=1:2 0 Position determination>

[0089] Input a: G1 = C1 + C3 + C5 + C7 + C9 + C11 + C13 + C15

[0090] =5C water +3Cair =403C air

[0091] Input b: G2+G3+G4=C2+C4+C6+C8+C10+C12+C14+C99

[0092] =4.5C water +3C air =363C air

[0093] <i=2:2 1 Position determination>

[0094] Input a: G2 = C2 + C6 + C10 + C14

[0095] =2C water +2C air =162C air

[0096] Input b: G3+G4=C4+C8+C12+C99

[0097] =2.5C water +C air =201C air

[0098] <i=3:2 2 Position determination>

[0099] Input a: G3 = C4 + C12

[0100] =C water +C air =81C air

[0101] Input b: G4=C8+C99

[0102] =1.5C water =120C air

[0103] <i=4:2 3 Position determination>

[0104] Input a: G4=C8

[0105] =C water =80C air

[0106] Input b: N / A = C99

[0107] =0.5C water =40C air

[0108] According to the above, in i=1, according to a>b, 2 0 The bit becomes 1, in i=2, according to a<b, 2 1 The bit becomes 0. In addition, when i=3, according to a<b, 2 2 The bit becomes 0, and in i=4, according to a>b, 2 3 The bit becomes 1. Therefore, if these are added together, the result is 1001 in binary and 9 in decimal.

[0109] Like this, in Figure 2 In the water level gauge shown, the water level is processed as a binary number. At a low water level when all electrodes 31 are not immersed in water, the binary number becomes 0000, and at a high water level when all electrodes 31 are immersed in water, the binary number becomes 1111 (15 in decimal).

[0110] In this example, the adjustment unit 70 is set to have a 0.5C water The capacitor with an electrostatic capacitance of 1 is always connected to the input b of the determination unit 90. 3 The adjustment unit 70 functions as a comparison with G4 when determining the position, but the adjustment unit 70 functions so that the two detection values ​​(electrostatic capacitances) whose magnitude relationship is determined by the determination unit 90 always become different values ​​from each other, that is, functions so that the magnitude relationship is not reversed due to an error factor, etc., which may cause erroneous detection. In addition, by adjusting the resistance value of the resistors 61 and 62, the sensitivity can be adjusted.

[0111] Hereinafter, Examples 2 to 5 will be described. Figure 2 The same reference numerals are given to corresponding parts of the structure of the first embodiment, and their detailed description is omitted.

[0112] Example 2

[0113] As described above, the adjustment unit 70 functions so that the detection value changes appropriately according to the water level without causing false detection. However, for example, in the case where the error in the electrostatic capacitance of the electrode 31 is uneven, if the combination of the electrode group is changed, the detection value may not change appropriately according to the water level only through the electrostatic capacitance of one adjustment unit 70.

[0114] For example, in Figure 2 In the water level gauge shown, it is considered that only the electrode 31 to which C4 is applied has +0.5C water That is, in the case of water level W, C4' = 1.5C water At this time, in i=1 to 4, the electrostatic capacitance connected to the inputs a and b of the determination unit 90 is as follows.

[0115] <i=1:2 0 Position determination>

[0116] Input a: G1 = C1 + C3 + C5 + C7 + C9 + C11 + C13 + C15

[0117] =5C water +3C air =403C air

[0118] Input b: G2+G3+G4=C2+C4'+C6+C8+C10+C12+C14+C99

[0119] =4.5C water +3C air +C99=363C air +C99

[0120] <i=2:2 1 Position determination>

[0121] Input a: G2 = C2 + C6 + C10 + C14

[0122] =2C water +2C air =162C air

[0123] Input b: G3+G4=C4'+C8+C12+C99

[0124] =2.5C water +C air +C99=201C air +C99

[0125] <i=3:2 2 Position determination>

[0126] Input a: G3=C4'+C12

[0127] =1.5C water +C air =121C air

[0128] Input b: G4=C8+C99

[0129] =C water +C99=80C air +C99

[0130] <i=4:2 3 Position determination>

[0131] Input a: G4=C8

[0132] =C water =80C air

[0133] Input b: N / A = C99

[0134] Since the true value of a binary number is 1001, it must be that a>b in i=1, a<b in i=2, a<b in i=3, and a>b in i=4. Therefore, in i=1, according to 403C air >363C air +C99, must be C99<40C air , in i=3, according to 121C air <80C air +C99, must be C99>41C air However, there is no C99 that satisfies both of them, and there is no C99 that satisfies 2 i One C99, namely, the adjustment unit 70, determines all the bits.

[0135] In order to deal with such a problem, in Example 2, Figure 6 As shown in FIG. 1 , a plurality of (four in this example, with reference numerals C101 to C104) adjustment units 70 are provided, and a switching unit 120 for switching the connection of the adjustment units 70 to the input b of the determination unit 90 is further provided. As shown in FIG. 1 , with reference numerals S11 to S14, the switching unit 120 includes four switches 121 for respectively connecting / disconnecting the connection of each adjustment unit 70, i.e., C101 to C104, to the input b.

[0136] In this example, by providing a plurality of adjustment units 70 in this manner and switching by the switching unit 120 , it is possible to select the adjustment unit 70 that functions according to the group (combination of groups) connected to the determination unit 90 .

[0137] Figure 7 The flowchart shown in the figure shows the process until the water level output of the water level meter based on the second embodiment, which is different from the above-mentioned Figure 4 In the flowchart shown, a step M4' of "turning on the switch connecting the adjustment unit corresponding to i and b" is added between steps M4 and M5, and a step M11' of "turning on the switch connecting the adjustment unit corresponding to n and b" is further added between steps M11 and M12.

[0138] Figure 8 Table 2 shows the relative Figure 5The contents of Table 1 shown in the figure add the on / off of the four switches 121, i.e., S11 to S14, of the switching unit 120 in i=1 to 4. In this example, in i=1, C101 is selected from the four adjustment units 70, i.e., C101 to C104, in i=2, C102 is selected, in i=3, C103 is selected, and in i=4, C104 is selected and connected to the input b of the determination unit 90. The on / off of the four switches 121 of the switching unit 120 is controlled by a control signal synchronized with a control signal from the control unit 110 that controls the switching unit 80. In addition, the electrostatic capacitance values ​​of the four adjustment units 70 are determined by a prior experiment.

[0139] Example 3

[0140] Fig. 9 1 is a diagram showing the structure of the third embodiment of the water level meter according to the present invention. In this example, a charging circuit 130 is provided as an input circuit instead of a carrier generating circuit 50, and electrostatic capacitance detection based on a switched capacitor is performed, and switches S11 to S14 are respectively provided between the four groups G1 to G4 formed by the electrodes 31 of the sensor unit 30 and the charging circuit 130, and a switching unit 80 having seven switches 81, namely, S1 to S7, is located between the four groups G1 to G4 and the distinguishing unit 90'. Furthermore, a switch S21 is provided between the adjusting unit 70 and the charging circuit 130, and a switch S22 is provided between the adjusting unit 70 and the distinguishing unit 90'.

[0141] The water level meter is also basically based on Figure 4 The water level detection is performed according to the flowchart shown in the figure. In each i where i=1 to 4, switches S1 to S7, S11 to S14, and S21 to S22 are as follows: Fig.11 is controlled as shown in Table 3.

[0142] The determination unit 90' determines the magnitude relationship of the electrostatic capacitance and outputs 1 or 0, but its structure (circuit structure) and operation are different from those of the determination unit 90. As an example, the case of i=3 is taken as an example. Fig.10 The timing diagram shown is for judging the C connected to input a and b respectively. a With C b The circuit operation of the determination unit 90' for determining the magnitude relationship will be described below.

[0143] When the switches S13, S14, and S21 are turned on and the switches S4, S7, and S22 are turned off, the third group G3 and the fourth group G4 of the sensor unit 30 and the adjustment unit 70 are charged with the voltage E0 generated by the charging circuit 130. a and C bEach of the switches S13, S14, and S21 is provided with an integration circuit and a sample-and-hold circuit (S / H circuit). If the switches S13, S14, and S21 are turned OFF and the switches S4, S7, and S22 are turned ON, then C a and C b The charges move to the integration circuit respectively. At this time, if the integration capacitor is set to C s , C a and C b The amplitude voltage V of each integrating circuit a , V b , it becomes as follows.

[0144] [Mathematical formula 8]

[0145]

[0146] V a , V b It can be obtained as a DC voltage, C a >C b When it becomes Fig.10 As shown in (a), C a <C b When it becomes Fig.10 (b) As shown. Thus, it is possible to determine C by comparing the voltage values. a With C b The size of the discriminating unit 90' is the same as the discriminating unit 90, in C a >C b Output 1 at C a <C b The water level determination unit 100 outputs 0. Figure 2 Similarly, the water level determination unit 100 in the embodiment converts the output of the determination unit 90' into a water level and outputs the converted water level.

[0147] Example 4

[0148] Fig.12 1 is a diagram showing a water level meter of Example 4. This water level meter is a modified example of the water level meter of Example 3, and is provided with two charging circuits. The voltage charged in each group G1 to G4 of the sensor unit 30 can be changed by the two charging circuits 130 and 140. Switches S15 to S17 are provided between the groups G2 to G4 and the charging circuit 140, respectively. In this example, in each i where i=1 to 4, switches S1 to S7, S11 to S17, and S21 to S22 are, for example, Fig.13 It is controlled as shown in Table 4.

[0149] According to this configuration, for example, when the sensitivity of the electrode 31 to water is to be adjusted, the voltages of the two integrating circuits of the determination unit 90 ′ are proportional to the voltage of the charging circuit. Therefore, such sensitivity adjustment can be performed by adjusting the voltages of the charging circuits 130 and 140 .

[0150] Example 5

[0151] Fig.14 This is a diagram showing a water level meter of Example 5. In this example, an A / D conversion unit 150 is provided between a switching unit 80 and a distinguishing unit 90, and an adjustment value storage unit 160 is further provided to store a pre-calculated adjustment value (electrostatic capacitance adjustment voltage value) as a digital value. Comparison of voltages based on analog circuits requires the use of an IC and a plurality of resistors. For example, as in the structure having four adjustment units 70 shown in Example 2, there is a disadvantage that the more adjustment values ​​there are, the larger the scale of the circuit becomes. The method of sequentially switching the connection between the group of sensor units 30 and the A / D conversion unit 150 of the switching unit 80 is the same as that of Example 1. In this example, the voltage is obtained. Figure 3 The waveform at point a and the waveform at point b in the A / D converter 150 are converted into digital data, so that the subsequent processing can be digitally processed. By using the adjustment value as the offset of the measured value of the waveform at point b, the same effect as the adjustment unit of Example 1 and Example 2 is achieved. In addition, the A / D converter 150 can also measure the differential voltage of the input a and the input b. In this case, the adjustment value is used as the offset of the differential voltage.

[0152] In the above, various embodiments of the water level meter according to the present invention are described. However, the water level meter according to the present invention divides a plurality of electrodes arranged in the water level detection direction and forming an electrostatic capacitance between the ground conductor into n groups, and the i-th group (i=1, 2, ..., n) is composed of the second electrode located at the bottom in the water level detection direction. i-1 (2k-1) (k is 1 to 2 n-i By repeatedly comparing the size of the electrostatic capacitance while changing the combination of the groups, it is possible to obtain a resolution corresponding to the number of electrodes.

[0153] Therefore, the number of wirings (wirings on the detection side) connecting the electrodes of the sensor section to the determination unit can be the number of groups, and only one determination unit is required.

[0154] In addition, for example, when the water level is detected at 1000 levels (a resolution of 1 / 1000 relative to the measurement range), Figure 1 In the case of a configuration like the conventional example shown, the number of the determination units and the number of electrode pairs are 1000, respectively, and the number of wirings to the detection side of the determination unit is 1000.

[0155] On the other hand, in the water level gauge according to the present invention, according to the above-mentioned group structure, 2 n -1 electrode measurement, that is, because it is possible to obtain 1 / (2 n -1), so when a resolution of 1 / 1000 is obtained, the number of groups can be 10, so only 10 wirings are required on the detection side.

[0156] The water level gauge can be used, for example, in measuring the water level of a river, and when the grounding conductor 40 is a metal pipe, the metal pipe is driven into the ground at the bottom of the river. In addition, the water level gauge can also be used, for example, as a liquid level gauge for detecting the liquid level in a tank.

[0157] Hereinafter, reference is made to non-limiting examples. Fig.16 and Fig.17 , the interface sensor 200 of the present disclosure and the liquid level meter including the interface sensor 200 are described from other aspects. Before this description, in order to facilitate understanding of the interface sensor 200 of the present disclosure, refer to Fig.15 The interface sensor 2 associated with the interface sensor 200 of the present disclosure is described. In addition, although the interface sensor 2 is not protected by the claims of the present application, the description of the interface sensor 2 is useful for understanding the interface sensor 200, and therefore, the description of the interface sensor 2 is incorporated into the description of the interface sensor 200 as required. In addition, the inclusion of the description is not necessarily explicit.

[0158] The interface sensor 2 is a sensor for determining the position of the interface between two substances (i.e., a first substance and a second substance that are different from each other). However, in order to accurately determine the position, the number of interfaces in the range from plane P(1) to plane P(M(1)) described later must be 1 or 0. As described later, the interface sensor 2 includes a first electrical conductor 5a and E second electrical conductors 5b (E is shown in the following formula (4)). E electrode pairs are formed between the first electrical conductor 5a and the E second electrical conductors 5b. The position of the interface between the first substance and the second substance is determined by utilizing a physical quantity generated in each of the E electrode pairs according to the properties of the first substance or the second substance existing between each of the E electrode pairs. The "interface" is the contact boundary between the first substance as a uniform phase and the second substance as a uniform phase. The "uniform phase" is an entity of a material system which is uniform in chemical composition and physical state (an entity of a material system which is uniform in chemical composition and physical state). In other words, when the physical properties and chemical properties of an arbitrary part V of the entity of a certain material system are respectively the same as the physical properties and chemical properties of an arbitrary part W different from the part V of the entity of the material system, the entity of the material system is a "homogeneous phase". A typical example of the interface sensor 2 is a sensor for determining the position of the interface between a liquid (e.g., water) as a first substance and a gas (e.g., air) as a second substance.

[0159] The structure of the interface sensor 2 is described. The symbols that appear in the following description have nothing to do with the symbols used in the description of the aforementioned embodiment. Furthermore, if the capacitance between two conductors having equal positive and negative charges is set to C, the resistance between the two conductors is set to R, the dielectric constant of the medium between the two conductors is set to ε, and the resistivity of the medium between the two conductors is set to ρ, then the relationship RC=ερ holds. Therefore, in the following, only the electrostatic capacitance of the electrode pair is described, and the description of the resistance of the electrode pair is omitted.

[0160] The interface sensor 2 includes a first electrical conductor 5a and K sensor blocks 3, wherein K is a predetermined integer satisfying 2≤K.

[0161] The K sensor blocks 3 are not limited to the following example, and are formed on F substrates 9 having a flat plate shape. F is a predetermined integer satisfying 1≤F≤K. When F<K, there is a substrate 9 having two or more sensor blocks 3. Fig.15In the example shown, F = 1. When F ≥ 2, the F substrates 9 are not limited to the following examples, and may be arranged on one plane, may be arranged like angle steel or channel steel, or may be arranged like triangular tubes or square tubes.

[0162] The first electric conductor 5a is, for example, metal. The first electric conductor 5a may be one electric conductor or may include two or more electric conductors.

[0163] When the first electrical conductor 5a is one electrical conductor, the shape of the first electrical conductor 5a is not limited to the following example, and may be a flat plate or a tube. When the first electrical conductor 5a has a tube shape, the cross-sectional shape of the tube in the cross section perpendicular to the long side direction of the tube is, for example, a circle or a rectangle. When the first electrical conductor 5a has a tube shape, the K sensor blocks 3 are usually arranged inside the first electrical conductor 5a, but are not limited thereto.

[0164] In the case where the first electrical conductor 5a includes more than two electrical conductors, the shape of each of the electrical conductors included in the first electrical conductor 5a is not limited to the following example, and may be a flat plate or a shape possessed by each of the constituent elements constituting the above-mentioned tube (for example, the shape of an object obtained by cutting the above-mentioned tube in a direction perpendicular to its long side direction (in short, a tube shorter than the above-mentioned tube), the shape of an object obtained by cutting the above-mentioned tube in the long side direction (for example, in the case of a cylinder, a 1 / 4 cylinder shape)). In the case where the first electrical conductor 5a includes more than two electrical conductors, the two or more electrical conductors may be independent of each other. That is, the two or more electrical conductors included in the first electrical conductor 5a may not be in contact with each other, and may not have the same potential as each other.

[0165] In the following, from the perspective of ease of understanding of the interface sensor 2, Fig.15 In the example shown, the first electrical conductor 5a is one electrical conductor. Fig.15 In FIG. 1 , considering the legibility of the drawing, the edge of the first electric conductor 5 a is clearly shown, and the first electric conductor 5 a is drawn as if transparent.

[0166] The k-th sensor block 3 among the K sensor blocks 3 includes M(k) second electrical conductors 5b and n(k) wires 7. The second electrical conductors 5b will be described later. The n(k) wires 7 are wires extending from the sensor block 3 and connected to the M(k) second electrical conductors 5b as described later. The n(k) wires 7 are connected to a detection circuit described later. Fig.15In the figure, considering the readability of the figure, only some of the second electrical conductors and some of the wires are given symbols. k is a parameter used to represent an integer satisfying 1≤k≤K, that is, k∈{x∈N:1≤x≤K}. N is the set of all positive integers. For each k∈{x∈N:1≤x≤K}, n(k) is a predetermined integer satisfying 2≤n(k). For each k∈{x∈N:1≤x≤K}, M(k) is represented by formula (1). "×" represents a multiplication operation. M(1), that is, the number of second electrical conductors 5b included in the first sensor block 3, determines the resolution of the interface sensor 2. That is, M(1) is consistent with the total number of "observation points" mentioned above (the total number is represented by the symbol Z in the description of the prior art). In detail, according to equations (4) and (5) shown later, in order for the total number L of wires 7 extending from the interface sensor 2 to be less than the sum of the total number of observation points M(1) and 1, M(1) must be 4 or M(1) must be 6 or M(1) ≥ 8.

[0167] [Mathematical formula 9]

[0168]

[0169] In the design of the interface sensor 2, the value of M(1) associated with the resolution of the interface sensor 2 is usually determined first. From this perspective, n(k) is a positive divisor of M(1) (except 1 and M(1)). Therefore, for each k∈{x∈N:1≤x≤K}, n(k)<M(1). Further, note that the representation of M(1) is not unique. For example, in the case of M(1)=60, as shown below,

[0170] M(1)=2×30 (i.e., K=2, n(1)=30, n(2)=2),

[0171] M(1)=3×20 (i.e., K=2, n(1)=20, n(2)=3),

[0172] M(1)=12×5 (i.e., K=2, n(1)=5, n(2)=12),

[0173] M(1)=4×3×5 (i.e., K=3, n(1)=5, n(2)=3, n(3)=4),

[0174] M(1)=5×6×2 (i.e., K=3, n(1)=2, n(2)=6, n(3)=5),

[0175] M(1)=2×3×2×5 (i.e., K=4, n(1)=5, n(2)=2, n(3)=3, n(4)=2),

[0176] M(1) has two or more representations (i.e., two or more factorizations). When M(1) has two or more representations, a person implementing the interface sensor 2 can arbitrarily select one representation in consideration of the ease of implementation of the interface sensor 2, the manufacturing cost of the interface sensor 2, the use environment of the interface sensor 2, and the like. That is, the two or more representations of M(1) mean the degree of freedom in the design of the interface sensor 2.

[0177] The second electrical conductor 5b is, for example, metal. The shape of the second electrical conductor 5b is not limited to the following example, and may be a rectangular flat plate or a circular flat plate. In the k-th (k∈{x∈N:1≤x≤K}) sensor block 3, M(k) electrode pairs are formed between the first electrical conductor 5a and the M(k) second electrical conductors 5b. The M(k) electrode pairs have the same electrostatic capacitance C when each of the M(k) electrode pairs is filled with the first material, for example. k On the other hand, in order to satisfy the condition that "the M(k) electrode pairs have the same electrostatic capacitance C when each of the M(k) electrode pairs is filled with the first substance, for example k "For the purpose of such a condition, the mth second electric conductor 5b among the M(k) second electric conductors 5b included in the kth (k∈{x∈N:1≤x≤K}) sensor block 3 is appropriately set. k The area of ​​the mth second electrical conductor 5b and the k The distance between the second electrical conductor 5b and the first electrical conductor 5a. k It is used to indicate that 1≤m k ≤M(k) integer parameter, that is, m k ∈{x∈N:1≤x≤M(k)}. For example, when the M(k) second electrical conductors 5b included in the k-th (k∈{x∈N:1≤x≤K}) sensor block 3 have the same area, the above condition can be achieved if the distances between the first electrical conductor 5a and the M(k) second electrical conductors 5b are equal to each other. Fig.15 In the example shown, the first electrical conductor 5a is in the shape of a rectangular flat plate having an area larger than the area of ​​one substrate 9 having K sensor blocks 3. Fig.15 In the example shown, K sensor blocks 3 are located on one surface of a substrate 9, and the first electrical conductor 5a is provided parallel to and facing the one surface of the substrate 9. Fig.15 In the figure, from the perspective of visibility, the first electrical conductor 5a is regarded as a transparent object and only the outline of the first electrical conductor 5a is shown. Fig.15), the first electrical conductor 5a overlaps with all the second electrical conductors 5b included in the K sensor blocks 3, and the distance between the edge of the first electrical conductor 5a and each second electrical conductor 5b is sufficiently large. Fig.15 In the example shown, the above condition is easily achieved when the M(k) second electrical conductors 5b included in the k-th (k∈{x∈N:1≤x≤K}) sensor block 3 have the same area. The electrostatic capacitance C of each of the M(k) electrode pairs included in the k-th sensor block 3 is k It can be connected to the electrostatic capacitance C of each of the M(j) electrode pairs included in the j-th (j≠k) sensor block 3. j The same, or different.

[0178] The mth one of the M(k) second electrical conductors 5b included in the kth (k∈{x∈N:1≤x≤K}) sensor block 3 k The second electrical conductor 5b is located in the r(k, m)th plane of M(1). k ) plane P(r(k,m k )). As mentioned above, m k It is used to indicate that 1≤m k ≤M(k) integer parameter, that is, m k ∈{x∈N:1≤x≤M(k)}. For each k∈{x∈N:1≤x≤K} and each m k ∈{x∈N:1≤x≤M(k)}, r(k,m k) is represented by formula (2). The M(1) planes P(1), ..., P(M(1)) are mutually inconsistent and parallel. The M(1) planes P(1), ..., P(M(1)) are arranged in space in the order that follows the size relationship of the elements of the set {x∈N: 1≤x≤M(1)} (that is, the size relationship of natural numbers). Specifically, between the 1st plane P(1) and the pth (p∈{x∈N: 3≤x≤M(1)}) plane P(p), there is the qth (q∈{x∈N: 2≤x≤p-1}) plane P(q). If described further simply, when the normal direction of the mutually parallel M(1) planes P(1), ..., P(M(1)) is called the first direction, the M(1) planes P(1), ..., P(M(1)) are arranged in this order in the first direction. For any g∈{x∈N:1≤x≤M(1)-2}, h∈{x∈N:g+1≤x≤M(1)-1}, the distance between the g-th plane P(g) and the g+1-th plane P(g+1), and the distance between the h-th plane P(h) and the h+1-th plane P(h+1) may be equal or unequal. For example, in a measurement range where the position of an interface is to be determined more accurately, the interval between adjacent planes may be reduced. In the k-th (k∈{x∈N:1≤x≤K}) sensor block 3, the M(k) second electrical conductors 5b are generally arranged in a straight line, but are not limited thereto, and may be arranged in a walking footprint shape, for example.

[0179] [Formula 10]

[0180]

[0181] From the perspective of the ease of design and manufacture of the interface sensor 2, the K sensor blocks 3 are usually arranged in the second direction orthogonal to the first direction. The total number of possible configuration patterns of the K sensor blocks 3 in the second direction is K! That is, k＝1 K k. In addition, when the first direction is a vertical direction, the "plane" may be replaced with, for example, a "horizontal plane (level)".

[0182] The mth one of the M(k) second electrical conductors 5b included in the kth (k∈{x∈N:1≤x≤K}) sensor block 3 k (m k ∈{x∈N:1≤x≤M(k)}) the second electric conductor 5b and the s(m)th of the n(k) wires 7 k ) wire 7 is connected. In this example, the mth k (m k ∈{x∈N:1≤x≤M(k)}) the second electric conductor 5b and the s(m k ) conductors 7 are connected to each other via branch lines 7x.k ) is satisfied 1≤s(m k )≤n(k), that is, s(m k )∈{x∈N:1≤x≤n(k)}. For each k∈{x∈N:1≤x≤K} and each m k ∈{x∈N:1≤x≤M(k)}, equation (3) holds. In equation (3), the symbol mod represents the remainder operation, m k mod n(k) is the dividend m k The remainder after Euclidean division by the divisor n(k).

[0183] [Mathematical formula 11]

[0184]

[0185] As can be seen from the above description, the number E of the second electrical conductors 5b included in the interface sensor 2 is given by equation (4), and the number L of the wires 7 drawn out from the interface sensor 2 is given by equation (5). Under the above conditions, L<M(1)+1 can be achieved.

[0186] [Mathematical formula 12]

[0187]

[0188] Next, an example of a method of determining the position of an interface using the interface sensor 2 is described. In the k-th (k∈{x∈N:1≤x≤K}) sensor block 3, a detection circuit (not shown) detects the position of the interface in the t-th k The electrode pair (i.e., k The synthesis of physical quantities (for example, synthetic electrostatic capacitance) generated in each of the electrode pairs formed by the second electrical conductor 5b and the first electrical conductor 5a connected by the wire 7 is equal to the synthesis of physical quantities (for example, synthetic electrostatic capacitance) generated in the tth k +1 electrode pair (i.e., with the t k The difference D(t) in the synthesis of physical quantities (for example, synthetic electrostatic capacitance) generated in each of the electrode pairs formed by the second electrical conductor 5b and the first electrical conductor 5a connected by +1 wire 7 is k ), and compare it with a predetermined threshold δ. k It is used to indicate that 1≤t k The integer parameter ≤ n(k)-1, that is, t k ∈{x∈N:1≤x≤n(k)-1}. The result of the comparison, for example, for a certain T k ∈{x∈N:1≤x≤n(k)-1} and D(T k)>δ, the candidate for the position of the interface is given as b(k)+1 intervals determined by the pair of two planes represented by equation (6). Where, in the case of k=K, y=0 is defined. An “interval” is the area between the two planes represented by equation (6). k And D(t k )≤δ, it is any of the following: the interface does not reach plane P(1), or the interface exceeds plane P(M(1)). In addition, the detection circuit can be a component of the interface sensor 2, or it can be a physical entity independent of the interface sensor 2. In the latter case, the detection circuit can also be a component of the liquid level meter including the interface sensor 2. The detection circuit is not limited, and can be a detection circuit of the prior art, or it can include an AC signal generator that generates an AC signal applied to the n(k)th conductor 7 for each k∈{x∈N:1≤x≤K}), and a signal generator that generates an AC signal applied to the n(k)th conductor 7 for each t k ∈{x∈N:1≤x≤n(k)-1}Comparison difference D(t k ) and the detection circuit of the comparator of the threshold δ can also be Figure 2 and Figure 6 The detection circuit shown (including the carrier generation circuit 50 and the determination unit 90) may also be Fig. 9 The detection circuit shown (including the charging circuit 130, a plurality of switches controlled by the control unit 110, and the determination unit 90') may also be Fig.12 The detection circuit shown (including the charging circuits 130, 140, a plurality of switches controlled by the control unit 110, and the determination unit 90') may also be a detection circuit including a PLD (programmable logic device). Examples of PLD include FPGA (field-programmable gate array).

[0189] [Mathematical formula 13]

[0190]

[0191] As an example, the position of the interface can be determined by the algorithm shown in Table 1. That is, except for the case where the interface does not reach the plane P(1) and the case where the interface exceeds the plane P(M(1)), the section common to each sensor block 3 is determined as the section where the interface exists. In the algorithm shown in Table 1, it is assumed that there is a section in the Kth sensor block 3 that satisfies D(T K )>δT K ∈{x∈N:1≤x≤n(K)-1} is the premise. For example, let K' be an integer satisfying 1<K'<K, and there is no sensor block 3 in the K'+1th sensor block 3 satisfying D(TK’+1 )>δT K’+1 ∈{x∈N:1≤x≤n(K'+1)-1}, there exists a sensor block 3 in the K'th sensor block 3 that satisfies D(T K’ )>δT K’ In the case of ∈{x∈N:1≤x≤n(K')-1}, K can be rewritten as K' in the algorithm shown in Table 1. When K'=1, an interface exists in the interval corresponding to y=0 among the b(1)+1 intervals determined by the pair of two planes represented by equation (6).

[0192] [Table 1]

[0193]

[0194] The interface sensor 2 may also include a second electrical conductor 5b for determining that the interface does not reach the plane P(1) and / or a second electrical conductor 5b for determining that the interface exceeds the plane P(M(1)). k And D(t k )≤δ, it is known that the interface does not reach the plane P(1), and therefore the second electric conductor 5b in the former is not essential.

[0195] exist Fig.15 A specific configuration example of the interface sensor 2 is shown in FIG. Fig.15 The configuration example shown is an example in which M(1)=30 and K=3. Fig.15 In the example shown, M(1)=2×5×3 is used as the factorization of 3 factors based on M(1). That is, n(1)=3, n(2)=5, n(3)=2. Therefore, according to formula (1), M(1)=30, M(2)=10, M(3)=2.

[0196] The m1th (m1∈{x∈N:1≤x≤30}) second electrical conductor 5b among the 30 second electrical conductors 5b included in the first sensor block 3 is located in the r(1,m1)th plane P(r(1,m1)) among the 30 planes. Here, according to formula (2), r(1,m1)=m1. In short, the pth (p∈{x∈N:1≤x≤30}) second electrical conductor 5b included in the first sensor block 3 is located in the pth plane P(p).

[0197] The m2-th (m2∈{x∈N:1≤x≤10}) second electrical conductor 5b among the 10 second electrical conductors 5b included in the second sensor block 3 is located in the r(2, m2)-th plane P(r(2, m2)) among the 30 planes. Here, according to formula (2), r(2, m2)=3×m2. In short, the p-th (p∈{x∈N:1≤x≤10}) second electrical conductor 5b included in the second sensor block 3 is located in the (3×p)-th plane P(3×p). For example, the 7-th (p=7∈{x∈N:1≤x≤10}) second electrical conductor 5b included in the second sensor block 3 is located in the 21-th plane P(21).

[0198] The m3-th (m3∈{x∈N:1≤x≤2}) second electrical conductor 5b of the two second electrical conductors 5b included in the third sensor block 3 is located in the r(3, m3)-th plane P(r(3, m3)) among the 30 planes. Here, according to formula (2), r(3, m3)=15×m3. In short, the p-th (p∈{x∈N:1≤x≤2}) second electrical conductor 5b included in the third sensor block 3 is located in the (15×p)-th plane P(15×p). For example, the first (p=1∈{x∈N:1≤x≤2}) second electrical conductor 5b included in the third sensor block 3 is located in the 15th plane P(15).

[0199] The m1th (m1∈{x∈N:1≤x≤30}) second electrical conductor 5b among the 30 second electrical conductors 5b included in the first sensor block 3 is connected to the s(m1)th wire 7 among the three wires 7. According to formula (3), for example, the 7th second electrical conductor 5b is connected to the 1st wire 7 ((7mod 3=1), the 17th second electrical conductor 5b is connected to the 2nd wire 7 (17mod 3=2), and the 24th second electrical conductor 5b is connected to the 3rd wire 7 (24mod 3=0).

[0200] The m2-th (m2∈{x∈N:1≤x≤10}) second electrical conductor 5b among the 10 second electrical conductors 5b included in the second sensor block 3 is connected to the s(m2)-th wire 7 among the five wires 7. According to formula (3), the first and sixth second electrical conductors 5b are connected to the first wire 7 (1mod 5=6mod 5=1), the second and seventh second electrical conductors 5b are connected to the second wire 7 (2mod 5=7mod 5=2), the third and eighth second electrical conductors 5b are connected to the third wire 7 (3mod 5=8mod 5=3), the fourth and ninth second electrical conductors 5b are connected to the fourth wire 7 (4mod 5=9mod 5=4), and the fifth and tenth second electrical conductors 5b are connected to the fifth wire 7 (5mod 5=10mod 5=0).

[0201] The m3th (m3∈{x∈N:1≤x≤2}) second electrical conductor 5b of the two second electrical conductors 5b included in the third sensor block 3 is connected to the s(m3)th wire 7 of the two wires 7. According to formula (3), the first second electrical conductor 5b is connected to the first wire 7 (1mod 2=1), and the second second electrical conductor 5b is connected to the second wire 7 (2mod 2=0).

[0202] According to formula (4), Fig.15 The number E of the second electrical conductors 5b included in the structure example of the interface sensor 2 shown is 42. According to equation (5), the number L of the wires 7 is 10. The total number of observation points M(1) is 30, so L<M(1)+1 holds. In addition, if based on Figure 1 In the water level gauge of the prior art shown in FIG. 1 , the number of wires 7 is 31 (= M(1) + 1). Furthermore, for example, although not shown, in the case where M(1) = 1440, K = 5, n(1) = 5, n(2) = 3, n(3) = 2, n(4) = 8, and n(5) = 6, the number L of wires 7 in the interface sensor 2 is 24. Figure 1 For the water level gauge of the prior art shown, the number of wires is 1441 (=M(1)+1).

[0203] exist Fig.15 In the example shown, the number F of substrates 9 is 1, but it may be F = 2 or F = 3. In the case of F = 2, for example, the first sensor block 3 and the second sensor block 3 are formed on the first substrate, and the third sensor block 3 is formed on the second substrate.

[0204] Next, the interface sensor 200 of the present disclosure will be described. While the interface sensor 2 includes K sensor blocks 3 , the interface sensor 200 includes one sensor block 300 and has a structure equivalent to that of the interface sensor 2 .

[0205] The interface sensor 200 is a sensor for determining the position of the interface between two substances (i.e., a first substance and a second substance that are different from each other). However, in order to accurately determine the position, the number of interfaces in the range from plane P(1) to plane P(E) described later must be 1 or 0. As described later, the interface sensor 200 includes a first electrical conductor 500a and E second electrical conductors 500b (E is shown in the following formula (7)). E electrode pairs are formed between the first electrical conductor 500a and the E second electrical conductors 500b. The position of the interface between the first substance and the second substance is determined by utilizing a physical quantity generated in each of the E electrode pairs according to the properties of the first substance or the second substance existing between each of the E electrode pairs. "Interface" and "homogeneous phase" are as described above. A typical example of the interface sensor 200 is a sensor for determining the position of the interface between a liquid (e.g., water) as the first substance and a gas (e.g., air) as the second substance.

[0206] The structure of the interface sensor 200 is described. The symbols that appear in the following description have nothing to do with the symbols used in the description of the aforementioned embodiment or the description of the interface sensor 2. Furthermore, if the capacitance between two conductors having equal positive and negative charges is set to C, the resistance between the two conductors is set to R, the dielectric constant of the medium between the two conductors is set to ε, and the resistivity of the medium between the two conductors is set to ρ, then the relationship RC=ερ holds, and therefore, only the electrostatic capacitance of the electrode pair is described below, and the description of the resistance of the electrode pair is omitted.

[0207] The interface sensor 200 includes a first electrical conductor 500a, E second electrical conductors 500b, L wires 700 drawn from the sensor block 300, and a wire selector 800. Generally, the E second electrical conductors 500b and the L wires 700 are formed on a substrate 900 having a flat plate shape. The substrate 900 is coated with a waterproof coating except for the E second electrical conductors 500b. The wire selector 800 is not limited to the following example, and may be formed on the substrate 900 or on other substrates. In the case where the first substance is a liquid, the wire selector 800 is preferably located in a place not immersed in the liquid, and if located in a place immersed in the liquid, it is subjected to waterproof treatment.

[0208] The first electric conductor 500a is, for example, metal. The first electric conductor 500a may be one electric conductor or may include two or more electric conductors.

[0209] When the first electric conductor 500a is one electric conductor, the shape of the first electric conductor 500a is not limited to the following example, and may be a flat plate or a tube. When the first electric conductor 500a has a tube shape, the cross-sectional shape of the tube in the cross section perpendicular to the long side direction of the tube is, for example, a circle or a rectangle. When the first electric conductor 500a has a tube shape, the sensor block 300 is usually arranged inside the first electric conductor 500a, but is not limited thereto.

[0210] In the case where the first electrical conductor 500a includes more than two electrical conductors, the shape of each of the electrical conductors included in the first electrical conductor 500a is not limited to the following example, and may be a flat plate or a shape of each of the components constituting the above-mentioned tube (for example, the shape of an object obtained by cutting the above-mentioned tube in a direction perpendicular to its long side direction (in short, a tube shorter than the above-mentioned tube), the shape of an object obtained by cutting the above-mentioned tube in the long side direction (for example, in the case of a cylinder, a 1 / 4 cylinder shape)). In the case where the first electrical conductor 500a includes more than two electrical conductors, the two or more electrical conductors may be independent of each other. However, it is preferred that the two or more electrical conductors included in the first electrical conductor 500a have the same potential as each other, for example, by contacting each other.

[0211] In the following, from the perspective of ease of understanding of the interface sensor 200, Fig.16 The first example shown and Fig.17 In the second example shown, the first electrical conductor 500a is one electrical conductor. Fig.16 as well as Fig.17 In FIG. 5 , considering the legibility of the figure, the edge of the first electrical conductor 005 a is clearly shown, and the first electrical conductor 500 a is depicted as transparent.

[0212] The sensor block 300 includes E second electrical conductors 500b and L wires 700. The second electrical conductors 500b will be described later. The L wires 700 are wires drawn out from the sensor block 300 and connected to a wire selector 800 described later. Fig.16 as well as Fig.17In the figure, considering the readability of the figure, only some of the second electrical conductors and some of the wires are given symbols. E is expressed by formula (7). L is expressed by formula (8). K is a predetermined integer satisfying 2≤K. j is a parameter used to represent an integer satisfying 1≤j≤K, that is, j∈{x∈N:1≤x≤K}. For each j∈{x∈N:1≤x≤K}, n(j) is a predetermined integer satisfying 2≤n(j). N is the set of all positive integers. E, that is, the number of second electrical conductors 500b included in the sensor block 300 determines the resolution of the interface sensor 200. That is, E is consistent with the total number of the above-mentioned "observation points" (the total number is represented by the symbol Z in the description of the prior art). Under the above conditions, L<E+1.

[0213] [Formula 14]

[0214]

[0215] n(j) is a positive divisor of E (excluding 1 and E). The representation of E is not unique. In the case where E has more than two representations (i.e., more than two factorizations), a person implementing the interface sensor 200 can arbitrarily select one representation in consideration of the ease of implementation of the interface sensor 200, the manufacturing cost of the interface sensor 200, the use environment of the interface sensor 200, etc. That is, more than two representations of E mean the degree of freedom in the design of the interface sensor 200. From the perspective of reducing the total number L of the wires 700, it is preferred that n(j) is a prime factor of E, that is, the right side of the formula (7) is a prime factorization (see formula (8)).

[0216] The second electrical conductor 500b is, for example, metal. The shape of the second electrical conductor 500b is not limited to the following example, and may be a rectangular flat plate or a circular flat plate. In the sensor block 300, E electrode pairs are formed between the first electrical conductor 500a and the E second electrical conductors 500b. The E electrode pairs have mutually identical electrostatic capacitances C when, for example, the first substance is filled between each of the E electrode pairs. On the other hand, the area of ​​the mth second electrical conductor 500b among the E second electrical conductors 5b included in the sensor block 300 and the distance between the mth second electrical conductor 500b and the first electrical conductor 500a are appropriately set for the purpose of satisfying the condition that "the E electrode pairs have mutually identical electrostatic capacitances C when, for example, the first substance is filled between each of the E electrode pairs." m is a parameter used to represent an integer satisfying 1≤m≤E, that is, m∈{x∈N:1≤x≤E}. For example, when the E second electrical conductors 500b included in the sensor block 300 have the same area, the above-mentioned condition can be achieved if the distances between the first electrical conductor 500a and the E second electrical conductors 500b are equal to each other. Fig.16 The first example shown and Fig.17 In the second example shown, the first electric conductor 500a is in the shape of a rectangular flat plate having an area larger than that of the substrate 900. Fig.16 The first example shown and Fig.17 In the second example shown, the sensor block 300 is located on one surface of the substrate 900, and the first electrical conductor 500a is provided parallel to and facing the one surface of the substrate 900. Fig.16 as well as Fig.17 In the figure, for the sake of visibility, the first electrical conductor 500a is regarded as a transparent object, and only the outline of the first electrical conductor 500a is shown. Fig.16 or Fig.17 ), the first electrical conductor 500a overlaps with all the second electrical conductors 500b included in the sensor block 300, and the distance between the edge of the first electrical conductor 500a and each second electrical conductor 500b is sufficiently large. Fig.16 The first example shown and Fig.17 In the second example shown, when the E second electric conductors 500b included in the sensor block 300 have the same area, the above-mentioned condition can be easily achieved.

[0217] The E second electrical conductors 500b are located on E planes that are inconsistent with each other and parallel to each other in the order of the size relationship of the elements of the set {x∈N: 1≤x≤E}. The E planes P(1), ..., P(E) are arranged in space in the order of the size relationship of the elements of the set {x∈N: 1≤x≤E} (i.e., the size relationship of natural numbers). Specifically, on the first plane P(1) and the pth plane P(E), the first plane P(1) and the pth plane P(E) are arranged in space in the order of the size relationship of the elements of the set {x∈N: 1≤x≤E} (i.e., the size relationship of natural numbers). a (p a ∈{x∈N:3≤x≤E}) plane P(p a ), there exists a pth b (p b ∈{x∈N:2≤x≤p a -1}) plane P(p b). To describe it more simply, when the normal direction of E mutually parallel planes P(1), ..., P(E) is called the first direction, the E planes P(1), ..., P(E) are arranged in this order in the first direction. For any g∈{x∈N: 1≤x≤E-2}, h∈{x∈N: g+1≤x≤E-1}, the distance between the gth plane P(g) and the g+1th plane P(g+1) may be equal to or different from the distance between the hth plane P(h) and the h+1th plane P(h+1). For example, in a measurement range in which it is desired to determine the position of the interface more accurately, the interval between adjacent planes may be reduced. The pth second electrical conductor 500b among the E second electrical conductors 500b is located on the pth plane P(p) among the E planes. p is a parameter used to represent an integer satisfying 1≤p≤E, that is, p∈{x∈N: 1≤x≤E}. The E second electric conductors 500b are usually arranged in a straight line, but are not limited thereto, and may be arranged in a footprint shape, for example. In addition, when the first direction is a vertical direction, the "plane" may be replaced with, for example, a "horizontal plane (level)".

[0218] For each p∈{x∈N:1≤x≤E-1}, the p-th second electric conductor 500b among the E second electric conductors 500b is connected to the s(p)-th wire 700 among the L wires 700. In this example, the p-th (p∈{x∈N:1≤x≤E-1}) second electric conductor 500b and the s(p)-th wire 700 are connected to each other via the branch line 700x. s(p) is represented by equation (9). In equation (9), the symbol mod represents a modulo operation, and a mod b is the remainder obtained by the Euclidean division of the dividend a by the divisor b. In equation (9), the symbol " / " appearing in the dividend of the modulo operation represents a division operation. In this description, n(0)=1.

[0219] [Mathematical formula 15]

[0220]

[0221] The r in equation (9) is determined by p∈W(r), that is, by the set W(r) to which p belongs. For each k∈{x∈N:1≤x≤K}, the kth set W(k) is expressed by equation (10). The K+1th set W(K+1) is the empty set In formula (10), the symbol “|” represents a multiple, that is, a|b means “b is a multiple of a”.

[0222] [Formula 16]

[0223]

[0224] If it is defined as W = {W(j): j∈N∧1≤j≤K}, then from formula (10), we can see that

[0225] 1)

[0226] 2)W(i)∈W,W(j)∈W,

[0227] 3)∪ j＝1 K W(j)={x∈N:1≤x≤E}

[0228] Therefore, That is, the set W(r) to which p belongs is uniquely determined.

[0229] The E-th second electrical conductor 500 b among the E second electrical conductors 500 b is connected to the L-th conductive wire 700 among the L conductive wires 700 .

[0230] The wire selector 800 can select any one of the L wires 700 .

[0231] Alternatively, for each k∈{x∈N:1≤x≤K}, the wire selector 800

[0232] 1) When k≠K and n(k)≠2,

[0233] For each y∈{x∈N:1≤x≤n(k)-2}, two wires 700 are simultaneously selected from the L wires 700, which are determined by the elements belonging to the set Y(y). For y=n(k)-1, two wires 700 are simultaneously selected from the L wires 700, which are determined by the elements belonging to the set Y(y). a The elements of (y) determine (2+Σ j＝k+1 K (n(j)-1)) wires 700,

[0234] 2) When k≠K and n(k)=2,

[0235] For y=n(k)-1, simultaneously select the L wires 700 that belong to the set Y a The elements of (y) determine (2+Σ j＝k+1 K (n(j)-1)) wires 700,

[0236] 3) In the case of k = K,

[0237] For each y∈{x∈N:1≤x≤n(k)−1}, two conductors 700 among the L conductors 700 that are determined by the elements belonging to the set Y(y) are simultaneously selected.

[0238] Among them, the set Y(y) is expressed by formula (11), the set Y a (y) is represented by equation (12). These sets are represented as the union of singletons.

[0239] [Mathematical formula 17]

[0240]

[0241] When the interface sensor 200 includes the wire selector 800 capable of simultaneously selecting two or more wires 700, the wire selector 800 preferably connects the simultaneously selected two or more wires 700 to two wires (wire a and wire b) as follows.

[0242] A) Regarding equation (11), the wire 700 identified by the element belonging to the set represented by equation (13) is connected to the wire a, and the wire 700 identified by the element belonging to the set represented by equation (14) is connected to the wire b.

[0243] B) Regarding equation (12), the wire 700 identified by the element belonging to the set represented by equation (13) is connected to the wire a, and the wire 700 identified by the element belonging to the set represented by equation (15) is connected to the wire b.

[0244] [Mathematical formula 18]

[0245]

[0246] The interface sensor 200 is equivalent to the interface sensor 2, so the method of determining the position of the interface using the interface sensor 200 is the same as the method of determining the position of the interface using the interface sensor 2. In the case where the interface sensor 200 includes a wire selector 800 capable of simultaneously selecting two or more wires 700, in the interface sensor 200, a detection circuit (not shown) compares the difference D between the synthesis of physical quantities (e.g., synthesis electrostatic capacitance) generated on each of the electrode pairs connected to the wire a through the wire 700 selected by the wire selector 800 and the synthesis of physical quantities (e.g., synthesis electrostatic capacitance) generated on each of the electrode pairs connected to the wire b through the wire 700 selected by the wire selector 800, and a predetermined threshold value δ. In addition, the detection circuit may be a component of the interface sensor 200 or a physical entity independent of the interface sensor 200. In the latter case, the detection circuit may also be a component of the liquid level meter including the interface sensor 200. The detection circuit is not limited, and can be a detection circuit of the prior art, or a detection circuit including an AC signal generator and a comparator that generates an AC signal applied to the Lth wire 700, or a detection circuit of the prior art. Figure 2 and Figure 6 The detection circuit shown (including the carrier generation circuit 50 and the determination unit 90) may also be Fig. 9 The detection circuit shown (including the charging circuit 130, a plurality of switches controlled by the control unit 110, and the determination unit 90') may also be Fig.12 The detection circuit shown (including the charging circuits 130, 140, a plurality of switches controlled by the control unit, and the determination unit 90') may also be a detection circuit including a PLD (programmable logic device). Examples of PLD include FPGA (field-programmable gate array).

[0247] As an example, the position of the interface can be determined by the algorithm shown in Table 2. In the algorithm, C(13) represents the synthesis of physical quantities (e.g., synthetic electrostatic capacitance) generated on each of the electrode pairs connected to the wire 700 determined by the elements of the set represented by formula (13), C(14) represents the synthesis of physical quantities (e.g., synthetic electrostatic capacitance) generated on each of the electrode pairs connected to the wire 700 determined by the elements of the set represented by formula (14), and C(15) represents the synthesis of physical quantities (e.g., synthetic electrostatic capacitance) generated on each of the electrode pairs connected to the wire 700 determined by the elements of the set represented by formula (15). When the output is P(0) or P(1), it means that the interface has not reached plane P(1). In addition, in the algorithm, overflow determination processing and error avoidance processing are not performed.

[0248] [Table 2]

[0249]

[0250] In the case where the total number Z of the "observation points" mentioned above is a prime number greater than 5, Z-1 is a composite number. Therefore, by setting the value of E to Z-1, an interface sensor having Z (where Z is a prime number greater than 5) observation points can be constructed. Specifically, the interface sensor has a structure in which an electrode pair and a conductor are added to the interface sensor 200 including E (where E=Z-1) second electrical conductors 500b, L conductors 700, and a conductor selector 800. In this structure, the added second electrical conductor is located on the P(E+1)th plane, and the electrode of the added second electrical conductor is connected to the added conductor. By determining whether the electrostatic capacitance value between the added second electrical conductor and the first electrical conductor 500a exceeds a prescribed reference value through a detection circuit, it is possible to determine whether the interface exceeds the P(E+1)th plane.

[0251] exist Fig.16 and Fig.17 1 and 2 are respectively shown as specific configuration examples of the interface sensor 200. These configuration examples are examples in the case where E=30 and K=3. Fig.16 and Fig.17 In each of the examples shown in , E=2×5×3 is used as the factorization based on 3 factors of E. That is, n(1)=3, n(2)=5, n(3)=2. In this case, L=8. See equations (7) and (8) for these facts.

[0252] like Fig.16 and Fig.17 As shown, the pth (p∈{x∈N:1≤x≤30}) electrode pair 500 is located in the pth plane P(p).

[0253] According to formula (10), W(3), W(2), and W(1) are determined as follows.

[0254] W(3)={15,30}

[0255] W(2)={3,6,9,12,18,21,24,27}

[0256] W(1)={1,2,4,5,7,8,10,11,13,14,16,17,19,20,22,23,25,26,28,29}

[0257] For example, when p=12, p∈W(2), that is, r=2. Therefore, according to formula (9), s(p)=6, and the 12th (=p) second conductor 500b is connected to the 6th (=s(p)) conductor 700. All calculation results are

[0258] p∈{1,4,7,10,13,16,19,22,25,28}→s(p)=1,

[0259] p∈{2,5,8,11,14,17,20,23,26,29}→s(p)=2,

[0260] p∈{3,18}→s(p)=3,

[0261] p∈{6,21}→s(p)=4,

[0262] p∈{9,24}→s(p)=5,

[0263] p∈{12,27}→s(p)=6,

[0264] p∈{15}→s(p)=7.

[0265] The 30th (=E)th second electric conductor 500 b is connected to the 8th (=L)th wire 700 .

[0266] Fig.16 The interface sensor 200 shown includes a wire selector 800, which can select any one of the L wires 700. Such a wire selector 800 is not limited to the following example, and includes L single-pole single-throw switches. One end of each of the L single-pole single-throw switches is connected to the corresponding wire 700 among the L wires 700. The other end of each of the L single-pole single-throw switches is not limited to the following example, and is connected to a C / V converter. When the value of L is not large, the wire selector 800 can also be a single-pole L-throw switch. When the wire selector 800 is a single-pole L-throw switch, the number of C / V converters connected to the wire selector 800 can be 1.

[0267] Fig.17 The interface sensor 200 shown includes a conductor selector 800 capable of simultaneously selecting more than two conductors 700. Such a conductor selector 800 is not limited to the following example, and includes L single-pole 3-throw switches. The input terminal of the single-pole 3-throw switch is connected to the corresponding conductor 700 among the L conductors 700. The first output terminal of the single-pole 3-throw switch is connected to the conductor b, the second output terminal is set to be terminated, and the third output terminal is connected to the conductor a. The conductor a and the conductor b are not limited to the following example, and are connected to a comparator. In this structural example, the conductor selector 800 connects the two or more conductors 700 selected simultaneously to the conductor a and the conductor b as follows.

[0268] Wire Selector 800 Fig.17 The following selection actions are performed in the structure shown.

[0269] In the case of k=1:

[0270] According to n(k)=3, equation (11) and equation (12), we get

[0271] Y(1)={1}∪{2},

[0272] Y a ={2}∪{3, 4, 5, 6, 7, 8}.

[0273] therefore,

[0274] When y=1, the wire selector is 800

[0275] Select the third output terminal of the single-pole 3-throw switch connected to the first wire 700,

[0276] Select the first output terminal of the single-pole 3-throw switch connected to the second conductor 700, and

[0277] Select the second output terminal of each single-pole 3-throw switch connected to the 3rd to 8th wires 700,

[0278] Thus, the first conductive line 700 and the second conductive line 700 are selected simultaneously.

[0279] When y=2, the wire selector is 800

[0280] Select the second output terminal of the single-pole 3-throw switch connected to the first wire 700,

[0281] Select the third output terminal of the single-pole 3-throw switch connected to the second conductor 700, and

[0282] Select the first output terminal of each single-pole 3-throw switch connected to the 3rd to 8th wires 700,

[0283] Thus, the 2nd to 8th wires 700 are selected simultaneously.

[0284] When k=2:

[0285] According to n(k)=5, equation (11) and equation (12), we get

[0286] Y(1)={3}∪{4},

[0287] Y(2)={4}∪{5},

[0288] Y(3)={5}∪{6},

[0289] Y a ={6}∪{7,8}.

[0290] therefore,

[0291] When y=1, the wire selector is 800

[0292] Select the third output terminal of the single-pole 3-throw switch connected to the third wire 700,

[0293] Select the first output terminal of the single-pole 3-throw switch connected to the fourth wire 700, and,

[0294] Select the second output terminal of each single-pole 3-throw switch connected to the 1st, 2nd, 5th-8th wires 700,

[0295] The third wire 700 and the fourth wire 700 are thereby selected simultaneously.

[0296] When y=2, the wire selector is 800

[0297] Select the third output terminal of the single-pole 3-throw switch connected to the fourth wire 700,

[0298] Select the first output terminal of the single-pole 3-throw switch connected to the fifth wire 700, and,

[0299] Select the second output terminal of each single-pole 3-throw switch connected to the 1st-3rd, 6th-8th wire 700,

[0300] The fourth wire 700 and the fifth wire 700 are thereby selected simultaneously.

[0301] When y=3, the wire selector is 800

[0302] Select the third output terminal of the single-pole 3-throw switch connected to the fifth wire 700,

[0303] Select the first output terminal of the single-pole 3-throw switch connected to the sixth wire 700, and,

[0304] Select the second output terminal of each single-pole 3-throw switch connected to the 1st to 4th, 7th and 8th wires 700,

[0305] Thus, the fifth wire 700 and the sixth wire 700 are selected simultaneously.

[0306] When y=4, the wire selector is 800

[0307] Select the second output terminal of the single-pole 3-throw switch connected to the 1st to 5th wire 700,

[0308] Select the third output terminal of the single-pole 3-throw switch connected to the sixth wire 700, and,

[0309] Select the first output terminal of each single-pole 3-throw switch connected to the 7th and 8th wires 700,

[0310] Thus, the sixth to eighth wires 700 are selected simultaneously.

[0311] When k=3:

[0312] According to n(k)=2 and formula (11), we get

[0313] Y(1)={7}∪{8}.

[0314] therefore,

[0315] When y=1, the wire selector is 800

[0316] Select the second output terminal of the single-pole 3-throw switch connected to the 1st to 6th wire 700,

[0317] Select the third output terminal of the single-pole 3-throw switch connected to the seventh wire 700, and,

[0318] Select the first output terminal of each single-pole 3-throw switch connected to the eighth wire 700,

[0319] The seventh wire 700 and the eighth wire are thereby selected simultaneously.

[0320] The controller that controls the operation of the wire selector 800 is well known, and thus illustration and description of the controller are omitted.

[0321] The liquid level meter of the present disclosure includes the above-mentioned interface sensor 200, the first substance is liquid, and the second substance is gas. In the liquid level meter, although the first direction is preferably a vertical direction, it is not limited thereto.

[0322] <Note>

[0323] Figures 2 to 14 The illustrated embodiment is a liquid level meter in the case where E is represented by a power of 2 and one of the E second electrical conductors is an electrode pair having a predetermined electrostatic capacitance in order to improve accuracy.

[0324] <Supplement>

[0325] Although the present invention has been described with reference to the illustrated embodiments, it will be appreciated by those skilled in the art that various changes may be made without departing from the scope of the present invention, and that elements thereof may be replaced by equivalents. Further, more modifications may be added without departing from the essential scope of the present invention in order to adapt a specific system, device, or component thereof to the teachings of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed for the implementation of the present invention, but includes all embodiments contained in the appended claims.

[0326] Furthermore, the use of terms such as "1st" and "2nd" does not indicate order or importance. Terms such as "1st" and "2nd" are used to distinguish elements. The terms used in this specification are used to illustrate the implementation methods and are by no means intended to limit the present invention. When the term "comprising" and its variations are used in this specification and / or the appended claims, it clarifies the presence of the features, steps, operations, elements, and / or components mentioned, but does not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or those groups. In the presence of terms such as "and / or", the relevant listed one or more elements and all combinations are included. In the claims and the specification, unless otherwise specified, "connected", "coupled", "joined", "linked", or synonyms of those terms, and all their forms do not necessarily deny that, for example, there is one or more intermediate elements between two elements that are "connected" or "coupled" to each other, or "linked" to each other. In the claims and the specification, when there is a term such as "arbitrary", unless otherwise specified, it should be understood to mean that the full name symbol For example, the expression "for any X" has the same meaning as "for all X" or "for each X".

[0327] Unless otherwise specified, all terms (including technical terms and scientific terms) used in this specification have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. Further, terms such as terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant technology and the present disclosure, and should not be interpreted ideally or too formally unless clearly defined.

[0328] In the description of the present invention, it should be understood that many technologies and steps have been disclosed. Each of them has its own advantages and can be used in combination with one or more other disclosed technologies, or with all technologies according to the situation. Therefore, in order to avoid cumbersomeness, in this specification, avoid describing all possible combinations of each technology or step. Even so, the specification and claims should be interpreted as such a combination is completely within the present invention and the claims.

[0329] For the structures, materials, acts, and equivalents corresponding to all functional elements associated with units or steps in the following claims, where they exist, it is intended to include the structure, material, or act for performing the function in combination with other elements.

[0330] The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Various changes and modifications are allowed within the scope of the present invention. The selected and described embodiments are embodiments for explaining the principles of the present invention and its practical application. The present invention is used as various embodiments with various changes or modifications, and various changes or modifications are determined according to the expected use. All such changes and modifications are intended to be included in the scope of the present invention as defined by the attached claims, and are intended to be given the same protection when interpreted according to the breadth given to fairness, legality and justice.

[0331] Explanation of symbols

[0332] 1 water tank; 2 interface sensor; 3 sensor block; 5 electrode pair; 5a electrode; 5b electrode; 6 electrode pair; 7 wire; 7x branch line; 7y branch line; 9 substrate; 10 reference line; 11-17 determination unit; 20 water level output unit; 30 sensor unit; 31 electrode; 40 ground conductor; 50 carrier generation circuit; 61, 62 resistor; 70 adjustment unit; 80 switching unit; 81 switch; 90, 90' determination unit; 100 water level determination unit; 110 control unit; 120 switching unit; 121 switch; 130, 140 charging circuit; 150 A / D conversion unit; 160 adjustment value storage unit; 200 interface sensor; 300 sensor block; 500a first electrical conductor; 500b second electrical conductor; 700 wire; 700x branch line; 800 wire selector; 900 substrate.

Claims

1. A liquid level meter, characterized in that: have: a ground conductor extending in a direction of liquid level detection; a sensor unit including a plurality of electrodes arranged in a liquid level detection direction and forming an electrostatic capacitance with the ground conductor; Adjustment Department; Switching unit; Discrimination unit; as well as Liquid level determination unit; The plurality of electrodes are divided into n groups, the i-th group consisting of the second electrode located at the bottom from the liquid level detection direction. i-1 (2k-1) positions of electrodes, where i = 1, 2, ..., n, and k is 1 to 2 n-i The natural number of The electrodes belonging to the same group among the plurality of electrodes are connected in parallel to each other and to the switching unit, For i=1, 2, ..., n-1, the determination unit determines the magnitude relationship between the electrostatic capacitance of the i-th group and the electrostatic capacitance of the group obtained by combining the i+1-th group to the n-th group, and further determines the magnitude relationship between the electrostatic capacitance of the n-th group and the electrostatic capacitance of the adjustment unit. In order to enable the determination by the determination unit, the switching unit sequentially switches the connection between the group and the determination unit. The liquid level determination unit determines the liquid level based on the determination made by the determination unit.

2. The liquid level meter according to claim 1, characterized in that: The adjustment unit functions so that the two electrostatic capacitances whose magnitude relationship is determined by the determination unit always have different values ​​from each other.

3. The liquid level meter according to claim 2, characterized in that: The adjusting units are provided in plurality, and the adjusting unit to function is switched according to the group connected to the determining unit.

4. The liquid level meter according to any one of claims 1 to 3, characterized in that: The ground conductor has a tubular shape surrounding the sensor unit.

5. The liquid level meter according to any one of claims 1 to 3, characterized in that: An A / D conversion unit is provided between the switching unit and the determining unit.

6. A sensor for determining the position of an interface between a first substance and a second substance, The sensor comprises a first electrical conductor, E second electrical conductors, L wires, and a wire selector, wherein: [Mathematical formula 19] K is a predetermined integer satisfying 2≤K, for each j∈{x∈N:1≤x≤K}, n(j) is a predetermined integer satisfying 2≤n(j), N is the set of all positive integers, The E second electrical conductors are located on E planes that are inconsistent with each other and parallel to each other in the order of the size relationship of the elements of the set {x∈N:1≤x≤E}. For each p∈{x∈N:1≤x≤E-1}, the pth second electrical conductor among the E second electrical conductors is connected to the s(p)th wire among the L wires, wherein, [Mathematical formula 20] n(0)=1, for each k∈{x∈N:1≤x≤K}, the kth set W(k) is [Formula 21] The K+1th set W(K+1) is an empty set, p∈W(r), The Eth second electrical conductor among the E second electrical conductors is connected to the Lth wire among the L wires. The wire selector can select any one of the L wires.

7. A sensor for determining the position of an interface between a first substance and a second substance, The sensor comprises a first electrical conductor, E second electrical conductors, L wires, and a wire selector, wherein: [Mathematical formula 22] K is a predetermined integer satisfying 2≤K, for each j∈{x∈N:1≤x≤K}, n(j) is a predetermined integer satisfying 2≤n(j), N is the set of all positive integers, The E second electrical conductors are located on E planes that are inconsistent with each other and parallel to each other in the order of the size relationship of the elements of the set {x∈N:1≤x≤E}. For each p∈{x∈N:1≤x≤E-1}, the pth second electrical conductor among the E second electrical conductors is connected to the s(p)th wire among the L wires, wherein, [Mathematical formula 23] n(0)=1, for each k∈{x∈N:1≤x≤K}, the kth set W(k) is [Formula 24] The K+1th set W(K+1) is an empty set, p∈W(r), The Eth second electrical conductor among the E second electrical conductors is connected to the Lth wire among the L wires. For each k∈{x∈N:1≤x≤K}, the above wire selector 1) When k≠K and n(k)≠2, For each y∈{x∈N:1≤x≤n(k)-2}, select two wires from the L wires, determined by the elements belonging to the set Y(y), where [Mathematical formula 25] For y=n(k)-1, select (2+Σ j＝k+1 K (n(j)-1)) conductors, where [Mathematical formula 26] 2) When k≠K and n(k)=2, Select the L wires above, which are determined by the elements belonging to the set Y (2+Σ j＝k+1 K (n(j)-1)) conductors, where [Mathematical formula 27] 3) In the case of k = K, For each y∈{x∈N:1≤x≤n(k)-1}, select two wires from the L wires, determined by the elements belonging to the set Y(y), where [Mathematical formula 28] 8. The sensor according to claim 6 or claim 7, characterized in that: For each j∈{x∈N:1≤x≤K}, the above n(j) is a prime factor of the above E.

9. The sensor according to any one of claims 6 to 8, characterized in that: The distance between one of any two second electrical conductors among the E second electrical conductors and the first electrical conductor is equal to the distance between the other of the two second electrical conductors and the first electrical conductor.

10. A liquid level meter, A sensor comprising any one of claims 6 to 9, The first substance is a liquid, The second substance is a gas.

11. The liquid level meter according to claim 10, The normal directions of the above E planes are vertical directions.

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