Sensor and liquid level meter for determining position of interface

Abstract

A liquid level meter is provided with an input circuit 30, a sensor unit 40, an adjustment unit 50, a switching unit 60, a determination unit 70, and a liquid level determination unit 80, the sensor unit 40 having a plurality of electrode pairs 41 arranged in a liquid level detection direction, the electrode pairs 41 being divided into n groups, the i-th group (i = 1, 2,..., n) comprising electrode pairs 41 at (2i-1)-(2k-1)-th (k is a natural number from 1 to 2n-i) positions from the lowermost position, and the n being a positive integer greater than or equal to 1). One end of the electrode pair 41 is connected to the input circuit 30, the other end is connected in parallel to the electrode pair 41 belonging to the same group and is connected to the switching unit 60, and the determination unit 70 determines the magnitude of the detection value of the i-th group and the magnitude of the detection value of the group combining the i + 1-th group to the n-th group for i = 1, 2,..., n-1, determines the magnitude of the detection value of the n-th group and the magnitude of the detection value obtained by the adjustment unit 50, and determines the magnitude of the detection value of the n-th group and the magnitude of the detection value obtained by the adjustment unit 50 for i = 1, 2,..., n-1. A switching means (60) sequentially switches the connections between the group and the determination means (70), and a liquid level determination means (80) determines the liquid level on the basis of the determination by the determination means (70).

Description

Technical Field

[0001] The present disclosure relates to a sensor for determining the position of an interface between two types of 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 7 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 in 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 in 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, according to the water level sensor of the prior art described above, in order to determine the water level with high resolution, a plurality of electrode pairs are required, and as a result, a plurality of wires corresponding to the plurality of electrode pairs are required.

[0010] For example, when Z observation points are set in the direction of the horizontal plane change in order to determine the water level with high resolution, 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 art, an interface sensor having a structure capable of making the total number L of wires led out from a sensor block 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 protection scope of the present invention, nor are they provided for the purpose of enabling persons other than the beneficiaries of the present invention (e.g., applicants and patentees) to limit the invention described in the protection scope of the present invention, 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 protection scope of the patent application at the time of application.

[0014] The sensor disclosed in the present invention is a sensor for determining the position of the interface of two types of substances (i.e., a first substance and a second substance that are different from each other). The sensor includes E electrode pairs, 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 the set of all positive integers.

[0015] [Mathematical formula 1]

[0016]

[0017] The E electrode pairs 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 p-th electrode pair among the E electrode pairs has: an electrode connected to the s(p)-th wire among the L wires, and an electrode connected to the L-th wire among the L wires. With respect to s(p), the following equation holds. In this equation, n(0)=1.

[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] The E-th electrode pair among the E electrode pairs has one electrode connected to the L-1-th conducting wire among the L conducting wires and the other electrode connected to the L-th conducting wire among the L conducting wires.

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

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

[0047] Figure 4 It is shown based on Figure 2 Table showing the operation of switches in water level measurement of a water level gauge.

[0048] Figure 5 It is a diagram for explaining the structure of Example 2 of the water level gauge based on the present invention.

[0049] Figure 6 It is a diagram for explaining the structure of Example 3 of the water level gauge based on the present invention.

[0050] Figure 7It is a diagram for explaining the structure of Example 4 of the water level gauge based on the present invention.

[0051] Figure 8 It is a diagram for explaining the structure of Example 5 of the water level gauge based on the present invention.

[0052] Fig. 9 Although it is related to the interface sensor of the present disclosure, it is an example of the structure of the interface sensor that is not protected by the protection scope of the present application.

[0053] Fig.10 This is a structural example of the interface sensor disclosed in the present invention.

[0054] Fig.11 This is a structural example of the interface sensor disclosed in the present invention. DETAILED DESCRIPTION

[0055] 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 8 In the related description, water is used as an example of liquid.

[0056] Example 1

[0057] Figure 2 The diagram shows the structure of the first embodiment of the water level meter according to the present invention. The water level meter includes an input circuit 30 , a sensor unit 40 , an adjustment unit 50 , a switching unit 60 , a determination unit 70 , a water level determination unit 80 , and a control unit 90 .

[0058] The sensor unit 40 has a plurality of (15 in this example) electrode pairs 41 arranged in the water level detection direction. The electrode pairs 41 detect the electrostatic capacitance between the electrodes in this example. Although the substrate of these electrode pairs 41 is omitted in the figure, they are arranged in a pattern on the substrate, and a waterproof coating is applied on the pattern. In addition, for the 15 electrode pairs 41, as shown in FIG. Figure 2 As shown, symbols C1 to C15 are given in order from the electrode pair located at the bottom.

[0059] The 15 electrode pairs 41 are divided into 4 groups. Here, the number of groups is set to n, and the n groups are referred to as the first to nth groups. The electrode pair 41 constituting the i-th group (i=1, 2, ..., n) is set to be located at the second position from the bottom in the water level detection direction. i-1 (2k-1) (k is from 1 to 2 n-i In this example, if C1 to C15 represent the electrode pairs 41 constituting each group of n=4, the following is obtained.

[0060] Group 1…C1, C3, C5, C7, C9, C11, C13, C15

[0061] Group 2…C2, C6, C10, C14

[0062] Group 3…C4, C12

[0063] Group 4…C8

[0064] One end of all electrode pairs 41 is connected to the input circuit 30, and the other end of the electrode pairs 41 belonging to the same group are connected in parallel to each other and to the switching unit 60. The input circuit 30 generates and outputs a carrier wave.

[0065] As indicated by the symbols S1 to S7, the switching unit 60 in this example includes seven switches 61, and has the following structure: the path is switched according to the on / off (ON / OFF) of these switches 61, thereby enabling the detection values ​​(electrostatic capacitance of each group) obtained by each group of the sensor unit 40 to be input (connected) to either of the two inputs a and b of the determination unit 70.

[0066] In this example, the adjustment unit 50 is a capacitor having electrostatic capacitance as described later, one end of which is connected to the input circuit 30 , and the other end of which is connected to the input b of the determination unit 70 .

[0067] The determination unit 70 includes a C / V converter for each of the two inputs a and b, and determines the magnitude relationship between two detection values ​​(capacitances) obtained from the inputs a and b by inputting the outputs of the C / V converters to a comparator for comparison.

[0068] The water level determination unit 80 determines the water level based on the determination of the determination unit 70 and outputs it to the outside. In addition, the on / off of the seven switches 61 of the switching unit 60 is controlled by a control signal from the control unit 90, and a signal synchronized with the control is also input from the control unit 90 to the water level determination unit 80.

[0069] Next, refer to Figure 3 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 3 In the example, the number of groups is set to n, G 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.

[0070] First, set i=1 (step M1), and turn OFF all switches 61 of the switching unit 60 (step M2). Then, turn ON the inputs a and G of the connection determination unit 70. iThe switch 61 further turns on the inputs b and G of the connection determination unit 70. i+1 , G i+2 , …, G n The switch 61 is turned on (steps M3 and M4). The determination unit 70 determines the magnitude relationship of the inputs a and b (step M5). If a>b, it outputs 1 to the water level determination unit 80. If a<b, it outputs 0 to the water level determination unit 80. The water level determination unit 80 treats it as 2. i-1 The bit value is stored (steps M6 and M7).

[0071] 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.

[0072] If i=n, ​​after turning off all switches 61 of the switching unit 60 (step M10), the inputs a and G of the connection determination unit 70 are turned on. n The switch 61 is turned on (step M11). The determination unit 70 determines the magnitude relationship of the inputs a and b (step M12). If a>b, it outputs 1 to the water level determination unit 80. If a<b, it outputs 0 to the water level determination unit 80. The water level determination unit 80 treats it as 2 n-1 The value of the bit is stored (steps M13 and M14), and the water level determination unit 80 refers to the memory and stores the 2 bits obtained in this way. 0 Position~2 n-1 The bit value, that is, the binary number is converted into a water level and output (step M15).

[0073] As such, in this example, the determination unit 70 determines the magnitude relationship between the detection value obtained by the i-th group and the detection value obtained by combining the groups from the i+1-th group to the n-th group for i=1, 2, ..., n-1, and further determines the water level by determining the magnitude relationship between the detection value obtained by the n-th group and the detection value obtained by the adjustment unit 50. The switching unit 60 sequentially switches the connection between the groups of the sensor unit 40 and the determination unit 70 so that such determination by the determination unit 70 can be performed.

[0074] Figure 4 The table shown shows that: Figure 2 The number n of the groups of water level gauges or sensor units 40 shown is 4. Figure 3 In the water level gauge where i is 1 to 4 in the flowchart shown, the seven switches 61, i.e., S1 to S7, of the switching unit 60 are turned on / off. 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 70 becomes as follows when i=1 to 4.

[0075] Input a Input b i=1:2 0 Position determination G1 G2+G3+G4 i=2:2 1 Position determination G2 G3+G4 i=3:2 2 Position determination G3 G4 i=4:2 3 Position determination G4 N / A (= not applicable)

[0076] Below, the water level W is located at Figure 2 The electrostatic capacitance connected to the inputs a and b of the determination unit 70 will be specifically described by taking the case where the ninth electrode pair C9 from the bottom is immersed in water, as shown by the two-dot chain line in FIG.

[0077] The electrostatic capacitance when the electrode pair 41 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 50 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 i=1 to 4, the electrostatic capacitance connected to input a and b becomes as follows.

[0078] <i=1:2 0 Position determination> ・Input a: G1=C1+C3+C5+C7+C9+C11+C13+C15 =5C water +3C air =403C air ・Input b: G2+G3+G4=C2+C4+C6+C8+C10+C12+C14+C99 =4.5C water +3C air =363C air <i=2:2 1 Position determination> ・Input a: G2=C2+C6+C10+C14 =2C water +2C air =162C air ・Input b: G3+G4=C4+C8+C12+C99 =2.5C water +C air =201C air <i=3:2 2 Position determination> ・Input a: G3=C4+C12 =C water +C air =81C air ・Input b: G4=C8+C99 =1.5C water =120C air <i=4:2 3 Position determination> ・Input a: G4=C8 =C water =80C air ・Input b: N / A=C99 =0.5C water =40 air

[0079] 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, 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.

[0080] Like this, in Figure 2 In the water level gauge shown, the water level is handled as a binary number. At a low water level when all electrode pairs 41 are not immersed in water, the binary number is 0000, and at a high water level when all electrode pairs 41 are immersed in water, the binary number is 1111 (decimal 15).

[0081] In this example, the adjustment unit 50 is set to have a 0.5C water The capacitor with an electrostatic capacitance of 2 is always connected to the input b of the determination unit 70. 3The adjustment unit 50 functions so that the two detection values ​​(electrostatic capacitances) whose magnitudes are determined by the determination unit 70 are always different from each other. That is, the adjustment unit 50 functions so that the magnitudes are not reversed due to error factors and the like, thereby preventing erroneous detection.

[0082] Hereinafter, embodiments 2 to 5 will be described. These embodiments 2 to 5 partially change the structure of embodiment 1, Figure 2 The same reference numerals are given to corresponding parts of the structure of the first embodiment, and their detailed description is omitted.

[0083] Example 2

[0084] As described above, the adjustment unit 50 functions so that the detection value changes appropriately according to the water level without causing erroneous detection. However, for example, when the capacitance of the electrode pair 41 has a large error or is inconsistent, the detection value may not change appropriately according to the water level only by the capacitance of the adjustment unit 50.

[0085] For example, in Figure 2 In the water level meter shown, it is considered that only the electrode pair 41 with C4 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 70 becomes as follows.

[0086] <i=1:2 0 Position determination> ・Input a: G1=C1+C3+C5+C7+C9+C11+C13+C15 =5C water +3C air =403C air ・Input b: G2+G3+G4=C2+C4'+C6+C8+C10+C12+C14+C99 =4.5C water +3C air +C99=363C air +C99 <i=2:2 1 Position determination> ・Input a: G2=C2+C6+C10+C14 =2C water +2C air =162C air ・Input b: G3+G4=C4'+C8+C12+C99 =2.5C water +C air +C99=201C air +C99 <i=3:2 2 Position determination> ・Input a: G3=C4'+C12 =1.5C water +C air =121C air ・Input b: G4=C8+C99 =C water +C99=80C air +C99 <i=4:2 3 Position determination> ・Input a: G4=C8 =C water =80C air ・Input b: N / A=C99

[0087] 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 for all determinations of the bit is the adjustment unit 50.

[0088] In order to deal with such a problem, in Example 2, Figure 5 As shown in the figure, a plurality of (in this example, four, with reference numerals C101 to C104) adjustment units 50 are provided, and further, a switching unit 100 for switching the connection to the input b of the determination unit 70 of the adjustment units 50 is provided. As shown in the reference numerals S11 to S14, the switching unit 100 includes four switches 101 for turning on / off the connection to the input b of each adjustment unit 50, namely, C101 to C104.

[0089] In this example, by providing a plurality of adjustment units 50 and switching them by the switching unit 100, it is possible to select the electrostatic capacitance required for adjustment according to the group (combination of groups) connected to the determination unit 70. In addition, the electrostatic capacitance values ​​of the four adjustment units 50, namely C101 to C104, are determined by prior experiments. Figure 3 Each process of i=1 to 4 in the flowchart shown is selected. The on / off of the four switches 101 of the switching unit 100 is controlled by a control signal from the control unit 90 in synchronization with a control signal for controlling the switching unit 60 .

[0090] Example 3

[0091] Since the switch 61 of the switching unit 60 has a gate capacitance, there is a possibility that the error caused by the gate capacitance affects the detection value. In the third embodiment, in order to deal with this problem, as shown in FIG. Figure 6 As shown, C / V conversion units 111 to 114 are provided between each group (Group 1 to Group 4: G1 to G4) of the sensor unit 40 and the switching unit 60, and the electrostatic capacitance value is converted into a voltage value in advance before being input into the switching unit 60 so as to eliminate the influence of the gate capacitance.

[0092] In this example, the adjustment unit 50 ′ uses a DC / DC converter or the like, and outputs a predetermined voltage determined by a previous test.

[0093] Two summing units 121 and 122 are provided between the switching unit 60 and the determining unit 70. Switches S1, S2, S4, and S6 are connected to the input of the summing unit 121, and switches S3, S5, and S7 and the adjusting unit 50' are connected to the input of the summing unit 122. The summing units 121 and 122 are summing circuits composed of, for example, operational amplifiers.

[0094] The output of the summing unit 121 is input to the input a of the discrimination unit 70, and the output of the summing unit 122 is input to the input b of the discrimination unit 70. According to such a structure, in this example, as in the first embodiment, Figure 4 The switching action shown in the table and Figure 3 The determination process is performed according to the flowchart shown.

[0095] Example 4

[0096] The fourth embodiment is a modified example of the structure of the third embodiment in which C / V converters 111 to 114 are provided between each group of sensor units 40 and the switching unit 60 .

[0097] In this example, if Figure 7As shown, a switching unit 60' is provided with four switches 61 shown as S1 to S4 corresponding to the four C / V conversion units 111 to 114, and an A / D conversion unit 130 for converting the detection value as a digital value is provided between the switching unit 60' and the determination unit 70. Furthermore, an adjustment value storage unit 140 for storing a pre-calculated adjustment value (electrostatic capacitance adjustment voltage value) as a digital value is provided.

[0098] The output of voltage based on an analog circuit requires the use of an IC and a plurality of resistors, and has the disadvantage that the larger the number of adjustment values, the larger the circuit scale, as in the configuration with four adjustment units 50 shown in Example 2. In this regard, in this example, the adjustment value is stored as a digital value, so the circuit does not become large-scale.

[0099] In this example, the four switches 61 of the switching unit 60' are turned on in sequence to obtain the voltage output of each group (the first to fourth groups: G1 to G4) as a digital value. In this example, the determination unit 70 compares the digital value input from the A / D conversion unit 130 with the G i (i=1~4) are stored in an associated manner. i After all digital values ​​(i=1 to 4) are obtained (stored), these digital values ​​and the adjustment values ​​stored in the adjustment value storage unit 140 (in this example, the four adjustment values ​​corresponding to i=1 to 4) are used to perform calculations, thereby performing each determination in i=1 to 4, that is, 2 0 Position~2 3 Position determination.

[0100] Example 5

[0101] Although the electrode pair 41 detects the electrostatic capacitance between the electrodes in the above-mentioned embodiments 1 to 4, the electrode pair 41 may also detect the resistance value between the electrodes. Figure 8 Such a water level gauge is shown as Figure 2 The water level meter of the first embodiment shown in the figure is a modified example. The adjustment unit 50" is a resistor in this example. The 15 electrode pairs 41 are given symbols R1 to R15 in order from the electrode pair located at the bottom in this example.

[0102] Below, the water level W is Figure 2 The case of the same position is taken as an example, and the resistance value connected to the input a and b of the determination unit 70 is specifically described. In addition, in this example, the input circuit 30 generates an input voltage and outputs the input voltage. In the determination unit 70, a bridge circuit or the like is used to determine which of the inputs a and b has a larger resistance value. In this example, in contrast to the case of detecting electrostatic capacitance, if a>b, the determination unit 70 outputs 0, and if a<b, the determination unit 70 outputs 1.

[0103] The resistance value when the electrode pair 41 is in the air is R air , the resistance value when in water is set to R water The resistor of the adjustment unit 50" is represented as R99 in the following, and the resistance value is 2R water . R air Set to R air ≒∞. In i=1~4, the resistance values ​​Ra and Rb connected to input a and b are as follows.

[0104] <i=1:2 0 Position determination> ・Input a: G1=R1+R3+R5+R7+R9+R11+R13+R15 1 / Ra=(5 / R water )+(3 / R air ) ∴Ra=R water / 5 ・Input b: G2+G3+G4=R2+R4+R6+R8+R10+R12+R14+R99 1 / Rb=(4.5 / R water )+(3 / R air ) ∴R b =R water / 4.5 <i=2:2 1 Position determination> ・Input a: G2=R2+R6+R10+R14 1 / Ra=(2 / R water )+(2 / R air ) ∴Ra=R water / 2 ・Input b: G3+G4=R4+R8+R12+R99 1 / Rb=(2.5 / R water )+(1 / R air ) ∴Rb=R water / 2.5 <i=3:2 2 Position determination> ・Input a: G3=R4+R12 1 / Ra = (1 / R water )+(1 / R air ) ∴Ra=R water ・Input b: G4=R8+R99 1 / Rb=1.5 / R water ∴Rb=R water / 1.5 <i=4:23 Position determination> ・Input a: G4=R8 1 / Ra=1 / R water ∴Ra=R water ・Input b: N / A=R99 1 / Rb=0.5 / R water ∴Rb=2R water

[0105] 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, in i=4, according to a<b, 2 3 The bit becomes 1. Therefore, when these are added together, a result of 1001 in binary number is obtained in this fifth embodiment, similarly to the first embodiment.

[0106] Although various embodiments of the water level meter according to the present invention have been described above, the water level meter according to the present invention divides a plurality of electrode pairs arranged in the water level detection direction into n groups, and the i-th group (i=1, 2, ..., n) is composed of the second electrode pairs located from the bottom in the water level detection direction. i-1 (2k-1) (k is from 1 to 2 n-i By changing the combination of groups and repeatedly comparing the size of the detection values, the resolution of the number of electrode pairs can be obtained.

[0107] Therefore, the number of wirings (wirings on the detection side) connecting from each electrode pair of the sensor unit to the determination unit can be the number of groups, and only one determination unit is required.

[0108] In addition, for example, if 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 the electrode pairs are 1000, respectively, and the number of wirings from the electrode pairs to the determination circuit is 1000.

[0109] In contrast, in the water level gauge according to the present invention, according to the above-mentioned group structure, 2 n -1 electrode pair, that is, because 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.

[0110] The above-mentioned water level gauge can be used, for example, to measure the water level of a river or the like, and can also be applied to, for example, a liquid level gauge for detecting the liquid level of a liquid in a tank or the like.

[0111] Hereinafter, reference is made to non-limiting examples. Fig.10 and Fig.11 , the interface sensor 200 of the present disclosure and the liquid level meter including the interface sensor 200 are described from other viewpoints. Prior to this description, in order to facilitate understanding of the interface sensor 200 of the present disclosure, refer to Fig. 9 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 protection scope of the present application, the description of the interface sensor 2 is helpful 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 needed. In addition, the inclusion of the description is not necessarily explicit.

[0112] The interface sensor 2 is a sensor for determining the position of the interface between two types of substances (i.e., a first substance and a second substance that are different from each other). However, in order to correctly 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 shown in the following formula (4), the interface sensor 2 includes E electrode pairs 5. The position of the interface between the first substance and the second substance is determined by utilizing the physical quantity generated in each of the E electrode pairs 5 according to the properties of the first substance or the second substance existing between each of the E electrode pairs 5. 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 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.

[0113] 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 5 is described, and the description of the resistance of the electrode pair 5 is omitted.

[0114] The interface sensor 2 includes K sensor blocks 3, wherein K is a predetermined integer satisfying 2≤K.

[0115] 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. 9 In 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.

[0116] The k-th sensor block 3 among the K sensor blocks 3 includes M(k) electrode pairs 5 and n(k)+1 wires 7. The M(k) electrode pairs 5 included in the k-th sensor block 3 have the same electrostatic capacitance C when the space between the M(k) electrode pairs 5 is filled with the first material, for example. k The electrostatic capacitance C of each of the M(k) electrode pairs 5 included in the k-th sensor block 3 is k The capacitance C of each of the M(j) electrode pairs 5 included in the j-th (j≠k) sensor block 3 can be j The n(k)+1 wires 7 are wires drawn out from the sensor block 3 and connected to the M(k) electrode pairs 5 as described later. The n(k)+1 wires 7 are connected to a detection circuit described later. Fig. 9In the figure, for the sake of clarity, only some electrode pairs and some conductors are given symbols. k is a parameter for representing 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 equation (1). “×” represents a multiplication operation. M(1), i.e., the number of electrode pairs 5 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” (the total number is represented by symbol Z in the description of the prior art). In detail, according to equations (4) and (5) shown later, in order to make the total number L of conductors 7 drawn out from the interface sensor 2 less than the sum of the total number of observation points M(1) and 1, M(1) must be ≥ 8. Furthermore, when M(1)=8, in order to make the total number L of the conductive wires 7 drawn out from the interface sensor 2 smaller than the sum of the total number of observation points M(1) and 1, K=2 is required.

[0117] [Mathematical formula 8]

[0118]

[0119] 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,

[0120] M(1)=2×30 (i.e., K=2, n(1)=30, n(2)=2),

[0121] M(1)=3×20 (i.e., K=2, n(1)=20, n(2)=3),

[0122] M(1)=12×5 (i.e., K=2, n(1)=5, n(2)=12),

[0123] M(1)=4×3×5 (i.e., K=3, n(1)=5, n(2)=3, n(3)=4),

[0124] M(1)=5×6×2 (i.e., K=3, n(1)=2, n(2)=6, n(3)=5),

[0125] M(1)=2×3×2×5 (i.e., K=4, n(1)=5, n(2)=2, n(3)=3, n(4)=2),

[0126] 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 production 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.

[0127] The mth electrode pair 5 of the M(k) electrode pairs 5 included in the kth (k∈{x∈N:1≤x≤K}) sensor block 3 k The electrode pair 5 is located in the r(k, m)th plane of M(1) k ) plane P(r(k,m k )). 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 expressed by formula (2). 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). To further simplify the description, 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) may be equal to or different from the distance between the h-th plane P(h) and the h+1-th plane P(h+1). For example, in a measurement range where it is desired to more accurately determine the position of an interface, the interval between adjacent planes may be reduced. In the k-th (k∈{x∈N:1≤x≤K}) sensor block 3, the M(k) electrode pairs 5 are typically configured in a straight line, but are not limited thereto, and may also be configured in a walking footprint shape, for example.

[0128] [Mathematical formula 9]

[0129]

[0130] From the perspective of the ease of design and manufacture of the interface sensor 2, the K sensor blocks 3 are usually arranged in a second direction orthogonal to the first direction. The total number of possible arrangement patterns of the K sensor blocks 3 in the second direction is K!, i.e., 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)”.

[0131] The mth electrode pair 5 of the M(k) electrode pairs 5 included in the kth (k∈{x∈N:1≤x≤K}) sensor block 3 k (m k ∈{x∈N:1≤x≤M(k)})The electrode pair 5 has the connection with the s(m k )-th wire 7, and the other electrode 5b connected to the n(k)+1-th wire 7. In this example, the m-th wire 7 is connected to the n(k)+1-th wire 7. k (m k ∈{x∈N:1≤x≤M(k)})One electrode 5a of the electrode pair 5 and the s(m k ) conductors 7 are connected to each other via branch line 7x. k The other electrode 5b of the electrode pair 5 (mk∈{x∈N:1≤x≤M(k)}) and the n(k)+1th conductor 7 are connected to each other via the branch line 7y. 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 from Euclidean division by the divisor n(k).

[0132] [Formula 10]

[0133]

[0134] As can be seen from the above description, the number E of electrode pairs 5 included in the interface sensor 2 is given by equation (4), and the number L of wires 7 drawn from the interface sensor 2 is given by equation (5). Under the above conditions, L<M(1)+1 can be achieved.

[0135] [Mathematical formula 11]

[0136]

[0137] 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 an interface in the interface with the t-th k The synthesis of the physical quantities (e.g., the synthesis of electrostatic capacitance) generated in each of the electrode pairs connected to the first wire 7 and the ... k The difference D(t) in the synthesis of physical quantities (e.g., synthetic electrostatic capacitance) generated in each of the electrode pairs connected by +1 wire 7 k ), and 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). In the case of k=K, it is defined as y=0. 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 situations: 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 that includes 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 for each k∈{x∈N:1≤x≤K}) and applies it to the n(k)+1th conductor 7, and a detection circuit 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 5 The detection circuit shown (including the input circuit 30 and the determination unit 70) may also be Figure 6 The detection circuit shown (including input circuit 30, discrimination unit 70, summing units 12, 122) can also be Figure 7The detection circuit shown (including the input circuit 80, the determination unit 70, and the A / D converter 130) may also be a detection circuit including a PLD (programmable logic device). Examples of the PLD include an FPGA (field-programmable gate array).

[0138] [Mathematical formula 12]

[0139]

[0140] 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(1), the interval common to each sensor block 3 is determined as the interval where the interface exists. In the algorithm shown in Table 1, it is assumed that there is a K-th 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 satisfying D(T K’+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).

[0141] [Table 1]

[0142]

[0143] The interface sensor 2 may also include an electrode pair for determining that the interface has not reached the plane P(1) and / or an electrode pair for determining that the interface has exceeded the plane P(M(1)). k And D (t k )≤δ, it can be seen that the interface does not reach plane P(1), so the former electrode pair is not necessary.

[0144] exist Fig. 9 A specific configuration example of the interface sensor 2 is shown in FIG. Fig. 9 The structure example shown is an example of the case where M(1)=30 and K=3. Fig. 9In 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.

[0145] The m1th (m1∈{x∈N:1≤x≤30}) electrode pair 5 among the 30 electrode pairs 5 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}) electrode pair 5 included in the first sensor block 3 is located in the pth plane P(p).

[0146] The m2th (m2∈{x∈N:1≤x≤10}) electrode pair 5 among the 10 electrode pairs 5 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 pth (p∈{x∈N:1≤x≤10}) electrode pair 5 included in the second sensor block 3 is located in the (3×p)th plane P(3×p). For example, the 7th (p=7∈{x∈N:1≤x≤10}) electrode pair 5 included in the second sensor block 3 is located in the 21st plane P(21).

[0147] The m3th (m3∈{x∈N:1≤x≤2}) electrode pair 5 of the two electrode pairs 5 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 pth (p∈{x∈N:1≤x≤2}) electrode pair 5 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}) electrode pair 5 included in the third sensor block 3 is located in the 15th plane P(15).

[0148] The m1th (m1∈{x∈N:1≤x≤30}) electrode pair 5 among the 30 electrode pairs 5 included in the first sensor block 3 has an electrode 5a connected to the s(m1)th wire 7 among the four wires 7, and an electrode 5b connected to the fourth wire 7 among the four wires 7. According to formula (3), for example, the electrode 5a of the 7th electrode pair 5 is connected to the first wire 7 (7 mod 3 = 1), the electrode 5a of the 17th electrode pair 5 is connected to the second wire 7 (17 mod 3 = 2), and the electrode 5a of the 24th electrode pair 5 is connected to the third wire 7 (24 mod 3 = 0).

[0149] The m2-th (m2∈{x∈N:1≤x≤10}) electrode pair 5 among the 10 electrode pairs 5 included in the second sensor block 3 has an electrode 5a on one side connected to the s(m2)-th wire 7 among the six wires 7, and an electrode 5b on the other side connected to the sixth wire 7 among the six wires 7. According to formula (3), the electrode 5a of each of the first and sixth electrode pairs 5 is connected to the first wire 7 (1 mod 5 = 6 mod 5 = 1), the electrode 5a of each of the second and seventh electrode pairs 5 is connected to the second wire 7 (2 mod 5 = 7 mod 5 = 2), the electrode 5a of each of the third and eighth electrode pairs 5 is connected to the third wire 7 (3 mod 5 = 8 mod 5 = 3), the electrode 5a of each of the fourth and ninth electrode pairs 5 is connected to the fourth wire 7 (4 mod 5 = 9 mod 5 = 4), and the electrode 5a of each of the fifth and tenth electrode pairs 5 is connected to the fifth wire 7 (5 mod 5 = 10 mod 5 = 0).

[0150] The m3-th (m3∈{x∈N:1≤x≤2}) electrode pair 5 of the two electrode pairs 5 included in the third sensor block 3 has an electrode 5a connected to the s(m3)-th wire 7 of the three wires 7, and an electrode 5b connected to the third wire 7 of the three wires 7. According to formula (3), the electrode 5a of one side of the first electrode pair 5 is connected to the first wire 7 (1 mod 2 = 1), and the electrode 5a of one side of the second electrode pair 5 is connected to the second wire 7 (2 mod 2 = 0).

[0151] According to formula (4), Fig. 9 The number E of the electrode pairs 5 included in the structure example of the interface sensor 2 shown is 42. According to formula (5), the number L of the wires 7 is 13. Since the total number of observation points M(1) is 30, L<M(1)+1 holds. In addition, if based on Figure 1 In the water level meter of the prior art shown in the figure, the number of wires is 31 (=M(1)+1). Further, for example, not shown but in the case where M(1)=1440, K=5, n(1)=5, n(2)=3, n(3)=2, n(4)=8, n(5)=6, the number L of wires 7 in the interface sensor 2 is 29. Figure 1 In the water level meter of the prior art shown, the number of wires is 1441 (=M(1)+1).

[0152] Although in Fig. 9In 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.

[0153] 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 .

[0154] 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 correctly 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 shown in the following formula (7), the interface sensor 200 includes E electrode pairs 500. 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 500 based on the properties of the first substance or the second substance existing between each of the E electrode pairs 500. "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.

[0155] 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. Therefore, in the following, only the electrostatic capacitance of the electrode pair 500 is described, and the description of the resistance of the electrode pair 500 is omitted.

[0156] The interface sensor 200 includes E electrode pairs 500, L wires 700 drawn from the sensor block 300, and a wire selector 800. Generally, the E electrode pairs 500 and the L wires 700 are formed on a substrate 900 having a flat plate shape. In addition to the E electrode pairs 500, the substrate 900 is coated with a waterproof coating. The wire selector 800 is not limited to the following example, and can 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 it is located in a place immersed in the liquid, a waterproof coating is applied.

[0157] When the space between each of the E electrode pairs 500 is filled with the first substance, for example, the E electrode pairs 500 have the same electrostatic capacitance C1. The E electrode pairs 500 are connected to the L wires 700 as described later. In addition to the Lth wire 700, the L-1 wires 700 are connected to the wire selector 800 described later. Fig.10 as well as Fig.11 In the figure, considering the readability of the figure, only a few electrode pairs and a few 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 electrode pairs 500 included in the sensor block 300 determines the resolution of the interface sensor 200. That is, E 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). Under the above conditions, L<E+1.

[0158] [Mathematical formula 13]

[0159]

[0160] 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 a 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)).

[0161] The E electrode pairs 500 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) exists. 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) can be equal to or unequal to 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 can be reduced. The pth electrode pair 500 among the E electrode pairs 500 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 electrode pairs 500 are usually arranged in a straight line, but are not limited thereto. For example, they may be arranged in a walking footprint shape. In addition, when the first direction is a vertical direction, the "plane" may be replaced by, for example, a "horizontal plane (level)".

[0162] For each p∈{x∈N:1≤x≤E-1}, the p-th electrode pair 500 among the E electrode pairs 500 has an electrode 500a on one side connected to the s(p)-th wire 700 among the L wires 700, and an electrode 500b on the other side connected to the L-th wire 700 among the L wires 700. In this example, the electrode 500a on one side of the p-th (p∈{x∈N:1≤x≤E-1}) electrode pair 500 and the s(p)-th wire 700 are connected to each other via a branch line 700x. In this example, the electrode 500b on the other side of the p-th (p∈{x∈N:1≤x≤E-1}) electrode pair 500 and the L-th wire 7 are connected to each other via a branch line 700y. s(p) is represented by formula (9). In formula (9), the symbol mod represents a remainder operation, and a mod b is the remainder obtained by dividing the dividend a by the divisor b by the Euclidean division. In formula (9), the symbol " / " appearing in the dividend of the remainder operation represents a division operation. In this description, n(0)=1.

[0163] [Formula 14]

[0164]

[0165] 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 represented by equation (10). The K+1th set W(K+1) is the empty set Ø. In equation (10), the symbol “|” represents a multiple, that is, a|b means “b is a multiple of a”.

[0166] [Mathematical formula 15]

[0167]

[0168] If it is defined as W = {W(j): j∈N ∧ 1≤j≤K}, then from formula (10), we can see that 1) ∀W(j)∈W, W(j)≠Ø 2) W(i)∈W, W(j)∈W, W(i)≠W(j) ⇒ W(i)∩W(j)= Ø 3) ∪ j=1 K W(j)={x∈N:1≤x≤E} holds. Therefore, ∀p∈{x∈N:1≤x≤E-1}, ∃!W(r)∈W st p∈W(r). That is, the set W(r) to which p belongs is uniquely determined.

[0169] The E-th electrode pair 500 among the E electrode pairs 500 includes an electrode 500 a connected to the L−1-th wire 700 among the L wires 700 , and an electrode 500 b connected to the L-th wire 700 among the L wires 700 .

[0170] The wire selector 800 can select any one of the L wires 700 , except the Lth wire 700 .

[0171] Alternatively, for each k∈{x∈N:1≤x≤K}, the wire selector 800

[0172] 1) When k≠K and n(k)≠2,

[0173] 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,

[0174] 2) When k≠K and n(k)=2,

[0175] 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,

[0176] 3) In the case of k=K,

[0177] 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.

[0178] Among them, the set Y(y) is expressed by formula (11), the set Y a (y) is expressed by equation (12). These sets are expressed as the union of singletons.

[0179] [Formula 16]

[0180]

[0181] 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.

[0182] 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.

[0183] 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.

[0184] [Mathematical formula 17]

[0185]

[0186] 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. When 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 5 The detection circuit shown (including the input circuit 30 and the determination unit 70) may also be Figure 6 The detection circuit shown (including input circuit 30, discrimination unit 70, summing units 12, 122) can also be Figure 7 The detection circuit shown (including the input circuit 80, the determination unit 70, and the A / D converter 130) may also be a detection circuit including a PLD (programmable logic device). Examples of the PLD include an FPGA (field-programmable gate array).

[0187] 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 this algorithm, overflow determination processing and error avoidance processing are not performed.

[0188] [Table 2]

[0189]

[0190] When the total number Z of the above-mentioned "observation points" 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 one electrode pair and one wire are added to the interface sensor 200 including E (where E=Z-1) electrode pairs 500, L wires 700, and a wire selector 800. In this structure, the added electrode pair is located on the P(E+1)th plane, and the electrode on one side of the added electrode pair is connected to the added wire, and the electrode on the other side is connected to the Lth wire 700. By determining by the detection circuit whether the electrostatic capacitance value of the added electrode pair exceeds the specified reference value, it is possible to determine whether the interface exceeds the P(E+1)th plane.

[0191] exist Fig.10 and Fig.11 1 and 2 are respectively shown as specific structural examples of the interface sensor 200. These structural examples are examples when E=30 and K=3. Fig.10 and Fig.11 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=9. See equations (7) and (8) for these facts.

[0192] like Fig.10 and Fig.11As shown, the pth (p∈{x∈N:1≤x≤30}) electrode pair 500 is located in the pth plane P(p).

[0193] According to formula (10), W(3), W(2), and W(1) are determined as follows.

[0194] W(3)={15,30}

[0195] W(2)={3,6,9,12,18,21,24,27}

[0196] W(1)={1,2,4,5,7,8,10,11,13,14,16,17,19,20,22,23,25,26,28,29}

[0197] For example, when p=12, p∈W(2), that is, r=2. Therefore, according to formula (9), s(p)=6, the electrode 500a of one side of the 12th (=p) electrode pair 500 is connected to the 6th (=s(p)) wire 700, and the electrode 500b of the other side of the 12th (=p) electrode pair 500 is connected to the 9th (=L) wire 700. All the calculation results are

[0198] p∈{1, 4, 7, 10, 13, 16, 19, 22, 25, 28}→s(p)=1,

[0199] p∈{2, 5, 8, 11, 14, 17, 20, 23, 26, 29}→s(p)=2,

[0200] p∈{3, 18}→s(p)=3,

[0201] p∈{6, 21}→s(p)=4,

[0202] p∈{9, 24}→s(p)=5,

[0203] p∈{12, 27}→s(p)=6,

[0204] p∈{15}→s(p)=7.

[0205] One electrode 500 a of the 30th (=E) electrode pair 500 is connected to the 8th (=L−1) lead wire 700 , and the other electrode 500 b of the 30th (=E) electrode pair 500 is connected to the 9th (=L) lead wire 700 .

[0206] Fig.10The interface sensor 200 shown includes a wire selector 800, and the wire selector 800 can select any one of the L wires 700, except the Lth wire 700. Such a wire selector 800 is not limited to the following example, and includes L-1 single-pole single-throw switches. One end of each of the L-1 single-pole single-throw switches is connected to a corresponding wire 700 in the L-1 wires 700 except the Lth wire 700. The other end of each of the L-1 single-pole single-throw switches is not limited to the following example, but is connected to a C / V converter. The structure of such a wire selector 800 can be connected to Figure 7 The structure of the detection circuit shown (which at least includes the A / D conversion unit 130, the control unit 90, and the determination unit 70) coexists. When the value of L is not large, the wire selector 800 can also be a single-pole (L-1) throw switch. When the wire selector 800 is a single-pole (L-1) throw switch, the number of C / V converters connected to the wire selector 800 can be 1.

[0207] Fig.11 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-1 single-pole three-throw switches. The input terminal of the single-pole three-throw switch is connected to the corresponding conductor 700 among the L-1 conductors 700 except the Lth conductor 700. The first output terminal of the single-pole three-throw switch is connected to the conductor b, the second output terminal is 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.

[0208] Wire Selector 800 Fig.11 The following selection actions are performed in the structure shown.

[0209] In the case of k=1:

[0210] According to n(k)=3, equation (11) and equation (12), we can get

[0211] Y(1)={1}∪{2},

[0212] Y a ={2}∪{3, 4, 5, 6, 7, 8}.

[0213] therefore,

[0214] When y=1, the wire selector is 800

[0215] Select the third output terminal of the single-pole 3-throw switch connected to the first wire 700,

[0216] Select the first output terminal of the single-pole 3-throw switch connected to the second conductor 700, and

[0217] Select the second output terminal of each single-pole 3-throw switch connected to the 3rd to 8th wires 700,

[0218] Thus, the first conductive line 700 and the second conductive line 700 are selected simultaneously.

[0219] When y=2, the wire selector is 800

[0220] Select the second output terminal of the single-pole 3-throw switch connected to the first wire 700,

[0221] Select the third output terminal of the single-pole 3-throw switch connected to the second conductor 700, and

[0222] Select the first output terminal of each single-pole 3-throw switch connected to the 3rd to 8th wires 700,

[0223] Thus, the 2nd to 8th wires 700 are selected simultaneously.

[0224] In the case of k=2:

[0225] According to n(k)=5, equation (11) and equation (12), we can get

[0226] Y(1)={3}∪{4},

[0227] Y(2)={4}∪{5},

[0228] Y(3)={5}∪{6},

[0229] Y a ={6}∪{7,8}.

[0230] therefore,

[0231] When y=1, the wire selector is 800

[0232] Select the third output terminal of the single-pole 3-throw switch connected to the third wire 700,

[0233] Select the first output terminal of the single-pole 3-throw switch connected to the fourth wire 700, and,

[0234] Select the second output terminal of each single-pole 3-throw switch connected to the 1st, 2nd, 5th-8th wires 700,

[0235] The third wire 700 and the fourth wire 700 are thereby selected simultaneously.

[0236] When y=2, the wire selector is 800

[0237] Select the third output terminal of the single-pole 3-throw switch connected to the fourth wire 700,

[0238] Select the first output terminal of the single-pole 3-throw switch connected to the fifth wire 700, and,

[0239] Select the second output terminal of each single-pole 3-throw switch connected to the 1st-3rd and 6th-8th wires 700,

[0240] The fourth wire 700 and the fifth wire 700 are thereby selected simultaneously.

[0241] When y=3, the wire selector is 800

[0242] Select the third output terminal of the single-pole 3-throw switch connected to the fifth wire 700,

[0243] Select the first output terminal of the single-pole 3-throw switch connected to the sixth wire 700, and,

[0244] Select the second output terminal of each single-pole 3-throw switch connected to the 1st to 4th, 7th and 8th wires 700,

[0245] Thus, the fifth wire 700 and the sixth wire 700 are selected simultaneously.

[0246] When y=4, the wire selector is 800

[0247] Select the second output terminal of the single-pole 3-throw switch connected to the 1st to 5th wire 700,

[0248] Select the third output terminal of the single-pole 3-throw switch connected to the sixth wire 700, and,

[0249] Select the first output terminal of each single-pole 3-throw switch connected to the 7th and 8th wires 700,

[0250] Thereby, the 6th to 8th wires 700 are selected simultaneously.

[0251] In the case of k=3:

[0252] According to n(k)=2 and formula (11), we can get

[0253] Y(1)={7}∪{8}.

[0254] therefore,

[0255] When y=1, the wire selector is 800

[0256] Select the second output terminal of the single-pole 3-throw switch connected to the 1st to 6th wire 700,

[0257] Select the third output terminal of the single-pole 3-throw switch connected to the seventh wire 700, and,

[0258] Select the first output terminal of each single-pole 3-throw switch connected to the eighth wire 700,

[0259] The seventh wire 700 and the eighth wire are thereby selected simultaneously.

[0260] The controller that controls the operation of the wire selector 800 is well known, and thus illustration and description of the controller are omitted.

[0261] 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.

[0262] <Note>

[0263] Figures 2 to 8 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 electrode pairs is an electrode pair having a predetermined electrostatic capacitance in order to improve accuracy.

[0264] <Supplement>

[0265] 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 invention, and that elements thereof may be replaced by equivalents. Further, without departing from the essential scope of the present invention, a large number of modifications may be added in order to make the system, equipment or its components of the provisions suitable for the teachings of the present invention. Therefore, the present invention is not limited to the disclosed definite embodiments for implementing the present invention, and comprises all embodiments included in the attached protection scope.

[0266] Further, 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 mode and are not intended to limit the present invention. The term "include" and its word form changes, when used in this specification and / or the attached protection scope, clarify the existence of the mentioned features, steps, operations, elements, and / or components, but do not exclude the existence or addition of one or more other features, steps, operations, elements, components, and / or the above groups. In the case of the existence of terms such as "and / or", all combinations of one or more elements listed in association are included. In the protection scope and specification of the present application, unless otherwise specified, "connect", "couple", "join", "connect", or synonyms of the above terms, and all word forms thereof do not necessarily deny that, for example, there is more than one intermediate component between two components that are "connected" or "coupled" or "connected" to each other. In the protection scope and specification of the present application, when there is a term such as "arbitrary", unless otherwise specified, it should be understood as a term representing the same meaning as the full name symbol ∀. For example, the expression "for any X" has the same meaning as "for all X" or "for each X".

[0267] 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 overly formally unless clearly defined.

[0268] 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 also be used in combination with one or more other disclosed technologies or with all technical combinations according to the circumstances. Therefore, in order to avoid being cumbersome, in this specification, all possible combinations of each technology or step are avoided. Even so, the protection scope of the specification and the application should be interpreted as that such a combination is completely within the scope of the protection scope of the present invention and the application.

[0269] For the structures, materials, actions, and equivalents corresponding to all functional components combined with units or steps in the protection scope of the present application below, if they exist, it is intended to include structures, materials, or actions used to perform functions in combination with other elements.

[0270] The embodiments of the present invention are described above, but the present invention is not limited to the above embodiments. Various changes and modifications are allowed within the scope of the main purpose 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. 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.

[0271] Description of Reference Numerals

[0272] 1 water tank; 2 interface sensor; 3 sensor block; 5 electrode pair; 5a electrode; 5b electrode; 6 electrode pair; 7 lead wire; 7x branch wire; 7y branch wire; 9 substrate; 10 reference wire; 11 to 17 determination unit; 20 water level output unit; 30 input circuit; 40 sensor unit; 41 electrode pair; 50, 50', 50" adjustment unit; 60, 60' switching unit; 61 switch; 70 determination unit; 80 water level determination unit; 90 control unit; 100 switching unit; 101 switch; 111 to 114 C / V conversion unit; 121, 122 summing unit; 130 A / D conversion unit; 140 adjustment value storage unit; 200 interface sensor; 300 sensor block; 500 electrode pair; 500a electrode; 500b electrode; 700 lead wire; 700x Branch line; 700y branch line; 800 wire selector; 900 base plate.

Claims

1. A liquid level meter, It is characterized in that It has an input circuit, a sensor unit, an adjustment unit, a switching unit, a determination unit, and a liquid level determination unit. The sensor unit includes a plurality of electrode pairs arranged in a liquid level detection direction, wherein the plurality of electrode pairs are divided into n groups, and the i-th group (i=1, 2, ..., n) includes the second electrode pair located from the bottom in the liquid level detection direction. i-1 (2k-1) (k is 1 to 2 n-i The electrode pairs are composed of natural numbers of positions. One end of all electrode pairs is connected to the input circuit, and the other end is connected to the electrode pairs belonging to the same group in parallel with each other and connected to the switching unit. The determination unit determines the magnitude relationship between the detection value obtained by the i-th group and the detection value obtained by combining the i+1-th group to the n-th group for i=1, 2, ..., n-1, and further determines the magnitude relationship between the detection value obtained by the n-th group and the detection value obtained by the adjustment unit. The switching unit sequentially switches the connection between the group and the discrimination unit so as to enable the discrimination by the discrimination unit. The liquid level determination unit determines the liquid level based on the determination made by the determination unit.

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

3. In the liquid level meter according to claim 2, It is characterized in that The adjusting section is provided in plurality, and the adjusting section to be made to function is switched according to the group connected to the determining unit.

4. In the liquid level meter according to any one of claims 1 to 3, It is characterized in that The electrode pair detects the resistance value between the electrodes.

5. In the liquid level meter according to any one of claims 1 to 3, It is characterized in that The electrode pair detects the electrostatic capacitance between the electrodes.

6. In the liquid level meter according to claim 5, It is characterized in that A C / V conversion unit is provided between each of the groups and the switching unit to convert the electrostatic capacitance into a voltage and input the voltage into the switching unit. A summing unit capable of performing the determination by the determination unit is provided between the switching unit and the determination unit.

7. In the liquid level meter according to any one of claims 1 to 3, It is characterized in that An A / D converter that converts the detection value into a digital value is provided between the switching unit and the determination unit.

8. A sensor for determining the position of an interface between a first substance and a second substance, It includes E electrode pairs, L wires and a wire selector. in, [Mathematical formula 18] 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 electrode pairs 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 p-th electrode pair among the E electrode pairs has an electrode connected to the s(p)-th wire among the L wires, and an electrode connected to the L-th wire among the L wires, wherein, [Mathematical formula 19] n(0)=1, for each k∈{x∈N:1≤x≤K}, the kth set W(k) is [Mathematical formula 20] The K+1th set W(K+1) is an empty set, p∈W(r), The E-th electrode pair among the E electrode pairs has one electrode connected to the L-1-th wire among the L wires, and the other electrode connected to the L-th wire among the L wires. The wire selector can select any one of the L wires, except the Lth wire.

9. A sensor for determining the position of an interface between a first substance and a second substance, It includes E electrode pairs, L wires and a wire selector. in, [Mathematical formula 21] 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 electrode pairs 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 p-th electrode pair among the E electrode pairs has an electrode connected to the s(p)-th wire among the L wires, and an electrode connected to the L-th wire among the L wires, wherein, [Mathematical formula 22] n(0)=1, for each k∈{x∈N:1≤x≤K}, the kth set W(k) is [Mathematical formula 23] The K+1th set W(K+1) is an empty set, p∈W(r), The E-th electrode pair among the E electrode pairs has one electrode connected to the L-1-th wire among the L wires, and the other electrode connected to the L-th 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 24] For y=n(k)-1, select (2+Σ j=k+1 K (n(j)-1)) conductors, where [Mathematical formula 25] 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 26] 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 27] 。 10. A sensor according to claim 8 or claim 9, It is characterized in that For each j∈{x∈N:1≤x≤K}, the above n(j) is a prime factor of the above E.

11. A liquid level meter, comprising the sensor according to any one of claims 8 to 10, The first substance is a liquid, The second substance is a gas.

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

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