JP5316111B2 - Leak detector - Google Patents

Description

  The present invention relates to a leak detection device that detects a leak.

  A leak detection system that detects a leak may be installed in a place such as a computer room or an article storage where it is necessary to prevent damage due to the leak.

  Patent Document 1 discloses a leak detection system that includes a leak sensor disposed at a leak detection location and a leak detector that detects leak from the output of the leak sensor.

  In the leak detection system disclosed in Patent Document 1, the leak sensor accommodates two conductors in an insulating film with a constant interval. The insulating coating is partially absent at the side edges of both conductors, both conductors are partially exposed to the outside from the lacked portions, and the exposed portions of the respective conductors serve as leakage detection electrodes. When an AC signal is applied between these electrodes, the leak detector will conduct electricity between the electrodes via the leak when a leak occurs, resulting in a closed circuit state, so detection according to the applied AC signal A signal can be detected, and the occurrence of liquid leakage can be detected.

  Further, Patent Document 2 includes a detection line having an electrode line made of a pair of conductors, a constant current power source, a voltage measurement unit, and a determination unit, and between the electrode lines at one end of the detection line when leaking is detected. Connect the constant current power supply, connect the voltage measurement means between the near end and the far end of the low voltage side electrode line of the detection line, and the judgment means will calculate the leakage position from the voltage value measured by the voltage measurement means. A liquid detection device is disclosed.

JP 2000-131176 A Japanese Patent Application Laid-Open No. 7-113719

  As described above, there is known a leak detection device that detects the occurrence of leak at one place or the leak position at one place in response to the occurrence of conduction between the conductors using a pair of conductors. .

  However, in the conventional liquid leakage detection device, it is not considered to detect a plurality of liquid leakage occurrences or a plurality of liquid leakage positions continuously using a pair of conductors.

  An object of the present invention is to provide a liquid leakage detection device that can detect the occurrence of liquid leakage in at least two places by using a pair of conductors.

  The leak detection device according to the present invention is a resistor having a resistance value proportional to the wiring length, one end of which is connected to a power supply unit outputting a predetermined level of leak detection current and the other end is grounded via a resistor. A first voltage measuring unit for measuring a voltage value at both ends of the wire and the resistor; one end is in an open state, the other end is grounded; A detection line that is electrically connected to the resistance line, and is wired on the detection line, and when the first leakage occurs, the first leakage point on the resistance line and the end of the resistance on the grounding point side The voltage is measured as a voltage value between the two points, and when the second leak occurs, the midpoint between the first leak point and the second leak point on the detection line and the ground side of the resistor A voltage measured by the second voltage measuring unit that measures the voltage as a voltage value between the ends and the first voltage measuring unit when the first leak occurs And the voltage value measured by the second voltage measuring unit, the voltage value measured by the first voltage measuring unit after the first leak occurrence, and the voltage value measured by the second voltage measuring unit And a leakage detector that detects occurrence of leakage at the second point.

  In one aspect of the liquid leakage detection device according to the present invention, the liquid leakage detection unit is measured by the voltage value measured by the first voltage measurement unit and the second voltage measurement unit when the first leakage occurs. The distance α between the other end of the resistance wire and the first leakage point on the resistance wire is calculated using the voltage value as a parameter, and measured by the first voltage measurement unit when the first leakage occurs. Voltage value measured by the second voltage measuring unit, voltage value measured by the first voltage measuring unit after the occurrence of the first leak, and measured by the second voltage measuring unit. The distance β between the other end of the resistance wire and the second leakage point on the assumption that the second leakage point on the resistance wire has occurred is calculated using the voltage value as a parameter, and the distance If the difference between α and the distance β is greater than or equal to a predetermined threshold, it is determined that a second leak has occurred. , It notifies the outside based on the leakage position of the second point on the distance beta, and wherein the.

  In one aspect of the liquid leakage detection device according to the present invention, the liquid leakage detection unit uses the resistance value of the resistor as R1, the voltage value measured by the first voltage measurement unit when the first liquid leakage occurs, and When the voltage values measured by the second voltage measuring unit are Va and Vb, respectively, and the resistance value per unit length of the resistance wire is X, the distance α is α = R1 (Vb−Va) / (X Va is calculated by Va), and the voltage value measured by the first voltage measuring unit and the voltage value measured by the second voltage measuring unit after the occurrence of the first leak are Va ′ and Vb, respectively. When the output voltage of the power supply unit is Vo, the distance β is β = (2Rc + (Rz−Rb) −Rx) / X, where Rc = (Vb′−Va ′) · R1 / Va ', Rz = (Vo−Va) · R1 / Va, Rb = (Vo−Va ′) · R1 / Va ′, Rx = And calculating by Vb-Va) · R1 / Va.

  According to the present invention, when the second leak occurs in addition to the first leak, the occurrence of the second leak can be detected.

It is a figure which shows the circuit structure of the leak detection apparatus which concerns on this embodiment. It is a figure which shows the functional block of the control part with which the leak detection apparatus which concerns on this embodiment is provided. It is a figure which shows a circuit state when a leak has generate | occur | produced in the resistance line and the detection line at one point. It is a figure which shows a circuit state at the time of a resistance line and a detection line electrically connected by the leak in the power supply part side from the 1st leak point in addition to the 1st leak point. FIG. 5 is a diagram showing a circuit state when a resistance line and a detection line are conducted by leakage at the end of the resistance line on the ground side from the first leakage point in addition to the first leakage point. is there. It is a figure for demonstrating the synthetic | combination resistance comprised by the resistance wire and leak resistance in the circuit shown in FIG. It is a figure for demonstrating the synthetic | combination resistance comprised by the resistance wire and leak resistance in the circuit shown in FIG. It is a flowchart which shows the process sequence which a leak position calculation part performs at the time of leak occurrence.

  DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a circuit configuration of a leak detection apparatus according to the present embodiment.

  In FIG. 1, one end of a signal line L is connected to a power supply unit 20 that outputs a constant voltage current, and a leakage detection current having a voltage value Vo is supplied via the signal line L as a leakage detection current of a predetermined level. Output. To the signal line L, a resistance line 30 having a resistance value Rz, a switch 12, and a resistor 32 having a resistance value R1 are connected in series. More specifically, one end of the resistance line 30 is connected to the other end of the signal line L, one end of the switch 12 is connected to the other end of the resistance line 30, and one end of the resistor 32 is connected to the other end of the switch 12. The other end of the resistor 32 is grounded.

  Furthermore, one end of the detection line La is connected to the contact point Pa between the resistance wire 30 and the switch 12, and the other end of the detection line La is connected to the contact point Pb via the voltage sensor 14 and grounded. In other words, the voltage sensor 14 is connected in parallel via the switch 12 and the resistor 32 connected in series via the detection line La, and detects the voltage value Va between the contact Pa and the contact Pb.

  Further, the detection line Lb is insulated from the resistance line 30 when no liquid leakage occurs, one end of the detection line Lb is opened, and the other end is grounded via the voltage sensor 16 and the contact Pb. The The voltage sensor 16 detects the voltage value Vb between the liquid leakage point Lb1 on the resistance wire 30 and the contact Pb when the resistance wire 30 and the detection wire Lb are conducted due to liquid leakage. The liquid leakage detection device includes a liquid leakage detection sensor for detecting liquid leakage, and a main body that determines the presence or absence of liquid leakage or calculates the position of the liquid leakage when it occurs based on the detection contents of the liquid leakage detection sensor. 4, the signal line L, the resistance line 30, and the detection line Lb function as a liquid leakage detection sensor in FIG. 4, and the control unit 10, the power supply unit 20, the voltage sensors 14 and 16, the detection line La, The switch 12 and the resistor 32 function as a main body control unit.

  The control unit 10 is configured by a microcomputer or the like, and controls on / off of the switch 12 and calculates a leakage position based on the voltage values Va and Vb acquired through the voltage sensors 14 and 16.

  FIG. 2 is a diagram illustrating functional blocks of the control unit 10.

  2, the control unit 10 includes a CPU 110, a ROM 112, a RAM 114, a storage device 120, and an input / output interface 150. The CPU 110, the ROM 112, the RAM 114, the storage device 120, and the input / output interface 150 are connected via a communication bus 160. Connected.

  The CPU 110 expands a basic control program such as a BIOS program stored in the ROM 112 in the RAM 114, and further stores a program 130 for detecting leakage and calculating the position of the leakage stored in the storage device 120. And the program 130 is executed to calculate the position of the liquid leakage.

  In the present embodiment, the storage device 120 stores a leakage position calculation unit 132 that functions as a leakage detection unit as the program 130. The leak position calculation unit 132 acquires the voltage value measured by the voltage sensors 14 and 16 via the input / output interface 150, detects the leak based on the acquired voltage value, and calculates the position of the leak. Details of the leak position calculation process will be described later.

  FIG. 3 shows a circuit state when the resistance wire 30 and the detection wire Lb are conducted by leakage at the leakage point Lb1. In other words, the resistance line 30 and the detection line Lb indicate a circuit state when leakage occurs at one point.

  FIG. 4 shows a circuit state when the resistance line 30 and the detection line Lb are conducted by leakage at the leakage point Lb2 on the power supply unit 20 side from the leakage point Lb1 in addition to the leakage point Lb1. That is, the circuit state in the case where leakage occurs at two points of the resistance line 30 and the detection line Lb is shown.

  FIG. 5 shows a circuit state in the case where the resistance wire 30 and the detection wire Lb are conducted by leakage at the leakage point Lb2 on the contact Pa side from the leakage point Lb1 in addition to the leakage point Lb1.

  In the present embodiment, when the second leak occurs after the first leak occurs, the leak detection device detects the second leak and the second leak. The leak position is calculated.

  First, referring to FIG. 3, when the first leak occurs, the leak position calculation unit 132 determines the first leak position (distance α from the other end (contact point Pa) of the resistance wire 30). The principle of calculating is described.

  The resistance value of the resistance wire 30 is 1 meter unit XΩ, the resistance value of the resistance wire 30 from the contact point Pa to the leakage point Lb1, that is, the first leakage position resistance value is Rx, the resistance value of the resistance 32 is R1, The current value Io of the constant voltage output from the power supply unit 20 and the resistance value of the liquid leakage resistance are Rs.

  Since the current flowing through the leakage resistance value Rs is very small compared to the current flowing through the resistor 32, the current value Io can be obtained by the equation (1).

  Io = Va / R1 (1)

  Further, the resistance value Rx can be obtained by equation (2).

  Rx = (Vb−Va) / Ia (2)

  Therefore, the distance α corresponding to the position of the first leakage can be obtained from the equation (3) based on the equations (1) and (2).

  α = Rx / X = R1 (Vb−Va) / (X × Va) (3)

  Subsequently, referring to FIG. 4, when the second leakage occurs on the power supply unit 20 side from the first leakage point Lb1, the leakage position calculation unit 132 determines whether the second leakage The principle of calculating the position (distance β from the contact point Pa of the resistance wire 30) will be described.

  Here, the voltage values measured by the voltage sensor 14 and the voltage sensor 16 after the occurrence of the first leakage are Va ′ and Vb ′, respectively, and the resistance value of the second leakage resistance is the first leakage. Like the resistance value of the liquid resistance, Rs, the resistance value of the resistance line 30 from the leakage point Lb2 to the leakage point Lb1, Ry, the resistance value of the resistance line 30 from the leakage point Lb2 to the contact Pa, that is, the second point is The leakage position resistance value at the time of occurrence is Rw, and the current flowing through the resistance wire 30 is Ib (≠ Io).

  Here, the second leakage position resistance value Rw can be expressed by Equation (4).

  Rw = Ry + Rx (4)

  FIG. 6 is a circuit showing the resistance line 30 and the first and second leakage resistance values Rs and Rs. As shown in FIG. 6, the resistance value Ry and the leakage resistance values Rs, Rs constitute a parallel circuit.

  Further, when the combined resistance value of the resistance value Ry and the leakage resistance values Rs and Rs is Ra, and the total combined resistance value of the resistance wire 30 including the combined resistance value Ra is Rb (≠ Rz), the combined resistance value Rb is , (5).

Rb = (Rz−Ry−Rx) + Ra + Rx
= Rz-Ry + Ra (5)

  Further, the voltage value Va ′ can be obtained by the equation (6).

  Va ′ = R1 × Ib (6)

  Furthermore, when the voltage value of the combined resistance value Ra is Vc, the voltage value Vc can be obtained by the equation (7).

  Vc = Ra × Ib (7)

  Here, the voltage component of the voltage value Vc appearing in the voltage value Vb ′ detected by the voltage sensor 16 is divided by the leakage resistance value Rs, and thus becomes ½ of the voltage value Vc. Therefore, the voltage value Vb ′ can be obtained by the equation (8).

  Vb ′ = Vc / 2 + (Rx + R1) × Ib (8)

  Furthermore, the voltage value between the leak point Lb2 of the resistance wire 30 and the contact Pa is obtained by the equation (9) from the equations (6) to (8).

  Vb'-Va '= Ra / 2 + RxIb (9)

  Further, when the resistance value with respect to the voltage value (Vb′−Va ′) is Rc, it can be expressed by Expression (10) using Expression (9).

  Rc = (Vb′−Va ′) / Ib = Ra / 2 + Rx (10)

  When formula (10) is expanded by Ra, it can be expressed by formula (11).

  Ra = 2Rc-2Rx (11)

  Further, the resistance value Ry can be expressed by equation (12) from equation (5).

  Ry = Ra + (Rz-Rb) (12)

  Therefore, the leakage position resistance value Rw at the second point can be expressed by equation (13) by substituting equations (11) and (12) into equation (1).

  Rw = 2Rc + (Rz-Rb) -Rx (13)

  As described above, the second leakage position β when the second leakage occurs on the power supply unit 20 side from the first leakage point Lb1 can be obtained by the equation (14).

  β = Rw / X = (2Rc + (Rz−Rb) −Rx) / X (14)

  As described above, the example in which the second leakage point Lb2 occurs on the power supply unit 20 side from the first leakage point Lb1 has been described.

  Next, as shown in FIG. 6, an example in which the second leakage point Lb2 occurs on the contact Pa side from the first leakage point Lb1 will be described.

  Here, if the resistance value of the resistance wire 30 between the leak point Lb1 and the leak point Lb2 is Ry ', the leak position resistance value Rw at the second point can be expressed by Expression (15).

  Rw = Rx−Ry ′ (15)

  FIG. 7 is a circuit showing the resistance wire 30 and the first and second leakage resistance values Rs and Rs. As shown in FIG. 7, the resistance value Ry 'and the leakage resistance values Rs and Rs constitute a parallel circuit.

  Further, when the combined resistance value of the resistance value Ry ′ and the leakage resistance values Rs and Rs is Ra, and the total combined resistance value of the resistance wire 30 including the combined resistance value Ra is Rb (≠ Rz), the combined resistance value Rb Can be expressed by equation (16).

  Rb = (Rz−Rx) + Ra + Rw (16)

  By substituting the equation (15) into the equation (16), the resistance value Rb can be expressed by the equation (17).

  Rb = Rz−Ry ′ + Ra (17)

  Further, the voltage value Va ′ can be obtained by the equation (18).

  Va ′ = R1 × Ib (18)

  Furthermore, when the voltage value of the combined resistance value Ra is Vc, the voltage value Vc can be obtained by the equation (19).

  Vc = Ra × Ib (19)

  Here, the voltage component of the voltage value Vc appearing in the voltage value Vb ′ detected by the voltage sensor 16 is divided by the leakage resistance value Rs, and thus becomes ½ of the voltage value Vc. Therefore, the voltage value Vb ′ can be obtained by the equation (20).

  Vb ′ = Vc / 2 + (Rw + R1) × Ib (20)

  Furthermore, the voltage value between the leak point Lb2 of the resistance wire 30 and the contact Pa is obtained by the equation (21) from the equations (18) and (20).

  Vb′−Va ′ = Vc / 2 + RwIb (21)

  Further, if the resistance value with respect to the voltage value (Vb′−Va ′) is Rc, it can be expressed by the equation (22) using the equations (19) and (21).

  Rc = (Vb′−Va ′) / Ib = Ra / 2 + Rw (22)

  When formula (22) is expanded by Ra, it can be expressed by formula (23).

  Ra = 2Rc-2Rw (23)

  Further, the resistance value Ry ′ can be expressed by the equation (24) from the equation (17).

  Ry '= Ra + (Rz-Rb) (24)

  Therefore, the second leakage position resistance value Rw can be expressed by equation (25) based on equations (15) and (24).

  Rw = Rx-Ra- (Rz-Rb) (25)

  Furthermore, by substituting the equation (23) into the equation (25) and developing with Rw, Rw can be expressed by the equation (26).

  Rw = 2Rc + (Rz−Rb) −Rx (26)

  As described above, the second leakage position β is expressed by the equation (27) as in the case where the leakage point Lb2 is on the contact Pa side from the leakage point Lb1 as in the power supply unit 20 side. Can do.

  β = Rw / X = (2Rc + (Rz−Rb) −Rx) / X (27)

  Here, the resistance values Rc, Rz, Rb, and Rx can be obtained by the following formulas based on the above formulas and the like.

Resistance value with respect to voltage value (Vb′−Va ′) at the time of occurrence of second leakage: Rc = (Vb′−Va ′) / Ib
Resistance value between both ends of the resistance wire 30 when the first liquid leak occurs: Rz = (Vo−Va) / Io
Resistance value between both ends of the resistance wire 30 when the second leak occurs: Rb = (Vo−Va ′) / Ib
Leakage position resistance value when the first leak occurs: Rx = (Vb−Va) / Io

  As described above, the leak position calculation unit 132 uses the resistance values Rz and Rx calculated when the first leak occurs, based on the formula (14) (formula (27)) and the second leak. The liquid position β can be calculated. The current value Io can be obtained by Va / R1 based on the voltage value Va at the time of occurrence of the first leakage and the resistance value R1 of the resistor 32 obtained in advance. Similarly, the current value Ib can be obtained from Va ′ / R1 based on the voltage value Va ′ at the time of occurrence of the second leakage and the resistance value R1 of the resistor 32 obtained in advance.

  Therefore, the resistance values Rc, Rz, Rb, and Rx are respectively the voltage values Va and Vb measured by the voltage sensors 14 and 16 when the first leakage occurs, and the voltage sensors 14 and 16 when the second leakage occurs. The voltage values Va ′ and Vb ′ measured in the above can be used as parameters to obtain the following values.

Resistance value with respect to voltage value (Vb′−Va ′) at the time of occurrence of second leakage: Rc = (Vb′−Va ′) · R1 / Va ′ (A)
Resistance value between both ends of the resistance wire 30 when the first leak occurs: Rz = (Vo−Va) · R1 / Va (B)
Resistance value between both ends of the resistance wire 30 when the second leak occurs: Rb = (Vo−Va ′) · R1 / Va ′ (C)
Leakage position resistance value at the time of occurrence of the first leak: Rx = (Vb−Va) · R1 / Va (D)

  Therefore, the second leak point Lb2 is the voltage values Va, Va ′, Vb measured by the voltage sensor 14 and the voltage sensor 16 when the first leak occurs and when the second leak occurs. , Vb ′ as parameters.

  FIG. 8 is a flowchart showing a processing procedure executed by the leak position calculation unit 132 when a leak occurs.

  In FIG. 8, the liquid leakage position calculation unit 132 detects the occurrence of liquid leakage when, for example, the voltage value Vb detected by the voltage sensor 16 changes by a predetermined value or more (S100). After detecting the occurrence of leakage, the leakage position calculation unit 132 turns on the switch 12 to measure the voltage at the voltage sensor 14 and the voltage sensor 16, and the first leakage from the voltage sensor 14 and the voltage sensor 16, respectively. The voltage values Va and Vb at the time of occurrence are obtained, and based on the first leakage position calculation formula (3), as the first leakage position, the contact points Pa and 1 that are the ends on the ground side of the resistance wire 30 are obtained. A distance α with respect to the leak point Lb1 is calculated (S102). Further, the liquid leakage calculation unit 132 calculates the resistance values Rz and Rx based on the equations (B) and (D), and registers them in a memory such as the RAM 114 (S104). Based on the calculated distance α, the leak position calculation unit 132 displays the first leak position on, for example, a liquid crystal display (not shown) included in the leak detection device, so that the first leak It is notified that the liquid has been generated (S106).

  Subsequently, for example, after the elapse of a predetermined period after detection of the first leak, the leak position calculation unit 132 uses the voltage sensor 14 and the voltage sensor 16 as voltage values after the first leak detection. The voltage values Va ′ and Vb ′ are respectively obtained from the above, and the resistance values Rz and Rx registered in the memory are read out, and the end of the resistance wire 30 on the ground side is read based on the formula (14) (formula (27)) The distance β between the contact point Pa, which is a portion, and the second leakage point Lb2 when it is assumed that the second leakage has occurred is calculated (S108). After calculating the distance β, the leak position calculation unit 132 determines whether or not the difference between the distance α and the distance β is equal to or greater than a predetermined threshold TH (S110).

  As a result of the determination, if the difference between the distance α and the distance β is smaller than the threshold value TH (the determination result in step S110 is negative “N”), it is determined that the second leak has not occurred, and a certain period of time has elapsed. Later, the second leakage position β is calculated again.

  On the other hand, if the difference between the distance α and the distance β is equal to or greater than the threshold value TH (the determination result in step S110 is affirmative “Y”), the leakage position calculation unit 132 determines that the second leakage has occurred. Based on the calculated distance β, the second leakage position is displayed on, for example, a liquid crystal display (not shown) provided in the leakage detection device, thereby notifying the user that the second leakage has occurred. (S112).

  As described above, according to the present embodiment, when the second leak occurs, the voltage sensor 14 and the voltage sensor 16 measured when the first leak and the second leak occur, respectively. The distance β between the contact point Pa of the resistance wire 30 and the second leakage point Lb2 is calculated using the voltage values Va, Va ′, Vb, and Vb ′ as parameters, and the second leakage is calculated based on the distance β. The liquid position can be notified.

  Since the second leak can be detected when the second leak occurs, the present invention can be applied to a leak detection device that detects the occurrence of a leak.

L signal line Lb detection line 10 control part 12 switch 14, 16 voltage sensor 20 power supply part 30 resistance line 32 resistance 110 CPU
112 ROM
114 RAM
120 Storage Device 130 Program 132 Leakage Position Calculation Unit (Leakage Detection Unit)
150 I / O interface 160 Communication bus

Claims (3)

One end is connected to a power supply unit that outputs a predetermined level of leakage detection current, and the other end is grounded via a resistor.
A first voltage measuring unit that measures a voltage value across the resistor;
One end is in an open state, the other end is grounded, and is in an insulated state with the resistance wire before leakage occurs, and a detection wire that is electrically connected to the resistance wire when leakage occurs,
When the first leakage occurs, the voltage is measured as a voltage value between the first leakage point on the resistance line and the end of the resistance on the ground point side, When the second leak occurs, a voltage is calculated as a voltage value between the midpoint of the first leak point and the second leak point on the detection line and the grounded end of the resistor. A second voltage measuring unit for measuring;
The voltage value measured by the first voltage measuring unit when the first leak occurs and the voltage value measured by the second voltage measuring unit, and the first voltage measurement after the first leak occurs A leakage detection unit that detects the occurrence of leakage at the second point by comparing the voltage value measured by the unit and the voltage value measured by the second voltage measurement unit;
A liquid leakage detection device comprising: The liquid leakage detection device according to claim 1,
The leak detector is
The first point on the resistance line and the other end of the resistance line with the voltage value measured by the first voltage measurement unit and the voltage value measured by the second voltage measurement unit when the first leakage occurs as parameters. And the voltage value measured by the first voltage measurement unit, the voltage value measured by the second voltage measurement unit, and one point when the first leak occurs Using the voltage value measured by the first voltage measuring unit and the voltage value measured by the second voltage measuring unit after the occurrence of eye leakage as parameters, the other end of the resistance wire and 2 on the resistance wire The distance β between the second leakage point and the second leakage point when it is assumed that the leakage of the point has occurred is calculated, and when the difference between the distance α and the distance β is equal to or greater than a predetermined threshold, two points It is determined that eye leakage has occurred, and the second leakage position is notified to the outside based on the distance β.
A leak detection apparatus characterized by the above. The liquid leakage detection device according to claim 2,
The leak detector is
The resistance value of the resistor is R1, and the voltage value measured by the first voltage measuring unit and the voltage value measured by the second voltage measuring unit when the first leak occurs are Va, Vb, and the resistance, respectively. When the resistance value per unit length of the line is X, the distance α is α = R1 (Vb−Va) / (X · Va)
Calculated by
Furthermore, the voltage value measured by the first voltage measuring unit and the voltage value measured by the second voltage measuring unit after the occurrence of the first leak are Va ′, Vb ′, and the output of the power supply unit, respectively. When the voltage is Vo, the distance β is β = (2Rc + (Rz−Rb) −Rx) / X
However,
Rc = (Vb′−Va ′) · R1 / Va ′
Rz = (Vo−Va) · R1 / Va
Rb = (Vo−Va ′) · R1 / Va ′
Rx = (Vb−Va) · R1 / Va
The liquid leakage detection device characterized by the above calculation.