Offset correction method for a potentiometer and potentiometer

Abstract

This invention provides an offset correction method for a potential difference measuring device that can accurately acquire the electric field underwater. [Solution] The offset correction method for the potential difference measuring device 100 is an offset correction method for a potential difference measuring device 100 having a pair of electrode sections 10 including a first measuring electrode 11a and a second measuring electrode 12a for measuring potential in water, and a potential difference measuring section 13 for measuring the potential difference between the pair of electrode sections 10, comprising the steps of: arranging the pair of electrode sections 10 at a predetermined first position and measuring a first potential difference V1 between the pair of electrodes; arranging the pair of electrode sections 10 at a second position in which the positions of the first measuring electrode 11a and the second measuring electrode 12a at the first position are reversed and measuring a second potential difference V2 between the pair of electrodes; and calculating a first underwater electric field Vs1 based on the first potential difference V1 and the second potential difference V2, correcting for at least the potential difference offset caused by something other than the object under inspection 80.

Description

[Technical Field]

[0001] The present invention relates to an offset correction method for a potential difference measurement device that measures potential difference in water, and to a potential difference measurement device. [Background Art]

[0002] Conventionally, potential difference measurement devices that measure potential difference in water have been known (see, for example, Patent Document 1).

[0003] Patent Document 1 above discloses an in-liquid potential measurement system (potential difference measurement device) including an in-liquid potential measurement electrode device having a measurement electrode for measuring potential in liquid, a control unit, and an amplifier. The in-liquid potential measurement system is configured such that a pair of in-liquid potential measurement electrode devices are arranged in liquid (seawater) to measure the potential difference in seawater. Further, the in-liquid potential measurement system is configured to amplify the potential difference measured by the pair of in-liquid potential measurement electrode devices with an amplifier, and observe the amplified potential difference with the control unit. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2017-044560 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] Although not disclosed in Patent Document 1, the potential difference measured by the electrode device (electrode unit) for measuring liquid potential includes an offset (deviation) in the potential difference due to manufacturing errors, etc. Furthermore, the potential difference measured by the electrode unit is offset (deviation) due to the temperature and dissolved oxygen content in the sea (water). In other words, when measuring the potential difference in water, the measured potential difference is offset (deviation) due to potential differences originating from sources other than the object being inspected, thus reducing the accuracy of measuring the potential difference from the object being inspected (underwater electric field). Therefore, there is a need for a technology that can accurately acquire the underwater electric field.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide an offset correction method for a potentiometer and a potentiometer that can accurately acquire an electric field underwater. [Means for solving the problem]

[0007] The first aspect of this invention relates to an offset correction method for a potential difference measuring device, which includes a pair of electrode sections including a first electrode and a second electrode for measuring potential in water, and a potential difference measuring section for measuring the potential difference between the pair of electrode sections, comprising the steps of: arranging the pair of electrode sections at a predetermined first position and measuring a first potential difference between the pair of electrodes; arranging the pair of electrode sections at a second position in which the positions of the first electrode and the second electrode at the first position are reversed and measuring a second potential difference between the pair of electrodes; and calculating an underwater electric field that corrects for at least the offset of the potential difference caused by something other than the object being inspected, based on the first potential difference and the second potential difference.

[0008] Furthermore, the potential difference measuring device in the second aspect of this invention comprises an underwater electric field sensor having a pair of electrode sections including a first electrode and a second electrode for measuring potential in water, and a potential difference measuring section for measuring the potential difference between the pair of electrode sections, and a control unit that calculates an underwater electric field that corrects for at least the potential difference offset caused by something other than the object being inspected, based on the potential difference measured by the underwater electric field sensor, wherein the control unit measures a first potential difference between the pair of electrode sections by arranging the pair of electrode sections at a predetermined first position, measures a second potential difference between the pair of electrode sections by arranging the pair of electrode sections at a second position in which the positions of the first electrode and the second electrode at the first position are reversed, and calculates an underwater electric field that corrects for the potential difference offset caused by something other than the object being inspected, based on the measured first potential difference and second potential difference. [Effects of the Invention]

[0009] In the offset correction method for the potential difference measuring device in the first phase described above, and in the potential difference measuring device in the second phase described above, the underwater electric field is calculated by correcting the offset of the potential difference caused by something other than the object under inspection, based on the first potential difference measured with the pair of electrode parts positioned at the first position, and the second potential difference measured with the pair of electrode parts positioned at the second position, inverting the positions of the first and second electrodes at the first position. Here, when measuring the potential difference with a potential difference measuring device, the positive and negative signs of the potential difference caused by something other than the object under inspection do not change even if the positions of the pair of electrode parts are reversed. On the other hand, the positive and negative signs of the potential difference caused by the object under inspection change when the positions of the pair of electrode parts are reversed. Therefore, between the first potential difference measured at the first position and the second potential difference measured at the second position, the positive and negative signs of only the potential difference caused by the object under inspection are reversed due to the reversal of the first and second electrodes. Furthermore, while the potential difference values ​​caused by the object under inspection, and those caused by other factors, change significantly over the long term, the changes in potential difference are practically negligible in the short term. Therefore, by calculating the underwater electric field based on the first and second potential differences, the offset (deviation) of the potential difference caused by factors other than the object under inspection can be corrected. As a result, the underwater electric field can be obtained with high accuracy. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing the overall configuration of the potentiometer. [Figure 2] This is a cross-sectional view of a pair of electrode sections. [Figure 3] This is a schematic diagram illustrating a configuration for measuring the potential difference at the first position. [Figure 4] This is a schematic diagram illustrating the configuration for measuring the potential difference at the second position. [Figure 5] This is a schematic diagram illustrating a configuration in which a pair of electrode sections are rotated and positioned at a first and second position to measure the potential difference. [Figure 6] This is a schematic diagram illustrating a configuration for measuring the potential difference at a predetermined angle different from that shown in Figure 5. [Figure 7] This is a schematic diagram illustrating the configuration for measuring the potential difference of an object under inspection. [Figure 8] This is a flowchart illustrating the process for calculating the first underwater electric field. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments embodying the present invention will be described based on the drawings.

[0012] (Overall configuration of the potentiometer) The overall configuration of the potentiometer 100 according to this embodiment will be described with reference to Figures 1 and 2.

[0013] As shown in Figure 1, the potential difference measuring device 100 comprises an underwater electric field sensor 1, a rotation mechanism 2, a control unit 3, and an angle acquisition unit 4.

[0014] The underwater electric field sensor 1 is used to measure the underwater electric field (UEP). The underwater electric field (potential difference) is a minute potential difference in the sea 90 (underwater). The underwater electric field sensor 1 has a pair of electrode sections 10 and a potential difference measuring section 13. The pair of electrode sections 10 include a first measuring electrode 11a and a second measuring electrode 12a for measuring potential in water. The underwater electric field sensor 1 is configured to measure the potential difference between the pair of electrode sections 10 without contact with the object under inspection 80 (see Figure 7) in the sea 90. Specifically, the underwater electric field sensor 1 is configured to measure the potential difference between the first measuring electrode 11a of the first electrode section 11 and the second measuring electrode 12a of the second electrode section 12 without contact with the object under inspection 80 in the sea 90. Furthermore, the first housing 11b of the first electrode unit 11 and the second housing 12b of the second electrode unit 12 may be used to measure by contacting marine organisms attached to the object to be inspected 80 in the sea 90. Note that "first measuring electrode 11a" and "second measuring electrode 12a" are examples of "first electrode" and "second electrode" as defined in the claims.

[0015] Furthermore, the potentiometer measuring device 100 according to this embodiment is used for at least one of position detection and corrosion measurement of an object to be inspected 80 located "in the sea". Moreover, the potentiometer measuring device 100 is not limited to position detection of an object to be inspected 80 located "in the sea", but is not particularly limited as long as it is used for position detection of an object to be inspected 80 located "in water". "In water" means, for example, seawater, lake water, river water, etc. Also, "in water" means, for example, water stored in artificial structures such as swimming pools, tanks, and aquariums. Furthermore, "water" in the context of "in water" means, for example, seawater, freshwater, brackish water, etc., and does not include pure water.

[0016] As shown in Figs. 2(a) and 2(b), the pair of electrode portions 10 includes a first electrode portion 11 and a second electrode portion 12. The pair of electrode portions 10 is used in the sea 90 (see Fig. 7) in a state of being in contact with seawater. The pair of electrode portions 10 is used in non-contact with the inspection object 80 in the vicinity of the inspection object 80 (see Fig. 7) in the sea 90. The pair of electrode portions 10 may be disposed and used on a self-propelled device such as an underwater robot, an underwater drone, or an autonomous unmanned underwater vehicle, or may be gripped and used by a diver.

[0017] The first electrode portion 11 includes a first measurement electrode 11a and a first housing 11b. The first measurement electrode 11a is configured to measure the potential of the sea 90. As an example, the first measurement electrode 11a is constituted by a silver-silver chloride electrode containing silver (Ag) and silver chloride (AgCl). The first measurement electrode 11a is connected to a first cable 113. The first measurement electrode 11a is connected to a potential difference measuring unit 13 (see Fig. 1) via the first cable 113.

[0018] The first measurement electrode 11a is disposed inside the first housing 11b. The first measurement electrode 11a has a cylindrical shape and is disposed so as to extend in the longitudinal direction of the first housing 11b. The first measurement electrode 11a is disposed in the sea 90 so as to be aligned with the second measurement electrode 12a at a predetermined interval. The first measurement electrode 11a and the second measurement electrode 12a are provided so as to maintain a constant interval.

[0019] The first housing 11b is configured to cover the first measurement electrode 11a. The first housing 11b is made of an insulating material such as resin, for example. As one example, the first housing 11b has a cylindrical shape. Specifically, the first housing 11b has a square cylindrical shape. A first opening 111 communicating with the outside is formed in a first end surface 110 on one side of the first housing 11b. The first opening 111 is configured to allow external seawater to flow into the first housing 11b. When the potential difference measuring apparatus 100 is in use, the first measurement electrode 11a is immersed in seawater that has flowed into the first housing 11b through the first opening 111. A first cable 113 is inserted through a third end surface 112 on the other side opposite to the first end surface 110 of the first housing 11b.

[0020] The second electrode unit 12 includes a second measurement electrode 12a and a second housing 12b. The second measurement electrode 12a is disposed inside the second housing 12b. The second measurement electrode 12a is connected to a potential difference measurement unit 13 (see FIG. 1) via a second cable 123. As one example, the second housing 12b also has a square cylindrical shape. A second opening 121 communicating with the outside is formed in a second end surface 120 on one side of the second housing 12b. A second cable 123 is inserted through a fourth end surface 122 on the other side opposite to the second end surface 120 of the second housing 12b. Since other configurations of the second electrode unit 12 are the same as those of the first electrode unit 11, detailed description thereof is omitted.

[0021] The second electrode unit 12 is disposed adjacent to the first electrode unit 11. Specifically, the pair of electrode units 10 are integrally provided in a state where the side surface on the second electrode unit 12 side of the first housing 11b of the first electrode unit 11 is in contact with the side surface on the first electrode unit 11 side of the second housing 12b of the second electrode unit 12. The pair of electrode units 10 are integrally formed in a state where the first opening 111 of the first electrode unit 11 and the second opening 121 of the second electrode unit 12 are separated by a predetermined distance.

[0022] As shown in Figure 1, the potential difference measuring unit 13 is configured to measure the potential difference between a pair of electrode units 10. Specifically, the potential difference measuring unit 13 is configured to measure the potential difference (underwater electric field) between the first measuring electrode 11a of the first electrode unit 11 and the second measuring electrode 12a of the second electrode unit 12 without contact with the object under inspection 80 (see Figure 7) placed in water. In other words, the potential difference measuring unit 13 is configured to measure the potential difference between the first measuring electrode 11a and the second measuring electrode 12a in a non-contact state with respect to the object under inspection 80.

[0023] The potential difference measuring unit 13 is housed inside the main housing 6. The main housing 6 can be placed on land, at sea, underwater 90, inside a ship, or in self-propelled equipment such as an underwater robot, underwater drone, or autonomous submersible. When the main housing 6 is placed at sea or underwater 90 and comes into contact with seawater, the inside of the main housing 6 is sealed to prevent water from entering. The potential difference measuring unit 13 may also be housed inside a housing other than the main housing 6.

[0024] The potential difference measuring unit 13 includes an amplifier 13a and an AD converter (ADC) 13b. The amplifier 13a is configured to generate a signal that amplifies the potential difference between the first measuring electrode 11a and the second measuring electrode 12a. One of the pair of input terminals of the amplifier 13a is connected to the first measuring electrode 11a via a first cable 113. The other of the pair of input terminals of the amplifier 13a is connected to the second measuring electrode 12a via a second cable 123.

[0025] The AD converter 13b is configured to convert the signal amplified by the amplifier 13a into a digital signal and output the converted digital signal to the control unit 3. As a result, the potential difference measuring unit 13 outputs the potential difference between the first measuring electrode 11a and the second measuring electrode 12a to the control unit 3. The AD converter 13b is connected to the amplifier 13a and the control unit 3.

[0026] The rotation mechanism 2 is configured to rotate a pair of electrode portions 10. The rotation mechanism 2 includes a holding portion that holds the pair of electrode portions 10, a drive source that generates a driving force to rotate the holding portion, and a drive force transmission member that transmits the driving force from the drive source to the holding portion.

[0027] The control unit 3 is configured to calculate a first underwater electric field Vs1 based on the potential difference measured by the underwater electric field sensor 1, correcting for at least the offset (deviation) of the potential difference caused by factors other than the object under inspection 80. The control unit 3 is also configured to calculate a second underwater electric field Vs2 in a direction different from the first underwater electric field Vs1. The control unit 3 includes a processor such as a CPU (Central Processing Unit) for calculation processing and a memory for temporary storage during calculations. Note that the first underwater electric field Vs1 is an example of the "underwater electric field" in the claims.

[0028] The control unit 3 is provided in the control device 30. The control device 30 is configured, for example, as a PC (personal computer). The control device 30 includes the control unit 3, a storage unit 31, and an input / output unit 32. The control device 30 is connected to the display device 33 and the input device 34.

[0029] The storage unit 31 includes a volatile memory device and a non-volatile memory device. The input / output unit 32 is composed of various interfaces for inputting and outputting signals to and from the control device 30. The input / output unit 32 is connected to the display device 33 and the input device 34. The display device 33 is, for example, a liquid crystal display device. The input device 34 includes a keyboard and a mouse. The control unit 3 acquires the first underwater electric field Vs1 and the second underwater electric field Vs2 via the input / output unit 32.

[0030] The control device 30 is located on land, at sea, or inside a ship. The control unit 3 does not necessarily have to be located in the control device 30. The control unit 3 may be housed inside the main housing 6, or it may be located inside a housing other than the main housing 6.

[0031] The angle acquisition unit 4 is configured to acquire the rotation angle when the pair of electrode units 10 are rotated by the rotation mechanism 2. Specifically, the angle acquisition unit 4 acquires the angle of the pair of electrode units 10 rotated by the rotation mechanism 2 at a predetermined sampling rate, with reference to a first position described later. The angle acquisition unit 4 is also connected to the control unit 3 via a cable 140. The angle acquisition unit 4 transmits the acquired angle to the control unit 3. The angle acquisition unit 4 includes, for example, a rotary encoder.

[0032] (Calculation of the underwater electric field by the control unit) Referring to Figures 3 to 6, the configuration in which the control unit 3 (see Figure 1) calculates the first underwater electric field Vs1 and the second underwater electric field Vs2 will be described.

[0033] Figure 3 shows the pair of electrode units 10 positioned in a first position. In this embodiment, the control unit 3 positions the pair of electrode units 10 in a predetermined first position and measures the first potential difference V1 between the pair of electrode units 10. Specifically, the control unit 3 acquires the first potential difference V1 [μV] between the first measuring electrode 11a and the second measuring electrode 12a output from the underwater electric field sensor 1 positioned in the first position.

[0034] Here, the first potential difference V1 includes the first underwater electric field Vs1, which is the underwater electric field of the object under inspection 80 (see Figure 7), as well as the potential difference offset (amount of deviation) caused by factors other than the object under inspection 80. Specifically, the first potential difference V1 includes the potential difference offset Vo1 due to individual differences between the first measuring electrode 11a and the second measuring electrode 12a, and the potential difference Vo2 due to the surrounding environment of the pair of electrode parts 10, as potential difference offsets caused by factors other than the object under inspection 80. The first potential difference V1 can be expressed as shown in the following equation (1). V1 = Vs1 + Vo1 + Vo2 ... (1) Here, V1 is the first potential difference. Vs1 is the first underwater electric field. Vo1 is the potential difference due to individual differences between the first measuring electrode 11a and the second measuring electrode 12a. Vo2 is the potential difference caused by the surrounding environment of the pair of electrode sections 10.

[0035] Vo1 is a potential difference due to individual differences between the first measuring electrode 11a and the second measuring electrode 12a, and therefore is difficult to measure directly. Furthermore, Vo1 changes over time when using the underwater electric field sensor 1. In addition, Vo2 is a potential difference caused by the surrounding environment of the pair of electrode parts 10. Vo2 changes depending on, for example, the water temperature and dissolved oxygen amount of the surrounding environment of the pair of electrode parts 10. Therefore, Vo2 changes over time. For example, Vo2 may change by several hundred μV after about 10 minutes. For this reason, when measuring the first potential difference V1 using the first measuring electrode 11a and the second measuring electrode 12a, it becomes difficult to obtain the first underwater electric field Vs1 with accuracy.

[0036] Therefore, in this embodiment, as shown in Figure 4, the control unit 3 uses the rotation mechanism 2 to position the pair of electrode sections 10 in a second position, in which the positions of the first measuring electrode 11a and the second measuring electrode 12a in the first position are reversed, and measures the second potential difference V2 between the pair of electrode sections 10. Specifically, after measuring the first potential difference V1, the control unit 3 uses the rotation mechanism 2 to rotate the pair of electrode sections 10 by 180 degrees to position the pair of electrode sections 10 in the second position and measures the second potential difference V2.

[0037] Here, the second potential difference V2 measured with the pair of electrode sections 10 positioned at the second position also includes the first underwater electric field Vs1, the offset of the potential difference Vo1 due to individual differences between the first measuring electrode 11a and the second measuring electrode 12a, and the offset of the potential difference Vo2 due to the surrounding environment of the pair of electrode sections 10. When measuring the potential difference with the potential difference measuring device 100, the potential difference caused by factors other than the object under inspection 80 does not change in sign even if the positions of the pair of electrode sections 10 are reversed. On the other hand, the potential difference caused by the object under inspection 80 changes in the second position because the positions of the first measuring electrode 11a and the second measuring electrode 12a in the pair of electrode sections 10 are reversed from the first position, so the sign of the first underwater electric field Vs1 is swapped. That is, in the second potential difference V2, the value of the underwater electric field becomes a negative value. The second potential difference V2 can be expressed as shown in the following equation (2). V2 = -Vs1 + Vo1 + Vo2 ... (2) Here, V2 is the second potential difference.

[0038] As shown in equations (1) and (2) above, in the first potential difference V1 and the second potential difference V2, only the first underwater electric field Vs1 has its sign reversed. Therefore, the first underwater electric field Vs1 can be calculated based on the first potential difference V1 and the second potential difference V2. Note that the first underwater electric field Vs1, the potential difference Vo1 due to individual differences in the first measuring electrode 11a and the second measuring electrode 12a, and the potential difference Vo2 due to the surrounding environment of the pair of electrode sections 10 change to a degree that cannot be ignored in the long term, but change to a degree that is practically negligible in the short term. Therefore, the first potential difference V1 and the second potential difference V2 are measured at time intervals within a range where these changes are practically negligible. For example, the control unit 3 measures the second potential difference V2 within 10 minutes after measuring the first potential difference V1.

[0039] The control unit 3 then calculates a first underwater electric field Vs1, correcting for potential difference offsets caused by factors other than the object under inspection 80, based on the measured first potential difference V1 and second potential difference V2. Specifically, the control unit 3 is configured to calculate the first underwater electric field Vs1, correcting for potential difference offsets caused by factors other than the object under inspection 80, by calculating the difference between the value of the first potential difference V1 and the value of the second potential difference V2. More specifically, the control unit 3 calculates the first underwater electric field Vs1 by dividing the difference between the value of the first potential difference V1 and the value of the second potential difference V2 by 2. In other words, the control unit 3 calculates the first underwater electric field Vs1 based on the following equation (3). Vs1 = (V1 - V2) / 2 ... (3)

[0040] The control unit 3 then measures the second potential difference V2 by changing the arrangement of the pair of electrode units 10 from the first position to the second position at the same location where the first potential difference V1 was measured. Note that the same location where the first potential difference V1 was measured does not mean that the first measuring electrode 11a and the second measuring electrode 12a are completely reversed between the first and second positions, but also allows for some positional displacement.

[0041] In this embodiment, as shown in Figure 5, the control unit 3 (see Figure 1) measures the first potential difference V1 and the second potential difference V2 by rotating the pair of electrode units 10 (first measuring electrode 11a and second measuring electrode 12a) by 180 degrees, thereby switching between the first and second positions. That is, the control unit 3 controls the rotation mechanism 2 (see Figure 1) in the first position state, thereby rotating the pair of electrode units 10 by 180 degrees along the arrow 40 to position the pair of electrode units 10 in the second position.

[0042] Furthermore, the control unit 3 controls the rotation mechanism 2 in the second position, thereby rotating the pair of electrode sections 10 180 degrees along the arrow 41 to position the pair of electrode sections 10 in the first position.

[0043] In this embodiment, the control unit 3 acquires a first potential difference V1 and a second potential difference V2 while rotating the pair of electrode parts 10 with the rotation mechanism 2. In this case, the control unit 3 controls the rotation mechanism 2 to rotate the pair of electrode parts 10 at a speed that allows the first potential difference V1 and the second potential difference V2 to be acquired when the pair of electrode parts 10 are positioned at the first and second positions. When the control unit 3 acquires the potential difference while rotating the pair of electrode parts 10 with the rotation mechanism 2, it acquires the potential difference measured by the underwater electric field sensor 1 as the first potential difference V1 each time the rotation angle acquired by the angle acquisition unit 4 (see Figure 1) becomes 0 degrees. Furthermore, when the control unit 3 acquires the potential difference while rotating the pair of electrode parts 10 with the rotation mechanism 2, it acquires the potential difference measured by the underwater electric field sensor 1 as the second potential difference V2 each time the rotation angle acquired by the angle acquisition unit 4 becomes 180 degrees with respect to the first position. The control unit 3 controls the rotation mechanism 2 so that the pair of electrode sections 10 rotate at a speed that allows a potential difference to be acquired at the 0-degree and 180-degree positions.

[0044] The control unit 3 is configured to calculate the first underwater electric field Vs1 each time the first potential difference V1 and the second potential difference V2 are acquired. That is, the control unit 3 calculates the first underwater electric field Vs1 for multiple predetermined angles, correcting for potential difference offsets caused by factors other than the object under inspection 80, based on the first potential difference V1 measured at multiple predetermined angles, each of which is a different angle, and the second potential difference V2 measured at each of the multiple predetermined angles with the positions of the pair of electrode parts 10 reversed.

[0045] In this embodiment, the control unit 3 stores the calculated first underwater electric field Vs1 in the storage unit 31 (see Figure 1). The control unit 3 may also store the calculated first underwater electric field Vs1 in the storage unit 31 in association with the position of the object under inspection 80 (see Figure 7) corresponding to the first position. Furthermore, the control unit 3 may calculate the first underwater electric field Vs1 in real time when the potential difference output from the underwater electric field sensor 1 is generated, and may also display the calculated first underwater electric field Vs1 in real time on the display device 33 (see Figure 1).

[0046] Furthermore, as shown in Figure 6, the potential difference (third potential difference V3 and fourth potential difference V4) can also be measured at positions rotated 90 degrees clockwise from the first and second positions shown in Figure 5, and the second underwater electric field Vs2 can be calculated from the difference between them. In other words, in this embodiment, the underwater electric field can be calculated for each of the multiple predetermined angles by rotating the pair of electrode units 10 and using the difference between the electric field measured at any multiple predetermined angles and the electric field measured at positions rotated 180 degrees from each of the multiple predetermined angles (i.e., the positions of the pair of electrode units 10 are reversed). As a result, a secondary effect can be obtained in which the underwater electric field at multiple predetermined angles can be measured by providing only the pair of electrode units 10.

[0047] (Measurement of the underwater electric field of the object being inspected using a potentiometer) Referring to Figure 7, the measurement of the first underwater electric field Vs1 of the object under inspection 80 using the potentiometer 100 will be explained.

[0048] As shown in Figure 7, an underwater structure 82 is positioned on the seabed. The underwater structure 82 is formed of, for example, steel whose main component is iron (Fe). The sacrificial anode 81 is installed in contact with the underwater structure 82. The sacrificial anode 81 is formed of, for example, zinc (Zn).

[0049] In this embodiment, the potential difference measuring device 100 measures the potential difference underwater, either by being placed on a self-propelled underwater device such as an underwater robot, underwater drone, or autonomous unmanned submersible, or by being held by a diver.

[0050] The sacrificial anode 81, formed from zinc (Zn), has a higher ionization tendency than the underwater structure 82, which is formed from steel whose main component is iron (Fe). In other words, the sacrificial anode 81, formed from zinc (Zn), is more easily ionized than the underwater structure 82, which is formed from steel. Therefore, the sacrificial anode 81 oxidizes (dissolves and corrodes) the underwater structure 82 while supplying a corrosion-preventive current 70. As a result, corrosion of the underwater structure 82 is suppressed.

[0051] In this embodiment, the control unit 3 measures the potential difference (first potential difference V1 to fourth potential difference V4) based on the corrosion protection current 70 flowing from the sacrificial anode 81 to the underwater structure 82. The control unit 3 then calculates the first underwater electric field Vs1 and the second underwater electric field Vs2.

[0052] Furthermore, the control unit 3 may use the calculated first underwater electric field Vs1 and second underwater electric field Vs2 to detect the position of the object under inspection 80.

[0053] (Offset correction processing for potentiometer) Next, referring to Figure 8, the process by which the potentiometer measuring device 100 (control unit 3) corrects the offset of the first underwater electric field Vs1 will be explained.

[0054] In step 200, the control unit 3 positions the pair of electrode units 10 at a predetermined first position and measures the first potential difference V1 between the pair of electrodes. Specifically, in step 200a, the control unit 3 controls the drive source of the rotating mechanism 2 to position the pair of electrode units 10 at the first position. Then, in step 200b, the control unit 3 measures the first potential difference V1 at the first position.

[0055] Next, in step 201, the control unit 3 stores the measured first potential difference V1 in the storage unit 31.

[0056] Next, in step 202, the control unit 3 places the pair of electrode units 10 in a second position, which is the reverse of the positions of the first measuring electrode 11a and the second measuring electrode 12a in the first position, and measures the second potential difference V2 between the pair of electrodes. Specifically, in step 202a, the control unit 3 controls the drive source of the rotation mechanism 2 to rotate the pair of electrode units 10 by 180 degrees and place them in the second position. Then, in step 202b, the control unit 3 measures the second potential difference V2 in the second position. In this embodiment, the control unit 3 rotates the pair of electrode units 10 by 180 degrees from the state in which the pair of electrode units 10 are placed in the first position to place them in the second position and measures the second potential difference V2. Also in this embodiment, the control unit 3 changes the arrangement of the pair of electrode units 10 from the first position to the second position at the same location where the first potential difference V1 was measured, and measures the second potential difference V2.

[0057] Next, in step 203, the measured second potential difference V2 is stored in the storage unit 31.

[0058] Next, in step 204, the control unit 3 reads the first potential difference V1 and the second potential difference V2 stored in the storage unit 31 from the storage unit 31.

[0059] Next, in step 205, the control unit 3 calculates a first underwater electric field Vs1 based on the first potential difference V1 and the second potential difference V2, correcting for at least the potential difference offset caused by factors other than the object under inspection 80. In this embodiment, the control unit 3 calculates the first underwater electric field Vs1 corrected for the potential difference offset caused by factors other than the object under inspection 80 by calculating the difference between the value of the first potential difference V1 and the value of the second potential difference V2. Specifically, the control unit 3 calculates the first underwater electric field Vs1 corrected for the potential difference Vo1 offset due to individual differences between the first measuring electrode 11a and the second measuring electrode 12a, and the potential difference Vo2 offset due to the surrounding environment of the pair of electrode sections 10, by calculating the difference between the value of the first potential difference V1 and the value of the second potential difference V2.

[0060] Next, in step 206, the control unit 3 determines whether or not to terminate the offset correction process. For example, the control unit 3 determines whether or not to terminate the offset correction process based on whether or not there has been an operation input to terminate the offset correction process. If there has been an operation input to terminate the offset correction process, the process terminates. If there has been no operation input to terminate the offset correction process, the process proceeds to step 200.

[0061] In other words, step 200, which measures the first potential difference V1, is performed each time the angle of the pair of electrode parts 10 reaches a predetermined angle (for example, 0 degrees) while acquiring the potential difference by rotating the pair of electrode parts 10. Similarly, step 202, which measures the second potential difference V2, is performed each time the angle of the pair of electrode parts 10 reaches a predetermined angle + 180 degrees while acquiring the potential difference by rotating the pair of electrode parts 10. Therefore, step 205, which calculates the first underwater electric field Vs1, is performed each time the first potential difference V1 and the second potential difference V2 are acquired. To put it another way, in step 205, which calculates the first underwater electric field Vs1, the control unit 3 calculates the first underwater electric field Vs1 for a plurality of predetermined angles, correcting for potential difference offsets caused by factors other than the object under inspection 80, based on the first potential difference V1 measured at a plurality of predetermined angles, each of which is a different angle, and the second potential difference V2 measured by reversing the position of the pair of electrode parts 10 at each of the plurality of predetermined angles.

[0062] [Differentiation] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than by the description of the embodiments above, and further includes all modifications (exceptions) within the meaning and scope equivalent to the claims. For example, the control unit may calculate the first underwater electric field with correction for the offset of the potential difference caused by something other than the object being inspected, without calculating the difference between the first potential difference and the second potential difference. In this case, the potential difference caused by something other than the object being inspected may be determined by equation (9) shown below, and then the first underwater electric field with correction for the offset of the potential difference caused by something other than the object being inspected may be calculated by subtracting the potential difference caused by something other than the object being inspected from the first potential difference based on equation (10) shown below. Vo1 + Vo2 = (V1 + V2) / 2 ... (9) Vs1 = V1 - (Vo1 + Vo2) ... (10) Furthermore, for example, the control unit may calculate a second underwater electric field corrected for potential difference offsets caused by factors other than the object being inspected, using equations (11) and (12) shown below. Vo1 + Vo2 = (V3 + V4) / 2 ... (11) Vs2 = V3 - (Vo1 + Vo2) ... (12) Furthermore, for example, the control unit may calculate the difference between the first potential difference value and the second potential difference value, and then display the value without dividing by 2 as the first underwater electric field on the display device. It is preferable to also display a statement indicating that the difference between the first potential difference value and the second potential difference value is displayed without dividing by 2. Furthermore, for example, the potential difference measuring device does not need to have a rotation mechanism. In this case, for example, a pair of electrode sections can be provided on a mobile body such as an underwater drone, and the control unit can move the mobile body to reverse the arrangement of the pair of electrode sections at the same location where the first potential difference was measured, thereby measuring the second potential difference. Furthermore, for example, the pair of electrode portions do not necessarily have to be formed integrally. Furthermore, for example, a pair of electrode sections may be configured such that the distance between the openings provided in each of the pair of electrode sections is variable. Furthermore, for example, the control unit may switch from the first position to the second position by rotating the pair of electrode sections 180 degrees clockwise, and then switch from the second position to the first position by rotating the pair of electrode sections 180 degrees counterclockwise. The pair of electrode sections may be moved (rotated) in any way as long as it is possible to switch between the first and second positions. The same applies to the third and fourth positions. Furthermore, for example, the control unit does not need to measure the first and second potential differences while rotating the pair of electrode sections. In this case, the control unit only needs to measure the first potential difference at the first position and the second potential difference at the second position once each, and calculate the first underwater electric field. The same applies to measuring the third and fourth potential differences. Furthermore, for example, the rotation mechanism may be configured to allow the user to rotate the pair of electrode sections. In this case, it is preferable that the rotation mechanism includes a mechanism for fixing the pair of electrode sections in each of the first and second positions. Furthermore, for example, the control unit only needs to calculate the first underwater electric field and does not need to calculate the second underwater electric field. Furthermore, for example, a pair of electrode sections may be composed of multiple pairs of electrode sections. That is, it may include a first measuring electrode, a second measuring electrode, and a third measuring electrode, with the first measuring electrode being shared, and configured as a first pair of electrode sections to measure the potential difference between the first measuring electrode and the second measuring electrode, and as a second pair of electrode sections to measure the potential difference between the first measuring electrode and the third measuring electrode. In this case, the third measuring electrode may be positioned in a direction perpendicular to the direction in which the second measuring electrode is located relative to the first measuring electrode. Furthermore, although the offset correction processing performed by the control unit has been described using a flow-driven flowchart that processes the operations sequentially according to the processing flow, the present invention is not limited to this. In the present invention, the offset correction processing performed by the control unit may be carried out by event-driven processing, which executes processing on an event-by-event basis. In this case, it may be carried out as a completely event-driven system, or a combination of event-driven and flow-driven systems may be used.

[0063] [Aspect] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following embodiments.

[0064] (Item 1) An offset correction method for a potentiometer having a pair of electrode sections including a first electrode and a second electrode for measuring potential in water, and a potentiometer measuring section for measuring the potential difference between the pair of electrode sections, The steps include: arranging the pair of electrode portions at a predetermined first position and measuring the first potential difference between the pair of electrodes; The steps include: arranging the pair of electrode portions in a second position in which the positions of the first electrode and the second electrode are reversed from the first position, and measuring the second potential difference between the pair of electrodes; An offset correction method for a potentiometer, comprising the steps of: calculating an underwater electric field based on the first potential difference and the second potential difference, correcting for at least the offset of the potential difference caused by something other than the object being inspected. When measuring potential difference using a potential difference measuring device, the potential difference caused by factors other than the object being inspected remains unchanged in sign even if the positions of the pair of electrodes are reversed. On the other hand, the potential difference caused by the object being inspected changes in sign when the positions of the pair of electrodes are reversed. Therefore, when measuring the first potential difference at the first position and the second potential difference at the second position, the sign of only the potential difference caused by the object being inspected is reversed due to the reversal of the first electrode (first measuring electrode) and the second electrode (second measuring electrode). Furthermore, while the values ​​of the potential difference caused by the object being inspected and the values ​​of the potential difference caused by factors other than the object being inspected change to a degree that cannot be ignored in the long term, the change in potential difference is practically negligible in the short term. Therefore, by calculating the underwater electric field (first underwater electric field) based on the first and second potential differences, the offset (deviation) of the potential difference caused by factors other than the object being inspected can be corrected. As a result, the underwater electric field can be obtained with high accuracy. (Item 2) The offset correction method for a potential difference measuring device according to item 1, wherein in the step of calculating the underwater electric field, the difference between the value of the first potential difference and the value of the second potential difference is calculated to calculate the underwater electric field with the potential difference offset corrected for causes other than the object being inspected. By calculating the difference between the first potential difference value and the second potential difference value, the underwater electric field (first underwater electric field) can be easily obtained with correction for potential difference offsets caused by factors other than the object being inspected. As a result, the underwater electric field can be obtained easily and accurately. (Item 3) The offset correction method for a potential difference measuring device according to item 2, wherein in the step of calculating the underwater electric field, the difference between the value of the first potential difference and the value of the second potential difference is calculated to calculate the underwater electric field, which is corrected for the potential difference offset due to individual differences in the first electrode and the second electrode, and the potential difference offset due to the surrounding environment of the pair of electrode parts. Here, the potential difference measured by the pair of electrodes includes an offset in the first electrode (first measuring electrode) and the second electrode (second measuring electrode) due to individual differences during manufacturing. Furthermore, the potential difference measured by the pair of electrodes also includes an offset in the potential difference due to the surrounding environment of the pair of electrodes, such as water temperature and dissolved oxygen content. Therefore, by configuring it as described above, it is possible to easily calculate the underwater electric field (first underwater electric field) corrected for the offset in the potential difference due to individual differences in the first electrode (first measuring electrode) and the second electrode (second measuring electrode), and the offset in the potential difference due to the surrounding environment of the pair of electrodes. As a result, even when it is difficult to individually measure the potential difference due to individual differences in the first electrode (first measuring electrode) and the second electrode (second measuring electrode), and the potential difference due to the surrounding environment of the pair of electrodes, it is possible to easily obtain an underwater electric field corrected for the offset in the potential difference due to individual differences in the first electrode (first measuring electrode) and the second electrode (second measuring electrode), and the offset in the potential difference due to the surrounding environment of the pair of electrodes. (Item 4) An offset correction method for a potential difference measuring device according to any one of items 1 to 3, wherein in the step of calculating the underwater electric field, the underwater electric field is calculated by first calculating the difference between the value of the first potential difference and the value of the second potential difference and then dividing by 2. Here, the positive and negative signs of the underwater electric field are reversed in the first and second potential differences, while the potential difference due to individual differences between the first electrode (first measuring electrode) and the second electrode (second measuring electrode), and the potential difference due to the surrounding environment of the pair of electrodes, are the same in sign. Therefore, when the difference between the value of the first potential difference and the value of the second potential difference is calculated, twice the value of the underwater electric field is obtained. Thus, as described above, by calculating the difference between the value of the first potential difference and the value of the second potential difference and then dividing by 2, the accurate value of the underwater electric field (first underwater electric field) can be easily obtained. (Item 5) An offset correction method for a potential difference measuring device according to any one of items 1 to 4, wherein, in the step of measuring the second potential difference, the arrangement of the pair of electrode parts is changed from the first position to the second position at the same location where the first potential difference was measured, and the second potential difference is measured. Here, in order to accurately correct the potential difference offset caused by factors other than the object being inspected, it is preferable to measure the first and second potential differences when the values ​​(absolute values) of the underwater electric field (first underwater electric field) included in the first and second potential differences are equal and their signs are reversed. Therefore, as described above, by measuring the first and second potential differences at the same position, it is possible to make the values ​​(absolute values) of the underwater electric field included in the first and second potential differences equal and their signs are reversed. As a result, the potential difference offset caused by the surrounding environment of the pair of electrodes can be accurately corrected. Note that the same position as where the first potential difference was measured does not mean that the first electrode (first measuring electrode) and the second electrode (second measuring electrode) are completely reversed at the first and second positions, but rather that some positional displacement is permitted. (Item 6) An offset correction method for a potential difference measuring device according to any one of items 1 to 5, wherein in the step of measuring the second potential difference, the pair of electrode portions are rotated 180 degrees from the state in which they are positioned at the first position to position the pair of electrode portions at the second position, and the second potential difference is measured. When positioning the pair of electrodes at the second position, they are rotated 180 degrees, allowing for easy measurement of the second potential difference at the second position regardless of the initial position of the first position. As a result, the degree of freedom in positioning the pair of electrodes at the start of measurement in the potential difference measuring device is increased, improving the convenience for the operator. (Item 7) The step of calculating the underwater electric field is: An offset correction method for a potential difference measuring device according to item 1, which calculates the underwater electric field at a plurality of predetermined angles by correcting for potential difference offsets caused by factors other than the object being inspected, based on the first potential difference measured at a plurality of predetermined angles, each of which is a different angle, and the second potential difference measured at each of the plurality of predetermined angles with the positions of the pair of electrode parts reversed. By acquiring the potential difference while rotating a pair of electrode sections, it is possible to acquire multiple underwater electric fields (first underwater electric field) at predetermined angles without providing multiple pairs of electrode sections. As a result, the complexity of the device configuration and the increase in the number of parts can be suppressed. (Item 8) An underwater electric field sensor having a pair of electrode sections including a first electrode and a second electrode for measuring potential in water, and a potential difference measuring section for measuring the potential difference between the pair of electrode sections, The system includes a control unit that calculates an underwater electric field based on the potential difference measured by the underwater electric field sensor, correcting for at least the offset of the potential difference caused by something other than the object being inspected. The control unit, The pair of electrode portions are placed in a predetermined first position and the first potential difference between the pair of electrode portions is measured. The pair of electrode portions are placed in a second position in which the positions of the first electrode and the second electrode are reversed from the first position, and the second potential difference between the pair of electrode portions is measured. A potential difference measuring device that calculates the underwater electric field, correcting for potential difference offsets caused by factors other than the object being inspected, based on the measured first and second potential differences. Similar to the offset correction method for the potentiometer described above, it is possible to provide a potentiometer capable of accurately acquiring the underwater electric field (first underwater electric field). (Item 9) The system further includes a rotating mechanism for rotating the pair of electrode portions, The control unit measures the second potential difference between the pair of electrode portions by using the rotation mechanism to position the pair of electrode portions in a second position in which the positions of the first electrode and the second electrode in the first position are reversed, as described in item 8. Because it is equipped with a rotation mechanism for rotating a pair of electrode sections, the pair of electrode sections can be easily positioned in a first position and a second position. As a result, it is possible to provide a potential difference measuring device that can accurately and easily acquire the underwater electric field (first underwater electric field). (Item 10) The potential difference measuring device according to item 10, wherein the control unit is configured to calculate the underwater electric field after correcting for potential difference offsets caused by factors other than the object being inspected, by calculating the difference between the value of the first potential difference and the value of the second potential difference. Similar to the offset correction method for the potentiometer described above, it is possible to provide a potentiometer that can easily and accurately acquire the underwater electric field (first underwater electric field). (Item 11) The potentiometer according to item 9 or 10, wherein the control unit measures the first potential difference, then rotates the pair of electrode portions by 180 degrees using the rotation mechanism to position the pair of electrode portions at the second position, and measures the second potential difference. Similar to the offset correction method for the potentiometer described above, it is possible to provide a potentiometer capable of accurately correcting offsets of the potentiometer caused by factors other than the object being inspected. (Item 12) The control unit calculates the underwater electric field at the plurality of predetermined angles, correcting for offsets of potential differences caused by factors other than the object being inspected, based on the first potential difference measured at a plurality of predetermined angles, each of which is a different angle, and the second potential difference measured at each of the plurality of predetermined angles with the positions of the pair of electrode portions reversed. This is the potential difference measuring device according to any one of items 8 to 11. Similar to the offset correction method for the potentiometer described above, it is possible to acquire multiple underwater electric fields (first underwater electric field) at multiple predetermined angles without providing multiple pairs of electrodes. As a result, it is possible to provide a potentiometer that can suppress the complexity of the device configuration and the increase in the number of parts. [Explanation of Symbols]

[0065] 1. Underwater electric field sensor 2 Rotation mechanism 3. Control Unit 4 Angle acquisition section 10 pairs of electrodes 11a 1st measurement electrode (1st electrode) 12a Second measurement electrode (second electrode) 13 Potential difference acquisition unit 80. Object under inspection 100 Potential difference measuring device V1 First potential difference V2 Second potential difference Vo1 Potential difference due to individual differences between the first and second measuring electrodes (potential difference due to individual differences between the first and second electrodes) Vo2 Potential difference caused by the surrounding environment of the pair of electrodes Vs1 First underwater electric field (underwater electric field) Vs2 Second Underwater Electric Field

Claims

1. An offset correction method for a potentiometer having a pair of electrode sections including a first electrode and a second electrode for measuring potential in water, and a potentiometer measuring section for measuring the potential difference between the pair of electrode sections, The steps include: arranging the pair of electrode portions at a predetermined first position and measuring the first potential difference between the pair of electrodes; The steps include: arranging the pair of electrode portions in a second position in which the positions of the first electrode and the second electrode are reversed from the first position, and measuring the second potential difference between the pair of electrodes; An offset correction method for a potential difference measuring device, comprising the steps of: calculating an underwater electric field based on the first potential difference and the second potential difference, correcting for at least the offset of the potential difference caused by something other than the object being inspected.

2. The offset correction method for a potential difference measuring device according to claim 1, wherein in the step of calculating the underwater electric field, the difference between the value of the first potential difference and the value of the second potential difference is calculated to calculate the underwater electric field with the offset of the potential difference caused by something other than the object being inspected corrected.

3. The offset correction method for a potential difference measuring device according to claim 2, wherein in the step of calculating the underwater electric field, the difference between the value of the first potential difference and the value of the second potential difference is calculated to calculate the underwater electric field corrected for the potential difference offset due to individual differences in the first electrode and the second electrode, and the potential difference offset due to the surrounding environment of the pair of electrode parts.

4. The offset correction method for a potential difference measuring device according to claim 3, wherein in the step of calculating the underwater electric field, the underwater electric field is calculated by first calculating the difference between the value of the first potential difference and the value of the second potential difference and then dividing by 2.

5. The offset correction method for a potential difference measuring device according to claim 1, wherein in the step of measuring the second potential difference, the arrangement of the pair of electrode portions is changed from the first position to the second position at the same location where the first potential difference was measured, and the second potential difference is measured.

6. The offset correction method for a potential difference measuring device according to claim 1, wherein in the step of measuring the second potential difference, the pair of electrode portions are rotated 180 degrees from the state in which they are positioned at the first position to position the pair of electrode portions at the second position, and the second potential difference is measured.

7. The step of calculating the underwater electric field is: An offset correction method for a potential difference measuring device according to claim 1, comprising calculating the underwater electric field at a plurality of predetermined angles, correcting for potential difference offsets caused by factors other than the object being inspected, based on the first potential difference measured at a plurality of predetermined angles, each of which is a different angle, and the second potential difference measured at each of the plurality of predetermined angles with the positions of the pair of electrode portions reversed.

8. An underwater electric field sensor having a pair of electrode sections including a first electrode and a second electrode for measuring potential in water, and a potential difference measuring section for measuring the potential difference between the pair of electrode sections, The system includes a control unit that calculates an underwater electric field based on the potential difference measured by the underwater electric field sensor, correcting for at least the offset of the potential difference caused by something other than the object being inspected. The control unit, The pair of electrode portions are placed in a predetermined first position and the first potential difference between the pair of electrode portions is measured. The pair of electrode portions are placed in a second position in which the positions of the first electrode and the second electrode are reversed from the first position, and the second potential difference between the pair of electrode portions is measured. A potential difference measuring device that calculates the underwater electric field, correcting for potential difference offsets caused by factors other than the object being inspected, based on the measured first and second potential differences.

9. The system further includes a rotating mechanism for rotating the pair of electrode portions, The potential difference measuring device according to claim 8, wherein the control unit uses the rotation mechanism to position the pair of electrode portions at the second position, inverting the positions of the first electrode and the second electrode at the first position, and measures the second potential difference between the pair of electrode portions.

10. The potential difference measuring device according to claim 9, wherein the control unit is configured to calculate the underwater electric field corrected for potential difference offsets caused by factors other than the object being inspected, by calculating the difference between the value of the first potential difference and the value of the second potential difference.

11. The potentiometer according to claim 10, wherein the control unit measures the first potential difference, then rotates the pair of electrode portions by 180 degrees using the rotation mechanism to position the pair of electrode portions at the second position, and measures the second potential difference.

12. The control unit calculates the underwater electric field at a plurality of predetermined angles, correcting for offsets of potential differences caused by factors other than the object being inspected, based on the first potential difference measured at a plurality of predetermined angles, each of which is a different angle, and the second potential difference measured at each of the plurality of predetermined angles with the positions of the pair of electrode portions reversed.

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