Corrosion-protective coating damage position detection device and corrosion-protective coating damage position detection method

Abstract

To provide a corrosion-protective coating damage position detection device and a corrosion-protective coating damage position detection method that reduce an operator's time and effort and enable efficient inspection.SOLUTION: A detection device according to one aspect of the present disclosure is a corrosion-protective coating damage position detection device that detects a position of a coating damage portion Bs in an underground buried object B, and includes a receiving device 10 having a wheel electrode 11 that detects a potential difference on a ground surface. The receiving device 10 includes: an input unit to which the potential difference on the ground surface is input; an A / D converter 16 that A / D converts the potential difference on the ground surface input to the input unit; and an input unit switcher 12 that switches a range of the potential difference on the ground surface. When a voltage value of a digital signal exceeds a first threshold T1, the input unit switcher 12 switches the range from a second range R2 to a first range R1. When the voltage value of the digital signal falls below the first threshold T1 and a further first weighting condition is satisfied, the input unit switcher 12 switches from the first range R1 to the second range R2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a corrosion protection coating damage location detection device and a corrosion protection coating damage location detection method. [Background technology]

[0002] A technology has been disclosed for detecting, from above ground, the location of a damaged portion of an underground object whose outer surface is covered with a corrosion-resistant coating. Patent Document 1 discloses a corrosion-resistant coating damage location detection device that displays the waveform of the earth surface potential difference detected by a receiving device on a display device and detects the location of the damage in the corrosion-resistant coating from the waveform.

[0003] An A / D converter is generally used for voltage measurements, including the measurement of the above-mentioned earth surface potential difference. An A / D converter is a device that extracts the voltage value of an analog signal at discrete intervals and converts it into a voltage value of a digital signal.

[0004] The above-mentioned corrosion protection coating damage location detection device is required to measure a wide range of voltages, from small values ​​of several tens of μV to large values ​​of several tens of volts.

[0005] For example, if the value of the voltage (hereinafter also referred to as "signal voltage") input to the A / D converter is too small for the measurement range (hereinafter also simply referred to as "range"), the resolution of the A / D converter may be poor. For this reason, when measuring the signal voltage, it is preferable to select an appropriate range depending on the magnitude of the signal voltage to be measured. In particular, when inspecting the location of damage to corrosion-resistant coating, it is necessary to be able to measure a wide range of voltages as described above, so it is unavoidable to frequently switch the range to the appropriate conditions when measuring the voltage input to the A / D converter.

[0006] The resolution of an A / D converter is expressed in bits. The larger the number of bits in an A / D converter, the smaller the signal (voltage) it can detect. For example, if the signal voltage is measured in the ±10V range, the resolution of a 12-bit A / D converter is 4.88mV. On the other hand, if the signal voltage is measured in the ±100V range, the A / D converter's resolution is 48.8mV. When the signal voltage is measured in the ±100V range, the A / D converter's resolution is one-tenth of that when measured in the ±10V range.

[0007] As described above, to address the problem of range switching resulting from degradation of resolution, switchers with an auto-range function that automatically selects an appropriate range depending on the value of the signal voltage are widely used. A switch is a device that can adjust the range of signal voltage values. It is located before the A / D converter and is composed of an attenuator, amplifier, etc. The auto-range function is a function that switches the signal voltage range to a larger range when the signal voltage exceeds a preset threshold, and to a smaller range when the signal voltage falls below the threshold, by feeding back the output of the A / D converter.

[0008] Patent Document 2 discloses an auto-range measuring device that automatically selects the optimal range from among multiple ranges to perform measurements. The auto-range measuring device automatically selects the optimal range from among multiple ranges to perform measurements, and is characterized by comprising: a range attenuator that attenuates an analog input by switching it to an attenuation amount according to the multiple ranges; an A / D converter that converts the output of the range attenuator into a digital signal; an optimal range comparator that compares the output data of the A / D converter with range range data to determine the optimal range; and a control circuit that switches the range attenuator to the maximum range that provides the maximum attenuation when measurement starts, and controls the optimal range comparator that switches the optimal range.

[0009] Specifically, the control circuit sends a switching control signal to the range switching circuit to switch the range of the range attenuator to the minimum range in response to a measurement start signal output from an external circuit. This causes the range switching circuit to switch to the minimum range at which the attenuation of the range attenuator is minimized. Therefore, the analog input value (analog signal) is added to the A / D converter via the range attenuator switched to the minimum range.

[0010] When measurement of an analog signal begins, the range attenuator switches to the minimum range, and the analog signal is A / D converted by the A / D converter. If the analog signal value is large, the bit one bit above the significant bit of the A / D converted output data, i.e., the MSB (Most Significant Bit), becomes "1."

[0011] Here, the overrange flag is set to "1" or "0" depending on the value of the MSB. The overrange flag detection circuit detects the overrange flag and determines whether it is overrange. If the MSB is "0", i.e., the overrange flag is "0", the analog signal can be measured at the minimum range. Therefore, the A / D converted output data of the analog input becomes the data output. If the MSB is "1", i.e., the overrange flag is "1", it determines whether the range attenuator is at the maximum range, and if it is not at the maximum range, it switches to the next higher range. Then, the process from the A / D conversion of the analog signal by the A / D converter to the overrange determination by the overrange flag detection circuit is repeated sequentially. When measuring the analog signal, the range can be switched gradually toward the minimum range using the under-range flag, which indicates that all bits above a specified bit in the A / D conversion output are "0."

[0012] By using the auto-range function, the switch automatically sets the optimum range for the signal measured, eliminating the need for manual range switching decisions and operations, thereby reducing the workload of the operator.

[0013] Patent Document 3 discloses an electrical signal measuring instrument that can make measurements by making the most of the resolution of an A / D converter by adjusting the reference voltage of the A / D converter according to the state of the signal under measurement. The electrical signal measuring instrument digitally converts the signal under measurement and performs various measurements, and is characterized by including an A / D converter with a reference voltage terminal that determines the full scale of the analog input, a signal preprocessing circuit that normalizes the signal under measurement to the input level of the A / D converter, reference voltage adjusting means that monitors the output of the A / D converter and adjusts the signal at the reference voltage terminal so that the peak value of this output falls within a predetermined range, an arithmetic circuit that performs various calculations on the output of the A / D converter, and a control circuit that controls the entire device, and the signal preprocessing circuit is characterized by including a signal attenuator and an amplifier and is configured to switch between multiple ranges.

[0014] The signal under test (Vin) is attenuated by a signal attenuator and then normalized to the input level of the A / D converter by an amplifier. The signal is then input to the A / D converter. The A / D converter converts the input signal into a digital value and sends the digital value as output to a digital signal processor (DSP) and a CPU via an isolation circuit. The DSP uses the output from the A / D converter to perform calculations to calculate the effective value, average value, etc. of the signal under test (Vin). The CPU is a control device that controls the entire voltage measuring instrument. Based on user instructions sent from the operating device, it displays necessary information on the display using the DSP's calculation results and the output from the A / D converter. The CPU also sends a range switching command to the range control circuit. Based on the range switching command, the range control circuit switches the range by adjusting the attenuation rate of the attenuator and the amplification rate of the amplifier. At this time, the CPU performs range conversion on the calculation results sent from the DSP based on the range switching command sent to the range control circuit. The CPU then displays the converted numerical value on the display. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Laid-Open No. 63-191049 [Patent Document 2] Japanese Patent Application Laid-Open No. 1991-165123 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-84191 Summary of the Invention [Problem to be solved by the invention]

[0016] However, because noise can occur inside the detector when switching ranges, applying the auto-range function to corrosion protection coating damage inspections can cause the following problems. In corrosion protection coating damage inspections, signal voltages are continuously detected while moving over the ground surface, and these signal voltages change depending on the detection location. When detecting signal voltages continuously while moving over the ground surface, if the signal voltage continues to fluctuate near the threshold, the range will be switched frequently. As a result, noise is displayed and recorded every time the range is switched, hindering the inspection.

[0017] On the other hand, the operator can determine the timing of the range change and manually change the range. When changing the range, the operator can temporarily stop measuring and recording the signal voltage. This allows noise caused by the change to be eliminated. Therefore, in corrosion protection coating damage inspections, range changes are often performed manually.

[0018] However, manually switching the range requires time and effort from the operator, which may result in a decrease in inspection efficiency.

[0019] An object of the present disclosure is to provide a corrosion protection coating damage location detection device and a corrosion protection coating damage location detection method that reduce the workload of an operator and enable efficient inspection. [Means for solving the problem]

[0020] The present disclosure has been made to solve the above problems, and proposes the following means. A corrosion protection coating damage location detection device according to one embodiment of the present disclosure is a corrosion protection coating damage location detection device that detects the location of a coating damage portion in an underground buried object having an outer surface coated with a corrosion protection coating, and includes a receiving device having a wheel electrode that moves along the underground buried object on the ground surface directly above the underground buried object to detect a potential difference on the ground surface. The receiving device includes an input unit to which the potential difference on the ground surface is input, an A / D converter that A / D converts the potential difference on the ground surface input to the input unit into a digital signal and outputs the digital signal, and a range switch that switches the range of the potential difference on the ground surface input to the input unit. The range includes a first range and a second range that is smaller than the first range. When the voltage value of the digital signal exceeds a first threshold value while the range is switched to the second range, the range switch switches from the second range to the first range. When the voltage value of the digital signal falls below the first threshold value while the range is switched to the first range, and a further first weighted condition is satisfied, the range switch switches from the first range to the second range.

[0021] A corrosion protection coating damage location detection method according to one embodiment of the present disclosure is a method for detecting the location of a coating damage portion in an underground buried object having an outer surface coated with a corrosion protection coating, the method including a detection step of moving a receiving device along the underground buried object on the ground surface directly above the underground buried object and detecting a potential difference on the ground surface using a wheel electrode; an A / D conversion step of A / D converting the potential difference on the ground surface using an A / D converter and outputting it as a digital signal; a range switching step of switching the range of the potential difference on the ground surface input to an input unit provided in the receiving device using a range switch; and displaying information based on the potential difference on a display unit. the range includes a first range and a second range smaller than the first range, and the range switching step includes a first switching step of switching the range from the second range to the first range by the range switcher when the voltage value of the digital signal exceeds a first threshold value while the range is switched to the second range, and a second switching step of switching from the first range to the second range by the range switcher when the voltage value of the digital signal falls below the first threshold value while the range is switched to the first range and a further first weighted condition is satisfied. [Effects of the Invention]

[0022] According to the present disclosure, it is possible to provide a corrosion protection coating damage location detection device and a corrosion protection coating damage location detection method that reduce the workload of an operator and enable efficient inspection. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic diagram of a detection device according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram of a receiving device of the detection device shown in FIG. [Figure 3] FIG. 10 is a diagram showing an example of the waveform of a parameter measured from a digital signal by a lock-in amplifier. [Figure 4] 4 is a flowchart illustrating a detection method according to the first embodiment. [Figure 5] 4A and 4B are diagrams illustrating an example of switching of an input destination of a detection signal by an input section switch in the first embodiment. [Figure 6] 10 is a flowchart illustrating a detection method according to a second embodiment. [Figure 7] 10 is a diagram showing an example of switching of the input destination of a detection signal by an input section switch in the second embodiment. FIG. [Figure 8] FIG. 10 is a schematic diagram of a receiving device according to a third embodiment. [Figure 9] 10 is a flowchart illustrating a detection method according to a third embodiment. [Figure 10] 13 is a diagram showing an example of switching of the input destination of a detection signal by an input section switcher in the third embodiment. FIG. [Figure 11] 10 is a flowchart illustrating a detection method according to a fourth embodiment. [Figure 12] FIG. 13 is a diagram showing an example of switching of the input destination of a detection signal by an input section switch in the fourth embodiment. [Figure 13] FIG. 10 is a schematic diagram of a receiving device according to a modified example of the first embodiment. [Figure 14] FIG. 11 is a schematic diagram of a receiving device according to a modified example of the third embodiment. [Figure 15] FIG. 10 is a schematic diagram of a receiving device according to a modified example of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] A detection device 100 and a detection method according to a first embodiment of the present disclosure will be described below with reference to the drawings. The detection device 100 according to this embodiment detects the location of a coating damage portion Bs in an underground buried object B having an anticorrosion coating on its outer surface. The underground buried object B may be, for example, a buried pipe or a metal pipe such as a steel pipe. As shown in FIGS. 1 and 2 , the detection device 100 includes a receiving device 10 and a measurement signal transmitter 40.

[0025] The receiving device 10 detects the ground surface potential difference directly above the underground buried object B. The receiving device 10 includes a wheel electrode 11, an input section switch 12 (corresponding to a range switch), a first input section 13, a second input section 14, an A / D converter 16, a controller 17, a signal processing device 20, and a display device 30. The term "potential difference" and the term "voltage" described below have the same meaning. Furthermore, the receiving device 10 includes a reference signal generator (not shown).

[0026] The wheel electrode 11 moves along the buried object B on the ground surface directly above the buried object B, and continuously detects the potential difference on the ground surface. As shown in Figures 1 and 2, two wheel electrodes 11 are provided in the receiving device 10. Therefore, the ground surface potential difference is the potential difference between the potential detected by one wheel electrode 11 and the potential detected by the other wheel electrode 11. The wheel electrodes 11 are connected to an input switch 12 . The wheel of the wheel electrode 11 is preferably made of, for example, a conductive sponge rubber wheel. A rotation signal generator such as an encoder (not shown) is provided on the wheel of the wheel electrode 11. The encoder (not shown) converts the amount of wheel rotation of the wheel electrode 11 into a travel distance, and the travel distance is displayed on a display device 30.

[0027] The detection of the potential difference on the ground surface by the detection device 100 is outlined below. First, a measurement signal transmitter 40 (described later) applies an AC voltage between an underground buried object B and a counter electrode 42 (described later) to pass an AC current. If the underground buried object B has a damaged coating Bs, a current I flows into the underground buried object B through the damaged coating Bs. Therefore, a potential difference occurs around the damaged coating Bs. An AC signal current is passed to generate a potential difference. Next, the wheel electrode 11 detects the potential difference generated on the ground surface along the underground buried object B as a detection signal. The detection signal is then input to the first input unit 13 or the second input unit 14 and A / D converted by the A / D converter 16. The A / D converted detection signal (hereinafter referred to as a digital signal) is processed by the signal processing device 20. The digital signal processed by the signal processing device 20 is displayed on the display device 30. Note that hereinafter, the voltage value of the digital signal refers to an absolute value.

[0028] The input switch 12 switches the input destination of the detection signal detected by the wheel electrode 11. In detail, first, a digital signal that has been A / D converted by the A / D converter 16 is input to the input switch 12 via the controller 17. Then, based on the digital signal, the input switch 12 switches whether the detection signal detected by the wheel electrode 11 is input to the first input unit 13 or the second input unit 14. As will be described later, the first input unit 13 and the second input unit 14 each have an input range of the detection signal. Therefore, the input unit switcher 12 switches the input destination of the detection signal to switch the range of the detection signal. For example, when the first input unit 13 has a first range R1 and the second input unit 14 has a second range R2, the input unit switcher 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14, and the range of the detection signal switches from the first range R1 to the second range R2.

[0029] The following describes the reason why the input section switcher 12 switches between the first input section 13 and the second input section 14 to which the detection signal is input. In this description, as an example, the first input section 13 has a detection signal range of ±100V, and the second input section 14 has a detection signal range of ±10V. If only the second input section 14 having a range of ±10V is used as the input destination for the detection signal, the detection signal cannot be properly detected when a potential difference on the ground surface exceeding 10V is detected. On the other hand, when only the first input unit 13 having a range of ±100 V is used as the input destination for the detection signal, it is possible to detect the potential difference of the high voltage earth surface, but when a small potential difference, for example less than 10 V, is detected, the resolution is inferior compared to when the second input unit 14 having a range of ±10 V is used as the input destination for the detection signal.

[0030] Therefore, under normal circumstances, the second input unit 14 is used as the input destination for the detection signal, and when a high voltage potential difference on the ground surface exceeding 10 V is detected, the first input unit 13 is used, thereby enabling accurate and appropriate detection of the potential difference on the ground surface.

[0031] A detection signal is input to the first input unit 13 and the second input unit 14. The first input unit 13 and the second input unit 14 have their own ranges in which the detection signal is input. The first input unit 13 or the second input unit 14 outputs the input detection signal to an A / D converter 16, which will be described later. The first input section 13 has a larger range than the second input section 14. For example, as described above, the second input section 14 has a range of ±10V and the first input section 13 has a range of ±100V.

[0032] The A / D converter 16 A / D converts the detection signal output from the first input unit 13 or the second input unit 14 into a digital signal. In particular, when a detection signal is input to the first input unit 13, the A / D converter 16 A / D converts the detection signal output from the first input unit 13. When a detection signal is input to the second input unit 14, the A / D converter 16 A / D converts the detection signal output from the second input unit 14. The A / D converter 16 is connected to a signal processing device 20, which will be described later. The A / D converter 16 outputs a digital signal to the controller 17 and the signal processing device 20.

[0033] The controller 17 controls the input unit switch 12. Specifically, the controller 17 controls the input unit switch 12 based on the digital signal output from the A / D converter 16, thereby controlling the switching of the input destination of the detection signal by the input unit switch 12.

[0034] The control of switching the detection signal input destination by the controller 17 will be described below. For example, the controller 17 controls the switching of the detection signal input destination by the input unit switcher 12 by setting a first threshold T1 of a constant voltage for the digital signal input from the A / D converter 16. The first threshold T1 is stored in the controller 17, for example. For example, when the voltage value of the digital signal exceeds the first threshold T1, the controller 17 controls the input unit switch 12 so that the detection signal is input to the first input unit 13. Thereafter, the input unit switch 12 switches the input destination of the detection signal to the first input unit 13. Furthermore, for example, when the voltage value of the digital signal falls below a first threshold T1 and a further first weighting condition is satisfied, the controller 17 controls the input switch 12 to switch the input destination of the detection signal from the first input unit 13 to the second input unit 14. Thereafter, the input switch 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14. The first weighting condition may be that a digital signal having a voltage value below the first threshold T1 is continuously output over a specified distance, or that a digital signal having a voltage value below the first threshold T1 is continuously output for a specified time. In other words, the input switch 12 may switch the input destination of the detection signal from the first input unit 13 to the second input unit 14 when a digital signal having a voltage value below the first threshold T1 is continuously output over a specified distance. Alternatively, the input section switcher 12 may switch the input destination of the detection signal from the first input section 13 to the second input section 14 when a digital signal with a voltage value below the first threshold value T1 is output continuously for a specified time.

[0035] The "designated distance" may be, for example, the distance traveled by the wheel electrode 11 measured by an encoder (not shown). The "designated time" may be, for example, the time taken for the wheel electrode 11 to travel, calculated based on the distance traveled measured by an encoder (not shown) and the speed (operator speed) at which the wheel electrode 11 travels along the underground buried object B. The "designated time" may be, for example, a time calculated by a clock built into the controller 17. These designated distances and designated times are stored in the controller 17, for example.

[0036] The signal processing device 20 processes the digital signal output from the A / D converter 16. The signal processing device 20 inputs the processed digital signal to the display device 30.

[0037] The signal processing device 20 may be, for example, a lock-in amplifier. A lock-in amplifier is a device that measures parameters such as the amplitude and phase of an AC signal. The lock-in amplifier in this embodiment measures the parameters of the digital signal based on the digital signal output from the A / D converter 16. The number of lock-in amplifiers included in the signal processing device 20 is not particularly limited. For example, the signal processing device 20 may include one lock-in amplifier. Although not shown, the signal processing device 20 may include, for example, two lock-in amplifiers corresponding to the first input unit 13 and the second input unit 14, respectively. That is, parameter measurement of the digital signal input to the first input unit 13, A / D converted by the A / D converter 16, and output may be performed by one of the lock-in amplifiers. Parameter measurement of the digital signal input to the second input unit 14, A / D converted by the A / D converter 16, and output may be performed by the other lock-in amplifier.

[0038] A reference signal generator (not shown) is connected to the lock-in amplifier. A reference signal is input to the lock-in amplifier by the reference signal oscillator (not shown). The reference signal is a frequency signal whose relative phase change with respect to the AC signal current output by a measurement signal generator 40 (described later) is the same within a range of at least 180 degrees / hour.

[0039] The lock-in amplifier measures the following parameters from the processed digital signal, as shown in Figure 3: Waveform of the digital signal amplitude A [Figure 3(a)] Waveform of Acosφ [Figure 3(b)] · Waveform of Asinφ [Fig. 3(c)] Phase φ waveform [Fig. 3(d)] Figure 3 shows an example of the waveform of a parameter measured from a digital signal by a lock-in amplifier. The horizontal axis in Figures 3(a) to 3(d) represents the distance from the coating damage Bs, with the coating damage Bs as the origin. The vertical axis in Figures 3(a), 3(b), and 3(c) represents the potential difference (mV) of the digital signal, and the vertical axis in Figure 3(d) represents the value of the phase φ of the digital signal.

[0040] Figure 3(a) shows that the potential difference is at a minimum at the origin, i.e., at the location of the damaged coating Bs. Figures 3(b) and 3(c) show that the sign of the potential difference is reversed at the location of the damaged coating Bs. Figure 3(d) shows that the phase φ is reversed at the location of the damaged coating Bs.

[0041] 2, the display device 30 displays various digital signals output from the signal processing device 20. For example, the display device 30 displays the amplitude A and phase φ output from the lock-in amplifier. For example, a known display is used as the display device 30. For example, the display device 30 includes displays such as a CRT (Cathode Ray Tube) display, a liquid crystal display, and an organic EL (Electro-Luminescence) display. For example, the display device 30 may be a display included in a known PC. For example, the display device 30 may be a pen recorder such as a known balance recorder. The operator detects the position of the damaged portion Bs of the coating of the underground buried object B based on the information displayed on the display device 30.

[0042] (Detection method) The detection device 100 according to the first embodiment has been described above. The detection method according to the first embodiment will be described below with reference to Figs. 4 and 5. The configuration for implementing the detection method according to this embodiment is not limited to the above-described detection device 100. Below, the detection method according to this embodiment will be described using the above-described detection device 100. The same applies to the detection methods according to the following embodiments.

[0043] The detection method according to this embodiment is a method for detecting the position of a coating damage portion Bs in an underground buried object B having an outer surface coated with a corrosion-resistant coating. The detection method according to this embodiment includes a detection step, an A / D conversion step, a range switching step, and a display step.

[0044] Furthermore, the range switching process includes a first switching process in which the input section switcher 12 switches the range from the second range R2 to the first range R1 when the voltage value of the digital signal exceeds a first threshold value T1 while the range is switched to the second range R2, and a second switching process in which the input section switcher 12 switches from the first range to the second range when the voltage value of the digital signal falls below the first threshold value T1 while the range is switched to the first range R1 and a further first weighted condition is satisfied. In the detection method according to this embodiment, the first weighting condition is that a digital signal having a voltage value below the first threshold T1 is output continuously over a specified distance, or that a digital signal having a voltage value below the first threshold T1 is output continuously for a specified time.

[0045] FIG. 4 is a flowchart illustrating the detection method according to the first embodiment. As shown in FIG. 4, first, the input section switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 to the second input section 14 (step S100).

[0046] Next, the A / D converter 16 A / D converts the detection signal detected by the wheel electrode 11 (corresponding to an A / D conversion step, step S101). In detail, first, the wheel electrode 11 provided in the receiving device 10 detects the ground surface potential difference above the underground buried object B as a detection signal (corresponding to a detection step). Thereafter, the A / D converter 16 A / D converts the detection signal as a digital signal and outputs the digital signal to the controller 17 and the signal processing device 20.

[0047] The detection process will now be described. First, in the detection step, the receiving device 10 is moved along the buried object B on the ground surface above the buried object B, and the wheel electrode 11 detects the potential difference on the ground surface as a detection signal. 1 and 2, a measurement signal transmitter 40 is provided in the underground buried object B. The measurement signal transmitter 40 is a device for generating a potential difference at the position of the coating damaged portion Bs. The measurement signal transmitter 40 is connected to an underground buried object B and a counter electrode 42 placed underground (inside the soil). The measurement signal transmitter 40 applies an AC voltage between the underground buried object B and the counter electrode 42, causing an AC current to flow. If the underground buried object B has a damaged coating Bs, a current I flows into the underground buried object B through the damaged coating Bs. Therefore, a potential difference occurs around the damaged coating Bs. As described above, in the detection step, the potential difference on the ground surface generated by the measurement signal transmitter 40 is detected by the wheel electrode 11.

[0048] 4, the controller 17 determines whether the voltage value of the digital signal output from the A / D converter 16 is equal to or greater than the first threshold value T1 (step S102). If the controller 17 cannot determine that the voltage value of the digital signal is equal to or greater than the first threshold value T1 (step S102: NO), the signal processing device 20 processes the digital signal output from the A / D converter 16 (step S103). Thereafter, the display device 30 displays the signal processed by the signal processing device 20 (corresponding to a display step, step S104).

[0049] After step S104 is executed, the wheel electrode 11 sequentially detects the ground surface potential difference as a detection signal along the underground buried object B (for example, at regular intervals or at regular distances), and the A / D converter 16 sequentially A / D converts the detection signals into digital signals. Thereafter, the controller 17 sequentially determines whether the voltage value of the digital signal output from the A / D converter 16 is equal to or greater than a first threshold value T1 (step S102).

[0050] When the controller 17 determines that the voltage value of the digital signal is equal to or greater than the first threshold T1 (step S102: YES), the controller 17 controls the input unit switch 12 to switch the output destination of the detection signal from the second input unit 14 to the first input unit 13 (corresponding to a first switching step, step S105). That is, the input unit switch 12 switches the range of the detection signal from the second range R2 of the second input unit 14 to the first range R1 of the first input unit 13. The method of controlling the switching of the input destination of the detection signal by the controller 17 is as described above.

[0051] Next, the controller 17 resets the cumulative sampling number C of the digital signal output from the A / D converter 16 to 0 (step S106). The cumulative sampling number C is a value that is sequentially added in step S112, which will be described later. The cumulative sampling number C is an integer equal to or greater than 0. The cumulative sampling number C is stored in the controller 17, for example. Next, the A / D converter 16 A / D converts the detection signal detected in step S101 (step S107).

[0052] Next, the controller 17 determines whether the voltage value of the digital signal output from the A / D converter 16 is smaller than the first threshold value T1 (step S108). If the controller 17 cannot determine that the voltage value of the digital signal is smaller than the first threshold value T1 (step S108: NO), the controller 17 resets the cumulative sampling number C of the digital signal output from the A / D converter 16 to 0 (step S109). Steps S110 and S111 executed after step S109 are similar to steps S103 and S104 described above, and therefore will not be described here. After step S111 is executed, similarly to after step S104 is executed, in step S107, the wheel electrodes 11 sequentially detect detection signals, and the detection signals are sequentially A / D converted into digital signals by the A / D converter 16. Thereafter, the controller 17 sequentially determines whether or not the voltage value of the digital signal output from the A / D converter 16 is smaller than the first threshold value T1 (step S108).

[0053] If the controller 17 determines that the voltage value of the digital signal is smaller than the first threshold T1 (step S108: YES), the controller 17 increments the cumulative sampling number C of the digital signal output from the A / D converter 16 by 1 (step S112). Thereafter, the controller 17 determines whether the cumulative sampling number C is smaller than a specified sampling number Cs (step S113). The specified sampling number Cs is stored in the controller 17, for example. The specified sampling number Cs is a value corresponding to a specified time or a specified distance. When the controller 17 determines that the cumulative sampling number C is smaller than the specified sampling number Cs (step S113: YES), the above steps S110 and S111 are executed. If the controller 17 does not determine that the cumulative sampling number C is smaller than the specified sampling number Cs (step S113: NO), the input unit switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 to the second input unit 14 (corresponding to a second switching step, step S100). That is, the input unit switch 12 switches the range of the detection signal from the first range R1 to the second range R2. Thereafter, in step S107, as after step S104 is executed, the detection signals are sequentially detected by the wheel electrode 11, and the detection signals are sequentially A / D converted into digital signals by the A / D converter 16.

[0054] Hereinafter, switching of the input destination of the detection signal by the input section switch 12 in the detection method of this embodiment will be described with reference to FIG. FIG. 5 is a diagram showing an example of switching of the input destination of the detection signal by the input switch 12. The horizontal axis in FIGS. 5(a) to 5(c) represents the moving distance of the wheel electrode 11 measured by an encoder (not shown). FIG. 5(a) is a diagram plotting the detection signal (digital signal) A / D converted by the A / D converter 16 every time the wheel electrode 11 moves a distance ΔD, with the vertical axis representing the voltage value of the digital signal. ΔD is the sampling interval of the A / D converter 16. FIG. 5(b) is a diagram showing the change in the value of the cumulative sampling number C, with the vertical axis representing the cumulative sampling number C. FIG. 5(c) is a diagram showing the input destination of the detection signal sequentially switched by the input switch 12.

[0055] First, before the wheel electrode 11 starts detecting the ground potential difference, the input destination of the detection signal is switched to the second input unit 14. Thereafter, as the wheel electrode 11 moves, the wheel electrode 11 sequentially detects the ground potential difference. Next, at a distance d1, the voltage value of the digital signal exceeds the first threshold value T1. In this case, the input section switcher 12 switches the output destination of the detection signal from the second input section 14 to the first input section 13 (step S105). Next, at a distance d2, the voltage value of the digital signal is below the first threshold value T1, so the controller 17 increments the cumulative sampling number C of the digital signal output from the A / D converter 16 by 1 (step S112). Next, at a distance d3, the voltage value of the digital signal exceeds the first threshold value T1 again. Therefore, the controller 17 sets the cumulative sampling number C of the digital signal output from the A / D converter 16 to 0 (step S109). Next, at a distance d4, the voltage value of the digital signal falls below the first threshold T1, and at a distance d5, the voltage value of the digital signal again exceeds the first threshold T1. Therefore, the above steps S112 and S109 are executed in sequence. Next, at a distance d6, the voltage value of the digital signal is below the first threshold value T1, so the controller 17 increments the cumulative sampling number C of the digital signal output from the A / D converter 16 by 1 (step S112). Next, at distance d7, the cumulative sampling number C becomes equal to the specified sampling number Cs, that is, the condition that the cumulative sampling number C is smaller than the specified sampling number Cs is no longer satisfied. Therefore, the input unit switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 from the first input unit 13 to the second input unit 14 (step S100). At distances after distance d7, the cumulative sampling number C is equal to the specified sampling number Cs, but is not limited to this. For example, the controller 17 may set the cumulative sampling number C to 0 at the timing when the input unit switch 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14.

[0056] The detection device 100 described above is a corrosion protection coating damage position detection device for detecting the position of a coating damage portion Bs in an underground buried object B having an outer surface coated with a corrosion protection coating, and is equipped with a receiving device 10 having a wheel electrode 11 that moves along the underground buried object B on the ground surface directly above the underground buried object B to detect a potential difference on the ground surface. The receiving device 10 includes an input unit to which the potential difference on the ground surface is input, an A / D converter 16 that A / D converts the potential difference on the ground surface input to the input unit into a digital signal and outputs the digital signal, and an input unit switch 12 (range The input section switch 12 has a first range R1 and a second range R2 that is smaller than the first range R1, and when the voltage value of the digital signal exceeds a first threshold T1 while the range is switched to the second range R2, the input section switch 12 switches the range from the second range R2 to the first range R1, and when the voltage value of the digital signal falls below the first threshold T1 while the range is switched to the first range R1, and when a further first weighted condition is satisfied, the input section switch 12 switches from the first range R1 to the second range R2.

[0057] According to the above configuration, when the range is switched to the second range R2 and the voltage value of the digital signal exceeds the first threshold T1, the input unit switcher 12 switches the range from the second range R2 to the first range R1, and when the range is switched to the first range R1 and the voltage value of the digital signal falls below the first threshold T1 and a further first weighted condition is satisfied, the input unit switcher 12 switches from the first range R1 to the second range R2. Therefore, when the voltage value of the digital signal exceeds the first threshold T1 while the range is switched to the second range R2, the input switch 12 immediately switches the range from the second range R2 to the first range R1. This allows the detection signal to be properly detected even when the detection signal exceeds the second range R2. Furthermore, by reducing the operator's effort in switching ranges, the position of the coating damage Bs can be detected efficiently. On the other hand, if the voltage value of the digital signal falls below the first threshold T1 while the range is switched to the first range R1, the input section switcher 12 does not immediately switch the range from the first range R1 to the second range R2. Even when the range is switched to the first range R1, the value of the detection signal can be detected as long as it is within the range of the first range R1. Therefore, when the voltage value of the digital signal falls below the first threshold T1 while the range is switched to the first range R1, and when a first weighting condition is further satisfied, the input switch 12 switches from the first range R1 to the second range R2. This reduces the frequency of range switching, thereby reducing the operator's effort in switching ranges. This allows for efficient detection of the location of damage to the corrosion-resistant coating.

[0058] According to the above detection device, the first weighting condition is that a digital signal having a voltage value below the first threshold T1 is output continuously over a specified distance, or that a digital signal having a voltage value below the first threshold T1 is output continuously for a specified time.

[0059] According to the above configuration, the first weighting condition is that a digital signal having a voltage value below the first threshold T1 is continuously output over a specified distance or continuously output for a specified time. Therefore, when the voltage value of the digital signal falls below the first threshold T1 while the range is switched to the first range R1, the input switch 12 switches from the first range R1 to the second range R2 when a digital signal having a voltage value below the first threshold T1 is continuously output over a specified distance or continuously output for a specified time. This reduces the frequency of range switching, thereby minimizing noise generated during range switching. This allows for highly accurate detection of the location of damage to the corrosion-resistant coating.

[0060] The detection method described above is a corrosion protection coating damage position detection method for detecting the position of a coating damage portion Bs in an underground buried object B having an outer surface coated with a corrosion protection coating, and includes a detection step of moving a receiving device 10 along the underground buried object B on the ground surface directly above the underground buried object B and detecting a potential difference on the ground surface with a wheel electrode 11, a range switching step of switching the range of the potential difference on the ground surface input to an input unit provided in the receiving device 10 with an input unit switch 12, and a display step of displaying information based on the potential difference on a display device 30 (corresponding to a display unit), the ranges being selected from a first range R1 and a second range R2. The range switching process includes a first switching process in which, when the voltage value of the digital signal exceeds a first threshold value T1 while the range is switched to the second range R2, the input section switcher 12 switches the range from the second range R2 to the first range R1, and a second switching process in which, when the voltage value of the digital signal falls below the first threshold value T1 while the range is switched to the first range R1 and a further first weighted condition is satisfied, the input section switcher 12 switches from the first range R1 to the second range R2.

[0061] According to the above method, the range switching step includes a first switching step of switching the range from the second range R2 to the first range R1 by the input switcher 12 when the voltage value of the digital signal exceeds the first threshold T1 while the range is switched to the second range R2, and a second switching step of switching from the first range R1 to the second range R2 by the input switcher 12 when the voltage value of the digital signal falls below the first threshold T1 while the range is switched to the first range R1 and a further first weighted condition is satisfied. Thus, in the first switching step, when the voltage value of the digital signal exceeds the first threshold T1, the input switcher 12 immediately switches the range from the second range R2 to the first range R1. On the other hand, in the second switching step, only when the voltage value of the digital signal falls below the first threshold T1 and a further first weighted condition is satisfied, the input switcher 12 switches from the first range R1 to the second range R2. This allows the detection signal to be properly detected even when it exceeds the second range R2. Furthermore, by reducing the operator's effort in switching ranges, the position of the coating damaged portion Bs can be detected efficiently. In the second switching step, when the voltage value of the digital signal falls below the first threshold T1 while the range is switched to the first range R1, and when a first weighting condition is satisfied, the input switch 12 switches from the first range R1 to the second range R2. This reduces the frequency of range switching, thereby reducing the operator's effort in switching ranges. This allows for efficient detection of the location of damage to the corrosion-resistant coating.

[0062] According to the above detection method, the first weighting condition is that a digital signal having a voltage value below the first threshold T1 is output continuously over a specified distance, or that a digital signal having a voltage value below the first threshold T1 is output continuously for a specified time.

[0063] According to the above method, the first weighting condition is that a digital signal having a voltage value below the first threshold T1 is continuously output over a specified distance or continuously for a specified time. Therefore, when the voltage value of the digital signal falls below the first threshold T1 while the range is switched to the first range R1, and a digital signal having a voltage value below the first threshold T1 is continuously output over the specified distance or continuously for the specified time, the input switch 12 switches the range from the first range R1 to the second range R2. This reduces the frequency of range switching, thereby minimizing noise generated during range switching. This allows for highly accurate detection of the location of damage to the corrosion-protective coating.

[0064] (Second embodiment) The detection device 200 and detection method according to this embodiment have the same configuration as the detection device 100 and detection method according to Embodiment 1. The differences from the detection device 100 and detection method according to Embodiment 1 will be described below.

[0065] The controller 17 in this embodiment controls switching of the detection signal input destination by the input unit switcher 12 by setting a first threshold value T1 and a second threshold value T2 that is smaller than the first threshold value T1 for the digital signal input from the A / D converter 16. The second threshold value T2 is stored in the controller 17, for example. For example, when the voltage value of the digital signal exceeds the first threshold T1, the input section switcher 12 switches the input destination of the detection signal from the second input section 14 to the first input section 13, as in the first embodiment. Furthermore, in this embodiment, the first weighting condition is that the voltage value of the digital signal falls below a second threshold T2 that is lower than the first threshold T1. Therefore, when the voltage value of the digital signal falls below the second threshold T2, the input unit switcher 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14. Therefore, the input unit switcher 12 in this embodiment differs from the input unit switcher 12 in the first embodiment in that when the voltage value of the digital signal falls below the second threshold T2, the input destination of the detection signal is immediately switched from the first input unit 13 to the second input unit 14.

[0066] Furthermore, in this embodiment, the first weighting condition may be that a digital signal having a voltage value below the second threshold T2 is continuously output over a specified distance, or that a digital signal having a voltage value below the second threshold T2 is continuously output for a specified time. In other words, the input switcher 12 may switch the input destination of the detection signal from the first input unit 13 to the second input unit 14 when a digital signal having a voltage value below the second threshold T2 is continuously output over a specified distance. Alternatively, the input switcher 12 may switch the input destination of the detection signal from the first input unit 13 to the second input unit 14 when a digital signal having a voltage value below the second threshold T2 is continuously output for a specified time.

[0067] (Detection method) The detection method according to this embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart illustrating the detection method according to this embodiment. The detection method according to this embodiment includes a detection step, an A / D conversion step, a range switching step, and a display step, similar to the first embodiment. Note that the detection step in this embodiment is similar to that in the first embodiment, and therefore will not be described here.

[0068] The detection method according to this embodiment differs from the detection method according to the first embodiment in that it includes step S207 (described later) in which the controller 17 determines whether the voltage value of the digital signal is smaller than a second threshold value T2. Furthermore, in this embodiment, the range switching process includes a first switching process in which the input destination of the detection signal is switched to the second input section 14 and the input switch 12 switches the input destination of the detection signal from the second input section 14 to the first input section 13 when the voltage value of the digital signal exceeds a first threshold T1, and a second switching process in which the input switch 12 switches the input destination of the detection signal from the first input section 13 to the second input section 14 when the input destination of the detection signal is switched to the first input section 13 and the voltage value of the digital signal falls below the first threshold T1 and a further first weighted condition is satisfied, wherein the first weighted condition is that the voltage value of the digital signal falls below a second threshold T2 which is smaller than the first threshold T1.

[0069] Steps S200 to S205 shown in Fig. 6 are the same as steps S100 to S105 shown in Fig. 4, and step S206 shown in Fig. 6 is the same as step S107 shown in Fig. 4. Therefore, the description here will be omitted.

[0070] After step S206 is executed, the controller 17 determines whether the voltage value of the digital signal is lower than the second threshold value T2 (step S207). If the controller 17 cannot determine that the voltage value of the digital signal is lower than the second threshold T2 (step S207: NO), steps S208 and S209 are executed. Steps S208 and S209 are similar to steps S103 and S104, and therefore will not be described here. If the controller 17 determines that the voltage value of the digital signal is lower than the second threshold T2 (step S207: YES), the input switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 from the first input unit 13 to the second input unit 14 (step S200). That is, the input switch 12 switches the range of the detection signal from the first range R1 to the second range R2.

[0071] In the detection method of the present embodiment described above, the first weighting condition may be that a digital signal having a voltage value below the second threshold T2 is continuously output over a specified distance, or that a digital signal having a voltage value below the second threshold T2 is continuously output for a specified time. Therefore, in step S207, if the controller 17 determines that the voltage value of the digital signal is below the second threshold T2, the input switcher 12 may switch the input destination of the detection signal from the first input unit 13 to the second input unit 14 when a digital signal having a voltage value below the second threshold T2 is continuously output over a specified distance. Alternatively, the input switcher 12 may switch the input destination of the detection signal from the first input unit 13 to the second input unit 14 when a digital signal having a voltage value below the second threshold T2 is continuously output for a specified time. In this case, the frequency of range switching can be reduced compared to when the first weighting condition is that the voltage value of the digital signal is below the second threshold T2, which is smaller than the first threshold T1. Furthermore, the controller 17 may use the cumulative sampling number C' and the specified sampling number Cs' to determine whether a digital signal having a voltage value below the second threshold T2 has been output continuously over a specified distance or whether a digital signal having a voltage value below the second threshold T2 has been output continuously for a specified time. The cumulative sampling number C' and the specified sampling number Cs' are the same as the cumulative sampling number C and the specified sampling number Cs in the first embodiment.

[0072] Hereinafter, switching of the input destination of the detection signal by the input section switcher 12 in the detection method according to this embodiment will be described with reference to FIG. Fig. 7 is a diagram showing an example of switching of the input destination of the detection signal by the input unit switch 12. The horizontal axis in Fig. 7(a) and Fig. 7(b) represents the moving distance of the wheel electrode 11 measured by an encoder (not shown). Fig. 7(a) is a diagram plotting the detection signal (digital signal) A / D converted by the A / D converter 16 every time the wheel electrode 11 moves a distance ΔD, with the vertical axis representing the voltage value of the digital signal. Fig. 7(b) is a diagram showing the input destination of the detection signal sequentially switched by the input unit switch 12.

[0073] First, before the wheel electrode 11 starts detecting the ground potential difference, the input destination of the detection signal is switched to the second input unit 14. Thereafter, as the wheel electrode 11 moves, the wheel electrode 11 sequentially detects the ground potential difference. Next, at a distance d1, the voltage value of the digital signal exceeds the first threshold value T1. In this case, the input section switcher 12 switches the output destination of the detection signal from the second input section 14 to the first input section 13 (step S205). Next, at a distance d2, the voltage value of the digital signal falls below the second threshold T2, so the input switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 from the first input unit 13 to the second input unit 14 (step S200).

[0074] In the detection device 200 described above, the first weighting condition is that the voltage value of the digital signal is lower than a second threshold T2 that is lower than the first threshold T1.

[0075] According to the above configuration, the first weighting condition is that the voltage value of the digital signal falls below the second threshold T2, which is smaller than the first threshold T1. Therefore, when the voltage value of the digital signal falls below the second threshold T2, the input destination of the detection signal is switched from the first input unit 13 to the second input unit 14. This reduces the frequency of range switching compared to immediately switching when the voltage value of the digital signal falls below the first threshold T1. This minimizes noise generated during range switching. This allows the location of damage to the corrosion-protective coating to be detected with high accuracy.

[0076] In the detection device 200 described above, the first weighting condition is that a digital signal having a voltage value below the second threshold T2 is output continuously over a specified distance, or that a digital signal having a voltage value below the second threshold T2 is output continuously for a specified time.

[0077] According to the above configuration, the first weighting condition is that a digital signal having a voltage value below the second threshold T2 is output continuously over a specified distance, or that a digital signal having a voltage value below the second threshold T2 is output continuously for a specified time. Therefore, in this case, the frequency of range switching can be reduced compared to when the first weighting condition is that the voltage value of the digital signal is below the second threshold T2, which is smaller than the first threshold T1. This further reduces noise generated during range switching. Therefore, the location of damage to the corrosion-resistant coating can be detected with high accuracy.

[0078] In the detection method described above, the first weighting condition is that the voltage value of the digital signal is lower than a second threshold T2 that is lower than the first threshold T1.

[0079] According to the above method, the first weighting condition is that the voltage value of the digital signal falls below a second threshold T2, which is smaller than the first threshold T1. Therefore, when the voltage value of the digital signal falls below the second threshold T2, the input destination of the detection signal is switched from the first input unit 13 to the second input unit 14. This reduces the frequency of range switching compared to immediately switching when the voltage value of the digital signal falls below the first threshold T1. This minimizes noise generated during range switching. This allows the location of damage to the corrosion-protective coating to be detected with high accuracy.

[0080] In the detection method described above, the first weighting condition is that a digital signal having a voltage value below the second threshold T2 is output continuously over a specified distance, or that a digital signal having a voltage value below the second threshold T2 is output continuously for a specified time.

[0081] According to the above method, the first weighting condition is that a digital signal having a voltage value below the second threshold T2 is output continuously over a specified distance, or that a digital signal having a voltage value below the second threshold T2 is output continuously for a specified time. Therefore, in this case, the frequency of range switching can be reduced compared to when the first weighting condition is that the voltage value of the digital signal is below the second threshold T2, which is smaller than the first threshold T1. This further reduces noise generated during range switching. Therefore, the location of damage to the corrosion-protective coating can be detected with high accuracy.

[0082] (Third embodiment) The detection device 300 and the detection method according to the third embodiment will be described below, focusing on the differences from the detection device 100 and the detection method according to the first embodiment.

[0083] As shown in Fig. 8, the receiving device 10 in this embodiment further includes a third input unit 15. Fig. 8 is a schematic diagram of the receiving device 10 in this embodiment. The third input unit 15 has a third range R3 that is smaller than that of the second input unit 14. The third input unit 15 outputs the input detection signal to an A / D converter 16. In this embodiment, the input unit switch 12 switches the input destination of the detection signal to any one of the first input unit 13, the second input unit 14, and the third input unit 15. Therefore, when the input unit switch 12 switches the input destination of the detection signal, the range of the detection signal is switched. For example, when the first input unit 13, the second input unit 14, and the third input unit 15 have a first range R1, a second range R2, and a third range R3, when the input unit switch 12 switches the input destination of the detection signal from the second input unit 14 to the third input unit 15, the range of the detection signal is switched from the second range R2 to the third range R3. For example, the same applies when the input unit switch 12 switches the input destination of the detection signal from the third input unit 15 to the second input unit 14, or when the input unit switch 12 switches the input destination of the detection signal from the first input unit 13 to the third input unit 15, etc.

[0084] In this embodiment, the controller 17 controls switching of the detection signal input destination by the input unit switcher 12 by setting a first threshold T1 and a third threshold T3 that is smaller than the first threshold T1 for the digital signal input from the A / D converter 16. The third threshold T3 is stored in the controller 17, for example.

[0085] For example, when the voltage value of the digital signal exceeds the third threshold T3, the input section switcher 12 switches the input destination of the detection signal from the third input section 15 to the second input section . Furthermore, for example, when the voltage value of the digital signal falls below the third threshold T3 while the input destination of the detection signal has been switched to the second input unit 14, and when a second weighted condition is satisfied, the input unit switcher 12 switches the input destination of the detection signal from the second input unit 14 to the third input unit 15. In this embodiment, the second weighted condition is that a digital signal having a voltage value below the third threshold T3 is output continuously over a specified distance, or that a digital signal having a voltage value below the third threshold T3 is output continuously for a specified time. In this case, when the voltage value of the digital signal falls below the third threshold T3 while the input destination of the detection signal is switched to the second input unit 14, and when a digital signal with a voltage value below the third threshold T3 is output continuously over a specified distance or when a digital signal with a voltage value below the third threshold T3 is output continuously for a specified time, the input unit switcher 12 switches the input destination of the detection signal from the third input unit 15 to the second input unit 14. Therefore, by reducing the frequency of input switching, it is possible to minimize noise generated when switching inputs. As a result, it is possible to detect the location of damage to the corrosion-protective coating with high accuracy.

[0086] (Detection method) The detection method according to this embodiment will be described with reference to Fig. 9. Fig. 9 is a flowchart illustrating the detection method according to this embodiment. The detection method according to this embodiment includes a detection step, an A / D conversion step, a range switching step, and a display step, similar to the first embodiment. Note that the detection step in this embodiment is similar to that in the first embodiment, and therefore will not be described here.

[0087] The range switching process includes a third switching process in which, when the input destination of the detection signal has been switched to the third input section 15 and the voltage value of the digital signal exceeds a third threshold T3 that is smaller than the first threshold T1, the input destination of the detection signal is switched from the third input section 15 to the second input section 14 by the input section switcher 12; and a fourth switching process in which, when the input destination of the detection signal has been switched to the second input section 14 and the voltage value of the digital signal falls below the third threshold T3 and a further second weighted condition is satisfied, the input destination of the detection signal is switched from the second input section 14 to the third input section 15 by the input section switcher 12. Furthermore, the second weighting condition is that a digital signal with a voltage value below the third threshold T3 is output continuously over a specified distance, or that a digital signal with a voltage value below the third threshold T3 is output continuously for a specified time.

[0088] First, the input unit switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 to the third input unit 15 (step S300). Step S301 executed after step S300 is the same as step S101 in the first embodiment, and therefore will not be described here.

[0089] Next, the controller 17 determines whether the voltage value of the digital signal output from the A / D converter 16 is equal to or greater than the third threshold value T3 (step S302).

[0090] If the controller 17 cannot determine that the voltage value of the digital signal is equal to or greater than the third threshold T3 (step S302: NO), steps S303 and S304 are executed. Steps S303 and S304 are similar to steps S103 and S104 described above, and therefore will not be described here.

[0091] When the controller 17 determines that the voltage value of the digital signal is equal to or greater than the third threshold T3 (step S302: YES), the controller 17 controls the input unit switch 12 to switch the output destination of the detection signal from the third input unit 15 to the second input unit 14 (corresponding to a third switching step, step S305). That is, the input unit switch 12 switches the range of the detection signal from the third range R3 of the third input unit 15 to the second range R2 of the second input unit 14.

[0092] Next, the controller 17 resets the second cumulative sampling number C2 of the digital signal output from the A / D converter 16 to 0 (step S306). The second cumulative sampling number C2 is a value that is sequentially added in step S313, which will be described later. The second cumulative sampling number C2 is the same as the cumulative sampling number C in the first embodiment, and therefore a detailed description thereof will be omitted.

[0093] Next, the A / D converter 16 A / D converts the detection signal detected in step S301 (step S307). Next, the controller 17 determines whether the voltage value of the digital signal output from the A / D converter 16 is equal to or greater than the first threshold value T1 (step S308). Steps S309 to S314, which are executed when the controller 17 cannot determine that the voltage value of the digital signal is equal to or greater than the first threshold value T1 (step S308: NO), will be described below. Steps S309 to S313 are the same as steps S108 to S112 in the first embodiment, and therefore will not be described here. Note that the second specified sampling number C2s shown in Fig. 9 is a value corresponding to the specified time or specified distance, similar to the specified sampling number Cs in the first embodiment.

[0094] After step S313 is executed, the controller 17 determines whether the second cumulative sampling number C2 is smaller than the second specified sampling number C2s (step S314). When the controller 17 determines that the second cumulative sampling number C2 is smaller than the second specified sampling number C2s (step S314: YES), the above steps S311 and S312 are executed. If the controller 17 does not determine that the second cumulative sampling number C2 is smaller than the second specified sampling number C2s (step S314: NO), the input unit switch 12 switches the input destination of the detection signal from the second input unit 14 to the third input unit 15 (corresponding to a fourth switching step, step S300). That is, the input unit switch 12 switches the range of the detection signal from the second range R2 to the third range R3. Thereafter, in step S301, as after step S304 is executed, the wheel electrodes 11 sequentially detect the detection signals, and the A / D converter 16 sequentially A / D converts the detection signals into digital signals.

[0095] The above has described steps S309 to S314, which are executed when the controller 17 cannot determine that the voltage value of the digital signal is equal to or greater than the first threshold value T1 (step S308: NO). If the controller 17 determines that the voltage value of the digital signal is greater than or equal to the first threshold T1 (step S308: YES), the controller 17 controls the input unit switch 12 to switch the output destination of the detection signal from the second input unit 14 to the first input unit 13 (step S315).

[0096] After step S315 is executed, steps S316 to S322 are executed. Steps S316 to S322 are the same as steps S306 to S313 except for step S308, and therefore a detailed description thereof will be omitted. Note that the first cumulative sampling number C1, which is reset to 0 in step S316, is the same as the cumulative sampling number C in the first embodiment, and therefore a detailed description thereof will be omitted.

[0097] After step S322 is executed, the controller 17 determines whether the first cumulative sampling number C1 is smaller than a first specified sampling number C1s (step S323). Note that the first specified sampling number C1s is a value corresponding to a specified time or a specified distance, similar to the specified sampling number Cs in the first embodiment. When the controller 17 determines that the first cumulative sampling number C1 is smaller than the first specified sampling number C1s (step S323: YES), the above steps S320 and S321 are executed. If the controller 17 does not determine that the first cumulative sampling number C1 is smaller than the first specified sampling number C1s (step S323: NO), the input unit switch 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14 (step S305). That is, the input unit switch 12 switches the range of the detection signal from the first range R1 to the second range R2. Thereafter, in step S305, the wheel electrodes 11 sequentially detect the detection signals, and the A / D converter 16 sequentially A / D converts the detection signals into digital signals.

[0098] Hereinafter, switching of the input destination of the detection signal by the input section switch 12 in the detection method of this embodiment will be described with reference to FIG. FIG. 10 shows an example of switching of the input destination of the detection signal by the input switch 12. The horizontal axes of FIGS. 10(a) to 10(d) represent the moving distance of the wheel electrode 11 measured by an encoder (not shown). FIG. 10(a) plots the detection signal (digital signal) A / D converted by the A / D converter 16 each time the wheel electrode 11 moves a distance ΔD, with the vertical axis representing the voltage value of the digital signal. FIGS. 10(b) and 10(c) show the changes in the first and second cumulative sampling numbers C1 and C2, respectively, with the vertical axis representing the first and second cumulative sampling numbers C1 and C2. FIG. 10(d) shows the input destination of the detection signal sequentially switched by the input switch 12.

[0099] First, before the wheel electrode 11 starts detecting the ground potential difference, the input destination of the detection signal is switched to the third input unit 15. Thereafter, as the wheel electrode 11 moves, the wheel electrode 11 sequentially detects the ground potential difference. At the distance d1, the voltage value of the digital signal exceeds the third threshold value T3. In this case, the input switch 12 switches the output destination of the detection signal from the third input unit 15 to the second input unit . At the distance d2, the voltage value of the digital signal exceeds the first threshold value T1. In this case, the input switch 12 switches the output destination of the detection signal from the second input unit 14 to the first input unit 13. At distances d3, d5, and d7, the voltage value of the digital signal is below the first threshold T1. Therefore, the controller 17 increments the first cumulative sampling number C1 of the digital signal output from the A / D converter 16 by 1. At distances d4 and d6, the voltage value of the digital signal exceeds the first threshold T1 again. In this case, the controller 17 sets the first cumulative sampling number C1 of the digital signal output from the A / D converter 16 to zero. At distance d8, the first cumulative sampling number C1 becomes equal to the first specified sampling number C1s, i.e., the condition that the first cumulative sampling number C1 is smaller than the first specified sampling number C1s no longer holds. Therefore, the input unit switch 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14. At the distance d9, the voltage value of the digital signal is below the third threshold T3. Therefore, the controller 17 increments the second cumulative sampling number C2 of the digital signal output from the A / D converter 16 by one. At the distance d10, the second cumulative sampling number C2 becomes equal to the second specified sampling number C2s, i.e., the condition that the second cumulative sampling number C2 is smaller than the second specified sampling number C2s is no longer satisfied. Therefore, the input unit switch 12 switches the input destination of the detection signal from the second input unit 14 to the third input unit 15. At distances after distance d8, the first cumulative sampling number C1 is equal to the first specified sampling number C1s, but is not limited to this. For example, the controller 17 may set the first cumulative sampling number C1 to 0 at the timing when the input unit switcher 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14. Furthermore, at distances after distance d9, the second cumulative sampling number C2 is equal to the second specified sampling number C2s, but is not limited to this. For example, the controller 17 may set the second cumulative sampling number C2 to 0 at the timing when the input unit switcher 12 switches the input destination of the detection signal from the second input unit 14 to the third input unit 15.

[0100] In the detection device 300 described above, the range includes a third range R3 that is smaller than the second range R2, and when the voltage value of the digital signal exceeds a third threshold T3 that is smaller than the first threshold T1 while the range is switched to the third range R3, the input section switcher 12 switches the range from the third range R3 to the second range R2, and when the voltage value of the digital signal falls below the third threshold T3 while the range is switched to the second range R2 and a further second weighted condition is satisfied, the input section switcher 12 switches the range from the second range R2 to the third range R3.

[0101] According to the above configuration, when the range is switched to the third range R3 and the voltage value of the digital signal exceeds a third threshold T3 that is smaller than the first threshold T1, the input unit switcher 12 switches the range from the third range R3 to the second range R2, and when the range is switched to the second range and the voltage value of the digital signal falls below the third threshold T3 and a further second weighted condition is satisfied, the input unit switcher 12 switches the range from the second range R2 to the third range R3. Therefore, when the range is switched to the third range R3 and the voltage value of the digital signal exceeds a third threshold T3 that is smaller than the first threshold T1, the input switch 12 switches the range from the third range R3 to the second range R2. This allows the detection signal to be properly detected even when the detection signal exceeds the third range R3. Furthermore, by reducing the operator's effort in switching ranges, the position of the coating damage Bs can be detected efficiently. On the other hand, if the voltage value of the digital signal falls below the third threshold T3 while the range is switched to the second range R2, the input section switcher 12 does not immediately switch the range from the second range R2 to the third range R3. Here, even if the range is switched to the second range R2, the value of the detection signal can be detected as long as the value is within the second range R2. Therefore, when the voltage value of the digital signal falls below the third threshold T3 while the range is switched to the second range R2, and when a second weighting condition is further satisfied, the input switch 12 switches from the second range R2 to the third range R3. This reduces the frequency of range switching, thereby reducing the operator's effort in switching ranges. This allows for efficient detection of the location of damage to the corrosion-resistant coating.

[0102] In the detection method described above, the range has a third range R3 that is smaller than the second range R2, and the range switching process includes a third switching process in which the input unit switcher 12 switches the range from the third range R3 to the second range R2 when the voltage value of the digital signal exceeds a third threshold T3 that is smaller than the first threshold T1 while the range is switched to the third range R3, and a fourth switching process in which the input unit switcher 12 switches the range from the second range R2 to the third range R3 when the voltage value of the digital signal falls below the third threshold T3 while the range is switched to the second range R2 and a further second weighted condition is satisfied. Therefore, in the third switching step, when the voltage value of the digital signal exceeds a third threshold T3 that is smaller than the first threshold T1, the input switch 12 switches the range from the third range R3 to the second range R2. This allows the detection signal to be properly detected even when the detection signal exceeds the third range R3. Furthermore, by reducing the operator's effort in switching ranges, the position of the coating damaged portion Bs can be detected efficiently. On the other hand, in the fourth switching step, when the voltage value of the digital signal falls below the third threshold T3 and a second weighting condition is satisfied, the input switch 12 switches the range from the second range R2 to the third range R3. This reduces the frequency of range switching, thereby reducing the operator's effort in switching ranges. This allows for efficient detection of the location of damage to the corrosion-resistant coating.

[0103] (Fourth embodiment) The detection device 400 according to the fourth embodiment will be described below. The configuration of the detection device 400 according to the fourth embodiment is similar to that of the detection device 300 according to the third embodiment. The differences from the detection device 300 according to the third embodiment will be described below.

[0104] The controller 17 in this embodiment controls switching of the detection signal input destination by the input unit switcher 12 by setting a first threshold T1, a fourth threshold T4 smaller than the first threshold T1, a third threshold T3, and a fifth threshold T5 smaller than the third threshold T3 for the digital signal input from the A / D converter 16. The fourth threshold T4 and the fifth threshold T5 are stored in the controller 17, for example. For example, when the voltage value of the digital signal falls below the fourth threshold T4, the input section switcher 12 switches the input destination of the detection signal from the first input section 13 to the second input section . Furthermore, in this embodiment, the second weighting condition is that when the voltage value of the digital signal falls below the fifth threshold T5, the input switch 12 switches the input destination of the detection signal from the second input unit 14 to the third input unit 15. Therefore, when the voltage value of the digital signal falls below the fifth threshold T5, the input switch 12 switches the range from the second range R2 to the third range R3. This reduces the frequency of range switching compared to immediately switching the range when the voltage value of the digital signal falls below the third threshold T3. This minimizes noise generated when switching ranges. This allows the location of damage to the corrosion-resistant coating to be detected with high accuracy.

[0105] (Detection method) The detection method according to this embodiment will be described with reference to Fig. 11. Fig. 11 is a flowchart illustrating the detection method according to this embodiment. The detection method according to this embodiment is similar to the detection method according to Embodiment 2. The differences from the detection method according to Embodiment 2 will be described below. The detection method according to this embodiment includes a detection step, an A / D conversion step, a range switching step, and a display step, similar to that of the second embodiment. Note that the detection step in this embodiment is similar to that of the first embodiment, and therefore will not be described here. Also, as described above, in this embodiment, the second weighting condition is that when the voltage value of the digital signal falls below the fifth threshold T5, the input section switcher 12 switches the input destination of the detection signal from the second input section 14 to the third input section 15.

[0106] 11, the input unit switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 to the third input unit 15 (step S400). Step S401, which is executed after step S400 is executed, is the same as step S201 (step S101) described above, and therefore will not be described here.

[0107] Next, the controller 17 determines whether the voltage value of the digital signal output from the A / D converter 16 is equal to or greater than the third threshold value T3 (step S402).

[0108] If the controller 17 cannot determine that the voltage value of the digital signal is equal to or greater than the third threshold T3 (step S402: NO), steps S403 and S404 are executed. Steps S403 and S404 are similar to steps S203 and S204 described above, and therefore will not be described here.

[0109] If the controller 17 determines that the voltage value of the digital signal is equal to or greater than the third threshold T3 (step S402: YES), the controller 17 controls the input unit switch 12 to switch the output destination of the detection signal from the third input unit 15 to the second input unit 14 (step S405). That is, the input unit switch 12 switches the range of the detection signal from the third range R3 of the third input unit 15 to the second range R2 of the second input unit 14.

[0110] Next, the A / D converter 16 A / D converts the detection signal detected in step S401 (step S406). Next, the controller 17 determines whether the voltage value of the digital signal output from the A / D converter 16 is equal to or greater than the first threshold value T1 (step S407). Steps S408 to S410 are executed when the controller 17 is unable to determine that the voltage value of the digital signal is equal to or greater than the first threshold value T1 (step S407: NO). These steps are similar to steps S207 to S209, and therefore will not be described here. Here, in step S207 in the second embodiment, if the controller 17 determines that the voltage value of the digital signal is lower than the second threshold T2 (step S207: YES), the input unit switcher 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14 (step S200). In step S408 in the present embodiment, if the controller 17 determines that the voltage value of the digital signal is lower than the fifth threshold T5 (step S408: YES), the input unit switcher 12 switches the input destination of the detection signal from the second input unit 14 to the third input unit 15 (step S400). That is, the input unit switcher 12 switches the range of the detection signal from the second range R2 to the third range R3.

[0111] If the controller 17 determines that the voltage value of the digital signal is equal to or greater than the first threshold T1 (step S407: YES), the controller 17 controls the input unit switch 12 to switch the output destination of the detection signal from the second input unit 14 to the first input unit 13 (step S411). That is, the input unit switch 12 switches the range of the detection signal from the second range R2 of the second input unit 14 to the first range R1 of the first input unit 13.

[0112] Steps S412 to S415 that are executed after step S411 are the same as steps S206 to S209 described above, and therefore a description thereof will be omitted here. Here, in step S207 in the second embodiment, if the controller 17 determines that the voltage value of the digital signal is lower than the second threshold T2 (step S207: YES), the input unit switcher 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14 (step S200). In step S413 in the present embodiment, if the controller 17 determines that the voltage value of the digital signal is lower than the fourth threshold T4 (step S413: YES), the input unit switcher 12 switches the input destination of the detection signal from the first input unit 13 to the second input unit 14 (step S405). That is, the input unit switcher 12 switches the range of the detection signal from the first range R1 to the second range R2.

[0113] Hereinafter, switching of the input destination of the detection signal by the input section switch 12 in the detection method according to this embodiment will be described with reference to FIG. 12(a) and 12(b) are diagrams showing an example of switching of the input destination of the detection signal by the input unit switch 12 in this embodiment. The horizontal axis of Fig. 12(a) and Fig. 12(b) is the moving distance of the wheel electrode 11 measured by an encoder (not shown). Fig. 12(a) is a diagram plotting the detection signal (digital signal) A / D converted by the A / D converter 16 every time the wheel electrode 11 moves a distance ΔD, with the vertical axis representing the voltage value of the digital signal. Fig. 12(b) is a diagram showing the input destination of the detection signal sequentially switched by the input unit switch 12.

[0114] First, before the wheel electrode 11 starts detecting the ground potential difference, the input destination of the detection signal is switched to the third input unit 15. Thereafter, as the wheel electrode 11 moves, the wheel electrode 11 sequentially detects the ground potential difference. At the distance d1, the voltage value of the digital signal exceeds the third threshold value T3. In this case, the input switch 12 switches the output destination of the detection signal from the third input unit 15 to the second input unit . At the distance d2, the voltage value of the digital signal exceeds the first threshold value T1. In this case, the input switch 12 switches the output destination of the detection signal from the second input unit 14 to the first input unit 13. At the distance d3, the voltage value of the digital signal is below the fourth threshold T4. Therefore, the input switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 from the first input unit 13 to the second input unit 14. At the distance d4, the voltage value of the digital signal is below the fifth threshold T5. Therefore, the input switch 12 switches the input destination of the detection signal detected by the wheel electrode 11 from the second input unit 14 to the third input unit 15.

[0115] (Variation) The technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure.

[0116] Furthermore, for example, in the fourth embodiment, if a digital signal with a voltage value below the fourth threshold T4 is output continuously over a specified distance, or if a digital signal with a voltage value below the fourth threshold T4 is output continuously for a specified time, the input section switcher 12 may switch the input destination of the detection signal from the first input section 13 to the second input section 14.

[0117] Fig. 13 is a schematic diagram of a receiving device according to a modification of the first embodiment. For example, as shown in Fig. 13, the input section switch 12 in this modification may be located after the A / D converter 16. In this case, the detection signal detected by the wheel electrode 11 is input to both the first input section 13 and the second input section 14. 13, this modification may further include two A / D converters 16 connected to the first input unit 13 and the second input unit 14, respectively. Therefore, the two detection signals input to the first input unit 13 and the second input unit 14, respectively, are A / D converted into digital signals by the two A / D converters 16. Thereafter, the controller 17 selects which of the two digital signals A / D converted by the A / D converter 16 is to be input to the input section switch 12. In this case, the first input unit 13 and the A / D converter 16 can be treated as one unit, and the second input unit 14 and the A / D converter 16 can be treated as another unit. As a result, for example, it becomes possible to use ready-made products as each of these units.

[0118] Fig. 14 is a schematic diagram of a receiving device according to a modification of the third embodiment. For example, as shown in Fig. 14, the input section switch 12 in this modification may be located after the A / D converter 16. Furthermore, in this modification, three A / D converters 16 may be provided, connected to the first input section 13, the second input section 14, and the third input section 15, respectively, as in the modification of the first embodiment.

[0119] Fig. 15 is a schematic diagram of a receiving device in a modified example of the first embodiment. For example, as shown in Fig. 15, the output of the signal processing device 20 may be connected to the controller 17 in this modified example. Note that in other embodiments, the output of the signal processing device 20 may also be connected to the controller 17.

[0120] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modified examples may be combined as appropriate.

[0121] (Addendum) <1> A detection device according to one embodiment of the present disclosure is a corrosion protection coating damage location detection device that detects the location of a coating damage portion in an underground buried object having a corrosion protection coating on its outer surface, and includes a receiving device having a wheel electrode that moves along the underground buried object on the ground surface directly above the underground buried object to detect a potential difference on the ground surface. The receiving device includes an input unit to which the potential difference on the ground surface is input, an A / D converter that A / D converts the potential difference on the ground surface input to the input unit into a digital signal and outputs the digital signal, and a range switch that switches the range of the potential difference on the ground surface input to the input unit, the range including a first range and a second range smaller than the first range. When the voltage value of the digital signal exceeds a first threshold value while the range is switched to the second range, the range switch switches from the second range to the first range. When the voltage value of the digital signal falls below the first threshold value while the range is switched to the first range, and a further first weighted condition is satisfied, the range switch switches from the first range to the second range.

[0122] According to the above configuration, when the voltage value of the digital signal exceeds the first threshold value while the range is switched to the second range, the range switcher switches the range from the second range to the first range, and when the voltage value of the digital signal falls below the first threshold value while the range is switched to the first range and a further first weighted condition is satisfied, the range switcher switches from the first range to the second range. Therefore, if the voltage value of the digital signal exceeds the first threshold while the range is switched to the second range, the range switch immediately switches the range from the second range to the first range. This allows the detection signal to be properly detected even if the detection signal exceeds the second range. Furthermore, by reducing the operator's effort in switching ranges, the location of the damaged coating can be detected efficiently. On the other hand, if the voltage value of the digital signal falls below the first threshold while the range is switched to the first range, the range switcher does not immediately switch the range from the first range to the second range. Here, even when the range is switched to the first range, the value of the detection signal can be detected as long as the value of the detection signal is within the first range. Therefore, when the voltage value of the digital signal falls below the first threshold while the range is switched to the first range, and when a first weighted condition is further satisfied, the range switch switches from the first range to the second range. Therefore, by reducing the frequency of range switching, the operator's effort in switching ranges can be reduced. Therefore, the location of damage to the corrosion-resistant coating can be detected efficiently.

[0123] <2> the above <1> In the detection device according to the present invention, the first weighting condition is that a digital signal having a voltage value below the first threshold is output continuously over a specified distance, or that a digital signal having a voltage value below the first threshold is output continuously for a specified time.

[0124] According to the above configuration, the first weighting condition is that a digital signal having a voltage value below the first threshold is output continuously over a specified distance or that a digital signal having a voltage value below the first threshold is output continuously for a specified time. Therefore, when the voltage value of the digital signal falls below the first threshold while the range is switched to the first range, and a digital signal having a voltage value below the first threshold is output continuously over the specified distance or for the specified time, the range switch switches from the first range to the second range. Therefore, by reducing the frequency of range switching, noise generated during range switching can be minimized. Therefore, the location of damage to the corrosion-protective coating can be detected with high accuracy.

[0125] <3> the above <1> In the detection device according to the above, a first weighting condition is that the voltage value of the digital signal is lower than a second threshold value that is lower than the first threshold value.

[0126] According to the above configuration, the first weighting condition is that the voltage value of the digital signal falls below a second threshold value that is smaller than the first threshold value. Therefore, when the voltage value of the digital signal falls below the second threshold value, the input destination of the detection signal is switched from the first input unit to the second input unit. This reduces the frequency of range switching compared to immediately switching when the voltage value of the digital signal falls below the first threshold value. This minimizes noise generated during range switching. This allows for highly accurate detection of the location of damage to the corrosion-resistant coating.

[0127] <4> the above <1> In the detection device according to the present invention, the first weighting condition is that a digital signal having a voltage value below the second threshold is output continuously over a specified distance, or that a digital signal having a voltage value below the second threshold is output continuously for a specified time.

[0128] According to the above configuration, the first weighting condition is that a digital signal having a voltage value below the second threshold is output continuously over a specified distance, or that a digital signal having a voltage value below the second threshold is output continuously for a specified time. Therefore, in this case, the frequency of range switching can be reduced compared to when the first weighting condition is that the voltage value of the digital signal is below a second threshold that is smaller than the first threshold. This further reduces noise generated during range switching. Therefore, the location of damage to the corrosion-protective coating can be detected with high accuracy.

[0129] <5> the above <1> In the detection device according to the above, the range includes a third range that is smaller than the second range, and the range switcher switches the range from the third range to the second range when the voltage value of the digital signal exceeds a third threshold that is smaller than the first threshold while the range is switched to the third range, and the range switcher switches the range from the second range to the third range when the voltage value of the digital signal falls below the third threshold while the range is switched to the second range and a further second weighted condition is satisfied.

[0130] According to the above configuration, when the range is switched to the third range and the voltage value of the digital signal exceeds a third threshold value that is smaller than the first threshold value, the range switcher switches the range from the third range to the second range, and when the range is switched to the second range and the voltage value of the digital signal falls below the third threshold value and a further second weighted condition is satisfied, the range switcher switches the range from the second range to the third range. Therefore, when the voltage value of the digital signal exceeds a third threshold value, which is smaller than the first threshold value, the range switch switches the range from the third range to the second range. This allows the detection signal to be properly detected even when the detection signal exceeds the third range. Furthermore, by reducing the operator's effort in switching ranges, the location of the damaged coating can be detected efficiently. On the other hand, if the voltage value of the digital signal falls below the third threshold while the range is switched to the second range, the range switcher does not immediately switch the range from the second range to the third range. Here, even when the range is switched to the second range, the value of the detection signal can be detected as long as the value of the detection signal is within the second range. Therefore, when the voltage value of the digital signal falls below the third threshold while the range is switched to the second range, and a second weighted condition is also satisfied, the range switch switches from the second range to the third range. Therefore, by reducing the frequency of range switching, the operator's effort in switching ranges can be reduced. Therefore, the location of damage to the corrosion-resistant coating can be detected efficiently.

[0131] <6> the above <5> In the detection device according to the present invention, the second weighting condition is that a digital signal having a voltage value below the third threshold is output continuously over a specified distance, or that a digital signal having a voltage value below the third threshold is output continuously for a specified time.

[0132] According to the above configuration, the second weighting condition is that a digital signal having a voltage value below the third threshold is output continuously over a specified distance or that a digital signal having a voltage value below the third threshold is output continuously for a specified time. Therefore, when the voltage value of the digital signal falls below the third threshold while the range is switched to the second range, and a digital signal having a voltage value below the third threshold is output continuously over the specified distance or for the specified time, the range switcher switches from the second range to the third range. Therefore, by reducing the frequency of range switching, noise generated during range switching can be minimized. Therefore, the location of damage to the corrosion-protective coating can be detected with high accuracy.

[0133] <7> the above <5> In the detection device according to the present invention, the second weighting condition is that the voltage value of the digital signal is lower than a fifth threshold that is lower than the third threshold.

[0134] According to the above configuration, the second weighting condition is that the voltage value of the digital signal falls below a fifth threshold, which is lower than the third threshold. Therefore, because the range is switched from the second range to the third range when the voltage value of the digital signal falls below the fifth threshold, the frequency of range switching can be reduced compared to immediately switching when the voltage value of the digital signal falls below the third threshold. This minimizes noise generated during range switching. Therefore, the location of damage to the corrosion-resistant coating can be detected with high accuracy.

[0135] <8> A detection method according to one embodiment of the present disclosure is a corrosion protection coating damage location detection method for detecting the location of a coating damage portion in an underground buried object having an outer surface coated with a corrosion protection coating, and includes a detection step of moving a receiving device along the underground buried object on the ground surface directly above the underground buried object and detecting a potential difference on the ground surface using a wheel electrode; a range switching step of switching the range of the potential difference on the ground surface input to an input unit provided in the receiving device using a range switch; and a display step of displaying information based on the potential difference on a display unit, wherein the ranges include a first range and a second range smaller than the first range, and the range switching step includes a first switching step of switching the range from the second range to the first range using the range switch when the voltage value of the digital signal exceeds a first threshold value while the range is switched to the second range, and a second switching step of switching from the first range to the second range by the range switch when the voltage value of the digital signal falls below the first threshold value while the range is switched to the first range and a further first weighted condition is satisfied.

[0136] According to the above method, the range switching step includes a first switching step of switching the range from the second range to the first range by the range switcher when the voltage value of the digital signal exceeds the first threshold while the range is switched to the second range, and a second switching step of switching the range from the first range to the second range by the range switcher when the voltage value of the digital signal falls below the first threshold while the range is switched to the first range and a first additional weighted condition is satisfied. Thus, in the first switching step, the range is immediately switched from the second range to the first range when the voltage value of the digital signal exceeds the first threshold. On the other hand, in the second switching step, the range is switched from the first range to the second range only when the voltage value of the digital signal falls below the first threshold and a first additional weighted condition is satisfied. This allows the detection signal to be properly detected even when the detection signal is detected beyond the second range. Furthermore, by reducing the operator's effort in switching ranges, the location of the damaged coating can be detected efficiently. In the second switching step, the range switch switches from the first range to the second range when the voltage value of the digital signal falls below the first threshold while the range is switched to the first range and a first weighted condition is further satisfied. This reduces the frequency of range switching, thereby reducing the operator's effort in switching ranges. This allows for efficient detection of the location of damage to the corrosion-resistant coating.

[0137] <9> the above <8> According to the detection method, the first weighting condition is that a digital signal having a voltage value below the first threshold is output continuously over a specified distance, or that a digital signal having a voltage value below the first threshold is output continuously for a specified time.

[0138] According to the above method, the first weighting condition is that a digital signal having a voltage value below the first threshold is output continuously over a specified distance or that a digital signal having a voltage value below the first threshold is output continuously for a specified time. Therefore, when the voltage value of the digital signal falls below the first threshold while the range is switched to the first range, and a digital signal having a voltage value below the first threshold is output continuously over the specified distance or for the specified time, the range is switched from the first range to the second range. Therefore, by reducing the frequency of range switching, noise generated during range switching can be minimized. Therefore, the location of damage to the corrosion-protective coating can be detected with high accuracy.

[0139] <10> the above <8> In the detection method according to the above, the first weighting condition is that the voltage value of the digital signal is lower than a second threshold value that is lower than the first threshold value.

[0140] According to the above method, the first weighting condition is that the voltage value of the digital signal falls below a second threshold value that is smaller than the first threshold value. Therefore, when the voltage value of the digital signal falls below the second threshold value, the input destination of the detection signal is switched from the first input unit to the second input unit. This reduces the frequency of range switching compared to immediately switching when the voltage value of the digital signal falls below the first threshold value. This minimizes noise generated during range switching. This allows the location of damage to the corrosion-protective coating to be detected with high accuracy.

[0141] <11> the above <8> In the detection method according to the present invention, the first weighting condition is that a digital signal having a voltage value below the second threshold is output continuously over a specified distance, or that a digital signal having a voltage value below the second threshold is output continuously for a specified time.

[0142] According to the above method, the first weighting condition is that a digital signal having a voltage value below the second threshold is output continuously over a specified distance, or that a digital signal having a voltage value below the second threshold is output continuously for a specified time. Therefore, in this case, the frequency of range switching can be reduced compared to when the first weighting condition is that the voltage value of the digital signal is below a second threshold that is smaller than the first threshold. This further reduces noise generated during range switching. Therefore, the location of damage to the corrosion-protective coating can be detected with high accuracy.

[0143] <12> the above <8> The range relating to the above includes a third range smaller than the second range, and the range switching step includes a third switching step of switching the range from the third range to the second range by the range switcher when the voltage value of the digital signal exceeds a third threshold value smaller than the first threshold value while the range is switched to the third range, and a fourth switching step of switching the range from the second range to the third range by the range switcher when the voltage value of the digital signal falls below the third threshold value while the range is switched to the second range and a further second weighted condition is satisfied.

[0144] According to the above method, the range includes a third range that is smaller than the second range, and the range switching step includes a third switching step of switching the range from the third range to the second range by the range switcher when the voltage value of the digital signal exceeds a third threshold value that is smaller than the first threshold value while the range is switched to the third range, and a fourth switching step of switching the range from the second range to the third range by the range switcher when the voltage value of the digital signal falls below the third threshold value while the range is switched to the second range and a further second weighted condition is satisfied. Therefore, in the third switching step, when the voltage value of the digital signal exceeds a third threshold value that is smaller than the first threshold value, the range switch switches the range from the third range to the second range. This allows the detection signal to be properly detected even when the detection signal exceeds the third range. Furthermore, by reducing the operator's effort in switching ranges, the location of the damaged coating can be detected efficiently. On the other hand, in the fourth switching step, when the voltage value of the digital signal falls below the third threshold and a second weighted condition is satisfied, the range is switched from the second range to the third range. This reduces the frequency of range switching, thereby reducing the operator's effort in switching ranges. This allows for efficient detection of the location of damage to the corrosion-resistant coating.

[0145] <13> the above <12> In the detection method according to the present invention, the second weighting condition is that a digital signal having a voltage value below the third threshold is output continuously over a specified distance, or that a digital signal having a voltage value below the third threshold is output continuously for a specified time.

[0146] According to the above method, the second weighting condition is that a digital signal having a voltage value below the third threshold is output continuously over a specified distance or that a digital signal having a voltage value below the third threshold is output continuously for a specified time. Therefore, when the voltage value of the digital signal falls below the third threshold while the range is switched to the second range, the range switch switches from the second range to the third range when a digital signal having a voltage value below the third threshold is output continuously over the specified distance or when a digital signal having a voltage value below the third threshold is output continuously for the specified time. Therefore, by reducing the frequency of range switching, noise generated during range switching can be minimized. Therefore, the location of damage to the corrosion-protective coating can be detected with high accuracy.

[0147] <14> the above <12> In the detection method according to the above, the second weighting condition is that the voltage value of the digital signal is lower than a fifth threshold that is lower than the third threshold.

[0148] According to the above method, the second weighting condition is that the voltage value of the digital signal falls below a fifth threshold, which is lower than the third threshold. Therefore, when the voltage value of the digital signal falls below the fifth threshold, the input destination of the detection signal is switched from the second input unit to the third input unit. This reduces the frequency of range switching compared to immediately switching when the voltage value of the digital signal falls below the third threshold. This minimizes noise generated during range switching. This allows the location of damage to the corrosion-protective coating to be detected with high accuracy. [Explanation of symbols]

[0149] 100 Detection device 10 Receiving device 11 Wheel electrode 12 Input switch 13 First input section 14 Second input section 15 Third input section 16 A / D converter 17 Controller 20 Signal Processing Device 30 Display device B Underground objects Bs Damaged coating area T1 First threshold T2 Second threshold T3 Third threshold R1 1st range R2 Second Range R3 3rd range

Claims

1. A corrosion protection coating damage location detection device for detecting the location of a coating damage portion in an underground buried object having a corrosion protection coating applied to its outer surface, comprising: a receiving device having wheel electrodes that move along the underground buried object on the ground surface directly above the underground buried object to detect a potential difference on the ground surface; The receiving device an input unit to which the potential difference of the earth's surface is input, an A / D converter that A / D converts the potential difference of the earth's surface input to the input unit into a digital signal and outputs the digital signal, and a range switch that switches the range of the potential difference of the earth's surface input to the input unit, The range includes a first range and a second range that is smaller than the first range, the range switcher switches the range from the second range to the first range when a voltage value of the digital signal exceeds a first threshold value while the range is switched to the second range; The range switcher switches from the first range to the second range when the voltage value of the digital signal falls below the first threshold while the range is switched to the first range and a further first weighted condition is satisfied.

2. 2. The detection device according to claim 1, wherein the first weighting condition is that the digital signal having a voltage value below the first threshold is output continuously over a specified distance, or that the digital signal having a voltage value below the first threshold is output continuously for a specified time.

3. The detection device according to claim 1 , wherein the first weighted condition is that the voltage value of the digital signal is below a second threshold that is lower than the first threshold.

4. 2. The detection device according to claim 1, wherein the first weighting condition is that the digital signal having a voltage value below a second threshold that is smaller than the first threshold is output continuously over a specified distance, or that the digital signal having a voltage value below the second threshold is output continuously for a specified time.

5. the range comprises a third range less than the second range; the range switcher switches the range from the third range to the second range when a voltage value of the digital signal exceeds a third threshold value that is smaller than the first threshold value while the range is switched to the third range; 2. The detection device according to claim 1, wherein the range switcher switches the range from the second range to the third range when a voltage value of the digital signal falls below the third threshold while the range is switched to the second range and a second weighted condition is satisfied.

6. 6. The detection device according to claim 5, wherein the second weighting condition is that the digital signal having a voltage value below the third threshold is output continuously over a specified distance, or that the digital signal having a voltage value below the third threshold is output continuously for a specified time.

7. The detection device according to claim 5 , wherein the second weighting condition is that the voltage value of the digital signal is below a fifth threshold that is lower than the third threshold.

8. A corrosion protection coating damage location detection method for detecting the location of a coating damage portion in an underground buried object having a corrosion protection coating applied to an outer surface thereof, comprising: a detecting step of moving a receiving device along the underground buried object on the ground surface directly above the underground buried object and detecting a potential difference on the ground surface using wheel electrodes; an A / D conversion step of A / D converting the potential difference of the earth surface by an A / D converter and outputting it as a digital signal; a range switching step of switching the range of the potential difference of the earth surface input to an input unit of the receiving device by a range switch; a display step of displaying information based on the potential difference on a display unit; Including, The range includes a first range and a second range that is smaller than the first range, The range switching step includes: a first switching step of switching the range from the second range to the first range by the range switcher when a voltage value of the digital signal exceeds a first threshold value while the range is switched to the second range; a second switching step of switching from the first range to the second range by the range switcher when the voltage value of the digital signal falls below the first threshold while the range is switched to the first range and a further first weighted condition is satisfied.

9. 9. The detection method according to claim 8, wherein the first weighting condition is that the digital signal having a voltage value below the first threshold is output continuously over a specified distance, or that the digital signal having a voltage value below the first threshold is output continuously for a specified time.

10. The detection method according to claim 8 , wherein the first weighted condition is that the voltage value of the digital signal is below a second threshold that is lower than the first threshold.

11. 9. The detection method according to claim 8, wherein the first weighting condition is that the digital signal having a voltage value below a second threshold that is smaller than the first threshold is output continuously over a specified distance, or that the digital signal having a voltage value below the second threshold is output continuously for a specified time.

12. the range comprises a third range less than the second range; the range switching step includes a third switching step of switching the range from the third range to the second range by the range switcher when a voltage value of the digital signal exceeds a third threshold value that is smaller than the first threshold value while the range is switched to the third range; and a fourth switching step of switching the range from the second range to the third range by the range switcher when a voltage value of the digital signal falls below the third threshold while the range is switched to the second range and a further second weighted condition is satisfied.

13. 13. The detection method according to claim 12, wherein the second weighted condition is that the digital signal having a voltage value below the third threshold is output continuously over a specified distance, or that the digital signal having a voltage value below the third threshold is output continuously for a specified time.

14. The detection method according to claim 12 , wherein the second weighted condition is that the voltage value of the digital signal is below a fifth threshold that is lower than the third threshold.

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