Thickness measuring device and thickness measuring method

Abstract

To provide a thickness measuring device, etc. that are able to continue thickness measurement even if the temperature of an object fluctuates.SOLUTION: A thickness measuring device includes: a correction unit configured to correct a duration of an eddy current detected by a detection unit, by using an approximate expression indicating a relation between the duration and a temperature and the temperature acquired by a temperature acquisition unit; a thickness derivation unit configured to obtain a thickness of an object, based on the corrected duration; an approximation unit configured to obtain an approximate expression, based on reference data including the plurality of eddy currents at the different temperatures of the object; and a storage unit configured to cumulatively store measurement data including the durations of the eddy currents and the temperatures. When a reacquisition condition related to a temperature variation of the object is satisfied, the approximation unit re-calculates the approximate expression, based on the durations and the temperatures included in the measurement data obtained by excluding measurement data satisfying an exclusion condition from the measurement data.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a thickness measuring device for measuring the thickness of an object. [Background technology]

[0002] Conventionally, there has been known a device for measuring the thickness of an object using eddy currents (see, for example, Patent Document 1). The object may be a pipe installed in a plant or the like. The measurement accuracy of such a thickness measuring device depends on the temperature of the object (fluid temperature inside the pipe). Patent Document 1 discloses a configuration for correcting the measurement value based on the temperature of the object. In such a thickness measuring device that corrects the measurement value based on temperature, if there is a temporary large temperature fluctuation, the device cannot follow the temperature change, resulting in a large error, and the measurement result may be removed as an outlier. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-117890 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned thickness measurement device, when the temperature of the object drops significantly not temporarily but continuously for a certain period of time, outliers occur continuously, and it may become impossible to continue monitoring the thickness. For example, this is the case when the operating conditions of a process in a plant are changed and maintained for a long period of time, resulting in a drop in the temperature of the pipe (object) for a long period of time.

[0005] An object of the present invention is to provide a thickness measuring device etc. that can continue to measure the thickness of an object even if the temperature of the object varies. [Means for solving the problem]

[0006] A thickness measurement device for continuously measuring the thickness of an object provided by a first aspect of the present invention includes an excitation unit for inducing an eddy current in the object via an excitation coil, a detection unit for detecting the eddy current in the object via a detection sensor, a temperature acquisition unit for acquiring the temperature of the object, a correction unit for correcting the duration of the eddy current detected by the detection unit using an approximation formula showing the relationship of the duration to the temperature and the temperature acquired by the temperature acquisition unit, a thickness derivation unit for determining the thickness of the object based on the duration corrected by the correction unit (hereinafter referred to as the corrected duration), an approximation unit for determining the approximation formula based on reference data including a plurality of eddy currents at different temperatures of the object, and a storage unit for cumulatively storing measurement data including the duration of the eddy current detected by the detection unit and the temperature acquired at the time of detection of an overcurrent when the thickness derivation unit starts deriving the thickness. When a reacquisition condition regarding the temperature fluctuation of the object is satisfied, the approximation unit re-determines the approximation formula based on the duration and temperature included in the measurement data excluding the measurement data that satisfies the exclusion condition from among the measurement data.

[0007] The device may further include a first judgment unit that judges whether a corrected duration of the duration of the detected eddy current is an outlier, and a second judgment unit that judges whether the temperature acquired at the time of detecting an overcurrent has changed by a predetermined value or more from a reference temperature, wherein the measurement data in the memory unit includes the corrected duration, the outlier, and the judgment result of the change amount, and the first judgment unit judges whether the corrected duration of the duration of the detected eddy current is an outlier based on the corrected duration included in the measurement data that does not correspond to an outlier, and the re-acquisition condition may include that the judgment result that is an outlier and has a change amount greater than or equal to a predetermined value continues for a predetermined period of time.

[0008] The exclusion condition may include that the determined result is an outlier and the amount of change is not equal to or greater than a predetermined value.

[0009] When the re-acquisition condition is satisfied, the approximation unit may re-obtain the approximation formula by recalculating the coefficients included in the approximation formula.

[0010] A thickness measurement method for continuously measuring the thickness of an object using a thickness measurement device, as provided by a second aspect of the present invention, includes inducing an eddy current in the object via an excitation coil, detecting the eddy current in the object via a detection sensor, acquiring the temperature of the object, correcting the duration of the eddy current detected by the detection unit using an approximation formula indicating the relationship between the duration and the temperature and the temperature acquired by the temperature acquisition unit, determining the thickness of the object based on the duration corrected by the correction unit, determining the approximation formula based on reference data including a plurality of eddy currents at different temperatures of the object, and, when the thickness derivation unit starts deriving the thickness, cumulatively storing measurement data including the duration of the eddy current detected by the detection unit and the temperature acquired at the time of detecting the duration. When a re-acquisition condition is satisfied, the approximation formula is determined again based on measurement data excluding measurement data that satisfies the exclusion condition from among the measurement data. Effect of the Invention

[0011] According to this invention, when the reacquisition condition regarding the temperature change of the object is satisfied, the approximation equation following the temperature change of the object is calculated again. Then, the duration can be corrected using the approximation equation calculated again, so that the thickness measurement can be continued. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a thickness measurement device according to an embodiment of the present invention. [Diagram 2] 2 is a block diagram showing a configuration of a control system of a control unit of the processing apparatus according to the embodiment of the present invention. FIG. [Diagram 3] 2 is a block diagram showing a configuration of a control system of a control unit of a computing device according to an embodiment of the present invention. FIG. [Figure 4] 1 is a graph showing a change over time in a voltage signal V(t) corresponding to an eddy current. [Diagram 5] 4 is a flowchart of thickness measurement according to an embodiment of the present invention. [Figure 6] 11 is a flowchart of a data collection subroutine for collecting reference data according to an embodiment of the present invention. [Figure 7] 4 is a flowchart of an approximate expression generating subroutine according to the embodiment of the present invention. [Figure 8] 1 is a graph showing duration deviation Δτ and temperature deviation ΔT. [Figure 9] 13 is a graph showing another example of the duration deviation Δτ and the temperature deviation ΔT. [Figure 10] 5 is a flowchart of a subroutine of a first determination process according to the embodiment of the present invention. [Figure 11] 10 is a flowchart of a subroutine of a second determination process according to the embodiment of the present invention. [Figure 12] 11 is a flowchart of an approximate expression re-creation subroutine according to the embodiment of the present invention. [Figure 13] 1 is a graph showing a change in plate thickness ratio over time and a graph showing a change in temperature of an object over time. [Figure 14] 13 is a graph showing a change in thickness ratio over time using the re-obtained approximation equation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A thickness measuring device (thickness measuring method) according to an embodiment of the present invention will be described with reference to the drawings.

[0014] 1 is a block diagram of a thickness measurement device 100. The thickness measurement device 100 measures the thickness of an object (a portion to be measured) 9 by pulsed eddy current testing (PEC). The thickness measurement device 100 includes a processing device 7 that controls a probe 1 and a calculation device 8 that determines the thickness of the object 9. For example, the object 9 is a metal pipe through which steam, drain, petroleum refinery products, or the like flows. The pipe is formed in a circular tube shape.

[0015] The probe 1 is used to generate an eddy current in the object 9 and to detect the generated eddy current. The probe 1 is a non-contact type probe and is placed close to the object 9. Note that the term "non-contact type" means that it can be used without contact, and does not exclude use in a contact state. The probe 1 is placed so as to face the surface of the object 9. For example, the probe 1 is placed on the object 9 via a spacer (not shown) having thermal insulation properties.

[0016] The probe 1 generates eddy currents in the object 9 by forming a varying magnetic field. The probe 1 also detects the changes in the eddy currents generated in the object 9 as induced voltages. Specifically, the probe 1 includes an excitation coil 11 that induces eddy currents in the object 9 with magnetic flux due to an excitation current, and a detection coil 12 that detects the eddy currents in the object 9. The probe 1 induces eddy currents in the object 9 with the excitation coil 11, and detects the induced eddy currents with the detection coil 12.

[0017] In addition, the probe 1 further includes a temperature sensor 15 that detects the temperature of the object 9, and detects the temperature of the object 9 by the temperature sensor 15. Furthermore, the probe 1 may further include a casing that houses the excitation coil 11, the detection coil 12, and the temperature sensor 15. The detection coil 12 is an example of a detection sensor.

[0018] In the example of Fig. 1, the excitation coil 11 and the detection coil 12 are arranged so that the axis of the excitation coil 11 and the axis of the detection coil 12 are aligned in a straight line. In this case, the detection coil 12 is arranged closer to the object 9. The probe 1 may have multiple pairs of the excitation coil 11 and the detection coil 12. In Fig. 1, the probe 1 has two pairs of the excitation coil 11 and the detection coil 12.

[0019] Furthermore, the probe 1 may include a core 13 inserted into the excitation coil 11 and the detection coil 12. The core 13 is generally U-shaped as a whole. More specifically, the core 13 is formed by stacking a plurality of generally U-shaped thin plates made of permalloy. A straight portion at one end of the core 13 is inserted into one set of the excitation coil 11 and the detection coil 12. A straight portion at the other end of the core 13 is inserted into the other set of the excitation coil 11 and the detection coil 12. The core 13 magnetically connects the two sets of the excitation coil 11 and the detection coil 12.

[0020] When a current is applied to the excitation coil 11, the excitation coil 11 forms a magnetic field in the direction of its axis. A current is applied to one excitation coil 11 and the other excitation coil 11 so that they form magnetic fields in opposite directions in the direction of the axis. As a result, a magnetic field is formed in the core 13 along the longitudinal direction of the core 13. That is, when one end of the core 13 is an N pole, the other end of the core 13 is an S pole. Conversely, when one end of the core 13 is an S pole, the other end of the core 13 is an N pole. For example, a magnetic flux is generated from one excitation coil 11 toward the object 9, and a magnetic flux is generated from the object 9 toward the other excitation coil 11. In detail, most of the magnetic flux generated from one excitation coil 11 exits in the direction of the axis of one excitation coil 11, enters the object 9, passes through the object 9 in an approximately arc shape, and enters the other excitation coil 11 toward the axis of the other excitation coil 11. By varying the current applied to the excitation coil 11, the magnetic field generated in the target 9 varies, and an eddy current is generated in the target 9.

[0021] Meanwhile, a magnetic flux penetrating the detection coil 12 is formed by eddy currents generated in a portion of the object 9 near the detection coil 12. When the magnetic flux penetrating the detection coil 12 changes, an induced electromotive force is generated in the detection coil 12. The detection coil 12 detects the eddy current in the object 9 by detecting this induced electromotive force. In other words, detecting an induced electromotive force by the detection coil 12 is also called detecting an eddy current.

[0022] The temperature sensor 15 is, for example, a thermocouple.

[0023] The processing device 7 uses the probe 1 to generate an eddy current in the object 9, detects the generated eddy current, and acquires the temperature of the object 9 at that time. The calculation device 8 calculates the thickness of the object 9 based on the duration of the eddy current detected by the processing device 7 (the time until the eddy current rapidly decays, which will be described in detail later). In addition, the calculation device 8 corrects the duration used in calculating the thickness of the object 9 based on the temperature of the object 9.

[0024] The processing device 7 has a transmitting unit 71, a receiving unit 72, a temperature measuring unit 73, a communication unit 74, a control unit 75, and a memory unit 76.

[0025] The transmitter 71 applies a pulsed excitation current to the excitation coil 11. The transmitter 71 has a pulse generator 71a and a transmission amplifier 71b. The pulse generator 71a generates a pulse signal based on a command from the control unit 75. The transmission amplifier 71b amplifies the pulse signal from the pulse generator 71a and outputs it to the excitation coil 11 as an excitation current.

[0026] The receiver 72 receives the induced electromotive force generated in the detection coil 12 in response to the eddy current in the target object 9. The receiver 72 has at least a receiving amplifier 72a which receives the voltage generated in the detection coil 12 and amplifies the voltage. The receiver 72 may further have a filter which applies filtering to the voltage signal.

[0027] The output of the temperature sensor 15 is input to the temperature measuring unit 73. The temperature measuring unit 73 may have a receiving amplifier that receives the detection signal of the temperature sensor 15 and amplifies the detection signal.

[0028] The communication unit 74 performs wireless communication with an external device. For example, the communication unit 74 transmits the voltage signal (i.e., the detection signal) detected by the receiving unit 72 and the detection signal detected by the temperature measuring unit 73 to the arithmetic device 8.

[0029] The control unit 75 controls the entire processing device 7. The control unit 75 performs various types of arithmetic processing. For example, the control unit 75 is formed of a processor such as a CPU (Central Processing Unit). The control unit 75 may be formed of an MCU (Micro Controller Unit), an MPU (Micro Processor Unit), an FPGA (Field Programmable Gate Array), a PLC (Programmable Logic Controller), a system LSI, or the like.

[0030] For example, the control unit 75 causes the transmission unit 71 to output an excitation current for only a predetermined period, while acquiring a detection signal via the reception unit 72 after the output of the excitation current is stopped. The control unit 75 also acquires a detection signal from the temperature measurement unit 73 at the same time that the control unit 75 acquires the detection signal from the reception unit 72. The control unit 75 stores the detection signals from the reception unit 72 and the temperature measurement unit 73 in the memory unit 76, and transmits the detection signal stored in the memory unit 76 to the calculation device 8 via the communication unit 74 as appropriate.

[0031] The storage unit 76 stores various data and programs executed by the control unit 75. For example, a control program is stored in the storage unit 76. The storage unit 76 is formed of a non-volatile memory, a hard disc drive (HDD), a solid state drive (SSD), or the like.

[0032] 2 is a block diagram showing the configuration of a control system of the control unit 75 of the processing device 7. The control unit 75 realizes various functions by reading out a control program from the storage unit 76 into a memory and developing the program. Specifically, the control unit 75 functions as an excitation unit 77 that induces an eddy current in the object 9 via the excitation coil 11, a detection unit 78 that detects the eddy current in the object 9 via the detection coil 12, a temperature acquisition unit 79 that acquires the temperature of the object 9, and a data collection unit 710 that collects reference data for correcting the duration.

[0033] The exciting unit 77 causes the transmitting unit 71 to apply an exciting current to the exciting coil 11. Specifically, the exciting unit 77 outputs a command to the pulse generator 71a to cause the pulse generator 71a to generate a pulse signal. As a result, the exciting current is applied to the exciting coil 11 from the transmitting amplifier 71b.

[0034] The detection unit 78 detects a voltage signal corresponding to the eddy current as the eddy current of the object 9. Specifically, the detection unit 78 detects a voltage signal corresponding to the induced electromotive force of the detection coil 12. More specifically, the detection unit 78 continues to detect the voltage signal for a predetermined period after the application of the excitation current to the excitation coil 11 is stopped. That is, the detection unit 78 detects a time-based change (i.e., a transient change) of the eddy current of the object 9 after the application of the excitation current to the excitation coil 11 is stopped. The detection unit 78 stores the detected eddy current, i.e., the voltage signal, in the storage unit 76. Hereinafter, for convenience of explanation, the voltage signal detected by the detection unit 78 may be simply referred to as the "eddy current". For example, the voltage signal corresponding to the eddy current stored in the storage unit 76 is also simply referred to as the "eddy current".

[0035] The temperature acquisition unit 79 acquires the temperature of the object 9 via the temperature sensor 15 when the detection unit 78 acquires (detects) a voltage signal. The temperature acquisition unit 79 stores the temperature of the object 9 in the storage unit .

[0036] In the storage unit 76, the eddy current detected by the detection unit 78 and the temperature of the object 9 acquired by the temperature acquisition unit 79 when the eddy current was detected are stored in association with each other. That is, the storage unit 76 stores the detection date and time (measurement date and time), the eddy current, and the temperature as one combination.

[0037] The data collection unit 710 acquires measurement data for thickness measurement and reference data for correction. In either case of measurement data or reference data, the data collection unit 710 acquires combination data of eddy current and temperature by performing excitation by the excitation unit 77, detection of eddy current by the detection unit 78, and acquisition of temperature by the temperature acquisition unit 79. The data collection unit 710 stores the acquired eddy current and temperature in the memory unit 76. When acquiring measurement data, the data collection unit 710 acquires combination data of eddy current and temperature at each predetermined measurement period.

[0038] When acquiring reference data, the data collection unit 710 collects multiple sets of eddy currents and temperatures during a predetermined collection period before correcting the duration of the eddy currents. Specifically, the data collection unit 710 collects multiple sets of eddy currents and temperatures as reference data by performing excitation by the excitation unit 77, detection of eddy currents by the detection unit 78, and acquisition of temperature by the temperature acquisition unit 79 multiple times. The collection period is a period during which changes in the thickness of the object 9 can be ignored, and varies depending on the physical properties and usage conditions of the object 9. As a result, the data collection unit 710 collects multiple eddy currents with different temperatures of the object 9. The multiple eddy currents are hardly affected by changes in the thickness of the object 9. The difference between the multiple collected eddy currents mainly depends on the temperature of the object 9.

[0039] The arithmetic device 8 is formed of a computer or a computer network (so-called cloud). The arithmetic device 8 includes a communication unit 81, a control unit 82, and a storage unit 83.

[0040] The control unit 82 controls the entire arithmetic device 8. The control unit 82 performs various arithmetic processing. For example, the control unit 82 is formed of a processor such as a CPU (Central Processing Unit). The control unit 82 may be formed of an MCU (Micro Controller Unit), an MPU (Micro Processor Unit), an FPGA (Field Programmable Gate Array), a PLC (Programmable Logic Controller), a system LSI, or the like.

[0041] The storage unit 83 stores programs and various data executed by the control unit 82. For example, the storage unit 83 stores a control program. The storage unit 83 is formed of a non-volatile memory, a hard disk drive (HDD), a solid state drive (SSD), or the like. The storage unit 83 also stores signals and the like transmitted from the processing device 7. Specifically, the storage unit 83 stores the eddy current and temperature of the object 9 acquired by the processing device 7. The storage unit 83 also stores the duration of the overcurrent, the corrected duration (hereinafter referred to as the corrected duration), the judgment result, the thickness of the object, and the like in addition to the eddy current and temperature of the object 9. Specifically, the eddy current and temperature of the object 9, the detected duration, the corrected duration, the judgment result, and the thickness of the object are stored as a set of measurement data in association with the detection date and time (measurement date and time). The measurement data for each measurement period is cumulatively stored in the storage unit 83. The determination results include the determination result of an outlier of the correction duration and the determination result of the amount of change in temperature, which will be described later.

[0042] 3 is a block diagram showing the configuration of a control system of the control unit 82 of the calculation device 8. The control unit 82 realizes various functions by reading out a control program from the storage unit 83 into a memory and developing the program. Specifically, the control unit 82 functions as a thickness derivation unit 84, an approximation unit 85, a correction unit 86, a first determination unit 87, and a second determination unit 88.

[0043] The thickness derivation unit 84 determines the thickness of the object 9 based on the duration of the eddy current in the object 9. As will be described in more detail, the eddy current induced in the object 9 by the excitation coil 11 permeates from the front surface of the object 9 (the surface facing the probe 1) to the back surface, and rapidly attenuates when it reaches the back surface. The duration of the eddy current in the object 9 is the time from when the eddy current is induced in the object 9 to when it rapidly attenuates. The duration of the eddy current in the object 9 is correlated with the thickness of the object 9.

[0044] The thickness derivation unit 84 determines the duration of the eddy current (specifically, a voltage signal) detected by the processing device 7. The thickness derivation unit 84 determines the thickness of the object 9 from the duration based on the correlation between the duration and the thickness.

[0045] The approximation unit 85 obtains an approximation equation indicating the relationship between the duration and the temperature of the target object 9, based on the reference data. The approximation unit 85 obtains the duration of each eddy current from the reference data stored in the storage unit 83. The approximation unit 85 obtains the approximation equation based on multiple sets of duration and temperature.

[0046] Furthermore, when the reacquisition condition regarding the temperature fluctuation of the object is satisfied, the approximation unit 85 re-obtains (re-calculates) the above approximation formula. The approximation unit 85 re-obtains the approximation formula based on the duration and temperature contained in the measurement data excluding the measurement data satisfying the exclusion condition from the measurement data stored in the storage unit 83. Details will be described later.

[0047] The correction unit 86 corrects the duration used in deriving the thickness by the above-mentioned thickness derivation unit 84, using the approximation formula and the temperature of the object 9. That is, measurement data including the eddy current of the object 9 and the temperature of the object 9 when the eddy current is detected is stored in the memory unit 83. The thickness derivation unit 84 obtains the duration from the eddy current stored in the memory unit 83. The correction unit 86 corrects the obtained duration based on the approximation formula and the temperature of the object 9. The thickness derivation unit 84 obtains the thickness of the object 9 based on the corrected duration.

[0048] Next, the relationship between eddy currents and the thickness of the object 9 will be described in detail. Fig. 4 is a graph showing the change over time of a voltage signal V(t) corresponding to an eddy current. The graph in Fig. 4 is a double logarithmic graph. In Fig. 4, a voltage signal V0(t) is a voltage signal of an object 9 having a thickness d0, and a voltage signal V1(t) is a voltage signal of an object 9 having a thickness d1 that is thinner than the thickness d0.

[0049] The eddy current attenuates as it penetrates into the object 9. The eddy current gradually attenuates from the front surface of the object 9 (the surface facing the probe 1) until it reaches the back surface, and then rapidly attenuates when it reaches the back surface. The voltage signal V(t) also shows a change similar to that of the eddy current. In other words, the transient change of the voltage signal V(t) corresponds to the transient change of the eddy current. The change in the voltage signal V(t) until the eddy current reaches the back surface of the object 9 is represented linearly on a double logarithmic graph. Thereafter, the voltage signal V(t) rapidly attenuates. The voltage signal V(t) that changes in this way is expressed by the following equation (1).

[0050]

number

[0051] As can be seen from equation (1), the voltage signal V(t) gradually attenuates but continues until time τ, at which point it rapidly attenuates. For ease of explanation, τ is referred to as the "duration". The duration τ is expressed by the following equation (2).

[0052] τ=σμd 2 (2) where σ is the electrical conductivity of the object 9 , μ is the magnetic permeability of the object 9 , and d is the thickness of the object 9 .

[0053] That is, the duration τ changes depending on the thickness d of the object 9. Assuming that the electrical conductivity σ and magnetic permeability μ of the object 9 are constant, the duration τ changes depending on the thickness d of the object 9. Furthermore, even if the duration τ and the thickness d change, τ / d2 remains constant. Therefore, if the duration τ0 for a known thickness d0 and the duration τx for an unknown thickness dx are known, the unknown thickness dx can be calculated based on the following formula (3).

[0054]

number

[0055] However, the electrical conductivity σ and magnetic permeability μ of the actual object 9 have temperature dependence. Therefore, the duration τ also has temperature dependence. For example, in the case of carbon steel, the electrical conductivity σ generally has a negative temperature characteristic, and the magnetic permeability μ generally has a positive temperature characteristic. For example, taking into account the temperature dependence of the electrical conductivity σ and the magnetic permeability μ, the duration τ can be expressed as in the following formula (4).

[0056]

number

[0057] By correcting the duration τ so that it corresponds to the first-order term of T and the second-order term of T in equation (4), a corrected duration τ′ according to the temperature of the object 9 can be obtained.

[0058] Next, the first judgment unit 87 judges whether or not the corrected duration is an outlier. The first judgment unit 87 judges whether or not the obtained corrected duration to be judged is an outlier, based on the corrected duration that does not correspond to an outlier among the corrected durations included in the measurement data stored in the memory unit 83. Specifically, when the following outlier judgment conditions (A1) and (A2) are met, the corrected duration to be judged is an outlier.

[0059] (A1) The corrected duration of the measurement data from the previous day (excluding outliers) is outside the range of ±2% from the average value. (A2) The corrected duration of the measurement data for the most recent five days (excluding outliers) is outside the range of ±3 standard deviations from the average value.

[0060] The standard deviation of the judgment condition (A2) is the standard deviation of the corrected duration (excluding outliers) of the measurement data for the most recent five days. The first judgment unit 87 stores the judgment result in the memory unit 83 in association with the measurement data of the corresponding corrected duration. For the corrected duration judged to be an outlier, the thickness of the object 9 is not calculated. The past periods of the measurement data, such as the above-mentioned previous day and the most recent five days, are examples, and any period may be set. Incidentally, outliers may be judged based on conditions other than the above-mentioned judgment conditions. Furthermore, the judgment condition may be either a single condition (for example, the above-mentioned condition (A2)) or a plurality of conditions.

[0061] When the corrected duration of the eddy current is an outlier, the second judgment unit 88 judges whether or not the temperature acquired at the time of detecting the duration has a change (difference) of a predetermined value or more (for example, 50°C) with respect to the reference temperature Tr. The reference temperature Tr is calculated by the approximation unit 85, which will be described later. The second judgment unit 88 stores the judgment result in the memory unit 83 in association with the measurement data of the corresponding corrected duration. Note that the second judgment unit 88 executes judgment when the corrected duration of the eddy current is an outlier, but is not limited to this. For example, the second judgment unit 88 may execute judgment together with the judgment by the first judgment unit 88 every time an overcurrent is detected. Note that the results of judgment by the first judgment unit 87 and the second judgment unit 88 are referred to in judging whether the reacquisition condition is satisfied in order to obtain the above-mentioned approximation formula again.

[0062] As described above, the reacquisition condition is a condition related to the temperature change of the object. Specifically, the reacquisition condition is that the corrected duration of the eddy current duration is an outlier, and the determination result that the temperature at the time of detection of the eddy current has a change amount of a predetermined value or more from the reference temperature continues for a predetermined period. That is, the reacquisition condition determines that the corrected duration has become an outlier due to a temperature change and continues for a predetermined period. The predetermined period is, for example, three days. Therefore, if the predetermined period does not continue, the temperature change is considered to be temporary and recalculation of the approximation formula is not performed. Note that conditions other than the above-mentioned reacquisition condition may be used. Also, the reacquisition condition may be either a single condition or a plurality of conditions.

[0063] As described above, in the thickness measurement device 100, the approximation unit 85 obtains an approximation equation showing the relationship of the duration to the temperature of the object 9, and the correction unit 86 corrects the duration τ using the approximation equation. Then, the thickness derivation unit 84 obtains the thickness of the object 9 based on the corrected duration τ'. Furthermore, when the reacquisition condition is satisfied, the approximation unit 85 obtains the approximation equation again based on the reacquisition condition. Then, correction is performed using the reacquisition of the approximation equation. Such thickness measurement will be described in more detail using a flowchart. FIG. 5 is a flowchart of thickness measurement.

[0064] First, in step S101, as a preparation stage for thickness measurement, the processing device 7 collects reference data. For example, the processing device 7 receives an external command and executes collection of reference data. Specifically, after the probe 1 has been installed on the object 9 and before the thickness measurement of the object 9 is started, the user operates the arithmetic device 8 to input execution of collection of reference data. The processing device 7 receives the collection command via the arithmetic device 8 and starts collection of the reference data. The user may directly input execution of collection to the processing device 7 by operating the processing device 7.

[0065] Collection of reference data is performed according to the flowchart of FIG. 6. FIG. 6 is a flowchart of a data collection subroutine for collecting reference data. In step S201, the processing device 7 determines whether a collection period has arrived. The collection period is a period during which eddy current detection and the like are repeatedly performed. The collection period is longer than the measurement period during which measurement data is obtained. If the collection period has not arrived, the processing device 7 repeats the determination of step S201 and waits for the arrival of the collection period.

[0066] When the collection period arrives, the processing device 7 determines in step S202 whether or not the current time is within a predetermined collection period. Specifically, the processing device 7 determines whether or not the collection period has elapsed since the start of collection of the reference data. The collection period is a period longer than the collection period.

[0067] If it is within the collection period, the processing device 7 acquires a set of reference data. Specifically, in step S203, the excitation unit 77 applies an excitation current to the excitation coil 11 to excite it. The excitation coil 11 forms a magnetic field in the axial direction by applying the excitation current. One excitation coil 11 and the other excitation coil 11 form magnetic fields in opposite directions in the axial direction. For example, a magnetic flux is generated from one excitation coil 11 toward the object 9, and a magnetic flux is generated from the object 9 toward the other excitation coil 11.

[0068] Next, in step S204, the excitation unit 77 stops outputting the excitation current, and the detection unit 78 detects the eddy current generated in the object 9. The detection unit 78 continues detecting the voltage signal for a predetermined period of time. In this way, the detection unit 78 detects the transient change (change over time) of the induced electromotive force of the detection coil 12, i.e., the transient change of the eddy current generated in the object 9.

[0069] Furthermore, in step S205, the temperature acquisition unit 79 acquires the temperature of the target object 9. The processing device 7 stores the set of eddy currents and temperatures in the storage unit 76. This completes the acquisition of the set of reference data.

[0070] After that, the processing device 7 returns to step S201 to determine whether the next collection period has arrived. When the next collection period arrives, if it is within the collection period, another set of reference data is acquired. That is, the processing device 7 acquires one set of reference data for each collection period until the collection period ends.

[0071] If the collection period has ended in step S202, the processing device 7 transmits the reference data stored in the memory unit 76, i.e., the multiple sets of eddy currents and temperatures, to the calculation device 8. This ends collection of reference data by the processing device 7. The calculation device 8 stores the received reference data in the memory unit 83. Note that the processing device 7 may be configured to transmit the reference data stored in the memory unit 76 to the calculation device 8 during the collection period. In this case, if data transmission cannot be completed due to wireless conditions, the reference data stored in the memory unit 76 may be retransmitted at a timing when communication is possible.

[0072] Next, in step S102 of the thickness measurement flowchart, the arithmetic device 8 creates an approximation equation. The creation of the approximation equation is executed according to the flowchart of Fig. 7. Fig. 7 is a flowchart of a subroutine for creating the approximation equation.

[0073] First, in step S301, the approximation unit 85 obtains the duration of each eddy current from the reference data stored in the storage unit 83. That is, the approximation unit 85 creates multiple sets of data of duration and temperature from multiple sets of reference data of eddy current and temperature.

[0074] Next, in step S302, the approximation unit 85 creates an approximation equation from a plurality of pairs of duration and temperature. The approximation equation created in step S302 is a provisional approximation equation.

[0075] For example, the approximation unit 85 obtains a reference duration τr and a reference temperature Tr from a plurality of sets of durations and temperatures. The approximation unit 85 sets the average value of the plurality of durations as the reference duration τr, and sets the average value of the plurality of temperatures as the reference temperature Tr. Alternatively, the approximation unit 85 may set the duration closest to the average value of the plurality of durations and the temperature at that time as the reference duration τr and the reference temperature Tr, respectively. Alternatively, the approximation unit 85 may set the temperature closest to the average value of the plurality of temperatures and the duration at that time as the reference temperature Tr and the reference duration τr, respectively. Alternatively, the approximation unit 85 may set the duration detected earliest among the plurality of sets of durations and temperatures and the temperature at that time as the reference duration τr and the reference temperature Tr, respectively.

[0076] The approximation unit 85 obtains the duration deviation Δτ (= τ - τr) and temperature deviation ΔT (= T - Tr) which are deviations from the reference duration τr and reference temperature Tr, from multiple sets of duration and temperature. For example, Fig. 8 is a graph showing the obtained duration deviation Δτ and temperature deviation ΔT. Each point in the graph represents one set of duration deviation Δτ and temperature deviation ΔT.

[0077] The approximation unit 85 obtains an approximation equation from a plurality of sets of duration deviation Δτ and temperature deviation ΔT by the least squares method. That is, the approximation unit 85 obtains an approximation equation showing the relationship of the duration deviation Δτ to the temperature deviation ΔT as an approximation equation showing the relationship of the duration to the temperature of the object 9. At this time, the conditions for obtaining the approximation equation are set. First, the approximation unit 85 sets the conditions for obtaining the approximation equation to a quadratic function as shown in equation (5) to obtain the approximation equation. In the example of FIG. 8, an approximation equation of a quadratic function as shown by a solid line is obtained.

[0078]

number

[0079] Next, in step S303, the approximation unit 85 determines whether the coefficient γ1 of the quadratic term of the obtained approximation formula is positive. In the example of Fig. 8, the coefficient γ1 of the quadratic term is positive. If the coefficient γ1 of the quadratic term is positive, the approximation unit 85 sets the obtained approximation formula as a definite approximation formula and ends the creation of the approximation formula.

[0080] FIG. 9 is a graph showing another example of the duration deviation Δτ and the temperature deviation ΔT. The solid line in the figure is a curve corresponding to the approximation formula of the quadratic function. In the example of FIG. 9, the coefficient γ1 of the quadratic term is negative. When the coefficient γ1 of the quadratic term is negative, the approximation unit 85 changes the condition for obtaining the approximation formula to a linear function as shown in equation (6) in step S304, and obtains the approximation formula again. In the example of FIG. 9, an approximation formula of a linear function as shown by the two-dot chain line is obtained. The approximation unit 85 regards the obtained approximation formula as a definite approximation formula, and ends the creation of the approximation formula.

[0081]

number

[0082] When the creation of the approximation formula is completed, the thickness measurement is started. For example, the thickness derivation unit 84 judges whether or not a predetermined measurement period has arrived in step S103 of the thickness measurement flow chart. The measurement period is a period for obtaining the thickness measurement of the object 9. If the measurement period has not arrived, the thickness derivation unit 84 repeats the judgment of step S103 and waits for the measurement period to arrive.

[0083] When the measurement period arrives, the thickness derivation unit 84 outputs a command to the processing device 7 to cause the processing device 7 to acquire measurement data. The measurement data is eddy current and temperature for measuring the thickness of the object 9. Specifically, when the processing device 7 receives a command from the calculation device 8, the excitation unit 77 applies an excitation current to the excitation coil 11 to excite it in step S104. Then, in step S105, the detection unit 78 detects the eddy current generated in the object 9. Furthermore, in step S106, the temperature acquisition unit 79 acquires the temperature of the object 9. The processing device 7 transmits a set of eddy current and temperature as measurement data together with the detection date and time to the calculation device 8. The calculation device 8 stores the received set of detection date and time, eddy current, and temperature in the memory unit 83 as measurement data.

[0084] Next, in step S107, the thickness derivation unit 84 obtains the duration τx of the eddy current from the measurement data stored in the storage unit 83. That is, the thickness derivation unit 84 obtains the duration τx of the overcurrent detected in step S105. Furthermore, the calculation device 8 stores the duration τx of the eddy current in the storage unit 83 by including it in the measurement data including the corresponding eddy current and temperature.

[0085] Thereafter, in step S108, the correction unit 86 corrects the duration τx calculated in step S107 using the approximation formula and the temperature of the corresponding measurement data. Specifically, the correction unit 86 calculates a temperature deviation ΔT (=Tx-Tr) which is the deviation between a reference temperature Tr and a temperature Tx of the measurement data. The correction unit 86 substitutes the calculated temperature deviation ΔT into the approximation formula to calculate a duration deviation Δτ. The correction unit 86 corrects the duration τx with the calculated duration deviation Δτ to calculate a corrected duration τx' (=τx+Δτ). The calculation device 8 also stores the corrected duration τx' in the memory unit 83 by including it in the measurement data including the corresponding eddy current and temperature.

[0086] Next, in step S109, the first judgment unit 87 executes a first judgment process to judge whether the correction duration τx' to be judged obtained in step S108 is an outlier or not. The first judgment process is executed according to the flowchart of Fig. 10. Fig. 10 is a flowchart of a subroutine that executes the first judgment process.

[0087] In step S401, the first judgment unit 87 refers to the measurement data in the memory unit 83 and derives the average value of the corrected durations derived during the previous day. The corrected duration τx' to be judged is not included in the derivation of the average value. Furthermore, among the corrected durations derived during the previous day, any corrected durations that are recognized as outliers are excluded. The previous day refers to the day before the day of detection of an overcurrent in the corrected duration τx' to be judged. Alternatively, the previous day may be any period up to 24 hours before the detection of an overcurrent in the corrected duration τx' to be judged.

[0088] Next, in step S402, the first judgment unit 87 judges whether or not the corrected duration τx' to be judged is outside the range of ±2% of the average value of the corrected duration. That is, it is judged whether or not the above-mentioned judgment condition (A1) is satisfied. If it is not outside the range, the first judgment unit 87 determines in step S403 that the corrected duration τx' to be judged is a normal value. The calculation device 8 stores the judgment result that the corrected duration τx' is a normal value in the memory unit 83, together with the measurement data including the corresponding eddy current and temperature.

[0089] On the other hand, if it is outside the above range, the first judgment unit 87, in step S404, refers to the measurement data in the memory unit 83, and derives the standard deviation and average value of the corrected duration derived for the most recent five days. The corrected duration τx' to be judged is not included in the derivation of the standard deviation, etc. The most recent five days means the most recent five days including the day on which the overcurrent of the corrected duration τx' to be judged was detected. Alternatively, it may be the most recent five days excluding the day on which the overcurrent of the corrected duration τx' to be judged was detected. Furthermore, the most recent five days may be the period from the time of the detection of the overcurrent of the corrected duration τx' to be judged up to 120 hours (24 hours x 5) before.

[0090] Next, in step S405, the first judgment unit 87 judges whether the correction duration τx' to be judged is outside the range of ±3 standard deviations from the average value of the correction duration. That is, it is judged whether the above-mentioned judgment condition (A2) is satisfied. If it is not outside the range, the first judgment unit 87 determines in step S403 that the correction duration τx' to be judged is a normal value. The calculation device 8 stores the judgment result that the correction duration τx' is a normal value in the memory unit 83, together with the measurement data including the corresponding eddy current and temperature.

[0091] On the other hand, if it is outside the above range, the first judgment unit 87 determines in step S406 that the corrected duration τx' to be judged is an outlier. The calculation device 8 stores the judgment result that the corrected duration τx is an outlier in the storage unit 83 together with the measurement data including the corresponding eddy current and temperature. This ends the first judgment process by the first judgment unit 87.

[0092] Next, in step S110, the thickness derivation unit 84 judges whether or not the corrected duration τx' of the judgment target is an outlier. If the judgment result is a normal value that is not an outlier, the thickness derivation unit 84 obtains the thickness dx of the object 9 by substituting the corrected duration τx' for τx in formula (3) in step S111. In addition, the calculation device 8 stores the thickness dx of the object 9 in the storage unit 83 by including it in the measurement data including the corresponding eddy current and temperature. Thereafter, in step S112, the thickness derivation unit 84 judges whether or not to end the thickness measurement. For example, the thickness derivation unit 84 judges whether or not a command to end the thickness measurement has been input. For example, the user operates the calculation device 8 to input the end of the thickness measurement. If the command to end the thickness measurement has not been input, the thickness derivation unit 84 returns to step S103 and judges whether or not the next measurement period has arrived. When the next measurement period arrives, the measurement data is acquired again, and the thickness of the object 9 is obtained based on the measurement data. That is, the calculation device 8 repeats the acquisition of measurement data and the derivation of the thickness of the object 9 for each measurement period. Furthermore, if an end command is input in step S112, the thickness measurement is ended.

[0093] On the other hand, if the correction duration τx' of the object to be judged is an outlier in step S110, the second judgment unit 88 executes a second judgment process in step S113 to judge the amount of change in the temperature of the object to be judged acquired in step S106. The second judgment process is executed according to the flowchart of Fig. 11. Fig. 11 is a flowchart of a subroutine that executes the second judgment process.

[0094] In step S501, the second judging unit 88 judges whether or not the temperature to be judged has a change (difference) from the reference temperature Tr that is equal to or greater than a predetermined value (for example, 50° C.).

[0095] If the amount of change is not equal to or greater than the predetermined value, the second judgment unit 88 determines in step S502 that the amount of change of the temperature to be judged is not equal to or greater than the predetermined value with respect to the reference temperature Tr. Furthermore, the calculation device 8 stores in the storage unit 83 the judgment result that the amount of change of the temperature is not equal to or greater than the predetermined value together with the measurement data including the corresponding eddy current and temperature.

[0096] On the other hand, if the amount of change is equal to or greater than the predetermined value, the second judgment unit 88 determines in step S503 that the temperature to be judged has an amount of change equal to or greater than the predetermined value relative to the reference temperature Tr. The calculation device 8 also stores the judgment result that the amount of change in the temperature is equal to or greater than the predetermined value in the storage unit 83 together with the measurement data including the corresponding eddy current and temperature. This ends the second judgment process by the second judgment unit 88.

[0097] Next, in step S114, approximation unit 85 determines whether the determination result shows that the temperature to be determined has changed by a predetermined amount or more. If the determination result shows that the amount of change is not the predetermined amount or more, the process proceeds to step S112. On the other hand, if the determination result shows that the amount of change is the predetermined amount or more, approximation unit 85 determines in step S115 whether a re-acquisition condition is met. The re-acquisition condition is that the corrected duration of the eddy current is an outlier, and the determination result that the temperature at the time of detection of the eddy current has changed by a predetermined amount or more from the reference temperature continues for a predetermined period of time.

[0098] The specified period is, for example, three days. For example, the specified period of three days refers to the most recent three days including the date on which the most recent overcurrent was detected. Alternatively, the most recent three days may be the period from the most recent overcurrent detection up to 72 hours (24 hours x 3). If the measurement data for all of the most recent three days stored in the memory unit 83 includes a determination result in which the corrected duration of the eddy current is an outlier and the temperature at the time of detection of the eddy current has changed by a specified value or more from the reference temperature, the reacquisition condition is determined to be met.

[0099] If the re-acquisition condition is not satisfied, the process proceeds to step S112. On the other hand, if the re-acquisition condition is satisfied, the approximation unit 85 executes approximation equation re-creation in step S116. The approximation equation re-creation is executed according to the flowchart of Fig. 12. Fig. 12 is a flowchart of a subroutine that executes re-approximation equation creation.

[0100] In step S601, the approximation unit 85 acquires all sets of data of duration and temperature contained in the measurement data from the memory unit 83, excluding the measurement data that satisfies the exclusion condition. The exclusion condition is that the judgment result contained in the measurement data is that the corrected duration is an outlier and the temperature does not have a change amount of a predetermined value or more. In other words, even if the corrected duration is an outlier, if the temperature does not have a change amount of a predetermined value or more, it is excluded because it is not an outlier due to a temperature change. Note that the exclusion condition may be only a single condition or may include multiple conditions.

[0101] Next, in step S602, the approximation unit 85 derives each coefficient of the approximation formula. That is, in the approximation formula currently being used for correction, only the coefficients are recalculated using all sets of data of duration and temperature acquired in step S601. Note that the reference duration τr and the reference temperature Tr are not changed.

[0102] For example, when the quadratic function is the approximate expression, new coefficients of γ1′, γ2′, and γ3′ are derived. Specifically, the same process as in step S302 is performed. The approximation unit 85 obtains the duration deviation Δτ (=τ-τr) and temperature deviation ΔT (=T-Tr) which are deviations from the reference duration τr and reference temperature Tr from the duration and temperature of each set acquired in step S601. The approximation unit 85 obtains new γ1′, γ2′, and γ3′ (approximation expression) from the duration deviation Δτ and temperature deviation ΔT of each set by the least square method. Then, the approximation unit 85 sets the derived coefficients γ1′, γ2′, and γ3′ to the approximate expression. In this way, a new approximate expression is created. In addition, when the linear function is the approximate expression, new coefficients of δ1′ and δ2′ may be derived in the same way. In this way, the re-creation of the approximate expression by the approximation unit 85 is completed. Then, the process proceeds to step S112.

[0103] In this way, the thickness measurement device 100 generates an eddy current in the object 9, detects the generated eddy current, and measures the thickness of the object 9 based on the duration τ of the eddy current. Here, since the duration τ of the eddy current has temperature dependency, the thickness measurement device 100 corrects the duration τ with the temperature of the object 9 using an approximation formula that indicates the relationship of the duration to the temperature of the object 9. The thickness measurement device 100 obtains the approximation formula from multiple sets of reference data of duration and temperature. At that time, the thickness measurement device 100 can improve the accuracy of the approximation of the approximation formula to the reference data by switching the conditions for obtaining the approximation formula. The thickness measurement device 100 can improve the accuracy of the temperature correction of the duration τ by correcting the duration τ using the approximation formula created in this way, and can therefore obtain the thickness of the object 9 with high accuracy.

[0104] The relationship of the duration to the temperature varies depending on the object 9. For example, whether the duration increases or decreases depending on the temperature, and whether the change is quadratic or linear, etc., are determined depending on the object 9. In this example, the thickness measurement device 100 first sets the condition for obtaining the approximation formula to a quadratic function to obtain the approximation formula. If the coefficient of the quadratic term of the obtained approximation formula is positive, the approximation formula is adopted. If the coefficient of the quadratic term is negative, the approximation formula is changed to a linear function as a condition for obtaining the approximation formula. As a result, an approximation formula of a linear function is obtained. In this example, the change in the duration depending on the temperature of the object 9 is most suitable for a quadratic function with a positive coefficient of the quadratic term. Next, a linear function is more suitable for the change in the duration depending on the temperature of the object 9 than a quadratic function with a negative coefficient of the quadratic term. By obtaining the approximation formula under the above-mentioned conditions, an approximation formula that matches such a tendency can be obtained.

[0105] In addition, the correction using the approximation formula may not be able to follow the temperature change depending on the amount of temperature fluctuation after the approximation formula is created, but if the reacquisition condition is met, the approximation formula is obtained again. For example, Figs. 13(A) and (B) are examples in which the temperature change after the approximation formula is created for the first time cannot be followed, and the thickness is not calculated appropriately. The thickness measurement in Figs. 13(A) and (B) is an example in which the correction using the approximation formula of this embodiment is applied, but the recalculation of the approximation formula is not executed. Fig. 13(A) is a graph showing the transition of the plate thickness ratio of the object 9 (measured portion) according to the elapsed time (number of days) from the start of measurement. That is, it is a graph showing the transition of the plate thickness of the object 9 (measured portion) when the thickness (plate thickness) d0 at the start of measurement is set to 1. Fig. 13(B) is a graph showing the transition of the temperature of the object 9 (measured portion) according to the elapsed time (number of days) from the start of measurement. Figs. 13(A) and (B) are the same object 9.

[0106] As shown in FIG. 13(B), there is little temperature fluctuation from the start of measurement until around 290 days, and it can be seen that the plate thickness ratio in FIG. 13(A) gradually decreases. In other words, it can be seen that the thickness of the object 9 gradually decreases (becomes thinner) as the number of days elapses, and that this is progressing normally. However, with a change in the operating conditions, the temperature of the object 9 fluctuates from 20°C to 30°C after around 290 days. Due to this temperature change, the plate thickness ratio changes in the area surrounded by the dashed line in FIG. 13(A). The corrected duration of the area surrounded by the dashed line in FIG. 13(A) is determined to be an outlier.

[0107] Although such a temperature change may be temporary, there are cases where the temperature change of the object 9 continues for a long period of time. Therefore, in this embodiment, when the reacquisition condition is satisfied as a case where the temperature change of the object 9 continues for a long period of time, the approximation formula is calculated again based on the measurement data. Then, the thickness measurement of the object 9 is continued using the recalculated approximation formula. For example, for the object 9 shown in FIG. 13(A), the approximation formula is recalculated as in this embodiment, and the thickness is calculated again using the recalculated approximation formula for the part surrounded by the dashed line in FIG. 13(A). The range Q in FIG. 14 corresponds to the part where the thickness is calculated again using the recalculated approximation formula for the part surrounded by the dashed line in FIG. 13(A). It can be seen that the connection with the existing data is also good. Therefore, even if the temperature change cannot be followed, the thickness measurement can be continued using the recalculated approximation formula. However, the part surrounded by the dashed line in the range Q in FIG. 14 is a part in the process of a sudden temperature change, and even if the recalculated approximation formula is used, the correction duration is an outlier and is excluded.

[0108] Note that although the ratio of the vertical axis to the horizontal axis is different between Figure 13(A) and Figure 14, the plate thickness ratio from 0 to approximately 290 days after the start of testing (excluding range Q) in Figure 14 uses the original (initial) approximation formula and shows the same values ​​as Figure 13(A).

[0109] As described above, when the reacquisition condition regarding the temperature fluctuation of the object is satisfied, the thickness measurement device 100 re-obtains the approximation equation following the temperature fluctuation of the object. Then, the re-obtained approximation equation can be used to correct the duration, so that the thickness measurement can be continued.

[0110] Other Embodiments As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, replacements, additions, omissions, etc. are appropriately performed. In addition, it is also possible to combine the components described in the above embodiment to form a new embodiment. In addition, among the components described in the attached drawings and detailed description, not only components essential for solving the problem but also components that are not essential for solving the problem in order to exemplify the technology may be included. Therefore, the fact that these non-essential components are described in the attached drawings and detailed description should not immediately be taken to mean that these non-essential components are essential.

[0111] The above embodiment may be configured as follows.

[0112] For example, the configuration of the thickness measuring device 100 is merely an example. The processing device 7 and the arithmetic device 8 may be configured integrally. That is, one device may have the functions of the processing device 7 and the arithmetic device 8. The processing device 7 and the arithmetic device 8 may be connected by wire. A plurality of processing devices 7 may be connected to one arithmetic device 8. The arithmetic device 8 may transmit data related to the calculated thickness to another device connected wirelessly or by wire.

[0113] The probe 1 is not limited to the above-mentioned configuration. For example, the probe 1 includes two sets of the excitation coil 11 and the detection coil 12, but the excitation coil 11 and the detection coil 12 may be one set or three or more sets. The excitation coil 11 and the detection coil 12 do not have to be arranged so that their respective axial centers are aligned. When the excitation coil 11 and the detection coil 12 are arranged so that their respective axial centers are aligned, the excitation coil 11 may be arranged closer to the object 9 than the detection coil 12. Furthermore, the detection unit of the probe 1 is not limited to the detection coil 12. The detection unit may be anything that can directly or indirectly detect the eddy current of the object 9, and may be, for example, a Hall element. Furthermore, the probe 1 does not have to include the core 13.

[0114] The temperature sensor 15 is not limited to a thermocouple. Any temperature sensor capable of detecting the temperature of an object may be used, for example, a thermistor. The number of temperature sensors 15 is not limited to one, and may be multiple.

[0115] Furthermore, the thickness measurement by the thickness measurement device 100 is merely an example. There are various thickness measurement methods by PEC, so any measurement method can be adopted. In addition, the method of calculating the thickness of the object 9 taking into account the temperature of the object 9 is not limited to the above-mentioned method.

[0116] Also, the method of correcting the duration τ of the eddy current is merely one example. For example, the reference data does not have to be data acquired by the probe 1 and object 9 that perform the actual thickness measurement. In other words, the reference data may be acquired by using a probe 1 and object 9 that are the same type as the probe 1 and object 9 that perform the thickness measurement but are different. The calculation device 8 may receive reference data acquired separately from the probe 1 and object 9 that perform the thickness measurement from the outside and create an approximation equation using the reference data.

[0117] The method for finding an approximation equation from the reference data may be a method other than the least squares method. The conditions for finding an approximation equation are not limited to the above-mentioned conditions. The conditions for finding an approximation equation and the conditions for switching between these conditions (hereinafter referred to as "switching conditions") may be changed depending on the object 9. For example, the conditions for finding an approximation equation that are initially set need not be a quadratic function, and need not be a linear function. Alternatively, the conditions for finding an approximation equation may not only be a linear function, but may also be limited to the positive or negative slope.

[0118] As described above, the switching condition is not limited to the quadratic term of the quadratic function being negative. For example, when the first condition for obtaining an approximate equation is a linear function, the switching condition may be that the slope of the obtained linear function (i.e., the coefficient of the linear term) is positive. Alternatively, the switching condition may be that the sum of squares of the residual of the approximate equation is equal to or greater than a predetermined threshold value.

[0119] Alternatively, the thickness measurement device 100 may be configured so that the user can set the conditions for obtaining the approximation formula. For example, the thickness measurement device 100 may be configured so that the conditions for obtaining the approximation formula can be selected and set by the user, with a linear function, a quadratic function with a positive coefficient of the quadratic term, and a quadratic function with a negative coefficient of the quadratic term. In this case, the thickness measurement device 100 may be configured to first create a provisional approximation formula under provisional conditions, and then present the provisional approximation formula to the user and accept changes to the conditions from the user. Alternatively, the thickness measurement device 100 may create an approximation formula according to the conditions set by the user from the beginning.

[0120] Furthermore, the creation of the approximation formula is not limited to before starting the thickness measurement. For example, the approximation formula may be created before starting the thickness measurement, and the reference data may be recollected after the thickness measurement is started, and the approximation formula may be updated.

[0121] In the above embodiment, when the approximation formula is calculated again, the approximation formula calculated again is used for the duration of the overcurrent detected thereafter, but this is not particularly limited. For example, even for measurement data in which the corrected duration is determined to be an outlier and the temperature has a change amount of a predetermined value or more before the approximation formula is calculated again, the corrected duration and thickness may be re-derived using the approximation formula calculated again. Note that, for measurement data that was not an outlier before the approximation formula was calculated again, it is not necessary to re-derive the thickness using the approximation formula calculated again.

[0122] The flowchart is merely an example. Steps in the flowchart may be changed, replaced, added, omitted, etc. as appropriate. The order of steps in the flowchart may be changed, and serial processing may be performed in parallel. For example, in the thickness measurement flowchart (FIG. 5), the temperature acquisition in step S106 may be performed before or in parallel with the excitation in step S104 or the eddy current detection in step S105.

[0123] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general purpose processors, special purpose processors, integrated circuits, Application Specific Integrated Circuits (ASICs), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. Processors are considered processing circuits or circuits because they include transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or the processor. [Industrial Applicability]

[0124] INDUSTRIAL APPLICABILITY The present invention is useful in a thickness measuring device for measuring the thickness of an object, etc., for continuing thickness measurement even if there is a temperature fluctuation. [Explanation of symbols]

[0125] 100 Thickness measuring device 11 Excitation coil 12 Detection coil (detection sensor) 15 Temperature Sensor 7 Processing Equipment 77 Excitation section 78 Detection section 79 Temperature acquisition section 710 Data Collection Unit 8 Arithmetic unit 83 Storage section 84 Thickness Derivation Section 85 Approximation part 86 Correction section 87 First Judgment Department 88 Second judgment section 9. Objects

Claims

1. A thickness measurement device for continuously measuring the thickness of an object, comprising: an excitation unit that induces an eddy current in the target object via an excitation coil; a detection unit that detects the eddy current of the object via a detection sensor; A temperature acquisition unit that acquires a temperature of the object; a correction unit that corrects a duration of the eddy current detected by the detection unit using an approximation expression indicating a relationship of the duration with respect to the temperature and the temperature acquired by the temperature acquisition unit; a thickness deriving unit that determines a thickness of the object based on the duration corrected by the correction unit (hereinafter referred to as a corrected duration); an approximation unit that determines the approximate formula based on reference data including a plurality of the eddy currents at different temperatures of the object; a storage unit configured to cumulatively store measurement data including a duration of the eddy current detected by the detection unit and the temperature acquired at the time of detection of the overcurrent when the thickness derivation unit starts to derive the thickness; Equipped with when a re-acquisition condition regarding the temperature fluctuation of the object is satisfied, the approximation unit re-determines the approximation formula based on the duration and the temperature included in the measurement data excluding the measurement data satisfying the exclusion condition from the measurement data. Thickness measuring device.

2. a first determination unit that determines whether a corrected duration of the detected eddy current is an outlier; a second determination unit that determines whether the temperature acquired when the overcurrent is detected is changed by an amount equal to or greater than a predetermined value with respect to a reference temperature; Furthermore, The measurement data in the storage unit includes the corrected duration, the outlier, and the determination results of the amount of change, The first determination unit determines whether or not a corrected duration of the detected eddy current is an outlier based on a corrected duration that does not correspond to the outlier among the corrected durations included in the measurement data, and The reacquisition condition includes that the determination result that is the outlier and has the change amount equal to or greater than the predetermined value continues for a predetermined period of time.

2. The thickness measurement device of claim 1.

3. The exclusion condition includes that the determination result is an outlier and the change amount is not equal to or greater than the predetermined value.

3. The thickness measurement device of claim 2.

4. When the re-acquisition condition is satisfied, the approximation unit re-obtains the approximation formula by recalculating coefficients included in the approximation formula.

2. The thickness measurement device of claim 1.

5. A thickness measurement method for continuously measuring the thickness of an object using a thickness measurement device, comprising: Inducing eddy currents in a target object via an excitation coil; detecting the eddy current of the object via a detection sensor; acquiring a temperature of the object; correcting the duration of the eddy current detected by the detection unit using an approximation expression indicating a relationship of the duration with respect to the temperature and the temperature acquired by the temperature acquisition unit; determining a thickness of the object based on the duration corrected by the correction unit; determining the approximation formula based on reference data including a plurality of the eddy currents at different temperatures of the object; When the thickness derivation unit starts to derive the thickness, cumulatively storing measurement data including the duration of the eddy current detected by the detection unit and the temperature acquired at the time of detection of the duration; Including, When a re-acquisition condition is satisfied, the approximation formula is re-obtained based on the measurement data excluding the measurement data satisfying the exclusion condition from the measurement data. Thickness measurement method.

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