JP2017215173A - Thickness measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thickness measuring device that determines if failure has occurred at a detector on the basis of the value of a dosage measured by the detector.SOLUTION: A thickness measuring device 1 includes: a radiation source 10 for radiating radioactive rays to a measurement object 90; a plurality of detectors 20 arranged at a position facing the radiation source via the measurement object for detecting radioactive rays passing through the measurement object and capable of moving in a nearly direct forward direction to a center axis of a radiation range of the radioactive rays; a storage unit for storing detection dosages detected by the respective detectors; and fault determination means for relatively determining a defective detector on the basis of the detection dosages detected by the respective detectors.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a thickness measuring apparatus.

  Conventionally, in a metal sheet rolling line or the like, a thickness measuring device that irradiates the rolled metal sheet with radiation and measures the thickness of the metal sheet from the amount of radiation attenuation after passing through the metal sheet has been used. Yes. In this thickness measuring apparatus, radiation is detected by a radiation detector, a detection signal is converted into a digital value by an A / D converter, and a plate thickness is calculated by a control unit.

  Since the radiation diffuses in the radiation direction, it is emitted in a fan shape. The radiation detector is arranged in the radiation diffusion direction, and can measure the thickness of a plurality of portions of the metal plate. If the detector is on the central axis of the radiation, the amount of the detected radiation decreases as the distance from the central axis increases.

  The failure determination of the radiation detector is determined as a failure when the detected dose of each detector greatly increases or decreases compared to the startup data at the time of calibration or when the detected dose changes greatly in a short time. However, because the failure of each detector is determined by the amount of change in the detected dose, a detector that can detect only a low radiation dose compared to other detectors is considered to be out of order because the amount of change in the detected dose is small. There is a problem that it cannot be diagnosed.

JP2015-158443A

  The problem to be solved by the present invention is to provide a thickness measuring device that determines the presence or absence of a failure of the detector based on the value of the radiation dose measured by the detector.

  In order to solve the above-described problem, the thickness measurement apparatus according to the embodiment is arranged at a position facing a radiation source that irradiates a measurement target with radiation, and the radiation source via the measurement target. A plurality of detectors capable of detecting the radiation transmitted through the center and moving in a substantially orthogonal direction with respect to a central axis of the radiation range of the radiation, and a radiation detection amount detected by each detector of the plurality of detectors And a failure determination means for relatively determining a failed detector based on a radiation detection amount detected by each detector of the plurality of detectors.

The perspective view of the thickness measuring apparatus which is 1st Embodiment. Sectional drawing of the thickness measuring apparatus which is 1st Embodiment. Schematic of the structure of the thickness measuring apparatus which is 1st Embodiment. Sectional drawing of the thickness measuring apparatus which is 1st Embodiment at the time of failure determination. The graph of the positional relationship of the radiation source in the detector of 1st Embodiment, and the change of the voltage value which concerns on a radiation dose. The graph of the maximum value of the voltage value of each detector of a detector group. The graph of the positional relationship of the radiation source in the detector of 2nd Embodiment, and the change of the voltage value which concerns on a radiation dose. The figure of the positional relationship of the radiation source in the detector of 4th Embodiment. The figure of the distance from the central axis of the radiation of the detector of a 4th embodiment. The figure of the distance from the central axis of the radiation of the detector of a 5th embodiment. The flowchart of the failure determination of a detector in case the detector group is moving to the right. The flowchart of the failure determination of a detector in case the detector group has moved to the left.

  Hereinafter, an embodiment of a thickness measuring device will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view of a thickness measuring apparatus according to the first embodiment. The thickness measuring apparatus 1 of the present embodiment is a thickness measuring apparatus having a C-type frame 2, and has wheels 3 below the C-type frame 2. A measurement object 90 such as a thin steel plate is allowed to flow between the C-shaped frames 2 to measure the plate thickness. Further, when the thickness measuring device 1 needs to be calibrated, the thickness measuring device 1 can be moved from the rolling line using the wheel 3.

  A radiation source 10 (10a, 10b) and a moving mechanism 11 are provided below the C-shaped frame 2 of the thickness measuring apparatus 1 of the present embodiment. On the upper side of the C-shaped frame 2, a detector group 20 (20 a, 20 b) composed of a plurality of detectors, a moving mechanism 21, a housing 22 that houses the detector group 20, and a preamplifier 23 are provided. The thickness measuring device 1 further has a control panel 60 electrically connected to the C-shaped frame 2.

  The radiation source 10 is a device that irradiates the measurement object 90 with radiation. Examples of radiation include X-rays and γ-rays, but are not limited thereto.

  The moving mechanism 11 is a mechanism that moves the radiation source 10 (10a, 10b) and adjusts the position. The moving mechanism 11 has a shaft 11a and a positioning motor 11b. The positioning motor 11b can move the radiation source 10 (10a, 10b) in the longitudinal direction of the C-frame 2 along the axis 11a.

  The detector group 20 is a device that detects radiation transmitted through the measurement object 90. The detector groups 20 are arranged at two positions with respect to the longitudinal direction of the C-shaped frame 2, and are arranged at positions facing the radiation source 10 through the measurement object 90. In this embodiment and the following embodiments, they are referred to as a detector group 20a and a detector group 20b. By disposing the detector group 20 (20a, 20b) at two locations, the thickness at both ends of the measurement object 90 can be measured.

  The housing 22 accommodates the detector groups 20a and 20b.

  The moving mechanism 21 is a mechanism that moves the detector group 20 (20a, 20b) via the housing 22 to adjust the position. The moving mechanism 21 has a shaft 21a and a positioning motor 21b. The positioning motor 21b can move the detector group 20 (20a, 20b) in the longitudinal direction of the C-frame 2 along the shaft 21a.

  The preamplifier 23 is provided in the housing 22. The radiation dose detected by the detector group 20 (20a, 20b) is converted to a digital value by an AD converter (not shown) and then amplified by the preamplifier 23.

  The control panel 60 is electrically connected to the C-type frame 2 and adjusts the moving mechanisms 11 and 21 to adjust the positions of the radiation source 10 (10a, 10b) and the detector group 20 (20a, 20b). It is possible. Further, it is possible to determine the failure of the detector group 20 and specify the failed detector. Further, the control panel 60 can calculate the thickness of the measurement object 90 from the voltage value related to the radiation dose detected by the detector group 20.

  FIG. 2 is a cross-sectional view of the thickness measuring apparatus 1 when measuring the thickness of the measurement object 90.

  In the thickness measuring apparatus 1, when the measuring object 90 flows between the radiation source 10 and the detector group 20 by the rolling line, the radiation source 10 irradiates the measuring object 90 with radiation such as X-rays. The detector group 20 detects radiation that has passed through the measurement object 90. For each detector in the detector group 20a, a1, a2,... Ai from the end of the C-shaped frame 2 toward the connecting portion, and the total number of detectors is n. The same applies to the detector group 20b.

  Since the radiation diffuses in the radiation direction, the detector directly above the radiation source 10, that is, the detector on the central axis of the radiation source 10 (the broken line portion in FIG. 2) detects the highest irradiation dose.

  The thickness measuring device 1 converts the radiation dose detected by the detector group 20 into a voltage value or a current value by an AD converter (not shown), and measures based on this value and pre-stored calibration curve data. The plate thickness of the object 90 is calculated (thickness calculation means).

  The thickness measuring apparatus 1 of this embodiment determines the presence or absence of a faulty detector in the detector group 20 before and after measuring the plate thickness of the measurement object 90. Hereinafter, the failure determination of the detector group 20 in this embodiment will be described in detail with reference to the drawings.

  FIG. 3 is a schematic diagram of the configuration of the thickness measuring apparatus according to the first embodiment. The thickness measuring apparatus 1 of the present embodiment includes a radiation source 10 (10a, 10b), a detector group 20 (20a, 20b) including a plurality of detectors, a detector driving unit 30, and a failure determination unit 40 (failure determination means). And a plate thickness calculator 50. The detector drive unit 30, the failure determination unit 40, and the plate thickness calculation unit 50 are provided in the control panel 60 of FIG.

  The detector driving unit 30 is electrically connected to the detector group 20 (20a, 20b), and can move the detector group 20 in a substantially perpendicular direction with respect to the central axis of the radiation emission range. is there. It is possible to adjust the positions of the detector groups 20a and 20b according to the width of the measurement object 90.

  The failure determination unit 40 stores, in the storage unit 41, radiation dose information corresponding to a change in the radiation reception state of the detector group 20 (20a, 20b). The failure determination unit 40 determines the failure of each detector from the radiation dose information of each detector group 20 stored in the storage unit 41. The storage unit 41 includes, for example, a memory, but is not limited thereto.

  The plate thickness calculator 50 is a device that calculates the plate thickness of the measurement object 90 based on the radiation dose value detected by the detector group 20 and the calibration curve data stored in advance.

  FIG. 4 is a cross-sectional view of the thickness measuring apparatus 1 of the present embodiment at the time of failure determination. The failure determination time is before and after the measurement of the measurement object 90 and is a case where the measurement object 90 does not exist between the C-type frames 2.

  The detector group 20 (20a, 20b) is connected to the detector drive unit 30 of the control panel 60 via the housing 22. The detector driving unit 30 can move the detector group 20 (20a, 20b) in the arrow direction in FIG. 4, that is, in the longitudinal direction of the C-shaped frame 2 via the moving mechanism 21 in FIG. 1.

  When the radiation source 10 (10a, 10b) is fixed and the detector group 20 (20a, 20b) is moved in the direction of the arrow, the central axis of radiation emitted from the radiation source 10 (10a, 10b) (in FIG. 4) The detector at the broken line) detects the highest radiation dose. The storage unit 41 of the failure determination unit 40 stores a value related to the radiation dose of each detector of the detector group 20. In the present embodiment, a value obtained by converting the detected radiation dose into a voltage value by an AD converter (not shown) and the preamplifier 23 (FIG. 1) is stored as a measured value. However, in the present embodiment and the following embodiments, the value stored in the storage unit 41 is not limited to a voltage value, and may be a current value, for example.

  FIG. 5 is a graph of the positional relationship of the radiation source 10 in a detector with the detector group 20 and the change in voltage value related to the radiation dose. A graph is a graph about the time change of the voltage value based on the radiation dose which the detector of a solid line detects among the detector groups 20, a horizontal axis is time, and a vertical axis | shaft is a voltage value. It is assumed that the detector group 20 has moved to the right side.

  On the left side of the graph, the target detector is located on the left side of the central axis (dashed line) of radiation, and approaches this central axis with time. For this reason, since the radiation dose to be detected increases with time, the voltage value also increases with time.

In the center of the graph, the target detector is near the central axis (broken line) of the radiation, and the detected radiation dose increases, so that the voltage value also has a peak value (maximum value). Hereinafter, the maximum value of the voltage is V _MAX .

  On the right side of the graph, the target detector is located on the right side of the central axis (dashed line) of radiation, and moves away from this central axis with time. For this reason, since the radiation dose to be detected decreases with time, the voltage value also decreases with time.

FIG. 6 is a graph for the maximum voltage value V _MAX of each detector of the detector group 20. In this embodiment and the following embodiments, the determination of the failure of the detector will be described using the detector group 20a as an example. However, the same applies to the detector group 20b, and is not limited to the detector group 20a.

Let a1, a2,... Ai for each detector and n be the total number of detectors. The maximum voltage value (V _{ai, MAX} ) related to each detector is defined as V _ai . That is, the following expression (1) is obtained.

V _ai = V _{ai, MAX} . . . Formula (1)
Moreover, the broken line of FIG. 6 is an average value (V _Ave ) of each detector voltage value, and is calculated by the following formula (2).

V _Ave = 1 / n · ΣV _ai . . . Formula (2)
It is assumed that the detector a4 measures a larger voltage value than the other detectors, and the detector a12 measures a smaller voltage value than the other detectors. Then, it is determined whether the voltage values V _a4 and V _a12 related to the detectors a4 and a12 have a predetermined value difference (V _th ) with respect to the average value V _Ave. The difference _Vth of the predetermined value is within the range of the alternate long and short dash line in FIG.

  Assume that the following inequalities (3) and (4) hold for the voltage values relating to the detectors a4 and a12.

V _th <| V _a4 −V _Ave | . . . Formula (3)
V _th <| V _a12 −V _Ave | . . . Formula (4)
Failure determination unit 40 in the control panel 60 in FIG. 4, the formula (3) to (4), the voltage value of the detector a4, a12 the difference _{V th} or more predetermined values with respect to the average value _{V Ave} Since it has the value of, it is determined that there is a failure. That is, in this embodiment, the failed detector is relatively determined from the average value V _Ave based on the radiation detection amount of each detector.

The predetermined value can be, for example, a value of ± 10% with respect to the average value V _Ave. However, the predetermined value is not limited to this, and may be a value that can be appropriately set by the user.

  In the present embodiment, the direction in which the detector group 20 moves is the right direction in FIG. 5, but is not limited thereto, and may be the left direction.

  As described above, the thickness measuring apparatus of the present embodiment determines the presence or absence of a failure of the detector based on the value of the radiation dose measured by each detector before and after the measurement of the plate thickness of the measurement object. Can do.

(Second Embodiment)
A perspective view, a cross-sectional view, a configuration diagram, and the like of the thickness measuring device of the present embodiment are the same as those of the first embodiment, and are the same as those of FIGS.

In the failure determination of the detector group 20, in the first embodiment, the failure determination is performed based on the difference between the average voltage value (V _Ave ) and the maximum voltage value (V _MAX ) of each detector. respect, the range in the present embodiment derives a standard deviation (sigma) from the maximum voltage value of each detector (V _ai), the maximum voltage value of each detector (V _ai) is the standard deviation (sigma) When it is outside, the detector is determined to be faulty. That is, the standard deviation (σ) value is used as the difference between the predetermined values in the present embodiment.

  The square of the standard deviation (σ) is derived from the following equation (5).

σ ² = 1 / n · Σ (V _ai -V _Ave ) ² . . . Formula (5)
It is assumed that the results shown in FIG. 6 are obtained for the voltage values measured by the detectors, and the following inequalities (6) and (7) hold for the voltage values related to the detectors a4 and a12.

V _a4 > V _Ave + σ. . . Formula (6)
V _a12 <V _Ave −σ. . . Formula (7)
In this case, since the voltage values measured by the detectors a4 and a12 are out of the range of the standard deviation σ, it is determined as a failure in this embodiment.

  As described above, the thickness measuring apparatus of the present embodiment determines the presence or absence of a failure of the detector based on the value of the radiation dose measured by each detector before and after the measurement of the plate thickness of the measurement object. Can do.

(Third embodiment)
A perspective view, a cross-sectional view, a configuration diagram, and the like of the thickness measuring device of the present embodiment are the same as those of the first embodiment, and are the same as those of FIGS.

In the failure determination of the detector group 20, in the first embodiment, the voltage value (V _ai ) related to each detector is set to the maximum value (V _{ai, MAX} ) of the detector from the equation (1). In the embodiment, the integrated value of the voltage value within a predetermined time.

  FIG. 7 is a graph of the positional relationship of the radiation source 10 in a detector ai having the detector group 20 and the change in voltage value related to the radiation dose. A graph is a graph about the time change of the voltage value based on the radiation dose which the detector ai detects among the detector groups 20, a horizontal axis is time and a vertical axis | shaft is a voltage value. It is assumed that the detector group 20 has moved to the right side.

  The graph shows the time change of the voltage value by a non-failed detector, the time change graph of the detector a4 that measures a higher voltage value than the other detectors, and the detector that measures the lower voltage value than the other detectors. It is a time change graph of a12.

  At time T1 in the graph, the target detector ai is located on the left side of the central axis (dashed line) of radiation, and approaches the central axis with time. For this reason, since the radiation dose to be detected increases with time, the voltage value also increases with time.

  In the center of the graph, the target detector is near the central axis (dashed line) of radiation, and the detected radiation dose increases, so the voltage value also has a peak value (maximum value).

  At time T2 in the graph, the target detector ai is located on the right side of the central axis of radiation (broken line), and moves away from the central axis with time. For this reason, since the radiation dose to be detected decreases with time, the voltage value also decreases with time.

In the present embodiment, integration is performed on the voltage values measured by the detectors ai during the period from the time T1 to the time T2, and the integration point is set as the voltage value V _ai related to each detector. This V _ai is represented by the following formula (8). However, the time range for integration is T1 to T2.

V _ai = ∫V (t) dt. . . Formula (8)
In this embodiment, the average value V _Ave of the voltage values is calculated from the voltage value V _ai related to each detector obtained from the equation (8). The equation to be calculated is the same as equation (2).

From equation (8), the detector a4 calculates a larger voltage value than the other non-failed detectors, and the detector a12 calculates a smaller voltage value than the other non-failed detectors. Thereafter, the difference between the voltage values V _a4 and V _a12 related to the detectors _a4 and _a12 and the average value V _Ave is calculated, and it is determined whether or not the difference between the predetermined values is present.

  Formulas used for failure determination by the failure determination unit 40 in the control panel 60 are the same as the equations (3) and (4).

(Modification of the third embodiment)
In the modified example of the third embodiment, failure determination is performed for each detector of the detector group 20 using the standard deviation as in the second embodiment. The voltage value V _ai relating to each detector is expressed by equation (8), the equation of the square of the standard deviation σ is the same as equation (5), and the failure determination equation of the detector is expressed by equations (6), (7 ).

That is, in the failure determination of the detector group 20, in the second embodiment, the voltage value (V _ai ) related to each detector is set as the maximum value (V _{ai, MAX} ) of the detector using Equation (1). However, in this embodiment, the integral value of the voltage value within a predetermined time is obtained from the equation (8).

  In the present embodiment, the direction in which the detector group 20 moves is the right direction in FIG. 7, but is not limited thereto, and may be the left direction.

  As described above, the thickness measuring apparatus of the present embodiment determines the presence or absence of a failure of the detector based on the value of the radiation dose measured by each detector before and after the measurement of the plate thickness of the measurement object. Can do.

(Fourth embodiment)
The perspective view and configuration diagram of the thickness measuring apparatus of the present embodiment are the same as those of the first embodiment. The thickness measuring apparatus of the present embodiment is a case where there is a detector that does not move to a position on the central axis of radiation for each detector of the detector group 20.

  FIG. 8 is a diagram showing the positional relationship of the radiation sources in the detector of this embodiment. It is assumed that there are 16 detectors a1 to a16 in the detector group 20 (20a). However, the total number of detectors in the present embodiment is not limited to this. Hereinafter, the detector group 20a will be described as an example, but the same applies to the detector group 20b.

  FIG. 8A is a diagram showing the positional relationship between each detector ai and the radiation source 10 when the detector group 20a is located at the leftmost end of the C-shaped frame 2 (not shown). In this case, it is assumed that the detector a11 in the detector group 20a is directly above the radiation source 10 and is on the central axis of the radiation source 10. It is assumed that the detector at the left end such as the detector a1 does not receive radiation.

  FIG. 8B is a diagram showing the positional relationship between each detector ai and the radiation source 10 when the detector group 20a is moving.

  FIG. 8C is a diagram showing the positional relationship between each detector ai and the radiation source 10 when the detector group 20a is located on the rightmost side. In this case, it is assumed that the detector a6 in the detector group 20a is directly above the radiation source 10 and on the central axis of the radiation source 10. The detector at the right end such as the detector a16 is assumed not to receive radiation.

  The detector group 20 (20a) can be moved to the left and right, and the detector group 20 (20a) is moved to the right from the state shown in FIG. To the state. Conversely, the detector group 20 (20a) is moved to the left from the state shown in FIG. 8C, and the state shown in FIG. 8B is reached via the state shown in FIG.

In the operations from (a) to (c) in FIG. 8 and the operations from (c) to (a), the detectors (a1 to a5) located on the left side of the detector a6, and the detector a11 The detectors (a12 to a16) located on the left side are not located on the central axis of radiation. For this reason, the present embodiment cannot make a failure determination using the voltage value V _ai when each detector a i is positioned on the central axis of the radiation as in the first embodiment.

  In the present embodiment, voltage values corresponding to the distances between the detectors ai, the central axis of the radiation, and the detectors ai are measured, and these are assumed to be compared to perform failure determination. Specific examples are described in detail below.

  FIG. 9 is a diagram of the distance between the detector ai and the central axis of the radiation of the thickness measuring apparatus according to this embodiment. (A) is a figure of the positional relationship in case the detector ai is located in the left side from the central axis (dashed line part) of a radiation. In this case, the distance between the detector ai and the central axis of the radiation is set to a minus (−) side distance. (B) is a figure of the positional relationship in case the detector ai is located on the central axis (dashed line part) of a radiation. In this case, the distance between the detector ai and the central axis of radiation is set to zero. (C) is a figure of the positional relationship in case the detector ai is located in the right side rather than the central axis (dashed line part) of a radiation. In this case, the distance between the detector ai and the central axis of the radiation is a plus (+) side distance.

In the thickness measurement apparatus of the present embodiment, the storage unit 41 in the failure determination unit 40 stores the distance between the detector ai and the central axis of radiation, and a voltage value corresponding to the distance. Table 1 below is an example of a table of voltage values relating to the radiation detection amount of each detector ai corresponding to the distance from the central axis.

  The distance from the central axis of radiation is set to a value of −30 cm to 30 cm, and the voltage values measured for each detector ai at these distances are tabulated.

  The detector a4 measures a higher voltage value than other detectors, and the detector a12 measures a lower voltage value than other detectors. Since the detectors a4 and a12 are not located on the central axis of radiation as described above, no numerical value is stored for a table whose distance from the center is 0 cm.

  Assuming that the detectors that can be located at a distance of −20 cm from the central axis are a1 to a5, the voltage values measured by the detectors a1 to a5 are stored in the rows of the distance −20 cm from the central axis. For the five values of the detectors a1 to a5 in the row, an average value or a standard deviation is calculated, and the voltage value of each detector is relatively compared to determine that the detector a4 is malfunctioning. Can do.

  Further, assuming that the detectors that can be located at a distance of −10 cm from the central axis are a3 to a8, the voltage values measured by the detectors a3 to a8 are stored in rows at a distance of −10 cm from the central axis. . For the six values of the detectors a3 to a8 in the row, an average value or standard deviation is calculated, and the voltage value of each detector is relatively compared to determine that the detector a4 is malfunctioning. Can do.

  Assuming that the detectors that can be located at a distance of 20 cm from the central axis are a12 to a16, the voltage values measured by the detectors a12 to a16 are stored in rows of a distance of 20 cm from the central axis. For the five values of the detectors a12 to a16 in the row, an average value or a standard deviation is calculated, and the voltage value of each detector is relatively compared to determine that the detector a12 is malfunctioning. Can do.

  Further, assuming that the detectors that can be located at a distance of 10 cm from the central axis are a9 to a14, the voltage values measured by the detectors a9 to a14 are stored in rows of a distance of 10 cm from the central axis. For the six values of the detectors a9 to a14 in the row, an average value or a standard deviation is calculated, and the voltage value of each detector is relatively compared to determine that the detector a12 has failed. Can do.

  In addition, when determining a failure from an average value, it is the same as that of 1st Embodiment. When a failure is determined from the standard deviation, it is the same as in the second embodiment.

  The distance values and voltage values shown in Table 1 are exemplary values for explaining the present embodiment, and are not limited to these values.

  As described above, the thickness measuring apparatus of the present embodiment determines the presence or absence of a failure of the detector based on the value of the radiation dose measured by each detector before and after the measurement of the plate thickness of the measurement object. Can do.

(Fifth embodiment)
A perspective view, a cross-sectional view, a configuration diagram, and the like of the thickness measuring device of the present embodiment are the same as those of the first embodiment, and are the same as those of FIGS. The thickness measurement apparatus of the present embodiment is configured so that, for each detector of the detector group 20, when the detector ai is at a position on the central axis of radiation, the detector ai and the adjacent detector ai ± 1 The failure is judged by comparing the measurement results every hour. Hereinafter, a failure determination method for the detector ai according to the thickness measurement apparatus of the present embodiment will be described in detail with reference to the drawings.

  FIG. 10 is a diagram of the distance from the central axis of the radiation of the detector of this embodiment. It is assumed that the detector group 20 moves to the right from time 0 to T3 and moves to the left from time T3 to T4. FIG. 10 shows the positional relationship between the radiation source 10 at a certain time t, the detector ai on the central axis of the radiation, and the detector ai ± 1 adjacent to the detector ai. The voltage values measured by the detectors ai, ai + 1, and ai-1 at time t are Vai (t), Vai + 1 (t), and Vai-1 (t), respectively.

  FIG. 11 is a flowchart of the failure determination of the detector ai when the detector group 20 is moving to the right.

  It is determined whether the detector ai exists on the central axis of radiation at a certain time t (step S101). When the detector ai exists on the central axis of the radiation (YES in step S101), the radiation dose detected by the detector ai and the detector ai + 1 adjacent to the moving direction side of the detector group 20 (that is, right adjacent). Is measured (Vai (t), Vai + 1 (t)) (step S102). When the detector ai does not exist on the central axis of radiation (NO in step S101), the detector ai-1 is not on the central axis of radiation due to the movement of the detector group 20, and thus the detector of the detector ai-1 Is on the central axis of radiation (step S101).

  The voltage value Vai (t) at a certain time t is compared with the voltage value Vai + 1 (t) (step S104). When the voltage value Vai (t) is larger than the voltage value Vai + 1 (t) (YES in step S104) ) Since the radiation amount detected by the detector ai on the radiation is larger than that of the adjacent detector ai + 1, it is determined as normal. Thereafter, it is determined whether or not the time t has passed the predetermined time T3 (step S105). If the time t has not reached T3, that is, while the detector group 20 is moving to the right (NO in step S105). ), Returning to step S101, the failure is repeatedly determined until time T3 is reached. When the time T3 is reached (YES in step S105), the detector group 20 does not move further to the right side, and thus the failure determination ends.

  When the voltage value Vai (t) is equal to or lower than the voltage value Vai + 1 (t) (NO in step S104), detection is performed because the radiation a detector ai on the radiation detects is smaller than or equal to the adjacent detector ai + 1. The device ai is determined to be faulty (step S106).

  FIG. 12 is a flowchart of the failure determination of the detector ai when the detector group 20 has moved to the left.

  It is determined whether the detector ai exists on the central axis of radiation at a certain time t (step S201). When the detector ai exists on the central axis of radiation (YES in step S201), the detector ai and the detector ai-1 adjacent to the moving direction side of the detector group 20 (that is, the left side) detect. Voltage values (Vai (t), Vai-1 (t)) related to the radiation dose are measured (step S202). When the detector ai does not exist on the central axis of radiation (NO in step S201), the detector ai + 1 is detected because the detector ai is off the central axis of radiation due to the movement of the detector group 20. Is on the central axis of radiation (step S201).

  The voltage value Vai (t) at a certain time t is compared with the voltage value Vai-1 (t) (step S204). When the voltage value Vai (t) is larger than the voltage value Vai-1 (t) ( YES in step S204), it is determined that the detector ai on the radiation is normal because the amount of radiation detected by the detector ai-1 is larger than that of the adjacent detector ai-1. Thereafter, it is determined whether or not the time t has passed the predetermined time T4 (step S205). If the time t has not reached T4, that is, while the detector group 20 is moving to the left (NO in step S205). ), The process returns to step S201, and the failure is repeatedly determined until the time T4 is reached. When the time T4 is reached (YES in step S205), the detector group 20 does not move further to the left side, and thus the failure determination ends.

  When the voltage value Vai (t) is equal to or lower than the voltage value Vai-1 (t) (NO in step S204), is the radiation detected by the detector ai on the radiation smaller than the adjacent detector ai-1? Since they are equal, the detector ai is determined to be faulty (step S206).

  As described above, the thickness measuring apparatus of the present embodiment determines the presence or absence of a failure of the detector based on the value of the radiation dose measured by each detector before and after the measurement of the plate thickness of the measurement object. Can do.

  In the above embodiment, the voltage value is used for the failure determination of each detector of the detector group 20, but the present invention is not limited to this. For example, the determination may be performed based on a current value corresponding to the radiation dose by an AD converter, or a value converted from the voltage value to the radiation dose.

  In the above embodiment, X-rays are used as radiation emitted from the radiation source 10, but γ-rays may be used, and the present invention is not limited to these.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1. Thickness measuring device,
2 ... C type frame,
10. Radiation source,
20 ... Detector group,
30 ... Detector drive unit,
40 .. failure determination part,
41 ... Memory part
50 ... Plate thickness calculator,
60 Control panel,
90: Measurement object.

Claims (8)

A radiation source for irradiating the object to be measured;
It is arranged at a position facing the radiation source through the measurement object, detects the radiation transmitted through the measurement object, and can move in a substantially perpendicular direction with respect to the central axis of the radiation range of the radiation. Multiple detectors;
A storage unit for storing a radiation detection amount detected by each detector of the plurality of detectors;
A failure determination means for relatively determining a failed detector based on a radiation detection amount detected by each detector of the plurality of detectors;
A thickness measuring device comprising:   The failure determination means moves the plurality of detectors, measures the radiation dose when each detector is on the central axis, calculates an average value from the measured values of each detector, and the measured values are averaged The thickness measurement apparatus according to claim 1, wherein the detector is determined to be faulty when a difference between the values is a predetermined value.   The failure determination means moves the plurality of detectors, measures a radiation dose when each detector is on the central axis, calculates a standard deviation from a measurement value of each detector, and out of a predetermined range The thickness measuring apparatus according to claim 1, wherein the detector from which the measurement value is derived is determined as a failure.   The failure determination means moves the plurality of detectors, calculates an integrated value from the detected value of the radiation dose within a predetermined time of each detector, calculates an average value from the integrated value of each detector, The thickness measuring apparatus according to claim 1, wherein when the integrated value has a difference of a predetermined value with respect to the average value, the detector is determined to be faulty.   The failure determination means moves the plurality of detectors, calculates an integrated value from the detected value of the radiation dose within a predetermined time of each detector, calculates a standard deviation from the integrated value of each detector, The thickness measuring apparatus according to claim 1, wherein the detector that derives the integral value outside the range is determined as a failure. The storage unit stores a distance between each detector and the central axis, and a radiation dose value corresponding to each distance,
The failure determination means relatively determines a failed detector based on a radiation dose value corresponding to each distance.
The thickness measuring device according to any one of claims 1 to 5.   The failure determination means moves the plurality of detectors, and when the detected amount of radiation of the detector on the central axis is smaller than the detected amount of radiation of the adjacent detector at that time, The thickness measuring apparatus according to claim 1, wherein a detector is determined to be faulty.   The thickness measurement apparatus according to any one of claims 1 to 7, wherein the radiation is X-rays or γ-rays.

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