JP2020095011A - Radiation thickness gauge with abnormality monitoring function and abnormality monitoring method for radiation thickness gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation type thickness gauge with an abnormality monitoring function capable of detecting an abnormality other than an operation abnormality of a shutter. SOLUTION: A radiation type thickness gauge 10 with an abnormality monitoring function includes a radiation source unit 12 having a radiation source and a shutter for freely shielding the radiation emitted from the radiation source, and a detector 14 for detecting the radiation. A frame 16 that holds the radiation source portion 12 and the detector 14 so as to sandwich the object O to be measured is provided. The radiation type thickness gauge 10 further includes an abnormality determining means for determining an abnormality of the radiation type thickness gauge 10 based on a plurality of detection voltages measured by the detector 14 at each time of zero calibration. [Selection diagram] Fig. 1

Description

The present invention relates to a radiation type thickness meter that irradiates an object to be measured, such as a steel plate, with radiation, and measures the thickness of the object to be measured from the amount of transmitted radiation, and more particularly to a device that monitors an abnormality thereof.

This type of radiation-type thickness gauge uses the property that radiation absorbs, scatters, and attenuates when it passes through an object to be measured, and measures the thickness of the object to be measured without contact. Is used to improve the dimensional accuracy of thin and thick plates. For example, in a rolling line, a gamma ray thickness gauge is installed in the immediate vicinity of the rolling mill exit side, and various automatic strip thickness control (AGC) for reducing strip thickness deviation is introduced.

The accuracy of steel plate thickness measurement is very important for ensuring the quality assurance and yield of the steel plate, and if any abnormality occurs in the radiation type thickness gauge, it is reliably detected and appropriate measures are taken. Is essential.

For example, in Patent Document 1, the level determination means determines whether the detection signal level output from the radiation detector is equal to or higher than a determination level corresponding to the shutter closed state. If the determination of the determination level is equal to or higher than a predetermined period, the shutter is released. There has been proposed a shutter abnormality detection device that determines that the shutter operation is abnormal by the abnormality determination means.

JP 62-44616 A

By the way, an abnormality of the radiation type thickness gauge may occur not only due to an abnormal operation of the shutter but also due to other internal defects of the structure or deterioration of the signal transmission cable. However, the conventional shutter abnormality detection device determines whether or not the detection signal level output from the radiation detector is equal to or higher than a predetermined determination level corresponding to the shutter closed state. It is only an abnormality, and an abnormality other than the above-described operation abnormality of the shutter cannot be detected.

Therefore, an object of the present invention is to make it possible to detect an abnormality other than the operation abnormality of the shutter in the radiation type thickness gauge.

In order to solve the above problems, the radiation type thickness gauge of the present invention is a radiation source and a radiation source unit having a shutter that releasably shields radiation emitted from the radiation source, and a detector that detects radiation, A frame that holds the radiation source section and the detector so as to sandwich the object to be measured, irradiates the object to be measured with radiation from the radiation source unit, and measures the amount of transmitted radiation that has passed through the object to be measured. In a radiation type thickness gauge for measuring the thickness of a measurement object, based on a plurality of detection voltages measured by the detector at each zero calibration, an abnormality determination means for determining abnormality of the radiation type thickness gauge is provided. ..

In a preferred aspect of the radiation type thickness gauge of the present invention, the abnormality determination means is configured by at least one determination condition selected from the following determination conditions A to D.
Judgment condition A: Judgment condition B in which the current value and the previous value of the detected voltage measured in the open state of the shutter at the time of the zero calibration are compared, and when the difference exceeds a certain value, it is judged as abnormal. : The maximum value and the minimum value are obtained from the present value of the detected voltage measured in the open state of the shutter at the time of the zero calibration and the past values of at least the two most recent times, and the difference exceeds a certain value. In this case, the determination condition C is determined to be abnormal: the current value of the detected voltage measured in the closed state of the shutter at the time of the zero calibration is compared with the previous value, and when the difference exceeds a certain value, it is determined to be abnormal. Judgment condition D: Judgment of the maximum value and the minimum value from the current value of the detection voltage measured in the closed state of the shutter at the time of the zero calibration and the past values of at least two times immediately thereafter, and the difference between them. If it exceeds a certain value, it is judged as abnormal

In a preferred aspect of the radiation type thickness gauge of the present invention, the abnormality determination means has two or more determination conditions selected from the determination conditions A to D, and is configured to sequentially determine.

In a preferred aspect of the radiation type thickness gauge of the present invention, the abnormality determining means is configured to omit the determination conditions after the determination condition that is abnormal among the determination conditions that are sequentially configured.

In order to solve the above-mentioned problems, an abnormality monitoring method for a radiation type thickness gauge according to the present invention detects a radiation source and a radiation source unit having a shutter that releasably shields the radiation emitted from the radiation source. A detector and a frame that holds the radiation source section and the detector so as to sandwich the measurement object, irradiates the measurement object with radiation from the radiation source section, and transmits the measurement object. In the abnormality monitoring method of the radiation type thickness gauge that measures the thickness of the measured object from the radiation dose, the abnormality of the radiation type thickness gauge is based on the multiple detection voltages measured by the detector at each zero calibration. Including determining.

In a preferred aspect of the radiation thickness gauge abnormality monitoring method of the present invention, determination condition A: a current value and a previous value of the detected voltage measured in the open state of the shutter at the time of the zero calibration are compared, When the difference exceeds a certain value, it is determined to be abnormal. Judgment condition B: The present value of the detected voltage measured in the open state of the shutter at the time of the zero calibration and the past value of at least two of the latest values. The maximum value and the minimum value are obtained from the inside, and when the difference exceeds a certain value, it is determined to be abnormal. Criteria C: This time of the detected voltage measured in the closed state of the shutter at the time of the zero calibration. The value is compared with the previous value, and if the difference exceeds a certain value, it is determined to be abnormal, and the determination condition D: This time of the detected voltage measured in the closed state of the shutter at the time of the zero calibration. The maximum value and the minimum value are obtained from the value and the past value of at least two times immediately after that value, and when the difference exceeds a certain value, it is determined to be abnormal, and any one of the determination conditions selected from Including using.

A preferred aspect of the abnormality monitoring method for the radiation thickness gauge of the present invention includes sequentially determining two or more determination conditions selected from the determination conditions A to D.

A preferred aspect of the abnormality monitoring method for the radiation type thickness gauge of the present invention includes sequentially determining the determination conditions, and omitting the determination conditions after the determination of abnormality.

When some abnormality that adversely affects the measurement result occurs in the radiation type thickness gauge, the detection voltage at the time of zero calibration changes, but according to the present invention, the detection voltage measured at each zero calibration is measured. Since the abnormality is determined from the transition of, it is possible to detect such an abnormality.

Furthermore, by using a plurality of different abnormality determination conditions, the abnormality monitoring capability can be enhanced. In addition, in the plurality of abnormality determination conditions that are sequentially determined, the processing after the first determination of abnormality is omitted, so that the abnormality determination processing can be made efficient.

It is a schematic block diagram of the radiation type thickness gauge with an abnormality monitoring function of one embodiment of this invention suitable for implementation of the abnormality monitoring method in the radiation type thickness meter of one embodiment of this invention. It is an example of a timing chart of zero calibration in the radiation type thickness gauge of FIG. It is an example of a calibration curve showing the relationship between the plate thickness and the voltage. This is an example of a quality assurance test performed when repairing a radiation thickness gauge. (A)-(d) is a flowchart which shows an example of the abnormality determination method implemented by the abnormality determination part. (A)-(d) is a flowchart which shows the other example of the abnormality determination method implemented by the abnormality determination part.

Embodiments of a radiation thickness gauge with an abnormality monitoring function and an abnormality monitoring method in the radiation thickness gauge according to the present invention will be described below in detail with reference to the drawings. Here, FIG. 1 is a radiation type thickness gauge with an abnormality monitoring function of one embodiment of the present invention (hereinafter, simply referred to as a radiation type, which is suitable for performing an abnormality monitoring method in the radiation type thickness meter of one embodiment of the present invention. It is a schematic configuration diagram of a thickness gauge).

The radiation type thickness gauge 10 of the present embodiment irradiates a moving object to be measured O, such as a moving steel plate, with radiation, and measures the thickness of the object to be measured O from the amount of transmitted radiation that has passed through the object to be measured O. In particular, the radiation source unit 12 that emits radiation such as gamma rays and X-rays, the detector 14 that detects radiation, and the object to be measured in a direction perpendicular to the pass line plane that conveys the object to be measured O. For example, a C-shaped frame 16 that holds the radiation source section 12 and the detector 14 so as to sandwich O, a carriage 20 that supports the frame 16 and travels (moves) on a rail 18 between an online position and an offline position, A control panel 22 for performing various kinds of arithmetic processing and control, and an analog recorder 24 for recording measurement results, for example, are provided.

The radiation source unit 12 is capable of opening and closing a radiation source (not shown) such as a γ-ray source or an X-ray source, a storage container (not shown) that stores the radiation source, and an opening of the storage container, and is radiated from the radiation source. And a shutter (not shown) that shields radiation in a releasable manner.

The detector 14 has an ionization chamber and a preamplifier (not shown), and the radiation emitted from the radiation source is converted into an electric signal by the ionization chamber and converted into an appropriate voltage signal by the preamplifier and adjusted.

In the control panel 22, an averaging unit 26 that performs analog/digital conversion of the detection voltage output from the detector 14, and a thickness that calculates the thickness of the object to be measured O based on the digitized detection voltage. An arithmetic unit 28, a zero calibration unit 30, and a sample calibration unit 32 are provided.

The zero calibration unit 30 moves the frame 16 to the offline position at predetermined calibration time intervals, for example, every 8 hours, and then detects the detector 14 when the shutter is open in the absence of the DUT O during radiation. And the detection voltage Vs of the detector 14 when the shutter is closed are measured to perform zero calibration. The detection voltages Vo and Vs are stored in the storage unit 34 each time zero calibration is performed. FIG. 2 shows a timing chart of zero calibration. When the zero calibration button (not shown) provided on the control panel 22 is pressed from the state during measurement or when a predetermined calibration time is reached, the carriage 20 moves to the offline position and the shutter is closed at the offline position. Then, the measurement of the voltage Vo is started. Then, the measurement of the voltage Vs is started without the object to be measured O and the shutter is open.

The sample calibration unit 32 actually measures a plurality of samples (thickness reference pieces) whose plate thicknesses are known, for example, after zero calibration, and creates (corrects) a calibration curve (calibration table) as shown in FIG. The created calibration curve is stored in the storage unit 34 in the control panel 22, the thickness calculation unit 28 reads the detection voltage when measuring the thickness of the object O to be measured, and calculates the thickness from the stored calibration curve. The material correction unit 36 (see FIG. 1) corrects the calculated value of the thickness of the object to be measured O calculated by the thickness calculator 28 in consideration of the material (density) of the object to be measured O.

The radiation type thickness gauge 10 utilizes the property that radiation is absorbed, scattered and attenuated when passing through the object to be measured O, and the thickness of the object to be measured O is expressed by the following formulas (1) to (3). Ask from.
Vz=Vo-Vs (1)
V=Vz·exp(−μ·t) (2)
Vh=V+f(t) (3)
Here, Vo represents the detection voltage of the detector 14 when there is no object to be measured O in the radiation and the shutter is open, and Vs is the detection voltage of the detector 14 when there is no object to be measured O and the shutter is closed. Represents a voltage, V represents a theoretical voltage value when the plate thickness is t, μ represents an absorption coefficient of the object to be measured O (for example, 0.9 in the case of iron), and f(t) represents A sample correction amount is shown for each plate thickness, and Vh is a voltage after the sample correction.

In the control panel 22, a measurement result is transmitted to the higher-order computer 38 via the network, a higher-order transmission unit 40, and whether or not the measurement result is within a predetermined target thickness range is monitored. An off-gauge determination unit 42 that determines an off-gauge (thickness defect) is provided.

By the way, in the manufacturing industry such as the steel industry, the accuracy of measuring the thickness of the product is very important for ensuring the quality assurance and the yield of the product. Therefore, when the radiation type thickness gauge 10 is repaired including the parts replacement, Often perform quality assurance tests before and after replacement. FIG. 4 shows an example of the procedure. In the quality assurance test, pre-repair inspection for confirming that there is no abnormality in the radiation type thickness gauge 10 before repair, connection check, and shutter opening/closing. Test, running test of carriage 20, plate thickness measurement test, drift test, zero calibration test, sample calibration test, sample remeasurement, transmission test to host computer 38, noise confirmation, etc. Testing and online monitoring.

In such a quality assurance test, although there are no abnormalities in the shutter open/close test, the measurement results are not stable, and there are cases in which it is erroneously determined to be an off-gauge a few weeks after startup. The malfunction of the radiation type thickness gauge 10 may have factors other than the abnormal operation of the shutter. However, when the conventional method of determining whether the voltage level output from the detector 14 is equal to or higher than a predetermined determination level corresponding to the shutter closed state cannot detect an abnormality due to such another factor. There is.

Therefore, in the present embodiment, in order to detect an abnormality other than the shutter operation abnormality, an abnormality of the radiation type thickness gauge 10 is detected based on a plurality of detection voltages measured by the detector 14 at each zero calibration. An abnormality determination unit 44 is provided on the control panel 22 as an abnormality determination means for determination.

More specifically, the abnormality determination unit 44 compares the current value and the previous value of the detection voltage Vo measured in the shutter open state at the time of zero calibration, and the absolute value of the difference (|current value-previous value| ) Exceeds a constant value α1 (mV), it is determined to be abnormal (hereinafter referred to as determination condition A). It is preferable that α1 be in the range of, for example, 0 (mV) to 10 (mV) or less, because the 8-hour drift record in the normal state has never exceeded this range. The cause of the abnormality such that the absolute value of the difference between the present value and the previous value of the detection voltage Vo exceeds α1 is that the radiation source is insufficiently fixed in the device that emits radiation (it is not completely fixed). , Mechanical backlash has occurred) etc. More preferably, if α1 is set to be in the range of 0 (mV) to 8 (mV) or less, it is possible to prevent overlooking and erroneous detection of an abnormality.

Instead of or in addition to the determination condition A, the abnormality determination unit 44 determines the maximum value and the minimum value from the current value of the detection voltage Vo measured in the shutter open state at the time of zero calibration and the past values at least two times immediately thereafter. The value is calculated, and when the difference exceeds a constant value α2 (mV), it is determined to be abnormal (hereinafter referred to as determination condition B). It is preferable to set α2 within a range of, for example, 0 (mV) to 20 (mV) or less, because the drift performance at the time of normal zero calibration (for example, one week) exceeds the range. Because I have never played. The cause of the abnormality such that the difference between the maximum value and the minimum value of the current value of the detection voltage Vo and the past value of at least the two most recent times thereof exceeds α2 is that the radiation source is not fixed in the device that emits the radiation. It may be sufficient (not completely fixed and mechanical backlash), screws for fixing the radiation source are gradually loosened, wiring is deteriorated and circuit resistance is gradually increased. More preferably, if α2 is set in the range of 0 (mV) to 15 (mV) or less, it is possible to prevent the abnormality from being overlooked and erroneous detection.

Instead of or in addition to the determination conditions A and B, the abnormality determination unit 44 compares the current value and the previous value of the detected voltage Vs measured in the shutter closed state at the time of zero calibration, and the absolute value of the difference ( When |current value-previous value|) exceeds a constant value β1 (mV), it is determined to be abnormal (hereinafter, referred to as determination condition C). β1 is preferably in the range of, for example, 0 (mV) or more and 1 (mV) or less, because the 8-hour drift record in the normal state has never exceeded this range. As a cause of the abnormality in which the absolute value of the difference between the current value and the previous value of the detected voltage Vs exceeds β1, it is considered that noise is mixed in the cable that transmits the electric signal detected by the detector 14 to the control panel 22. Be done. More preferably, if β1 is set in the range of more than 0 (mV) and 0.5 (mV) or less, oversight or erroneous detection of abnormality can be suppressed.

Instead of or in addition to the determination conditions A to C, the abnormality determination unit 44 determines the maximum value from the current value of the detected voltage Vs measured in the shutter closed state at the time of zero calibration and the past value of at least the latest two times. And a minimum value, and when the difference exceeds a constant value β2 (mV), it is determined to be abnormal (hereinafter referred to as determination condition D). β2 is preferably in the range of, for example, 0 (mV) over 2 (mV), because the drift record at the time of normal zero calibration (for example, one week) exceeds this range. Because there is nothing. As the cause of the abnormality in which the difference between the maximum value and the minimum value of the current value of the detected voltage Vs and the past value of at least the two most recent times thereof exceeds β2, the electric signal detected by the detector 14 is controlled by the control panel 22. It is conceivable that noise is mixed in the cable transmitted to the. More preferably, if β2 is set in the range of 0 (mV) to 1.5 (mV) or less, it is possible to prevent overlooking and erroneous detection of an abnormality.

It should be noted that in the determination conditions B and D, when the number of times of measurement to be targeted is increased, there is a risk of erroneous detection due to drift due to climate change. Is desirable.

5A to 5D show an example of an abnormality determination method performed by the abnormality determination unit 44 for each zero calibration (measurement of Vo and Vs) by the zero calibration unit 30. First, the example shown in FIG. 5A corresponds to the above determination condition A, and in step S10, the abnormality determination unit 44 causes the current detection voltage Vo when the object to be measured O is not present in the radiation and the shutter is open this time. The value and the previous value are read from the storage unit 34, and in step S11, the absolute value of the read difference between the present value and the previous value is compared with a constant value α1. Alarm) is output.

The example shown in FIG. 5B corresponds to the above determination condition B, and in step S20, the abnormality determination unit 44 determines that the current value of the detected voltage Vo when there is no DUT O during radiation and the shutter is open. In addition, the past values of the latest at least two times are read from the storage unit 34, the maximum value and the minimum value are extracted from the read three or more detection voltages in step S21, and the extracted maximum value is extracted in step S22. The difference between the value and the minimum value is compared with a constant value α2, and if α2 is exceeded, an abnormality signal (alarm) indicating an abnormality is output in step S23. Further, the number of past values when obtaining the maximum value and the minimum value is preferably 3 to 5 times, because the determination accuracy improves as the number of times increases, but the detection of an abnormality may be delayed. Because there is.

The example shown in FIG. 5C corresponds to the above determination condition C, and in step S30, the abnormality determination unit 44 determines that the current value of the detected voltage Vs when there is no DUT O in the radiation and the shutter is closed. And the previous value is read from the storage unit 34, and in step S31, the absolute value of the difference between the read current value and the previous value is compared with a constant value β1, and if β1 is exceeded, an abnormal signal (alarm) indicating an abnormality is issued in step S32. ) Is output.

The example shown in FIG. 5D corresponds to the above determination condition D, and in step S40, the abnormality determination unit 44 determines that the current value of the detected voltage Vs when the DUT O is not present in the radiation and the shutter is closed. In addition, the past values of the latest at least two times are read from the storage unit 34, the maximum value and the minimum value are extracted from the read three or more detection voltages in step S41, and the extracted maximum value is extracted in step S42. The difference between the value and the minimum value is compared with a constant value β2, and if β2 is exceeded, an abnormality signal (alarm) is output in step S43 to notify the abnormality. Further, the number of past values when obtaining the maximum value and the minimum value is preferably 3 to 5 times, because the determination accuracy improves as the number of times increases, but the detection of an abnormality may be delayed. Because there is.

FIGS. 6A to 6D show another example of the abnormality determining method performed by the abnormality determining unit 44 for each zero calibration (measurement of Vo and Vs) by the zero calibration unit 30. 6(a) and 6(c) are the same as FIGS. 5(a) and 5(c), respectively, and a description thereof will be omitted.

The example shown in FIG. 6B corresponds to the above determination condition B, and in step S20, the abnormality determination unit 44 determines that the current value of the detected voltage Vo when there is no DUT O during radiation and the shutter is open. In addition to the above, the maximum value and the minimum value of the past detection voltage Vo are read from the storage unit 34. In step S21, it is compared whether the number N of measurements is 1 or the current value is larger than the maximum value. If the number N of measurements is 1 or the current value is large, the maximum value is set in step 22. After setting the current value, the process proceeds to the next step S23, and if not, the process proceeds to the next step S23. In step S23, it is compared whether the number N of measurements is 1 or the current value is smaller than the minimum value. If the number N of measurements is 1 or the current value is small, the minimum value is set to the current value in step S24. After that, the process proceeds to the next step S25, and if not, the process proceeds to the next step S25. In step S25, the difference between the maximum value and the minimum value is compared with the constant value α2, and if α2 is exceeded, an abnormal signal (alarm) indicating the abnormality is output in step S26. If not, the maximum value and the minimum value are stored in the storage unit 34. When N=1, the maximum value and the minimum value are the same, and when N=2, the maximum value-minimum value is equal to the absolute value of the difference between the current value and the previous value, so N=3 or more, that is, It is desirable to use the current value of the detected voltage and the past value of at least twice the latest value.

The example shown in FIG. 6D corresponds to the above-mentioned determination condition D, and in step S40, the abnormality determination unit 44 determines that the current value of the detected voltage Vs when the DUT O is not present in the radiation and the shutter is closed. In addition, the maximum value and the minimum value of the past detection voltage Vs are read out from the storage unit 34. In step S41, it is compared whether the number of measurements N is 1 or the current value is larger than the maximum value. If the number of measurements N is 1 or the current value is large, the maximum value is determined in step S42. After setting this value, the process proceeds to the next step S43, and if not, the process proceeds to the next step S43. In step S43, it is compared whether the number of measurements N is 1 or the current value is smaller than the minimum value. If the number of measurements N is 1 or the current value is small, the minimum value is set to the current value in step S44. After that, the process proceeds to the next step S45, and if not, the process proceeds to the next step S45. In step S45, the difference between the maximum value and the minimum value is compared with the constant value β2, and if β2 is exceeded, an abnormality signal (alarm) indicating an abnormality is output in step S46. If not, the maximum value and the minimum value are stored in the storage unit 34. When N=1, the maximum value and the minimum value are the same, and when N=2, the maximum value-minimum value is equal to the absolute value of the difference between the current value and the previous value, so N=3 or more, that is, It is desirable to use the current value of the detected voltage and the past value of at least twice the latest value.

Although not shown, the abnormality determination unit 44 uses the determination conditions used in the abnormality determination method shown in FIGS. 5A to 5D or 6A to 6D in order to enhance the abnormality monitoring capability. Any two or three of A to D, or all four may be implemented. In this case, a plurality of abnormality determination processes are sequentially performed in a predetermined order, and when it is determined to be abnormal by any of the determination calculations, an abnormality signal is output and the calculation is terminated without performing the residual determination process. .. Therefore, the abnormality determination processing can be performed efficiently.

When some abnormality that adversely affects the measurement result occurs in the radiation thickness gauge 10, the detection voltage at the time of zero calibration changes. According to the present embodiment, the measurement is performed at each zero calibration. Since the abnormality is determined from the transition of the detection voltages Vo and Vs, such abnormality can be detected.

In particular, when the difference between the current value and the previous value of the detection voltage Vo measured with the shutter open at the time of zero calibration exceeds a constant value α1, or when the current value and the past value of Vo are multiple times (for example, five times). When the difference between the maximum value and the minimum value exceeds a constant value α2, it is determined as an abnormality, so that the abnormality such as the radiation source not being completely fixed or the inside of the radiation thickness gauge 10 or the operation of the shutter. It is possible to detect defects and the like.

In addition, when the difference between the current value and the previous value of the detected voltage Vs measured in the shutter closed state at the time of zero calibration exceeds a constant value β1, or when the current value and the past value of Vs are obtained for a plurality of times (for example, five times). When the difference between the maximum value and the minimum value exceeds the constant value β2, it is determined to be abnormal, so that noise is mixed into the cable that transmits the electrical signal detected by the detector 14 to the control panel 22, malfunction of the shutter, and the like. , It is possible to detect abnormalities at locations other than the radiation source.

According to the present invention, it is possible to detect an abnormality other than the operation abnormality of the shutter in the radiation thickness gauge.

10 Radiation Thickness Gauge 12 Radiation Source Section 14 Detector 16 Frame 18 Rail 20 Truck 22 Control Panel 24 Recorder 26 Average Processing Section 28 Thickness Calculation Section 30 Zero Calibration Section 32 Sample Calibration Section 34 Storage Section 36 Material Correction Section 38 Upper computer 40 Upper transmission unit 42 Off gauge determination unit 44 Abnormality determination unit

Claims (8)

A radiation source and a radiation source unit having a shutter that releasably shields the radiation emitted from the radiation source, a detector for detecting the radiation, and the radiation source unit and the detector so as to sandwich an object to be measured. In a radiation type thickness gauge for irradiating the object to be measured with radiation from the radiation source part and measuring the thickness of the object to be measured from the amount of transmitted radiation that has passed through the object to be measured,
A radiation thickness gauge, comprising: abnormality determination means for determining abnormality of the radiation thickness gauge based on a plurality of detection voltages measured by the detector at each zero calibration. The radiation type thickness meter according to claim 1, wherein the abnormality determination means is configured by at least one determination condition selected from the following determination conditions A to D.
Judgment condition A: Judgment condition B in which the current value and the previous value of the detected voltage measured in the open state of the shutter at the time of the zero calibration are compared, and when the difference exceeds a certain value, it is judged as abnormal. : The maximum value and the minimum value are obtained from the present value of the detected voltage measured in the open state of the shutter at the time of the zero calibration and the past values of at least the two most recent times, and the difference exceeds a certain value. In this case, the determination condition C is determined to be abnormal: the current value of the detected voltage measured in the closed state of the shutter at the time of the zero calibration is compared with the previous value, and when the difference exceeds a certain value, it is determined to be abnormal. Judgment condition D: Judgment of the maximum value and the minimum value from the current value of the detection voltage measured in the closed state of the shutter at the time of the zero calibration and the past values of at least two times immediately thereafter, and the difference between them. If it exceeds a certain value, it is judged as abnormal The radiation type thickness according to claim 2, wherein the abnormality determination unit has two or more determination conditions selected from the determination conditions A to D and is configured to sequentially determine. Total. The radiation type thickness gauge according to claim 3, wherein the abnormality determining means is configured to omit the determination conditions after the determination condition of abnormality among the determination conditions that are sequentially configured. .. A radiation source and a radiation source unit having a shutter that releasably shields the radiation emitted from the radiation source, a detector that detects the radiation, and the radiation source unit and the detector that sandwich the object to be measured. An abnormality monitoring method for a radiation type thickness gauge, comprising: a frame for irradiating the object to be measured with radiation from the radiation source part and measuring the thickness of the object to be measured from the amount of transmitted radiation transmitted through the object to be measured. At
An abnormality monitoring method for a radiation thickness gauge, comprising: determining abnormality of the radiation thickness gauge based on a plurality of detection voltages measured by the detector at each zero calibration. Judgment condition A: Comparing the present value and the previous value of the detected voltage measured in the open state of the shutter at the time of the zero calibration, and if the difference exceeds a certain value, it is judged to be abnormal. B: The maximum value and the minimum value are obtained from the present value of the detected voltage measured in the open state of the shutter at the time of the zero calibration and the past values of at least the two most recent values, and the difference exceeds a certain value. If it is determined to be abnormal, the determination condition C: the current value and the previous value of the detection voltage measured in the closed state of the shutter at the time of the zero calibration are compared, and the difference exceeds a certain value. And the determination condition D: a maximum value and a minimum value from the present value of the detected voltage measured in the closed state of the shutter at the time of the zero calibration and the past value of at least two times immediately thereafter. The radiation-type thickness according to claim 5, further comprising: determining the abnormality and determining an abnormality when the difference exceeds a certain value, and using one of the determination conditions selected from the following. Abnormality monitoring method of the gauge. The abnormality monitoring method for a radiation thickness gauge according to claim 6, further comprising sequentially determining two or more determination conditions selected from the determination conditions A to D. The abnormality monitoring method for a radiation thickness gauge according to claim 7, further comprising: sequentially determining the determination conditions and omitting the determination conditions after the determination that the abnormality has occurred.

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