A dual-mode passive nuclear level gauge with multiple photomultiplier tubes and its measurement method

Abstract

This application discloses a multi-photomultiplier tube dual-mode passive nuclear level gauge and its measurement method, relating to the field of industrial measurement technology. The measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge includes: S1: Presetting a working mode in the processing unit, the preset working modes including a first working mode and a second working mode; S2: After receiving an external instruction or the preset conditions are met, the processing unit starts or selects the corresponding working mode and obtains nuclear radiation data under that working mode; S3: Based on the nuclear radiation data under that working mode, the processing unit generates level data, or generates and outputs level data. This application can meet the measurement requirements under normal environmental conditions or the technical state of the level gauge, and can also eliminate internal or external interference of the level gauge through time-matching technology, improving the measurement capability of the passive nuclear level gauge under conditions of interference in the measurement environment or significant internal interference, thus achieving accurate measurement.

Description

Technical Field

[0001] This application relates to the field of industrial measurement technology, and in particular to a multi-photomultiplier tube dual-mode passive nuclear level gauge and its measurement method. Background Technology

[0002] Passive nuclear level gauges measure the level of materials within a container by measuring the nuclear radiation (especially gamma rays) released by radioactive substances such as sodium and cesium. Based on their overall structural characteristics, passive nuclear level gauges can be categorized into integrated passive nuclear level gauges, split-type nuclear level gauges, and multi-probe passive nuclear level gauges.

[0003] In existing technologies, the processing unit of a passive nuclear level gauge uses a relatively simple technical approach when processing the acquired photomultiplier tube electrical signals: it acquires the electrical signals from each photomultiplier tube and then generates nuclear radiation data. For multi-probe level gauges, the nuclear radiation data measured by multiple probes are comprehensively calculated to generate integrated nuclear radiation data. For example, the invention patent CN104568061A, entitled "Multi-probe Passive Nuclear Level Gauge," discloses various methods for integrating multiple probes. Although the methods of comprehensive calculation vary, they are all based on the idea of ​​first generating the nuclear radiation data from each probe and then performing comprehensive calculations.

[0004] However, in actual industrial applications, when passive nuclear level gauges measure materials in containers, they are affected by many complex factors, such as the state of the material at different levels within the container, the differences in the material's own radioactive characteristics, the actual volume of the container, changes in the mass of the passive nuclear level gauge itself, the quality of the power supply, changes in interference sources in the measurement environment, and the impact of nuclear radiation testing in industrial settings. Existing electrical signal processing technologies are difficult to achieve accurate adaptation across all scenarios, resulting in passive nuclear level gauges being unable to guarantee the accuracy and reliability of measurements in actual applications.

[0005] Furthermore, in existing passive nuclear level gauges, the weak nuclear radiation signals released by the material are extremely weak in the signal acquisition components (such as photomultiplier tubes and signal acquisition modules), and are easily drowned out by the noise of the equipment itself. This results in the weak nuclear radiation signals not being effectively identified, further restricting the accuracy and stability of level measurement. Summary of the Invention

[0006] The purpose of this application is to provide a dual-mode passive nuclear level gauge with multiple photomultiplier tubes and its measurement method. By utilizing time coincidence technology, interference can be eliminated or suppressed. By setting different features for the two working modes, it can adapt to more different measurement scenarios. It can meet the measurement requirements under normal environmental conditions or level gauge technical conditions. It can also eliminate internal or external interference of the level gauge through time coincidence technology, thereby improving the measurement capability of the passive nuclear level gauge under conditions where there is interference in the measurement environment or significant internal interference, and achieving accurate measurement.

[0007] To achieve the above objectives, this application provides a measurement method for a dual-mode passive nuclear level gauge with multiple photomultiplier tubes, comprising the following steps: S1: Preset a working mode in the processing unit, wherein the preset working mode includes: a first working mode and a second working mode; in the first working mode, the processing unit acquires pulse signals from each signal acquisition module to generate nuclear radiation data for each channel and / or total nuclear radiation data; in the second working mode, the processing unit generates nuclear radiation data based on the pulse time of the electrical signals from each signal acquisition module through time conformity processing, wherein the time conformity processing includes: treating pulses whose time interval between electrical signal pulse times does not exceed the time conformity judgment threshold as simultaneous events and counting the number of pulses; or, the processing unit directly counts the number of pulses output by the time conformity module and generates nuclear radiation data based on the number of pulses; S2: After receiving an external instruction or a preset condition is met, the processing unit starts or selects the corresponding working mode and obtains the nuclear radiation data in that working mode;

[0008] S3: The processing unit generates material level data based on the nuclear radiation data in this working mode, or generates material level data and outputs it.

[0009] As mentioned above, the preset conditions include at least the following: the comparison value or change value of each nuclear radiation data independently generated by each signal acquisition module meets the preset requirements; the total nuclear radiation data of the passive nuclear level gauge meets the preset requirements; the environmental interference level meets the preset requirements; the material type meets the preset requirements; the time conditions meet the preset requirements; and the comparison value of nuclear radiation data under the two working modes meets the preset requirements.

[0010] As described above, before step S1, there is also step S1': correcting the time deviation of each signal acquisition module so that the electrical signal pulse time output by each signal acquisition module is under a unified time reference, so as to serve as the statistical basis for judging whether the electrical signal pulse time is the same or similar in step S1.

[0011] As shown above, the processing unit sets a corresponding mode identifier for each working mode. When the corresponding working mode is started and the nuclear radiation data in that working mode is obtained, the corresponding mode identifier and the nuclear radiation data are output to the external device to prompt the user about the real-time working mode.

[0012] As described above, the processing unit configures different nuclear radiation data statistical algorithms for each working mode. In the first working mode, the nuclear radiation data statistical algorithm is a statistical time algorithm with a preset duration ≤ T1 to ensure measurement response speed. In the second working mode, the nuclear radiation data statistical algorithm is a statistical time algorithm with a preset duration ≥ T2 to obtain stable nuclear radiation measurement data. Wherein, T1 < T2.

[0013] As described above, after step S2 and before step S3, step S3' is included: comparing the difference between the nuclear radiation data of the second working mode and the nuclear radiation data of the first working mode; if the difference is greater than or equal to a preset first difference threshold, the processing unit adjusts the pulse discrimination threshold of the signal acquisition module; when the difference is greater than or equal to a preset second difference threshold, the pulse discrimination threshold is increased to ≥V1 to suppress noise; when the difference is greater than or equal to the preset first difference threshold and less than the second difference threshold, the pulse discrimination threshold is decreased to ≤V2 to acquire weak signals, where V2 < V1.

[0014] This application also provides a multi-photomultiplier tube dual-mode passive nuclear level gauge, comprising: N photomultiplier tubes, at least one scintillation crystal, N signal acquisition modules, and a processing unit; the processing unit has N electrical signal interfaces; wherein N is a natural number greater than or equal to 2; the photosensitive surface of each photomultiplier tube is connected to the optical output end of the scintillation crystal; the N photomultiplier tubes are connected one-to-one to the input ends of the N signal acquisition modules; the output ends of the N signal acquisition modules are connected one-to-one to the N electrical signal interfaces of the processing unit; the processing unit is configured to execute the above-described measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge to generate level data, or generate and output level data; or, including: N The system comprises one photomultiplier tube, at least one scintillation crystal, N signal acquisition modules, a timing synchronization module, and a processing unit. The processing unit has N electrical signal interfaces, where N is a natural number greater than or equal to 2. The photosensitive surface of each photomultiplier tube is connected to the optical output end of the scintillation crystal. The N photomultiplier tubes are connected one-to-one to the input ends of the N signal acquisition modules. The output ends of the N signal acquisition modules are connected to the input end of the timing synchronization module and the N electrical signal interfaces of the processing unit. The output end of the timing synchronization module is connected to the processing unit. The processing unit is configured to execute the above-described measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge to generate level data or generate and output level data.

[0015] The beneficial effects achieved by this application are as follows:

[0016] The multi-photomultiplier tube dual-mode passive nuclear level gauge and its measurement method of this application can not only meet the measurement requirements under normal environment or level gauge technical conditions, but also eliminate internal or external interference of the level gauge through time coincidence technology, thereby improving the measurement capability of the passive nuclear level gauge under the condition that there is interference in the measurement environment or significant internal interference, and achieving accurate measurement. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0018] Figure 1 A schematic diagram of one embodiment of a multi-photomultiplier tube dual-mode passive nuclear level gauge;

[0019] Figure 2 A schematic diagram of one embodiment of the circuit structure of a timing-compliant module;

[0020] Figure 3 A schematic diagram of another embodiment of the circuit structure for a timing-compliant module;

[0021] Figure 4 The waveform diagram for the time-matching module;

[0022] Figure 5 This is a flowchart of one embodiment of the measurement method for a multi-photomultiplier tube dual-mode passive nuclear level gauge. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] As one embodiment, this application provides a multi-photomultiplier tube dual-mode passive nuclear level gauge, comprising: N photomultiplier tubes, at least one scintillation crystal, N signal acquisition modules, and a processing unit; the processing unit has N electrical signal interfaces; wherein, N is a natural number greater than or equal to 2; the photosensitive surface of each photomultiplier tube is connected to the optical output end of the scintillation crystal; the N photomultiplier tubes are connected one-to-one to the input ends of the N signal acquisition modules; the output ends of the N signal acquisition modules are connected one-to-one to the N electrical signal interfaces of the processing unit; the processing unit is configured to execute the measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge described below, so as to generate level data, or generate level data and output it.

[0025] Specifically, the photosensitive surface of the photomultiplier tube is optically coupled to the optical output end of the scintillation crystal. The photomultiplier tube is electrically connected to the signal acquisition module. The signal acquisition module is electrically connected to the arithmetic processor. The connection process may adopt conventional connection methods in this field (such as mechanical fixed connection, circuit wire connection, interface adapter connection, etc.) for structural connection. The specific connection details are existing technology and will not be described in detail here.

[0026] As another embodiment, this application provides a multi-photomultiplier tube dual-mode passive nuclear level gauge, comprising: N photomultiplier tubes, at least one scintillation crystal, N signal acquisition modules, a timing synchronization module, and a processing unit; the processing unit has N electrical signal interfaces; wherein, N is a natural number greater than or equal to 2; the photosensitive surface of each photomultiplier tube is connected to the optical output end of the scintillation crystal; the N photomultiplier tubes are connected one-to-one to the input ends of the N signal acquisition modules; such as Figure 1 As shown, the output terminals of the N signal acquisition modules are all electrically connected to the input terminal of the time synchronization module and the N electrical signal interfaces of the arithmetic processor; the output terminal of the time synchronization module is connected to the arithmetic processor; the arithmetic processor is configured to execute the measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge described below, so as to generate level data, or generate level data and output it.

[0027] Specifically, the photosensitive surface of the photomultiplier tube is optically coupled to the optical output end of the scintillation crystal. The photomultiplier tube is electrically connected to the signal acquisition module. The signal acquisition module is electrically connected to the time synchronization module and the arithmetic processor. The time synchronization module is electrically connected to the arithmetic processor. The connection process may adopt conventional connection methods in the field (such as mechanical fixed connection, circuit wire connection, interface adapter connection, etc.) for structural connection. The specific connection details are existing technology and will not be described in detail here.

[0028] The time coincidence module is responsible for filtering the pulse signals output by the signal acquisition module based on their time correlation. It only transmits signals that meet the time coincidence condition to the processing processor, thereby identifying or eliminating interference signals. This allows the processing processor to receive material signals that meet the time coincidence condition. The processing processor then generates accurate material level or nuclear radiation data based on the material signals that have eliminated interference signals as much as possible.

[0029] The core of the timing synchronization module implementation lies in the fact that many noise signals, including those from the internal circuitry of the passive nuclear level gauge, external power supply interference, or weak environmental interference, lack temporal consistency. In particular, the noise signals of the various detectors integrated with the scintillation crystal, photomultiplier tube, and signal acquisition module often differ, and when one detector malfunctions, the noise difference between it and the others becomes even more pronounced. External weak radioactive interference, grounding interference, and electrostatic interference from the detectors can also sometimes cause differences. These differences result in the temporal characteristics of the noise in the signals from each detector not being consistent with the nuclear radiation signal from the material. The timing synchronization module can filter out pulses that do not meet the timing coincidence requirements, generating a single pulse signal based on the pulse signals that meet the timing coincidence repetition requirements. This effectively allows only the nuclear radiation signal released by the material to pass through the timing synchronization module. Of course, since multiple timing-synchronized pulses are combined into a single pulse signal, the number of pulse signals received by the processing unit is reduced.

[0030] As an example, such as Figure 2 As shown, the circuit structure of the timing synchronization module consists of a shaping module and a synchronization logic module. The pulses IN1 and IN2 output from the signal acquisition module are fed into the shaping module, shaped, and then output from pulses OUT1 and OUT2. These pulses are then input into the synchronization logic module, which finally outputs the synchronization signal and transmits it to the processing unit.

[0031] As another embodiment, such as Figure 3 As shown, the circuit structure of the timing coincidence module consists of two monostable multivibrators (i.e.: Figure 3 The signal acquisition module consists of monostable multivibrator 1 and monostable multivibrator 2, AND gate, and NOT gate. The pulse IN1 output by the signal acquisition module is connected to the first monostable multivibrator (i.e., ...). Figure 3 The first monostable multivibrator is connected to the second monostable multivibrator (i.e., the pulse IN2 is connected to the second monostable multivibrator). Figure 3 The first monostable multivibrator (i.e., the first one) is shaped into a monostable multivibrator (i.e., the second one). Figure 3 The output pulse OUT1 of the monostable multivibrator 1 and the second monostable multivibrator (i.e.: Figure 3 The pulse OUT2 output by the monostable multivibrator 2) is first input to the AND gate, then output from the AND gate to the NOT gate, and finally output from the NOT gate as a coincidence signal and transmitted to the arithmetic processor.

[0032] Specifically, the principle details and waveform description of the timing synchronization module are as follows: Monostable multivibrator 1 is triggered on the rising edge of pulse IN1, generating a pulse signal with a width of t1; Monostable multivibrator 2 is triggered on the falling edge of pulse IN2, generating a pulse signal with a width of t2; the pulse signals with widths of t1 and t2 enter the logic circuit of AND gate and NOT gate, and only when the two times overlap, a synchronization signal is output, and the synchronization time is t1 + t2; Figure 4 As shown, the waveform diagram visualizes this process: the rising edge of pulse IN1 and the falling edge of pulse IN2 trigger pulses with pulse widths of t1 and t2, respectively. After logical operation, a coincident signal with a time span of t1+t2 is output, which is finally passed to the arithmetic processor.

[0033] It should be noted that in actual implementation, the output terminals of each signal acquisition module can be directly connected to both the input terminal of the time synchronization module and the input terminal of the arithmetic processor. Alternatively, a switching device can be used to select and switch between the input terminals of the time synchronization module and the arithmetic processor. The switching device can also be controlled by the arithmetic processor.

[0034] Furthermore, the specific value of N is set according to actual needs. For example, N=2, a multi-photomultiplier tube dual-mode passive nuclear level gauge includes: two photomultiplier tubes, at least one scintillation crystal, two signal acquisition modules, and a processing unit. The photosensitive surface of each photomultiplier tube is connected to the optical output end of the scintillation crystal; one photomultiplier tube is connected to the input end of one signal acquisition module, and the other photomultiplier tube is connected to the input end of another signal acquisition module; the output ends of the two signal acquisition modules are connected one-to-one to the two electrical signal interfaces of the processing unit.

[0035] Furthermore, the specific number and structure of the scintillation crystals can be set according to actual needs. In this application, cylindrical scintillation crystals are preferred, which can achieve good optical coupling matching with photomultiplier tubes. When the cylindrical scintillation crystals are parallel to the horizontal plane, parallel to the outer wall of the container, or the cross-section of the outer wall, high linearity measurement of the material level change process can be achieved.

[0036] In application scenarios, each photomultiplier tube can be matched with one scintillation crystal, or two photomultiplier tubes can be optically coupled to the two ground windows of a dual-window scintillation crystal. Multiple probes with a single photomultiplier tube matched with a scintillation crystal can form a multi-photomultiplier tube dual-mode passive nuclear level gauge, and one or more probes with dual photomultiplier tubes combined with a scintillation crystal can also form a multi-photomultiplier tube dual-mode passive nuclear level gauge.

[0037] like Figure 5 As shown, this application provides a measurement method for a multi-photomultiplier tube dual-mode passive nuclear level gauge, comprising the following steps:

[0038] S1: A preset working mode is established in the processing unit, wherein the preset working mode includes: a first working mode and a second working mode; in the first working mode, the processing unit acquires pulse signals from each signal acquisition module to generate nuclear radiation data for each channel and / or total nuclear radiation data; in the second working mode, the processing unit generates nuclear radiation data based on the pulse time of the electrical signals from each signal acquisition module through time conformity processing, wherein the time conformity processing includes: treating pulses whose time interval between electrical signal pulse times does not exceed the time conformity judgment threshold as simultaneous events and counting the number of pulses; or, the processing unit directly counts the number of pulses output by the time conformity module and generates nuclear radiation data based on the number of pulses.

[0039] Specifically, the generation of nuclear radiation data based on pulse count in both the first and second operating modes can be achieved using existing technologies. For example, based on the fundamental principle that pulse count is positively correlated with nuclear radiation intensity, the nuclear radiation data can be calculated by counting the number of pulses per unit time. It should be noted that the passive nuclear level gauge is essentially a scintillator counter, representing nuclear radiation in a count format.

[0040] This application pre-sets two electrical signal processing modes (i.e., a first working mode and a second working mode) in a single multi-photomultiplier tube dual-mode passive nuclear level gauge. The first working mode performs comprehensive calculations on all nuclear radiation data to generate the nuclear radiation data, which can be achieved using existing technologies, such as the averaging method, weighted averaging method, or filtering algorithm. In fact, the first working mode can completely utilize the existing technology published under CN104568061A, entitled "Multi-probe passive nuclear level gauge."

[0041] In the second operating mode, the pulse timing conformance technology can be implemented either by the processing unit based on its own algorithm or by the processing unit acquiring signals from a specially configured timing conformance module. When the processing unit implements the technology based on its own algorithm, the processing unit of the multi-photomultiplier tube dual-mode passive nuclear level meter first marks the pulses of each electrical signal acquisition module and records the pulse time of each signal acquisition module. Pulse times with intervals not exceeding the threshold for similar pulse times are considered the same or similar pulse times, and these are used as the nuclear radiation data of the multi-photomultiplier tube dual-mode passive nuclear level meter. For example, if the number of pulses with the same or similar pulse times among the two signal acquisition modules is 300, then 300 is used as the nuclear radiation data of the multi-photomultiplier tube dual-mode passive nuclear level meter. Alternatively, the product of the pulse counts (e.g., 3 × 300 = 900) can be used as the nuclear radiation data of the multi-photomultiplier tube dual-mode passive nuclear level meter.

[0042] In this process, when counting the number of pulses with the same or similar electrical signal pulse durations, a pulse discrimination threshold (e.g., discrimination voltage) is used to discriminate the electrical signals of each signal acquisition module to obtain the pulse count. This allows a portion of the noise signal within the circuit to be eliminated before counting the pulses with the same or similar electrical signal pulse durations. The discrimination voltage is between 1.5V and 4.5V. For the remaining noise signal in the circuit after discrimination, existing technologies cannot further discriminate it. However, this application can filter out the pulse count of the same or similar electrical signal pulse durations (i.e., nuclear radiation released from materials) through a timing matching scheme, thereby effectively eliminating noise signals within the discrimination voltage range, resulting in a significantly higher signal-to-noise ratio.

[0043] In this application, when the multi-photomultiplier tube dual-mode passive nuclear level gauge does not include a time synchronization module, in the second operating mode, the processing unit generates nuclear radiation data based on the electrical signal pulse times of each signal acquisition module through time synchronization processing. The time synchronization processing includes treating pulses whose time intervals do not exceed a time synchronization judgment threshold as simultaneous events and counting the number of pulses. The specific value of the time synchronization judgment threshold is set according to actual needs.

[0044] When a dual-mode passive nuclear level gauge with multiple photomultiplier tubes includes a time synchronization module, in the second operating mode, the processing unit directly counts the number of pulses output by the time synchronization module and generates nuclear radiation data based on the pulse count. It should be noted that the new pulse signal or data sent to the processing unit after the time synchronization module identifies the pulses in the electrical signals sent by the multiple signal acquisition modules is not a single pulse from the input electrical signals sent by each signal acquisition module, but rather a new signal generated by the time synchronization module. This signal represents the existence of a time-synchronized pulse event in the electrical signals of the multiple signal acquisition modules within the statistical time. Regardless of the number of signal acquisition modules, if a time-synchronized pulse exists after passing through the time synchronization module, only a new pulse signal or data will be generated. The time synchronization module can transmit time synchronization event information to the processing unit in the form of analog signals or data signals.

[0045] When executing the second working mode, the processor itself needs to mark the pulse time when it counts the time matching pulse events. Therefore, it is difficult to compare with a dedicated time matching module in terms of efficiency and performance, but it is cheaper.

[0046] S2: After receiving external instructions or when preset conditions are met, the processing unit starts or selects the corresponding working mode and obtains the nuclear radiation data under that working mode.

[0047] Specifically, for passive nuclear level gauges, the most important task is to measure the material level inside the container. The core function of a passive nuclear level gauge is to output the material level data inside the container to external devices such as the operating unit. In actual work or specific work scenarios, users can issue external commands to the processing processor to use the corresponding working mode through the human-machine interface or buttons configured on the multi-photomultiplier tube dual-mode passive nuclear level gauge itself. In addition, users can also use dedicated wired or wireless devices to issue external commands to the processing processor to use the corresponding working mode, instructing the processing processor to operate in which mode.

[0048] Furthermore, the processing unit can activate or select the corresponding operating mode according to preset conditions. The preset conditions include at least: the comparison value or change value of each nuclear radiation data independently generated by each signal acquisition module meets the preset requirements; the total nuclear radiation data of the passive nuclear level gauge meets the preset requirements; the environmental interference level meets the preset requirements; the material type meets the preset requirements; the time conditions meet the preset requirements; and the comparison value of nuclear radiation data in the two operating modes meets the preset requirements.

[0049] The comparison or change values ​​of the nuclear radiation data generated independently by each signal acquisition module meet the preset requirements. Because the nuclear radiation released by the material has a consistent effect on each detector (the scintillation crystal, photomultiplier tube, and signal acquisition module connected in sequence), the nuclear radiation values ​​or changes in nuclear radiation values ​​of each detector are basically consistent in the first working mode. If one detector's nuclear radiation value is greater than that of other detectors, it indicates that one detector may have abnormal noise interference, or if the change in nuclear radiation value measured by another detector is greater than that of other detectors, it indicates that that detector may have abnormal noise interference. For example, if the processor is originally operating in the first working mode, and a detector value is 300 greater than that of other detectors, or the change is greater than that of other detectors by 20%, then the preset requirement is to activate the second working mode to eliminate the data distortion problem caused by abnormal detector noise.

[0050] In practical implementation, the processing unit can simultaneously acquire nuclear radiation data from each signal acquisition module in the first operating mode, or generate total nuclear radiation data based on the nuclear radiation data from each signal acquisition module (this can be a direct sum of the nuclear radiation data from each signal acquisition module, or the total nuclear radiation data can be calculated using other conventional methods). This total nuclear radiation data is the nuclear radiation data used by the passive nuclear level gauge to generate the material level. In the second operating mode, the number of pulses meeting the time repetition requirements is acquired, and the passive nuclear level gauge's nuclear radiation data is generated based on this pulse number. However, whether the nuclear radiation data generated in the first or second operating mode is used as the material's nuclear radiation data or the basis for generating the material level depends on the processing unit's selection based on preset requirements after preset conditions are met.

[0051] The total nuclear radiation data of the passive nuclear level gauge meets the preset requirements. Because the time-matching scheme not only removes noise signals but also some material signals, the total nuclear radiation data of the passive nuclear level gauge is very low. If the total nuclear radiation data is too low, although the signal is clean, it no longer has the energy to identify material changes. Therefore, a second operating mode can be preset. If the total nuclear radiation data of the passive nuclear level gauge is less than 300, the processor starts the first operating mode, or selects the nuclear radiation data generated in the first operating mode as the passive nuclear level gauge data to generate the material level, thus better identifying material changes.

[0052] The environmental interference level has reached the preset requirements. Obviously, if the interference in the environment or the measurement environment reaches a certain level, such as when it is severe, the second operating mode will be activated to eliminate the noise caused by environmental interference. Environmental interference registration is usually provided by external sensor components responsible for monitoring the environment; for example, in the application of passive nuclear level gauges, a nuclear radiation detector is sometimes specifically configured to monitor environmental conditions. Classifying and labeling environmental interference is a common practice. When the environmental interference level is relatively low, or even nonexistent, the processor can activate the first operating mode, or select the nuclear radiation data from the first operating mode as the nuclear radiation data for the passive nuclear level gauge to generate the material level.

[0053] The material type meets the preset requirements. Since passive nuclear level gauges measure the nuclear radiation released by radioactive substances contained within the material itself, the intensity of nuclear radiation released by the same quantity of material can vary significantly depending on the material type. In practical applications, existing passive nuclear level gauges are typically equipped with a material type identification and correction instrument for real-time measurement of the material's radioactivity characteristics, which can generate material type data in real time. When the material's radioactivity characteristics are strong, the nuclear radiation released will be strong. At this time, the noise inside or outside the passive nuclear level gauge is very small compared to the material signal, and further noise removal is unnecessary. Therefore, the processing unit starts or selects the first operating mode.

[0054] The timing conditions meet the preset requirements. When noise or interference cannot be directly distinguished, the processor can be preset to operate in a first working mode for a period of time, and then in a second working mode for a period of time, allowing users to distinguish the different data under the two working modes. Furthermore, some interference in industrial settings follows a temporal pattern; for example, flaw detection or fan startup at night may interfere with the operation of the passive nuclear level gauge. Therefore, the processor can be preset to enter the second working mode at 8 PM and to switch to the first working mode at 6 AM when flaw detection or fan shutdown.

[0055] The comparison values ​​of nuclear radiation data in the two operating modes meet the preset requirements. The nuclear radiation data obtained in the first operating mode can be compared with the data in the second operating mode. For example, if the difference between the nuclear radiation data in the first operating mode and the second operating mode is greater than 600, it indicates that the interference is of a comparative intensity. At this time, the second operating mode is activated, or the data in the second operating mode is selected as the nuclear radiation data of the passive nuclear level gauge to generate material nuclear radiation or material level.

[0056] In addition, the startup of a passive nuclear level gauge can also be preset. For example, after the multi-photomultiplier tube dual-mode passive nuclear level gauge is powered on and starts working, the processing unit enters the preset working mode. For example, after the multi-photomultiplier tube dual-mode passive nuclear level gauge starts working, it directly enters the first working mode of data addition.

[0057] S3: The processing unit generates material level data based on the nuclear radiation data in this working mode, or generates material level data and outputs it.

[0058] Specifically, generating material level data based on nuclear radiation data from a passive nuclear level gauge, or generating level data and outputting it to an external device, is a very common technique in this field. Step S3 can be achieved using existing technology, so it will not be described in detail here.

[0059] Furthermore, before step S1, there is also step S1': correcting the time deviation of each signal acquisition module so that the electrical signal pulse time output by each signal acquisition module is under a unified time reference, so as to serve as the statistical basis for judging whether the electrical signal pulse time is the same or similar in step S1.

[0060] Specifically, in practical applications, due to the characteristics of hardware components, although multiple photomultiplier tubes may simultaneously capture the same nuclear radiation event, the pulses of the electrical signals acquired by the passive nuclear level gauge may have time deviations. If the time deviations of each signal acquisition module are not corrected, the processing unit will be unable to accurately count the pulse signals with matching times. Therefore, in practical applications, it is necessary to pre-analyze the pulses and time deviations acquired by each signal acquisition module and preset the time deviation value. For example, if the pulse time value of the first signal acquisition module deviates from the standard time by 0.01 ns, and the pulse time value of the second signal acquisition module deviates from the standard time by 0.03 ns, the processing unit, after counting the pulse times, will subtract the deviation value of 0.01 ns from the pulse time of the first signal acquisition module to obtain the corrected time, and subtract the deviation value of 0.03 ns from the pulse time of the second signal acquisition module to obtain the corrected time. It should be noted that the actual deviation correction method for each signal acquisition module is consistent, because this deviation belongs to the overall circuit performance deviation; therefore, the pulses on each signal acquisition module must be processed using the same correction logic.

[0061] Furthermore, the processing unit sets a corresponding mode identifier for each working mode. When the corresponding working mode is started and the nuclear radiation data in that working mode is obtained, the corresponding mode identifier and the nuclear radiation data are output to the external device to prompt the user about the real-time working mode.

[0062] Specifically, in practical applications, the multi-photomultiplier tube dual-mode passive nuclear level gauge adopts different operating modes based on different needs. Since the nuclear radiation data generated by various operating modes may differ significantly in quantity and characteristics, it is necessary to inform users (especially remote users) of the current operating mode. The processing unit sets a corresponding mode identifier for each operating mode. When the corresponding operating mode is activated and the nuclear radiation data under that mode is obtained, the corresponding mode identifier is output along with the nuclear radiation data to an external device. The external device (e.g., a remote operating device) can determine the current operating mode by parsing the mode identifier. For example, if the multi-photomultiplier tube dual-mode passive nuclear level gauge outputs the mode identifier in digital format, with 01 representing the first operating mode and 00 representing the second operating mode, the external device can display the corresponding operating mode after parsing the digital signal.

[0063] Furthermore, the processing unit configures different nuclear radiation data statistical algorithms for each working mode; in the first working mode, the nuclear radiation data statistical algorithm is a statistical time algorithm with a preset duration ≤ T1 to ensure measurement response speed; in the second working mode, the nuclear radiation data statistical algorithm is a statistical time algorithm with a preset duration ≥ T2 to obtain stable or more nuclear radiation measurement data; where T1 < T2.

[0064] Specifically, in the first working mode, there are more effective nuclear radiation signals from the materials, and a statistical time algorithm with a preset duration of ≤T1 is used, which results in a fast response speed to changes in the materials.

[0065] In practical applications, using a time-matching scheme results in fewer valid nuclear radiation signals. Effective nuclear radiation signals from some materials may be excluded because the time frame cannot meet the same or similar requirements, leading to very low nuclear radiation data. If the nuclear radiation data is very low, it becomes difficult to distinguish differences between different material levels. To address the issue of low nuclear radiation data per unit statistical time, the second working mode increases the statistical time (i.e., adopts a statistical time algorithm with a preset duration ≥ T2) to increase the number of valid nuclear radiation signals obtained, thus acquiring stable nuclear radiation measurement data.

[0066] Furthermore, after step S2 and before step S3, step S3' is included: comparing the difference between the nuclear radiation data of the second working mode and the nuclear radiation data of the first working mode; if the difference is greater than or equal to a preset first difference threshold, the processing unit adjusts the pulse discrimination threshold of the signal acquisition module; when the difference is greater than or equal to a preset second difference threshold, the pulse discrimination threshold is increased to ≥V1 to suppress noise; when the difference is greater than or equal to the preset first difference threshold and less than the second difference threshold, the pulse discrimination threshold is decreased to ≤V2 to acquire weak signals, where V2 < V1.

[0067] Specifically, since the timing-matching scheme (i.e., the second operating mode) can greatly eliminate the influence of noise, this application determines the noise status of the current multi-photomultiplier tube dual-mode passive nuclear level gauge by comparing the difference between the nuclear radiation data in the second operating mode and the nuclear radiation data in the first operating mode. If the current noise level is relatively low (i.e., when the difference is greater than or equal to a preset first difference threshold and less than a second difference threshold), the processing unit can lower the lower limit of the pulse discrimination threshold (i.e., lower the pulse discrimination threshold to ≤V2), allowing more weak signals from materials to be statistically analyzed and obtaining more significant nuclear radiation data. If the difference is greater than or equal to a preset second difference threshold (i.e., the current noise is relatively high), it indicates that there is too much noise, and the processing unit needs to increase the pulse discrimination threshold to further suppress the noise in the first operating mode.

[0068] The beneficial effects achieved by this application are as follows:

[0069] The multi-photomultiplier tube dual-mode passive nuclear level gauge and its measurement method of this application can not only meet the measurement requirements under normal environment or level gauge technical conditions, but also eliminate internal or external interference of the level gauge through time coincidence technology, thereby improving the measurement capability of the passive nuclear level gauge under the condition that there is interference in the measurement environment or significant internal interference, and achieving accurate measurement.

[0070] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the scope of protection of this application is intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application. Obviously, those skilled in the art can make various alterations and variations to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of protection of this application and its equivalents, this application also intends to include these modifications and variations.

Claims

1. A measurement method for a multi-photomultiplier tube dual-mode passive nuclear level gauge, characterized in that, Includes the following steps: S1: Preset operating modes in the processing unit, wherein the preset operating modes include: a first operating mode and a second operating mode; In the first operating mode, the arithmetic processor acquires pulse signals from each signal acquisition module and generates individual nuclear radiation data and / or total nuclear radiation data; In the second operating mode, the arithmetic processor generates nuclear radiation data based on the pulse times of the electrical signals from each signal acquisition module through time conformity processing. The time conformity processing includes: treating pulses whose time intervals between electrical signal pulse times do not exceed the time conformity judgment threshold as simultaneous events and counting the number of pulses; or, the arithmetic processor directly counts the number of pulses output by the time conformity module and generates nuclear radiation data based on the number of pulses. S2: After receiving an external instruction or when a preset condition is met, the processing unit starts or selects the corresponding working mode and obtains the nuclear radiation data under that working mode. S3: The processing unit generates material level data based on the nuclear radiation data in this working mode, or generates material level data and outputs it.

2. The measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge according to claim 1, characterized in that, The preset conditions include at least the following: the comparison value or change value of each nuclear radiation data independently generated by each signal acquisition module meets the preset requirements; the total nuclear radiation data of the passive nuclear level gauge meets the preset requirements; the environmental interference level meets the preset requirements; the material type meets the preset requirements; the time conditions meet the preset requirements; and the comparison value of nuclear radiation data in the two working modes meets the preset requirements.

3. The measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge according to claim 1, characterized in that, Before step S1, there is also step S1': correcting the time deviation of each signal acquisition module so that the electrical signal pulse time output by each signal acquisition module is under a unified time reference, so as to serve as the statistical basis for judging whether the electrical signal pulse time is the same or similar in step S1.

4. The measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge according to claim 1, characterized in that, The processing unit sets a corresponding mode identifier for each working mode. When the corresponding working mode is started and the nuclear radiation data in that working mode is obtained, the corresponding mode identifier and the nuclear radiation data are output to the external device to prompt the user about the real-time working mode.

5. The measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge according to claim 1, characterized in that, The processing unit is configured with different nuclear radiation data statistical algorithms for each operating mode; In the first working mode, the nuclear radiation data statistical algorithm is: a statistical time algorithm with a preset duration ≤ T1 is adopted to ensure the measurement response speed; In the second working mode, the nuclear radiation data statistical algorithm is as follows: a statistical time algorithm with a preset duration ≥ T2 is used to obtain stable nuclear radiation measurement data; where T1 < T2.

6. The measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge according to claim 1, characterized in that, After step S2 and before step S3, step S3' is also included: The difference between the nuclear radiation data in the second working mode and the nuclear radiation data in the first working mode is compared. If the difference is greater than or equal to the preset first difference threshold, the pulse discrimination threshold of the signal acquisition module is adjusted by the processing unit. When the difference is greater than or equal to the preset second difference threshold, the pulse discrimination threshold is increased to ≥V1 to suppress noise; when the difference is greater than or equal to the preset first difference threshold and less than the second difference threshold, the pulse discrimination threshold is decreased to ≤V2 to acquire weak signals, where V2 < V1.

7. A dual-mode passive nuclear level gauge with multiple photomultiplier tubes, characterized in that, include: N photomultiplier tubes, at least one scintillation crystal, N signal acquisition modules, and a processing unit; The processing unit has N electrical signal interfaces; where N is a natural number greater than or equal to 2. The photosensitive surface of each photomultiplier tube is connected to the optical output end of the scintillation crystal; N photomultiplier tubes are connected one-to-one to the input terminals of N signal acquisition modules; The output terminals of N signal acquisition modules are connected one-to-one with the N electrical signal interfaces of the processing unit; The processing unit is configured to execute the measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge as described in any one of claims 1-6, to generate level data, or to generate and output level data; Alternatively, it may include: N photomultiplier tubes, at least one scintillation crystal, N signal acquisition modules, a timing module, and a processing unit; the processing unit has N electrical signal interfaces; where N is a natural number greater than or equal to 2; The photosensitive surface of each photomultiplier tube is connected to the optical output end of the scintillation crystal; N photomultiplier tubes are connected one-to-one to the input terminals of N signal acquisition modules; The outputs of N signal acquisition modules are all connected to the input of the time comparability module and the N electrical signal interfaces of the processing unit. The output of the time synchronization module is connected to the processing unit. The processing unit is configured to execute the measurement method of the multi-photomultiplier tube dual-mode passive nuclear level gauge as described in any one of claims 1-6, to generate level data, or to generate and output level data.

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