A multi-photomultiplier tube electric signal synthesis passive nuclear level gauge

Abstract

This application discloses a passive nuclear level gauge using multi-photomultiplier tube electrical signal synthesis, relating to the field of industrial measurement technology. It includes: N photomultiplier tubes, at least one scintillation crystal, N signal acquisition modules, an electrical signal synthesis module, and a processing module. The processing module includes: a first electrical signal interface; 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 end of the electrical signal synthesis module is connected to the first electrical signal interface of the processing module; and the N input ends of the electrical signal synthesis module are connected one-to-one to the output ends of the N signal acquisition modules. This application can achieve the identification of weakly radioactive materials or materials at long distances through multi-photomultiplier tube electrical signal synthesis, greatly improving the detection performance of the passive nuclear level gauge.

Description

Technical Field

[0001] This application relates to the field of industrial measurement technology, and in particular to a passive nuclear level gauge that synthesizes electrical signals from multiple photomultiplier tubes. 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 module of passive nuclear level gauges uses a relatively simple technical solution 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 values ​​measured by multiple probes are comprehensively calculated to generate a combined nuclear radiation value. 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 values ​​of each probe and then performing a comprehensive calculation.

[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 limiting the accuracy of level measurement and the ability to detect materials at long distances. Utility Model Content

[0006] The purpose of this application is to provide a passive nuclear level gauge that synthesizes electrical signals from multiple photomultiplier tubes. This gauge can identify materials with weak nuclear radiation or materials at long distances through the synthesis of electrical signals from multiple photomultiplier tubes, greatly improving the detection performance of the passive nuclear level gauge. At the same time, it can perform normal measurements using existing technology under strong material radiation conditions. It can also use a time coincidence module or time coincidence algorithm to eliminate external interference caused by circuits, power supply and synchronization. It uses an ADC sampling module to achieve accurate analysis of the signal.

[0007] To achieve the above objectives, this application provides a passive nuclear level gauge using multi-photomultiplier tube electrical signal synthesis, comprising: N photomultiplier tubes for converting optical signals into electrical signals; at least one scintillation crystal for converting acquired nuclear radiation into optical signals; N signal acquisition modules for acquiring electrical signals from the photomultiplier tubes; an electrical signal synthesis module for synthesizing multiple electrical signals output from at least two of the N photomultiplier tubes into a single synthesized electrical signal; and a computational processing module for acquiring and calculating the single synthesized electrical signal to generate nuclear radiation data and / or level data; wherein N is a natural number greater than or equal to 2; wherein the computational processing module includes: a first electrical signal interface; 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 end of the electrical signal synthesis module is connected to the first electrical signal interface of the computational processing module; and the N input ends of the electrical signal synthesis module are connected one-to-one to the output ends of the N signal acquisition modules.

[0008] As described above, the arithmetic processing module also includes: N second electrical signal interfaces, which are connected one-to-one with N signal acquisition modules to receive the electrical signals of the photomultiplier tubes acquired by the signal acquisition modules.

[0009] As described above, if there are two signal acquisition modules, one of them is directly electrically connected to the second electrical signal interface of the arithmetic processing module, and is also electrically connected to the electrical signal synthesis module; the other signal acquisition module is electrically connected to the electrical signal synthesis module; the electrical signal synthesis module is electrically connected to the arithmetic processing module through the first electrical signal interface; if there are three or more signal acquisition modules, at least two of them are electrically connected to the electrical signal synthesis module, the electrical signal synthesis module is connected to the first electrical signal interface, and at least one signal acquisition module is directly electrically connected to the second electrical signal interface of the arithmetic processing module without going through the electrical signal synthesis module.

[0010] As mentioned above, it also includes: a time synchronization module, the outputs of N signal acquisition modules are all connected to the input of the time synchronization module; the output of the time synchronization module is connected to the input interface of the arithmetic processing module; and an ADC sampling module, the input of the ADC sampling module is connected to the output of each electrical signal acquisition module, and the output of the ADC sampling module is connected to the arithmetic processing module.

[0011] As described above, it further includes: a signal switching module, the outputs of N signal acquisition modules are all connected to the input of the signal switching module, and the input of the signal synthesis module and the input of the arithmetic processing module are all connected to the output of the signal switching module; or, it further includes: N signal switching modules, the outputs of N signal acquisition modules are connected one-to-one with the inputs of N signal switching modules, and the input of the signal synthesis module and the input of the arithmetic processing module are all connected to the output of the signal switching module.

[0012] As shown above, there are two signal switching modules and two signal acquisition modules; the output of one signal acquisition module is connected to the input of one signal switching module, the output of one signal switching module is connected to one input of the signal synthesis module, and the output of one signal switching module is connected to one input of the arithmetic processing module; the output of the other signal acquisition module is connected to the input of the other signal switching module, the output of the other signal switching module is connected to the other input of the signal synthesis module, and the output of the other signal switching module is connected to the other input of the arithmetic processing module; or, there is one signal switching module and one signal acquisition module. Two signal acquisition modules are configured; the output of one module is connected to the input of the signal switching module and the electrical signal synthesis module; the output of the other module is connected to the input of the signal switching module; the output of the signal switching module is connected to the arithmetic processing module; and the electrical signal synthesis module is connected to the first electrical signal interface. Alternatively, there is one signal switching module and two signal acquisition modules; the output of one module is connected to the input of the signal switching module and the electrical signal synthesis module; the output of the other module is connected to the input of the signal switching module; the signal switching module is connected to the arithmetic processing module; and the electrical signal synthesis module is connected to the first electrical signal interface.

[0013] As shown above, the arithmetic processing module is also equipped with a control interface, which is connected to the signal switching module.

[0014] As shown above, the electrical signal synthesis module is an analog adder circuit; the analog adder circuit includes: an operational amplifier, N independent input resistors and a feedback resistor; the inverting input terminal of the operational amplifier is connected one-to-one with the output terminals of N signal acquisition modules through the N independent input resistors, the output terminal of the operational amplifier is connected to the inverting input terminal of the operational amplifier through the feedback resistor, the non-inverting input terminal of the operational amplifier is connected to the reference voltage, and the output terminal of the operational amplifier is connected to the first electrical signal interface of the operational processing module.

[0015] As described above, the signal acquisition module is an analog filtering circuit; the analog filtering circuit includes: a comparator, a DC blocking capacitor, a reference voltage source, a pull-up resistor, and a pull-up voltage source; the inverting input of the comparator is connected to the output of the photomultiplier tube through the DC blocking capacitor, the non-inverting input of the comparator is connected to the reference voltage source to receive the reference voltage, and the output of the comparator is connected to the pull-up voltage source through the pull-up resistor to receive the pull-up voltage; the output of the comparator is connected to the electrical signal synthesis module and / or the arithmetic processing module.

[0016] As shown above, the signal switching module is an analog switch.

[0017] The beneficial effects achieved by this application are as follows:

[0018] (1) The passive nuclear level gauge synthesized by multiple photomultiplier tubes of this application can effectively identify weak nuclear radiation signals and improve the ability to measure weak signals.

[0019] (2) The passive nuclear level gauge synthesized by multiple photomultiplier tubes in this application has a wide range of applications. It can be applied to both multi-probe passive nuclear level gauges with multiple photomultiplier tubes and integrated passive nuclear level gauges with multiple photomultiplier tubes.

[0020] (3) The passive nuclear level gauge synthesized by multi-photomultiplier tube electrical signal of this application has at least two working modes, which can be flexibly switched according to different application scenarios and has strong adaptability.

[0021] (4) The passive nuclear level gauge of the multi-photomultiplier tube electrical signal synthesis of this application has the ability to collect the electrical signals of each photomultiplier tube and the comprehensive electrical signal after the synthesis of the electrical signals of each photomultiplier tube. It has comprehensive functions and rich measurement dimensions.

[0022] (5) The passive nuclear level gauge synthesized by the multi-photomultiplier tube electrical signal of this application can be used to measure normally under strong material radiation conditions using existing technology, and can also use time coincidence module or time coincidence algorithm to eliminate external interference generated by circuit, power supply and synchronization; and use ADC sampling module to achieve accurate analysis of signal. Attached Figure Description

[0023] 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.

[0024] Figure 1 A schematic diagram of the structure of Example 1 of a passive nuclear level gauge for synthesizing electrical signals from multiple photomultiplier tubes;

[0025] Figure 2 A schematic diagram of the structure of Example 2 of a passive nuclear level gauge for synthesizing electrical signals from multiple photomultiplier tubes;

[0026] Figure 3 A schematic diagram of the structure of Example 3 of a passive nuclear level gauge for synthesizing electrical signals from multiple photomultiplier tubes;

[0027] Figure 4 A schematic diagram of the structure of Example 4 of a passive nuclear level gauge for synthesizing electrical signals from multiple photomultiplier tubes;

[0028] Figure 5 A schematic diagram of the structure of Example 5 of a passive nuclear level gauge for synthesizing electrical signals from multiple photomultiplier tubes;

[0029] Figure 6 A schematic diagram of one embodiment of an analog adder circuit;

[0030] Figure 7 This is a schematic diagram of one embodiment of an analog filter circuit;

[0031] Figure 8 This is a schematic diagram of the structure of one embodiment of a simulated switch chip;

[0032] Figure 9 A schematic diagram of one embodiment of the circuit structure of a timing-compliant module;

[0033] Figure 10 A schematic diagram of another embodiment of the circuit structure for a timing-compliant module;

[0034] Figure 11 The waveform diagram for the time-matching module;

[0035] Figure 12 This is a flowchart of one embodiment of the measurement method. Detailed Implementation

[0036] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0037] This application provides a passive nuclear level gauge using multi-photomultiplier tube electrical signal synthesis, comprising: N photomultiplier tubes for converting optical signals into electrical signals; at least one scintillation crystal for converting acquired nuclear radiation into optical signals; N signal acquisition modules for acquiring electrical signals from the photomultiplier tubes; an electrical signal synthesis module for synthesizing multiple electrical signals output from at least two of the N photomultiplier tubes into a single synthesized electrical signal; and a computational processing module for acquiring and calculating the single synthesized electrical signal to generate nuclear radiation data and / or level data; wherein N is a natural number greater than or equal to 2; wherein the computational processing module includes: a first electrical signal interface; 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 end of the electrical signal synthesis module is connected to the first electrical signal interface of the computational processing module; and the N input ends of the electrical signal synthesis module are connected one-to-one to the output ends of the N signal acquisition modules.

[0038] Specifically, the connection between the photomultiplier tube, scintillation crystal, signal acquisition module, electrical signal synthesis module, and arithmetic processing module can be achieved using conventional connection methods in this field (such as mechanical fixed connection, circuit wire connection, interface adapter connection, etc.). Specific connection details are not elaborated here as they belong to existing technology.

[0039] In existing passive nuclear level gauges, the weak nuclear radiation signals emitted by materials are extremely weak in the signal acquisition stage and are easily drowned out by the noise of the photomultiplier tubes and the signal acquisition module itself, making it impossible for existing technologies to identify such weak signals (for example, the effective electrical signal identification threshold is 2 volts, while the electrical signal generated by weak nuclear radiation is only 1.6 volts, which cannot be counted by the processing module). However, the multi-photomultiplier tube electrical signal synthesis passive nuclear level gauge of this application, by simultaneously measuring the weak nuclear radiation of materials by multiple photomultiplier tubes in the same device, synthesizes and superimposes the electrical signals from the multiple photomultiplier tubes; if the weak electrical signals collected by each photomultiplier tube are all 1.6 volts, the synthesized signal can generate a strong electrical signal of 3.2 volts, exceeding the 2-volt identification threshold and being identified as an effective material radiation signal by the processing module; at the same time, the noise signals of the photomultiplier tubes and the signal acquisition module, due to their lack of synchronization, will not be superimposed into an effective signal to enter the identification range. Therefore, this application can significantly improve the signal-to-noise ratio and achieve accurate measurement of weak nuclear radiation signals of materials by using a technical solution of synchronous measurement with multiple photomultiplier tubes and electrical signal synthesis, thus solving the core problem that existing technologies cannot identify weak signals.

[0040] Furthermore, the specific values ​​of the signal acquisition module are set according to actual needs, for example: Figure 1 As shown, N=2, the passive nuclear level gauge with multi-photomultiplier tube electrical signal synthesis includes: 2 photomultiplier tubes, at least one scintillation crystal, and two signal acquisition modules (i.e.: Figure 1 The system includes signal acquisition module 1, signal acquisition module 2, electrical signal synthesis module, and a processing module. The photosensitive surface of each photomultiplier tube is connected to the optical output terminal of the scintillation crystal; one photomultiplier tube is connected to one signal acquisition module (i.e.,...). Figure 1 The input terminal of signal acquisition module 1 is connected, and another photomultiplier tube is connected to another signal acquisition module (i.e.: Figure 1 The input terminal of the signal acquisition module 2) is connected; the output terminal of the electrical signal synthesis module is connected to the first electrical signal interface of the arithmetic processing module; one input terminal of the electrical signal synthesis module is connected to one signal acquisition module (i.e.: Figure 1 The output terminal of signal acquisition module 1 is connected to the signal acquisition module 2, and the other input terminal of the electrical signal synthesis module is connected to another signal acquisition module 3 (i.e., signal acquisition module 4). Figure 1 Connect the output terminal of the signal acquisition module 2 in the middle.

[0041] 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.

[0042] 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 passive nuclear level gauge with multi-photomultiplier tube electrical signal synthesis, and one or more probes with dual photomultiplier tubes combined with a scintillation crystal can also form this level gauge.

[0043] Specifically, the passive nuclear level gauge with multi-photomultiplier tube electrical signal synthesis provided in this application has at least two photomultiplier tubes. In micro-signal synthesis applications, its measurement performance is superior to technical solutions using the same specifications but based on comprehensive calculations of measured values. Since nuclear radiation in the measurement environment typically significantly affects and limits the measurement performance of weak signals, the passive nuclear level gauge with multi-photomultiplier tube electrical signal synthesis in this application also includes a nuclear radiation shielding component to shield against ambient nuclear radiation in the measurement environment, thereby obtaining better measurement results.

[0044] Furthermore, the processing module also includes: N second electrical signal interfaces, which are connected one-to-one with N signal acquisition modules to receive the electrical signals of the photomultiplier tubes acquired by the signal acquisition modules.

[0045] Specifically, the values ​​for the second electrical signal interface are set according to actual needs, for example: Figure 2 As shown, N=2, the arithmetic processing module also includes: two second electrical signal interfaces; one input terminal and one second electrical signal interface of the electrical signal synthesis module are both connected to a signal acquisition module (i.e.: Figure 2 The output terminal of signal acquisition module 1) is connected to the other input terminal and the other second electrical signal interface of the electrical signal synthesis module are both connected to the other signal acquisition module (i.e.: Figure 2 The output of the signal acquisition module 2) is connected; the output of the electrical signal synthesis module is connected to the first electrical signal interface of the arithmetic processing module.

[0046] Furthermore, as an embodiment, if there are two signal acquisition modules, one of the signal acquisition modules is directly electrically connected to the second electrical signal interface of the arithmetic processing module, and at the same time, the signal acquisition module is also electrically connected to the electrical signal synthesis module; the other signal acquisition module is electrically connected to the electrical signal synthesis module; the electrical signal synthesis module is electrically connected to the arithmetic processing module through the first electrical signal interface.

[0047] Furthermore, as another embodiment, if there are three or more signal acquisition modules, at least two of the signal acquisition modules are electrically connected to the electrical signal synthesis module, the electrical signal synthesis module is connected to the first electrical signal interface, and at least one signal acquisition module is directly electrically connected to the second electrical signal interface of the arithmetic processing module without going through the electrical signal synthesis module.

[0048] Specifically, the passive nuclear level gauge using multi-photomultiplier tube electrical signal synthesis in this application simultaneously possesses an electrical signal synthesis circuit and a direct-connection circuit for signal acquisition. The processing module can acquire either the synthesized electrical signal provided by the electrical signal synthesis circuit or a single-channel electrical signal provided by the direct-connection circuit. In practical applications, the system can select to acquire electrical signals from both circuits simultaneously, acquire only the electrical signal from the synthesis circuit, or acquire only the electrical signal from the direct-connection circuit, depending on the requirements. If simultaneous acquisition of electrical signals from both circuits is required, the timing consistency of the electrical signals in the electrical signal synthesis circuit and the direct-connection circuit for signal acquisition can be achieved through parallel allocation in the circuit design.

[0049] Furthermore, as an embodiment, the passive nuclear level gauge for multi-photomultiplier tube electrical signal synthesis also includes: a signal switching module, the output terminals of N signal acquisition modules are all connected to the input terminal of the signal switching module, the input terminal of the signal synthesis module and the input terminal of the arithmetic processing module are all connected to the output terminal of the signal switching module, and the signal switching module can selectively switch and transmit the electrical signals of the photomultiplier tubes acquired by the corresponding N signal acquisition modules to the electrical signal synthesis module or the arithmetic processing module.

[0050] Furthermore, as another embodiment, the passive nuclear level gauge with multiple photomultiplier tube electrical signal synthesis also includes: N signal switching modules, the output terminals of the N signal acquisition modules are connected one-to-one with the input terminals of the N signal switching modules, the input terminals of the signal synthesis module and the input terminals of the arithmetic processing module are both connected to the output terminals of the signal switching modules, and the signal switching modules can selectively switch and transmit the electrical signals of the photomultiplier tubes acquired by the corresponding signal acquisition modules to the electrical signal synthesis module or the arithmetic processing module.

[0051] Furthermore, such as Figure 3 As shown, there are two signal switching modules (i.e.: Figure 3 The signal switching module 1 and signal switching module 2 are in the middle, and there are two signal acquisition modules (i.e.: Figure 3 Signal acquisition module 1 and signal acquisition module 2 in the middle); one signal acquisition module (i.e.: Figure 3 The output of the signal acquisition module 1) is connected to a signal switching module (i.e.: Figure 3 The input terminal of signal switching module 1) is connected to a signal switching module (i.e.: Figure 3 The output of the signal switching module 1) is connected to one input of the signal synthesis module, and the signal switching module (i.e.: Figure 3 The output of the signal switching module 1) is connected to one input of the arithmetic processing module. This signal switching module (i.e.: Figure 3 The signal switching module 1) can selectively switch the signal acquisition module (i.e.: Figure 3The signal acquisition module 1) in the signal acquisition module acquires the electrical signal from the photomultiplier tube and transmits it to one input terminal of the electrical signal synthesis module or one input terminal of the arithmetic processing module to switch the signal acquisition module (i.e.: Figure 3 The signal acquisition module 1) acquires the transmission path of the electrical signal from the photomultiplier tube; another signal acquisition module (i.e.: Figure 3 The output of signal acquisition module 2) is connected to another signal switching module (i.e.: Figure 3 The input terminal of signal switching module 2) is connected to another signal switching module (i.e.: Figure 3 The output of signal switching module 2) is connected to another input of the signal synthesis module, and the other signal switching module (i.e.: Figure 3 The output of the signal switching module 2) is connected to another input of the arithmetic processing module. Figure 3 The signal switching module 2) can selectively switch the signal acquisition module (i.e.: Figure 3 The electrical signal acquired by the signal acquisition module 2) of the photomultiplier tube is transmitted to another input terminal of the electrical signal synthesis module or another input terminal of the arithmetic processing module to switch the signal acquisition module (i.e.: Figure 3 The signal acquisition module 2) in the middle acquires the transmission path of the electrical signal of the photomultiplier tube.

[0052] Furthermore, as another embodiment, such as Figure 4 As shown, there is one signal switching module and two signal acquisition modules (i.e.: Figure 4 Signal acquisition module 1 and signal acquisition module 2 in the middle); one signal acquisition module (i.e.: Figure 4 The output of signal acquisition module 1) is connected to the input of signal switching module and electrical signal synthesis module, respectively; another signal acquisition module (i.e.: Figure 4 The output of signal acquisition module 2) is connected to the input of signal switching module; the signal switching module can selectively connect another signal acquisition module (i.e.: Figure 4 The signal acquisition module 2) acquires the electrical signal from the photomultiplier tube and transmits it to the processing module. Simultaneously, another signal acquisition module (i.e.: Figure 4 The signal acquisition module 1) acquires the electrical signal from the photomultiplier tube and transmits it to the electrical signal synthesis module, or the signal switching module disconnects from the processing module. At this time, the two signal acquisition modules (i.e.: Figure 4 The electrical signals acquired by the photomultiplier tube from signal acquisition modules 1 and 2 are both transmitted to the electrical signal synthesis module to switch to another signal acquisition module (i.e.: Figure 4 The electrical signal transmission path of the signal acquisition module 2) in the middle; the electrical signal synthesis module is connected to the first electrical signal interface.

[0053] Furthermore, as another embodiment, such as Figure 5 As shown, there is one signal switching module and two signal acquisition modules (i.e.: Figure 5 Signal acquisition module 1 and signal acquisition module 2 in the middle); one signal acquisition module (i.e.: Figure 5 The output of signal acquisition module 1) is connected to the input of signal switching module and electrical signal synthesis module, respectively; another signal acquisition module (i.e.: Figure 4 The output of the signal acquisition module 2) is connected to the input of the signal switching module; the signal switching module is connected to the arithmetic processing module; the electrical signal synthesis module is connected to the first electrical signal interface; when the signal switching module switches to a signal acquisition module (i.e.: Figure 5 When the signal acquisition module 1 is in the middle, the two signal acquisition modules (i.e.: Figure 5 The electrical signals from the photomultiplier tube acquired by signal acquisition module 1 and signal acquisition module 2 are both transmitted to the processing module. Simultaneously, the two signal acquisition modules (i.e.: Figure 5 The electrical signals acquired by the photomultiplier tube by signal acquisition module 1 and signal acquisition module 2 are both transmitted to the electrical signal synthesis module; when the signal switching module switches to another signal acquisition module (i.e.: Figure 4 When the signal acquisition module 2 is in the middle, another signal acquisition module (i.e.: Figure 4 The signal acquisition module 2) in the middle acquires the electrical signal of the photomultiplier tube and transmits it to the arithmetic processing module. One signal acquisition module (i.e.: Figure 4 The signal acquisition module 1) acquires the electrical signal from the photomultiplier tube and transmits it to the electrical signal synthesis module.

[0054] Furthermore, the arithmetic processing module also has a control interface for controlling the working state of the signal switching module, and the control interface is connected to the signal switching module.

[0055] Specifically, the control interface of the arithmetic processing module can be implemented using existing technologies in the field, without the need for additional complex structure design, and can fully meet the conventional control requirements of the signal switching module. For example, GPIO, SPI, I2C, or UART interfaces can be used, and the operating status of the signal switching module can be controlled through conventional control logic such as level signals and serial commands of existing control interfaces.

[0056] Furthermore, the electrical signal synthesis module is an analog adder circuit.

[0057] Specifically, the analog adder circuit is used to synthesize multiple electrical signals. This analog adder circuit can be implemented using existing technology, so it will not be described in detail here.

[0058] Furthermore, such as Figure 6As shown, as an example, the analog adder circuit includes: an operational amplifier, N independent input resistors (e.g., resistors R1-Rn), and a feedback resistor (i.e.: Figure 6 The operational amplifier's inverting input is connected one-to-one to the outputs of N signal acquisition modules via N independent input resistors. The operational amplifier's output is connected to its inverting input via a feedback resistor, forming a negative feedback loop. The operational amplifier's non-inverting input is connected to a reference voltage (i.e., Rf). Figure 6 The Vref1 in the operational amplifier is used to achieve signal phase correction; the output of the operational amplifier is connected to the first electrical signal interface of the operational processing module to transmit the synthesized electrical signal to the operational processing module.

[0059] Furthermore, the specific values ​​of the N independent input resistors are set according to actual needs. In this application, it is preferred that the value of each independent input resistor is 2Rf (i.e., R1 = R2 = ... = Rn = 2Rf) to ensure that the signals of each channel are superimposed with equal weight.

[0060] Furthermore, the signal acquisition module is an analog filtering circuit.

[0061] Specifically, the analog filter circuit is used to collect the electrical signal of the photomultiplier tube. This analog filter circuit can be implemented using existing technology, so it will not be described in detail here.

[0062] Furthermore, such as Figure 7 As shown, in one embodiment, the analog filter circuit includes: a comparator, a DC blocking capacitor, a reference voltage source, and a pull-up resistor (i.e.: Figure 7 R1) and pull-up voltage source; the inverting input of the comparator is connected to the output of the photomultiplier tube (i.e., R1) through a DC blocking capacitor. Figure 7 The PMT output terminal of the comparator is connected to the reference voltage source, and the non-inverting input terminal of the comparator is connected to the reference voltage source. The output terminal of the comparator is connected to the pull-up voltage source through the pull-up resistor to receive the pull-up voltage. The output terminal of the comparator is connected to the electrical signal synthesis module and / or the arithmetic processing module.

[0063] Specifically, the reference voltage is an adjustable reference voltage, with a value range of 1.5-3.5V, but not limited to 1.5-3.5V, used to set the pulse discrimination threshold.

[0064] The specific value of the pull-up resistor is set according to actual needs, and is preferably 10kΩ in this application. The specific value of the pull-up voltage is set according to actual needs, and is preferably 5V in this application. The 10kΩ pull-up resistor and the 5V pull-up voltage source can form a TTL (transistor-to-transistor logic) level output. Adding a Schmitt trigger (e.g., 74HC14) to the analog filter circuit can eliminate signal jitter.

[0065] Furthermore, the signal switching module is an analog switch.

[0066] Specifically, the analog switch can be implemented using existing technology, so it will not be elaborated further.

[0067] As an example, such as Figure 8 As shown, the signal switching module uses an SGM3157YC6 analog switch chip in an SC70-6 package. The pin functions of this analog switch chip are as follows: pin 1 is normally open (NO), pin 2 is ground (GND), pin 3 is unused (NC), pin 4 is common (COM), pin 5 is positive power supply (V+), and pin 6 is control input (IN). By controlling the level signal at the control input (IN), the channel switching between the normally open (NO) and common (COM) terminals can be achieved, thus completing the signal selection control. Its hardware connection and operating logic are existing technologies and will not be described in detail here.

[0068] Furthermore, as an example, the signal switching module can integrate a computing controller to switch signal transmission paths according to a set time interval. For instance, the signal switching module can execute signal switching actions according to instructions from its own controller, such as switching the signal transmission path cyclically every 3 seconds using a built-in timer.

[0069] Specifically, the signal switching module changes the transmission path of the electrical signal from the signal acquisition module into the processing module through a switching action. By utilizing the signal switching function of the signal switching module, the synthesized electrical signal and the electrical signal from the signal acquisition module can be effectively isolated, preventing mutual interference between the two.

[0070] Furthermore, the passive nuclear level gauge synthesized from multiple photomultiplier tubes of this application can specifically take the following forms:

[0071] (1) Integrated dual-mode multi-photomultiplier tube level gauge: integrates multiple photomultiplier tubes, and realizes the switching between two working modes of synthetic measurement and separate channel measurement through the internal signal switching module.

[0072] (2) Multi-probe passive nuclear level gauge: It contains multiple independent probes, each probe is equipped with a signal acquisition module and a photomultiplier tube, and the signal switching module realizes the synthesis and transmission or independent transmission of multi-probe signals;

[0073] (3) Dual photomultiplier tube integrated level gauge: The detection unit is composed of two photomultiplier tubes combined with a scintillation crystal. The output signal is processed by the signal acquisition module and then by the electrical signal synthesis module to achieve the synthesis of dual electrical signals.

[0074] Furthermore, the passive nuclear level gauge using multi-photomultiplier tube electrical signal synthesis also includes: a time alignment module, used to perform time correlation filtering on the pulse signals output by multiple signal acquisition modules, transmitting only signals that meet the time coincidence condition to the arithmetic processing module; the output terminals of N signal acquisition modules are all connected to the input terminal of the time alignment module; the output terminal of the time alignment module is connected to the input interface of the arithmetic processing module; and an ADC sampling module, used to acquire and convert the pulse parameters of the electrical signals output by each electrical signal acquisition module, and send the pulse parameters to the arithmetic processor via digital signals. The pulse parameters include at least: time parameters, waveform characteristics, amplitude parameters, and noise-related parameters. The electrical signal acquisition modules are connected to the arithmetic processing module through the ADC sampling module, with the input terminal of the ADC sampling module correspondingly connected to the output terminal of each electrical signal acquisition module, and the output terminal of the ADC sampling module connected to the arithmetic processing module.

[0075] As an example, such as Figure 9 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 a synchronization signal and transmits it to the processing module.

[0076] As another embodiment, such as Figure 10 As shown, the circuit structure of the timing coincidence module consists of two monostable multivibrators (i.e.: Figure 2 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 2 The first monostable multivibrator is connected to the second monostable multivibrator (i.e., the pulse IN2 is connected to the second monostable multivibrator). Figure 2 The first monostable multivibrator (i.e., the first one) is shaped into a monostable multivibrator (i.e., the second one). Figure 2 The output pulse OUT1 of the monostable multivibrator 1 and the second monostable multivibrator (i.e.: Figure 2 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 processing module.

[0077] 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 11As 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 processing module.

[0078] Furthermore, the passive nuclear level gauge that synthesizes multiple photomultiplier tube electrical signals also includes a signal switching component connected to a time synchronization module or an ADC sampling module, which can selectively switch and transmit the electrical signals of the photomultiplier tubes acquired by the corresponding signal acquisition module to the time synchronization module, the ADC sampling module, or the arithmetic processing module.

[0079] like Figure 12 As shown in the figure, as an embodiment, this application provides a measurement method applied to the above-mentioned passive nuclear level gauge that synthesizes electrical signals from multiple photomultiplier tubes without a signal switching module. The measurement method includes the following steps:

[0080] S1: The operation processing module presets at least two of the following working modes: first working mode, second working mode, third working mode and fourth working mode, of which the first working mode must be included.

[0081] The first working mode is as follows: the output signal of the signal acquisition module is directly transmitted to the electrical signal synthesis module; after the electrical signal synthesis module generates the synthesized electrical signal, the arithmetic processing module counts the number of pulses of the synthesized electrical signal and generates nuclear radiation data based on the number of pulses.

[0082] The second working mode is as follows: 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.

[0083] The third working mode is as follows: the output signal of the signal acquisition module is directly transmitted to the arithmetic processing module; the arithmetic processing module counts the number of pulses of the electrical signal of the photomultiplier tube acquired by each signal acquisition module, and then performs comprehensive calculation based on the number of pulses to generate a comprehensive value as nuclear radiation data;

[0084] The fourth working mode is as follows: the calculation and processing module selects pulses that match the material characteristics or removes interfering pulses from the pulse data of the ADC sampling module, and then generates the nuclear radiation data of the passive nuclear level gauge.

[0085] Specifically, the generation of nuclear radiation data based on pulse count in both the first and second working 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 is calculated by counting the number of pulses per unit time. The generation of a comprehensive value as nuclear radiation data based on the combined calculation of each pulse count in the third working mode can also be achieved using existing technologies, such as the average method, weighted average method, or filtering algorithm. The nuclear radiation data generated by the processing module in the fourth working mode, after filtering pulses that match material characteristics or removing interfering pulses from the pulse data of the ADC sampling module, can also be achieved using existing technologies.

[0086] S2: After receiving an external instruction or determining that the preset triggering conditions for any preset working mode have been met, the arithmetic processing module starts or enters the corresponding working mode and obtains the nuclear radiation data under that working mode.

[0087] Furthermore, the preset conditions of this application include: working type, temperature, moisture content, material type, time conditions, measured values ​​under specific working modes, and comparative values ​​of measured values ​​under each mode.

[0088] Specifically, when the overall nuclear radiation value meets the switching threshold: if the overall nuclear radiation value generated by multiple signal acquisition modules is less than a preset value, the system switches to nuclear radiation data generated by a single synthesized electrical signal; if the nuclear radiation data corresponding to the synthesized signal is greater than the preset value, the system switches to nuclear radiation data generated by multiple signal acquisition modules. This switching can prevent the synthesized signal from being too strong, causing the electrical signal to exceed limits / oversaturate, or achieve accurate measurement and resolution in scenarios with weak material signals.

[0089] When the moisture content and material type meet the mode switching conditions: if the material type value is extremely low (weak radioactive properties of the material) or the moisture content is high (the radioactivity of the material is easily absorbed by water), switch to the synthetic signal working mode; if the material type value is high (strong nuclear radiation released by the material), switch to the multi-signal acquisition module working mode.

[0090] When a photomultiplier tube is malfunctioning: If the photomultiplier tube is determined to be damaged, switch to the operating mode of each signal acquisition module. The status of each photomultiplier tube can be easily determined by independently measuring its electrical signal, avoiding noise superposition interference from the signal synthesis circuit.

[0091] When verifying the synchronization of operating modes: the arithmetic processing module controls the signal switching circuit to operate sequentially in at least two operating modes, comparing the nuclear radiation-related measurement data in different modes. If the data difference is large, it indicates that the synthesized signal has not achieved a synchronization effect, and it is determined that the operating mode should be used in each signal acquisition mode.

[0092] When a stable working mode needs to be selected: compare the fluctuation range within the preset time period under the two working modes, and select the working mode with the smaller fluctuation range.

[0093] In practice, users can send external commands to the passive nuclear level gauge via a wireless remote control or human-machine interface to enable it to enter the set execution mode.

[0094] 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 the material level data.

[0095] Specifically, the material level data can be a specific material level value, displayed on a display of a passive nuclear level gauge configured with electrical signals synthesized from multiple photomultiplier tubes, or transmitted to other equipment via digital signals, or calculated based on the nuclear radiation data corresponding to a determined working mode to output analog output current data as material level data to other equipment.

[0096] As an example, this application provides a measurement method applied to the above-mentioned passive nuclear level gauge with multiple photomultiplier tube electrical signal synthesis including a signal switching module. The measurement method includes the following steps: S1': preset at least two of the following working modes in the calculation and processing module: a first working mode, a second working mode, a third working mode, and a fourth working mode, wherein the first working mode must be included.

[0097] The first working mode is as follows: the arithmetic processing module controls the signal switching module to transmit the output signal of the signal acquisition module to the electrical signal synthesis module; after the electrical signal synthesis module generates the synthesized electrical signal, the arithmetic processing module counts the number of pulses of the synthesized electrical signal and generates nuclear radiation data based on the number of pulses.

[0098] The second working mode is as follows: the arithmetic processing module controls the signal switching module to transmit the output signal of the signal acquisition module to the time conformance module; after the time conformance module performs time correlation filtering on the signal to generate an electrical signal, the arithmetic processing module counts the number of pulses of the electrical signal and generates nuclear radiation data based on the number of pulses.

[0099] The third working mode is as follows: the arithmetic processing module controls the signal switching module so that the output signal of the signal acquisition module is directly transmitted to the arithmetic processing module; the arithmetic processing module counts the number of pulses of the electrical signal of the photomultiplier tube acquired by each signal acquisition module, and then performs comprehensive calculation based on the number of pulses to generate a comprehensive value as nuclear radiation data;

[0100] The fourth working mode is as follows: the calculation and processing module selects pulses that match the material characteristics or removes interfering pulses from the pulse data of the ADC sampling module, and then generates the nuclear radiation data of the passive nuclear level gauge.

[0101] S2': After receiving an external instruction or determining that the preset triggering conditions for a certain working mode have been met, the arithmetic processing module starts or enters the corresponding working mode and obtains the nuclear radiation data under that working mode.

[0102] 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.

[0103] As an example, the processing module is configured with at least two operating modes: operating mode 1 is used to measure the electrical signal synthesized from the electrical signals of at least two photomultiplier tubes to generate measurement data related to nuclear radiation; operating mode 2 is used to measure the independent electrical signal of each photomultiplier tube to generate nuclear radiation related measurement data for each signal, and generate nuclear radiation related measurement data after comprehensive calculation.

[0104] The specific implementation method for switching working modes is as follows:

[0105] During the initial and continuous monitoring phases, after the processing module is powered on, it enters a preset working mode by default (such as working mode 2: independent signal measurement mode) and continuously monitors key parameters.

[0106] During the intelligent judgment and switching phase (triggered by preset conditions), the processing module sends instructions to the signal switching module based on the following preset conditions to dynamically switch the working mode:

[0107] Under signal strength judgment conditions, if the comprehensive nuclear radiation value is lower than the preset threshold d when in working mode 2, it indicates that the material signal is weak. The operation and processing module controls the signal switching module to switch to working mode 1 (electrical signal synthesis mode) to achieve accurate measurement and identification of weak signals by utilizing its high sensitivity. If the nuclear radiation data corresponding to the synthesized electrical signal is close to or exceeds the preset threshold of the ADC range when in working mode 1, there is a risk of signal saturation distortion. The operation and processing module controls the signal switching module to switch back to working mode 2 to ensure measurement accuracy and system safety by processing independent and unsaturated electrical signals.

[0108] Under the condition of material property judgment, if the material has extremely weak radioactivity (such as the material type parameter showing that the material has extremely weak radioactivity) or high moisture content (the moisture parameter showing severe signal attenuation), the calculation and processing module switches to working mode 1 according to the preset rules; otherwise, when the material has extremely strong radioactivity, working mode 2 is selected by default to prevent signal saturation.

[0109] Under equipment health diagnostic conditions, the independent electrical signals of each photomultiplier tube are analyzed periodically or in real time (easily achieved in operating mode 2) to determine whether they are damaged or degraded. If an abnormality is found in a photomultiplier tube, the processing module locks into operating mode 2 to isolate the fault channel and prevent noise from the faulty tube from being superimposed on the normal signal in the synthesis mode.

[0110] In the material level data generation and output stage, the computing module generates and outputs the material level value in the container (in the form of digital display, communication or analog current signal) based on the nuclear radiation data collected in the current effective working mode and through the built-in material level algorithm model.

[0111] This solution is highly responsive and intelligent, and can proactively adapt to environmental changes, ensuring measurement accuracy while maximizing system reliability.

[0112] Specifically, the passive nuclear level gauge and its measurement method based on multi-photomultiplier tube electrical signal synthesis of this application can utilize multi-photomultiplier tube signal synthesis to identify weak nuclear radiation signals. Simultaneously, by leveraging the principle of no correlation between noise signals, it effectively suppresses noise superposition during multi-signal synthesis, improving weak signal measurement capabilities. It is adaptable to application scenarios of multi-probe and integrated multi-photomultiplier tube passive nuclear level gauges, offering broad applicability. Two preset working modes are provided: Mode 1 allows independent measurement and calculation of each photomultiplier tube's electrical signal, generating independent measurement data; Mode 2 allows measurement and calculation of the synthesized electrical signal, generating comprehensive measurement data. The two modes can be flexibly switched according to the scenario, ensuring both measurement data accuracy and weak signal measurement capabilities, thus improving the coverage of horizontal measurement distances for containers.

[0113] The beneficial effects achieved by this application are as follows:

[0114] (1) The passive nuclear level gauge and measurement method of the multi-photomultiplier tube electrical signal synthesis of this application can effectively identify weak nuclear radiation signals and improve the measurement capability of weak signals.

[0115] (2) The passive nuclear level gauge and measurement method for synthesizing electrical signals of multiple photomultiplier tubes in this application have a wide range of applications. They can be applied to multi-probe passive nuclear level gauges with multiple photomultiplier tubes, as well as integrated passive nuclear level gauges with multiple photomultiplier tubes.

[0116] (3) The passive nuclear level gauge and measurement method of the multi-photomultiplier tube electrical signal synthesis of this application has at least two working modes, which can be flexibly switched according to different application scenarios and are highly adaptable.

[0117] (4) The passive nuclear level gauge and measurement method for synthesizing multiple photomultiplier tube electrical signals of this application has the ability to collect the electrical signals of each photomultiplier tube and the comprehensive electrical signal after the synthesis of the electrical signals of each photomultiplier tube. It has comprehensive functions and rich measurement dimensions.

[0118] (5) The passive nuclear level gauge and measurement method of the multi-photomultiplier tube electrical signal synthesis of this application can be used to measure normally under strong material radiation. It can also use time coincidence module or time coincidence algorithm to eliminate external interference generated by circuit, power supply and synchronization; and use ADC sampling module to realize accurate analysis of signal.

[0119] 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 passive nuclear level gauge for synthesizing electrical signals from multiple photomultiplier tubes, characterized in that, include: N photomultiplier tubes for converting optical signals into electrical signals, at least one scintillation crystal for converting acquired nuclear radiation into optical signals, N signal acquisition modules for acquiring electrical signals from the photomultiplier tubes, an electrical signal synthesis module for combining multiple electrical signals output from at least two of the N photomultiplier tubes into a single synthesized electrical signal, and a computational processing module for acquiring and calculating the single synthesized electrical signal to generate nuclear radiation data and / or material level data; wherein, N is a natural number greater than or equal to 2; The arithmetic processing module includes: a first electrical signal interface; 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 of the electrical signal synthesis module is connected to the first electrical signal interface of the arithmetic processing module; The N input terminals of the electrical signal synthesis module are connected one-to-one with the output terminals of the N signal acquisition modules.

2. The passive nuclear level gauge for multi-photomultiplier tube electrical signal synthesis according to claim 1, characterized in that, The processing module also includes N second electrical signal interfaces, which are connected one-to-one with N signal acquisition modules to receive the electrical signals from the photomultiplier tubes acquired by the signal acquisition modules.

3. The multi-photomultiplier tube electrical signal synthesis passive nuclear inventory meter of claim 2, wherein, If there are two signal acquisition modules, one of the signal acquisition modules is directly electrically connected to the second electrical signal interface of the arithmetic processing module, and at the same time, the signal acquisition module is also electrically connected to the electrical signal synthesis module; the other signal acquisition module is electrically connected to the electrical signal synthesis module; the electrical signal synthesis module is electrically connected to the arithmetic processing module through the first electrical signal interface. If there are three or more signal acquisition modules, at least two of them are electrically connected to the electrical signal synthesis module, the electrical signal synthesis module is connected to the first electrical signal interface, and at least one signal acquisition module is directly electrically connected to the second electrical signal interface of the arithmetic processing module without going through the electrical signal synthesis module.

4. The passive nuclear level gauge for multi-photomultiplier tube electrical signal synthesis according to claim 1, characterized in that, Also includes: The time synchronization module has its output terminals connected to the input terminals of all N signal acquisition modules; the output terminals of the time synchronization module are connected to the input interface of the arithmetic processing module. The ADC sampling module has its input terminal connected to the corresponding output terminal of each electrical signal acquisition module, and its output terminal connected to the arithmetic processing module.

5. The multi-photomultiplier tube electrical signal synthesis passive nuclear inventory meter of claim 2, wherein, Also includes: The outputs of one signal switching module and N signal acquisition modules are all connected to the input of the signal switching module. The inputs of the signal synthesis module and the arithmetic processing module are all connected to the output of the signal switching module. Alternatively, it may also include: N signal switching modules, with the outputs of the N signal acquisition modules connected one-to-one to the inputs of the N signal switching modules, and the inputs of the signal synthesis module and the arithmetic processing module both connected to the outputs of the signal switching modules.

6. The passive nuclear level gauge for multi-photomultiplier tube electrical signal synthesis according to claim 4, characterized in that, There are two signal switching modules and two signal acquisition modules. The output of one signal acquisition module is connected to the input of one signal switching module, the output of one signal switching module is connected to one input of the signal synthesis module, and the output of one signal switching module is connected to one input of the arithmetic processing module. The output of the other signal acquisition module is connected to the input of the other signal switching module, the output of the other signal switching module is connected to the other input of the signal synthesis module, and the output of the other signal switching module is connected to the other input of the arithmetic processing module. Alternatively, there is one signal switching module and two signal acquisition modules; the output of one signal acquisition module is connected to the input of the signal switching module and the electrical signal synthesis module respectively; the output of the other signal acquisition module is connected to the input of the signal switching module; the output of the signal switching module is connected to the arithmetic processing module, and the electrical signal synthesis module is connected to the first electrical signal interface.

7. The multi-photomultiplier tube electrical signal synthesis passive nuclear inventory meter of claim 4, wherein, The processing module is also equipped with a control interface, which is connected to the signal switching module.

8. The passive nuclear level gauge for multi-photomultiplier tube electrical signal synthesis according to claim 1, characterized in that, The electrical signal synthesis module is an analog adder circuit; The analog adder circuit includes: an operational amplifier, N independent input resistors and a feedback resistor; The inverting input of the operational amplifier is connected one-to-one with the output of N signal acquisition modules through N independent input resistors. The output of the operational amplifier is connected to the inverting input of the operational amplifier through a feedback resistor. The non-inverting input of the operational amplifier is connected to a reference voltage. The output of the operational amplifier is connected to the first electrical signal interface of the operational processing module.

9. The multi-photomultiplier tube electrical signal synthesis passive nuclear inventory meter of claim 1, wherein, The signal acquisition module is an analog filtering circuit; The analog filter circuit includes: a comparator, a DC blocking capacitor, a reference voltage source, a pull-up resistor, and a pull-up voltage source; The inverting input of the comparator is connected to the output of the photomultiplier tube via a DC blocking capacitor. The non-inverting input of the comparator is connected to a reference voltage source to receive a reference voltage. The output of the comparator is connected to a pull-up voltage source via a pull-up resistor to receive a pull-up voltage. The output of the comparator is connected to the electrical signal synthesis module and / or the arithmetic processing module.

10. The multi-photomultiplier tube electrical signal synthesis passive nuclear inventory meter of claim 4, wherein, The signal switching module is an analog switch.

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