External Radiation Detection Using Gamma Modulators

Abstract

The invention relates to a radioactivity measuring device for determining the pulse intensity of an interference signal from an external radiation source, wherein the radioactivity measuring device determines a filling level or a limit level of a filling material in a container. The radioactivity measuring device (10) comprises a detector (30) configured to receive pulses of a useful signal modulated with a modulation frequency from a gamma ray emitter (20) and also to receive pulses of an interference signal from an external radiation source (25). The measuring device (10) further comprises an average value generator (50) configured to output a first count rate (N1) of pulses at an average value generator output (59) and a bandpass system (40) comprising a bandpass filter (45) with an adjustable passband frequency range, the low-pass filter being configured to output a second count rate (N2) of pulses at an output of the bandpass system (49). The measuring device (10) further comprises a subtractor (60) configured to generate a differential count rate (N3) between the first count rate (N1) and the second count rate (N2).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of German patent application 10 2018 215 675.1 filed on September 14, 2018, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The invention relates to a radioactivity measuring device for determining the strength of an interference signal from an external radiation source, wherein the radioactivity measuring device is designed to carry out a fill level determination or a limit level determination of a filling material in a container. The invention also relates to the use of such a measuring device for fill level measurement or limit level measurement, a method for determining the strength of an interference signal and the use of such a measuring device, a program element and a computer-readable medium having such a program element stored thereon. Background Art

[0004] For example, radioactive measuring devices can be used to determine the filling level or the limit level of the filling material. Such measuring devices are used in particular to indicate a certain level of the filling material, for example in a container, i.e. to determine whether a predetermined upper or lower limit value of the level in the container has been reached. In radioactive measuring devices, for example, a gamma ray emitter is used as an emitter, i.e. a useful signal is generated which can be received by a detector. In some cases, the signal received by the detector may be superimposed with an interference signal. The interference signal may be generated by an external radiation source, for example by a radioactive isotope, for example, which is used, for example, for checking welds in containers. This may therefore interfere with the measurements of the measuring device itself and also with the measurements of other machines located in the area of ​​the measuring device. Summary of the invention

[0005] It is therefore an object of the present invention to provide an improved radioactivity measuring device.

[0006] One aspect of the invention relates to a radioactivity measuring device for determining the intensity of interference signals from external radiation sources when determining a filling level or a limit level of a filling material in a container. The radioactivity measuring device comprises a detector which is configured to receive pulses of a useful signal modulated with a modulation frequency from a gamma-ray emitter and also to receive pulses of interference signals from external radiation sources. The number of pulses per time period corresponds to the intensity of the gamma-ray source (i.e., for example, the useful signal and / or the interference signal). The detector for the gamma-ray radiation can be a counter tube, for example a Geiger-Müller counter tube. ) or a scintillation counter. For example, the detector can count the number of ionized particles, for example, each particle is detected as a pulse in the detector. The number of particles and / or pulses can be summed within a predetermined time period and / or related to a predetermined time period, such as "1000 particles (or pulses) per second". A gamma-ray emitter can be used as a particle source to provide a useful signal. The useful signal from the gamma-ray emitter can be modulated, that is, the gamma-ray emitter can be an active timing emitter (active getakteter Strahler) with a frequency (i.e., a modulation frequency or a timing frequency). The frequency of the modulated useful signal can be substantially constant. In addition to the useful signal, the detector can also receive pulses of interference signals from external radiation sources. The interference signal can be unmodulated. For example, the interference signal can be generated by radioactive measuring isotopes, isotopes for weld inspection or other gamma-ray sources, the radiation of which is variable, in particular variable in an unpredictable manner. The reception of the useful signal and the interference signal can be carried out during the filling level determination or limit level determination of the filling level or limit level of the filling material in the measuring container. One of the effects utilized by the invention is that the useful signal is modulated while the interfering signal is not modulated.

[0007] The measuring device also includes an average value generator configured to output a first count rate of pulses. Here, the count rate can be expressed as a rate, i.e., the number of pulses per unit time and / or a specific time period, and the count rate can also be the number of pulses normalized within the specific time period. Here, the first count rate corresponds to an average value of a first number of pulses received by the detector within the predetermined time period within the predetermined time period.

[0008] The measuring device also includes a bandpass system configured to output a second count rate of pulses. The bandpass system has, for example, a bandpass filter with an adjustable passband frequency range. For example, the bandpass system includes a bandpass filter with an adjustable passband frequency range. Here, the adjustable passband frequency range of the bandpass filter corresponds to the modulation frequency of the modulated useful signal from the gamma-ray emitter. Here, "adjustable passband frequency range" can mean that the passband frequency range can be adjusted to, for example, the frequency range of the modulated useful signal before the measurement. If the frequency of the modulated useful signal is known and constant, the frequency range corresponds to a bandpass with a fixed passband frequency range. "Adjustable passband frequency range" can also mean that the frequency of the modulated useful signal is determined at the beginning of the measurement (for example, by an FFT module (FFT: Fast Fourier Transform)) and the bandpass filter is adjusted to the passband frequency range. Here, the frequency band of the bandpass filter can be selected according to the frequency of the strongest signal output by the detector, which corresponds to, for example, the strongest amplitude in the FFT spectrum. The FFT module can be part of the bandpass system. An “adjustable passband frequency range” may also mean that the frequency of the modulated useful signal is also determined during the measurement and the passband filter is adjusted or adapted to this passband frequency range. For example, the frequency of the modulated useful signal may change due to temperature fluctuations during the measurement. In this case, the second count rate corresponds to a second number of pulses received by the detector within the predetermined time period within the passband frequency range of the passband filter within the predetermined time period.

[0009] In addition, the measuring device also includes a subtractor configured to form a differential count rate. The differential count rate corresponds to the difference between the first count rate and the second count rate and / or is related to the difference. Before subtracting the second count rate from the first count rate, the first count rate and / or the second count rate can be normalized, for example, by a constant. The differential count rate can also be normalized after the subtraction. Therefore, the differential count rate corresponds to the intensity of the interference signal from the external radiation source.

[0010] Since the useful signal is modulated but the interference signal is not modulated, the interference signal can be separated from the useful signal by the measuring device according to the invention. Therefore, not only can the measured value for determining the filling level or the limit level of the filling material be obtained from the received (modulated plus unmodulated) signal by the measuring device, but also the presence of external radiation and / or the intensity of external radiation can be determined, that is, the quantitative value of the external signal can be determined by the measuring device. By determining the quantitative value of the interference signal, not only can the external radiation be suppressed very effectively, but this value can also be used to initiate predefined actions, such as display and / or recording of the interference signal.

[0011] In one embodiment, the differential count rate is compared to a threshold value and an action is triggered if the threshold value is exceeded. The threshold value may be a count rate above which the presence of external radiation is determined. The threshold value may be a count rate above which at least one partial function of the measuring device and / or at least one partial function of other devices is severely disturbed.

[0012] In one embodiment, the action includes suspending temperature control. For example, the temperature control may involve the temperature control of a scintillation counter and / or other equipment of the measuring device. For example, this may be based on the fact that if the external radiation exceeds a certain threshold, some temperature controls may be disturbed, so that the function of these temperature controls is no longer relied upon, and thus the suspension of these temperature controls can prevent damage.

[0013] In one embodiment, the action includes storing a timestamp and / or an intensity value of the interference signal. For example, the timestamp may indicate the start and / or end of the occurrence of the interference signal. The intensity value of the interference signal may include an intensity, such as an average value of the intensity over a portion of the measurement time period and / or an average value of multiple intensities of the interference signal at multiple time points. For example, this may be stored in a non-volatile memory and may subsequently be read out again for diagnostic purposes, such as to record (e.g., external) extraneous radiation time.

[0014] In one embodiment, the action includes issuing a warning, which may include a warning light, a warning sound, and / or the display of specific display content.

[0015] The above actions may be triggered individually, collectively, sequentially, or in any combination.

[0016] In one embodiment, the measuring device further comprises a frequency determination module, which is configured to determine the modulation frequency of the modulated useful signal from the gamma-ray emitter and adjust the passband frequency range of the bandpass filter with an adjustable passband frequency range to the modulation frequency of the modulated useful signal. For example, this can be performed by an FFT module, which determines the frequency of the strongest signal output by the detector and uses this frequency to adjust the passband frequency range of the adjustable bandpass filter. By using this device, no tuning is required between the frequency of the modulated useful signal and the detector. In addition, continuous adaptation can be allowed for the changing frequency of the useful signal.

[0017] In one embodiment, the adjustable passband frequency range of the bandpass filter has a center frequency between 0.05 Hz and 20 Hz, in particular with a center frequency of 1 Hz. The frequency of the modulated useful signal (and therefore the bandpass filter tuned to the useful signal) varies relatively slowly with the counting rate of the particles. For example, the Q value of the bandpass filter can be less than 20%, in particular less than 10%. The modulated useful signal substantially retains its frequency and varies at most slowly, for example due to changes in ambient temperature.

[0018] In one embodiment, the predetermined time period for measuring the first count rate and the second count rate is between 0.02 and 50 seconds, for example between 0.05 and 20 seconds, in particular 1 second. This range corresponds in particular to the properties of the modulated useful signal.

[0019] In an embodiment, the first count rate corresponds to an average value of a first number of pulses received by the detector within a predetermined time period. Here, the first count rate may be proportional to k times the average value of the first number of pulses, in particular k=1 / 2. For example, the first count rate may be multiplied by a factor k=1 / 2 or normalized with this factor. This may be based on the fact that, in the presence of external radiation, the average value corresponds approximately to half the measured count rate. It should be noted that in the presence of external radiation, the average value (measured at the detector) is increased by the value of the external radiation.

[0020] In one embodiment, the measuring device further comprises a modulator, which controls a displaceable membrane around the gamma-ray emitter and / or the electronic circuit, wherein the modulator is configured to modulate the signal of the gamma-ray emitter to generate a modulated signal. The displaceable membrane can be implemented as a rotating screen, for example made of lead, which has an opening and rotates around the gamma-ray emitter, so that the gamma rays appear approximately in the form of a lighthouse with a screen rotating around the light. For example, the electronic circuit can be implemented as an oscillating circuit or as a pulse or signal generator and a D / A converter (possibly with a low-pass filter). The modulated signal can be a sine wave, a sinusoidal curve, up to a rectangular wave. Here, the fundamental frequency can advantageously be separated by a simple low-pass filter.

[0021] Another aspect of the invention relates to a method for determining the intensity of interference signals from external radiation sources during fill level determination or limit level determination by means of a radioactivity measuring device as described above and / or as described below. The method comprises the following steps:

[0022] a) receiving pulses of a useful signal modulated with a modulation frequency from a gamma-ray emitter and also receiving interference signals from an external radiation source via a detector;

[0023] b) outputting a first counting rate through an average value generator;

[0024] c) outputting a second counting rate through a bandpass system;

[0025] d) forming, by a subtractor, a differential count rate obtained by subtracting the second count rate from the first count rate; and

[0026] e) Output differential count rate.

[0027] In one embodiment, steps b) and c) are performed in parallel and / or quasi-parallel. Quasi-parallel execution can be achieved, for example, by a single processor system.

[0028] In one embodiment, the method has the following additional steps:

[0029] f) comparing the differential count rate to a threshold; and

[0030] g) If the threshold is exceeded, an action is triggered.

[0031] A further aspect of the invention relates to the use of a measuring device as described above and below for determining a filling level or a limit level of a filling material, in particular a liquid and bulk material.

[0032] A further aspect of the invention relates to a program element which, when executed on a processor unit of a measuring device, instructs the measuring device to carry out a method as described above and below.

[0033] Another aspect of the invention relates to a computer-readable medium having stored thereon a program element as described above and below.

[0034] All features described above and below with reference to one aspect of the invention may equally be features of one or more other aspects of the invention. In particular, all features described with respect to the measuring device may also be features and / or steps of the method, and vice versa.

[0035] For further clarification, the present invention will be described with reference to the embodiments shown in the accompanying drawings. These embodiments are to be understood as illustrative only and not limiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A measuring device according to an exemplary embodiment of the invention is schematically shown.

[0037] Figure 2 An example of an input signal of a detector receiving a modulated useful signal and an interference signal is schematically shown.

[0038] Figure 3Schematically shows the output of the bandpass system according to the present invention. Figure 2 Example of a signal.

[0039] Figure 4 Schematically shows the output of the average value generator according to the present invention. Figure 2 Example of a signal.

[0040] Figure 5 The output of the measuring device in the embodiment of the present invention is schematically shown. Figure 2 Example of a signal.

[0041] Figure 6 A flow chart is shown for illustrating the steps of a method according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0042] Figure 1 A measuring device 10 according to an exemplary embodiment of the present invention is schematically shown. The measuring device 10 has a gamma ray emitter 20, which is configured to send a modulated useful signal. The gamma ray emitter 20 can be controlled by a modulator 22, which applies a predetermined frequency to the gamma ray emitter. The gamma ray emitter 20 can send the modulated useful signal in multiple directions (for example, towards a container 95). The container 95 includes a filling material 90. The filling material 90 can include a liquid and / or a loose material.

[0043] A detector 30 is arranged at the side of the container 95 opposite to the gamma ray emitter 20, and the detector 30 is configured to receive radiation pulses from a gamma ray source. One of the gamma ray sources is the gamma ray source 20. The intensity of the gamma rays received by the detector 30 depends on the filling level 97 of the container 95. If the filling level 97 is so high that the filling material 90 is located between the gamma ray emitter 20 and the detector 30, the modulated useful signal is attenuated by the filling material 90. If there is no filling material 90 between the gamma ray emitter 20 and the detector 30, the detector 30 receives a higher intensity modulated gamma ray from the gamma ray emitter 20. This effect can be used to determine the filling level or limit level of the filling material 90 in the container 95. However, the detector 30 can not only receive gamma rays from the modulated gamma ray emitter 20, but the detector 30 can also receive pulses from other gamma ray sources, such as pulses of interference signals from an external radiation source 25. The interfering signal may be unmodulated and therefore have a different frequency characteristic than the modulated gamma-ray emitter 20 .

[0044] The pulses generated by the detector 30 are transferred from the detector output 39 of the detector 30 in the measuring device 10 to the average generator 50 and the bandpass system 40. The average generator 50 is configured to output a first count rate N1 of pulses at the average generator output 59. To this end, the average generator 50 forms an average value of the first number of pulses within a predetermined time period. The pulses may include the entire frequency spectrum received by the detector 30. Therefore, the average value of the average generator 50 counts all pulses from the detector 30 within the predetermined time period.

[0045] The bandpass system 40 includes a bandpass filter 45 with an adjustable passband frequency range. For example, the bandpass filter 45 can be adjusted to the passband frequency range by the FFT module 42. The passband frequency range can correspond to the frequency of the modulated useful signal. For example, the passband frequency range can be adjusted at the beginning of the measurement and / or during the measurement. With the help of the bandpass filter 45, only pulses in the passband frequency range are basically filtered out from the pulses received from the detector 30. The bandpass system 40 counts these pulses and, if necessary, passes them to the bandpass system output 49 as a second count rate N2 after normalization. Normalization can also be performed in the normalization module 65 after the bandpass system output 49. The second count rate N2 can be passed to the first output 75 of the measuring device 10.

[0046] A differential count rate N3 is formed in the subtractor 60. The differential count rate N3 corresponds to the difference between the first count rate N1 and the second count rate N2 and / or is related to the difference. The differential count rate N3 can be transferred to the second output terminal 70 of the measuring device 10. Therefore, the useful signal measurement value is present at the output terminal of the measuring device 10 (i.e., the first output terminal 75), and the interference signal measurement value is present at the second output terminal 70. Both of these measurements can be used by downstream modules (not shown). The measuring device 10 can at least partially include one or more processor units 80. Here, the processor unit 80 can include at least an average value generator 50, a passband system 40 and / or a normalization module 65.

[0047] Figure 2 The detector 30 receiving the modulated useful signal and the interference signal is schematically shown (see Figure 1). The x-axis shows the time axis, on which the measured values ​​in the time range of 80 s to 150 s are plotted. The y-axis shows the count rate N as can be measured at the output signal 39 of the detector 30. The sine wave of the modulated useful signal from the gamma-ray emitter 20 can be clearly seen. In the time range from 90 s to about 115 s and from 140 s onwards, the sine wave is superimposed with an unmodulated interference signal. In the undisturbed range from 80 s to 90 s and from 115 s to 140 s, the count rate is about 0.1×10 4 and 1.1×10 4 The count rate fluctuates between pulses, and in the disturbed region, the count rate is about 1.6×10 4 and 2.6×10 4 The amplitude of the interference signal is therefore higher than the amplitude of the modulated useful signal in this example. All values ​​are purely exemplary.

[0048] Figure 3 Schematically shows the bandpass system 40 (see Figure 1 ) at the output 49 of the bandpass system Figure 2 The x-axis and y-axis show the Figure 2 The curve shown represents the useful signal as can be measured at the output 75 of the measuring device 10. It is obvious that the counting rate is substantially in the range of 1.0×10 4 The filling level 97 in the container 95 therefore does not change or changes only slightly in the time range shown.

[0049] Figure 4 The average value generator 50 (see Figure 1 ) at the output terminal 59 of the average value generator Figure 2 The x-axis and y-axis show the Figure 2 Same time range or count rate. This represents the average value of the sum of the wanted signal plus the interference signal.

[0050] Figure 5 The measuring device 10 (see Figure 1 ) at the output terminal 70 Figure 2 The x-axis and y-axis show the Figure 2 The same time range or count rate. This indicates a pure interference signal, namely the differential count rate N3. This signal can be further processed, for example, in the following way: the differential count rate N3 is compared with a threshold value N4 (dashed line) and an action is triggered when the threshold value N4 is exceeded. For example, the action can be a notification "interference signal present" on a connected display.

[0051] Figure 6 A flowchart 100 is shown for illustrating the steps of a method according to an exemplary embodiment of the present invention. In step 101, a detector 30 (see Figure 1 ) receives pulses of a useful signal modulated with a modulation frequency from a gamma-ray emitter 20, and additionally receives an interference signal from an external radiation source 25. In step 102, a first count rate N1 is outputted by an average value generator 50. In step 103, a second count rate N2 is outputted by a bandpass system 40. Step 102 may be performed in parallel, quasi-parallel, or sequentially (102 after 103 or 103 after 102). In step 104, a differential count rate N3 is formed by a subtractor 60, wherein the differential count rate N3 is obtained by subtracting the second count rate N2 from the first count rate N1. In step 104, the differential count rate N3 is outputted.

[0052] In addition, it should be pointed out that "comprising" and "having" do not exclude any other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. It should also be noted that features or steps that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Reference signs in the claims should not be considered as limitations.

[0053] Reference numerals list

[0054] 10 Radioactivity measuring device

[0055] 20 Gamma-ray emitter

[0056] 22 Modulator

[0057] 25 External radiation sources

[0058] 30 Detector

[0059] 39 Detector output

[0060] 40 Bandpass System

[0061] 42 Frequency determination module, FFT module

[0062] 45 Bandpass filter

[0063] 49 Bandpass system output

[0064] 50 Average Generator

[0065] 59 Average value generator output

[0066] 60 Subtractor

[0067] 65 Normalization module

[0068] 75, 70 The first and second output terminals of the measuring device

[0069] 80 Processor Units

[0070] 90 Filling material

[0071] 95 Containers

[0072] 97 Filling level

[0073] 100 Flowchart

[0074] 101~105 Methods and Steps

Claims

1. A radioactivity measuring device (10) for determining the intensity of pulses of interference signals from an external radiation source (25) during the determination of a filling level or a limit level of a filling material (90) in a container (95), the measuring device (10) comprising: a detector (30) configured to receive pulses of a useful signal modulated with a modulation frequency from a gamma-ray emitter (20) and also to receive pulses of said interference signal from said external radiation source (25); an average value generator (50) configured to output a first count rate (N1) of the pulses of the modulated useful signal and the interference signal at an average value generator output (59), wherein the first count rate (N1) corresponds to an average value of a first number of pulses received by the detector (30) within a predetermined time period within the predetermined time period; a bandpass system (40) comprising a bandpass filter (45) having a passband frequency range, the bandpass filter being configured to output a second count rate (N2) of the pulses of the modulated useful signal and the interference signal at a bandpass system output (49), wherein the passband frequency range of the bandpass filter (45) corresponds to the modulation frequency of the modulated useful signal from the gamma-ray emitter (20), and wherein the second count rate (N2) corresponds to a second number of pulses received by the detector (30) within the predetermined time period within the passband frequency range of the bandpass filter (45); and A subtractor (60) is configured to form a differential count rate (N3), wherein the differential count rate (N3) corresponds to a difference between the first count rate (N1) and the second count rate (N2), such that the differential count rate (N3) corresponds to the strength of the interference signal from the external radiation source (25).

2. The measuring device (10) according to claim 1, in, The differential count rate (N3) is compared to a threshold (N4), and when the threshold (N4) is exceeded, an action is triggered.

3. The measuring device (10) according to claim 2, in, The action includes suspending temperature control.

4. The measuring device (10) according to claim 2, in, The actions include storing a timestamp and / or a value of the strength of the interfering signal.

5. The measuring device (10) according to claim 2, in, The action includes issuing a warning.

6. The measuring device (10) according to any one of claims 1 to 5, in, The measuring device (10) further comprises a frequency determination module (42) configured to determine the modulation frequency of the modulated useful signal from the gamma-ray emitter (20) and to adjust the passband frequency range of the bandpass filter (45) having an adjustable passband frequency range to the modulation frequency of the modulated useful signal.

7. The measuring device (10) according to claim 6, in, The adjustable passband frequency range of the bandpass filter (45) has a center frequency between 0.05 and 20 Hz.

8. The measuring device (10) according to any one of claims 1 to 5, in, The predetermined time periods of the first count rate (N1), the second count rate (N2), and the differential count rate (N3) are between 0.02 and 50 seconds.

9. The measuring device (10) according to any one of claims 1 to 5, in, The first count rate (N1) is proportional to k times the average value of the first number of pulses.

10. The measuring device (10) according to any one of claims 1 to 5, further comprising: a modulator that controls a displaceable membrane around the gamma-ray emitter (20) and / or electronic circuitry, The modulator is configured to modulate a signal of the gamma ray emitter (20) to generate the modulated signal.

11. The measuring device (10) according to claim 7, in, The adjustable passband frequency range of the bandpass filter (45) has a center frequency of 1 Hz.

12. The measuring device (10) according to claim 8, in, The predetermined time periods of the first count rate (N1), the second count rate (N2), and the differential count rate (N3) are between 0.05 and 20 seconds.

13. The measuring device (10) according to claim 8, in, The predetermined time periods of the first count rate (N1), the second count rate (N2) and the differential count rate (N3) are 1 second.

14. The measuring device (10) according to claim 9, in, k＝1 / 2。 15. A method for determining the intensity of an interference signal from an external radiation source (25) during the determination of a fill level or a limit level by means of a radioactivity measuring device (10) according to any of the preceding claims, the method comprising the following steps: a) receiving, through a detector (30), a useful signal modulated by a modulation frequency from a gamma-ray emitter (20), and also receiving the interference signal from the external radiation source (25); b) outputting a first counting rate (N1) through an average value generator (50); c) outputting a second counting rate (N2) through a bandpass system (40); d) forming, by a subtractor (60), a differential count rate (N3) obtained by subtracting the second count rate (N2) from the first count rate (N1); and e) Outputting the differential count rate (N3).

16. The method according to claim 15, further comprising the steps of: f) comparing the differential count rate (N3) to a threshold value (N4); and g) If said threshold (N4) is exceeded, an action is triggered.

17. Use of the measuring device (10) according to any one of claims 1 to 14 for determining a filling level or a limit level of a filling material (90).

18. Use of the measuring device (10) according to claim 17, in, The filling material is a liquid and / or a loose material.

19. A program element which, when executed on a processor unit (80) of a measuring device (10), instructs the measuring device (10) to carry out the method according to claim 15 or 16.

20. A computer-readable medium having stored thereon a program element according to claim 19.

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