EXTERNAL RADIATION DETECTION WITH A GAMMA MODULATOR

Abstract

A radiometric measuring device for determining an intensity of pulses of an interference signal from an external radiation source, wherein the radiometric measuring device carries out fill level or limit level determination of a filling material in a container. The radiometric measuring device has a detector which is configured to receive pulses of a useful signal modulated with a modulation frequency from a gamma emitter and additionally pulses of the interference signal from the external radiation source. Further, the measuring device comprises an averager configured to output a first count rate of the pulses at an averager output, and a bandpass system comprising a bandpass with adjustable passband frequency range configured to output a second count rate of the pulses at a bandpass system output. The measuring device further comprises a subtractor adapted to form a differential count rate between the first count rate and the second count rate.

Claims

1-15. (canceled)

16. A radiometric measuring device for determining an intensity of pulses of an interference signal from an external radiation source during a filling level or limit level determination of a filling material in a container, the radiometric measuring device comprising: a detector configured to receive pulses of a useful signal modulated with a modulation frequency from a gamma emitter and additional pulses of the interference signal from the external radiation source; an averager configured to output a first count rate of the pulses at an averager output, wherein the first count rate corresponds to an average of a first number of pulses within a predefined time period received from the detector over the predefined time period; and a bandpass system including a bandpass filter having a passband frequency range configured to output a second count rate of the pulses at a bandpass system output, wherein the passband frequency range of the bandpass filter corresponds to the modulation frequency of the modulated useful signal from the gamma emitter, and wherein the second count rate corresponds to a second number of pulses within the predefined time period received by the detector in a bandpass frequency range of the bandpass filter over the predefined time period; and a subtractor configured to form a differential count rate, wherein the differential count rate corresponds to a difference between the first count rate and the second count rate, such that the differential count rate corresponds to an intensity of the interfering signal from the external radiation source.

17. The radiometric measuring device according to claim 16, wherein the differential count rate is compared with a threshold value and, if the threshold value is exceeded, an action is triggered.

18. The radiometric measuring device according to claim 17, wherein the action includes suspending a temperature control.

19. The radiometric measuring device according to claim 17, wherein the action includes storing a time stamp and/or a value of an intensity of the interference signal.

20. The radiometric measuring device according to claim 17, wherein the action includes issuing a warning.

21. The radiometric measuring device according to claim 16, wherein the radiometric measuring device further includes a frequency determination module configured to determine the modulation frequency of the modulated useful signal from the gamma emitter and to adjust the passband frequency range of the bandpass filter with adjustable passband frequency range to the modulation frequency of the modulated useful signal.

22. The radiometric measuring device according to claim 16, wherein the passband frequency range of the bandpass filter has a center frequency between 0.05 and 20 Hertz, in particular of 1 Hertz.

23. The radiometric measuring device according to claim 16, wherein the predefined period of the counting rates is between 0.02 and 50 seconds, for example between 0.05 and 20 seconds, and in particular 1 second.

24. The radiometric measuring device according to claim 16, wherein the first counting rate is proportional to k times a mean value of the first number of pulses, in particular with k=1/2.

25. The radiometric measuring device according to claim 16, further comprising: a modulator driving a movable aperture around the gamma emitter and/or an electronic circuit, wherein the modulator is configured to modulate a signal from the gamma emitter to produce the modulated signal.

26. A method of determining an intensity of an interference signal from an external radiation source during a fill level or boundary level determination, by way of a radiometric measuring device for determining an intensity of pulses of an interference signal from an external radiation source during a filling level or limit level determination of a filling material in a container, the radiometric measuring device including a detector configured to receive pulses of a useful signal modulated with a modulation frequency from a gamma emitter and additional pulses of the interference signal from the external radiation source, an averager configured to output a first count rate of the pulses at an averager output, wherein the first count rate corresponds to an average of a first number of pulses within a predefined time period received from the detector over the predefined time period, and a bandpass system including a bandpass filter having a passband frequency range configured to output a second count rate of the pulses at a bandpass system output, wherein the passband frequency range of the bandpass filter corresponds to the modulation frequency of the modulated useful signal from the gamma emitter, and wherein the second count rate corresponds to a second number of pulses within the predefined time period received by the detector in a bandpass frequency range of the bandpass filter over the predefined time period, and a subtractor configured to form a differential count rate, wherein the differential count rate corresponds to a difference between the first count rate and the second count rate, such that the differential count rate corresponds to the intensity of the interfering signal from the external radiation source, the method comprising: receiving, by way of the detector, pulses of a useful signal modulated with a modulation frequency from a gamma emitter and, in addition, the interfering signal from the external radiation source; outputting a first count rate, by way of the averager; outputting a second count rate, by way of a bandpass system; forming a differential count rate, by way of the subtractor, which subtracts the second count rate from the first count rate; and outputting the differential count rate.

27. The method according to claim 26, further comprising: comparing the differential count rate with a threshold value; and if the threshold value is exceeded, triggering an action.

28. A non-transitory computer-readable medium having stored thereon a program that when executed by a computer causes the computer to implement a method of determining an intensity of an interference signal from an external radiation source during a fill level or boundary level determination, by way of a radiometric measuring device for determining an intensity of pulses of an interference signal from an external radiation source during a filling level or limit level determination of a filling material in a container, the radiometric measuring device including a detector configured to receive pulses of a useful signal modulated with a modulation frequency from a gamma emitter and additional pulses of the interference signal from the external radiation source, an averager configured to output a first count rate of the pulses at an averager output, wherein the first count rate corresponds to an average of a first number of pulses within a predefined time period received from the detector over the predefined time period, and a bandpass system including a bandpass filter having a passband frequency range configured to output a second count rate of the pulses at a bandpass system output, wherein the passband frequency range of the bandpass filter corresponds to the modulation frequency of the modulated useful signal from the gamma emitter, and wherein the second count rate corresponds to a second number of pulses within the predefined time period received by the detector in a bandpass frequency range of the bandpass filter over the predefined time period, and a subtractor configured to form a differential count rate, wherein the differential count rate corresponds to a difference between the first count rate and the second count rate, such that the differential count rate corresponds to the intensity of the interfering signal from the external radiation source, the method comprising: receiving, by way of the detector, pulses of a useful signal modulated with a modulation frequency from a gamma emitter and, in addition, the interfering signal from the external radiation source; outputting a first count rate, by way of the averager; outputting a second count rate, by way of the bandpass system; forming a differential count rate, by way of the subtractor, which subtracts the second count rate from the first count rate; and outputting the differential count rate.

29. The method according to claim 26, wherein the differential count rate is compared with a threshold value and, if the threshold value is exceeded, an action is triggered.

30. The method according to claim 29, wherein the action includes suspending a temperature control.

31. The method according to claim 29, wherein the action includes storing a time stamp and/or a value of an intensity of the interference signal.

32. The method according to claim 29, wherein the action includes issuing a warning.

33. The method according to claim 26, wherein the passband frequency range of the bandpass filter has a center frequency between 0.05 and 20 Hertz, in particular of 1 Hertz.

34. The method according to claim 26, wherein the predefined period of the counting rates is between 0.02 and 50 seconds, for example between 0.05 and 20 seconds, and in particular 1 second.

35. The method according to claim 26, wherein the first counting rate is proportional to k times a mean value of the first number of pulses, in particular with k=1/2.

Description

DESCRIPTION OF THE FIGURES

[0029] FIG. 1 schematically shows a measuring device according to an embodiment of the present invention;

[0030] FIG. 2 schematically shows an example of an input signal of a detector receiving a modulated useful signal and an interference signal;

[0031] FIG. 3 schematically shows an example of the signal of FIG. 2 at the output of a bandpass system according to the present invention;

[0032] FIG. 4 shows schematically an example of the signal of FIG. 2 at the output of an averaging system according to the present invention;

[0033] FIG. 5 shows schematically an example of the signal of FIG. 2 at the output of a measuring device in one embodiment of the present invention;

[0034] FIG. 6 shows a flow chart illustrating steps of a method according to an embodiment of the present invention.

[0035] FIG. 1 schematically shows a measuring device 10 according to an embodiment of the present invention. The measuring device 10 comprises a gamma emitter 20 configured to emit a modulated useful signal. The gamma emitter 20 may be driven by a modulator 22, which applies a predefined frequency to the gamma emitter. The gamma emitter 20 may emit the modulated useful signal in a plurality of directions, for example in the direction of a container 95. The container 95 comprises a filling material 90. The fill material 90 may comprise a liquid and/or a bulk material.

[0036] On the opposite side of the container 95 to the gamma emitter 20 is arranged a detector 30 which is configured to receive pulses from radiation from gamma sources. One of the gamma sources is the gamma emitter 20. The intensity of the gamma rays received by the detector 30 depends on the fill level 97 of the container 95. If the level 97 is so high that the fill material 90 is between the gamma emitter 20 and the detector 30, then the modulated useful signal is attenuated by the fill material 90. If there is no fill material 90 between the gamma emitter 20 and the detector 30, then the detector 30 receives a higher intensity of modulated gamma rays from the gamma emitter 20. This effect may be used to determine the level or boundary level of the fill material 90 in the container 95. However, the detector 30 may not only receive gamma rays from the modulated gamma emitter 20, but the detector 30 may also receive pulses from other gamma sources, for example pulses of the interfering signal from an external radiation source 25. The interfering signal may be unmodulated and consequently may have a different frequency characteristic than the modulated gamma emitter 20.

[0037] The pulses generated by the detector 30 are directed, from the detector output 39 of the detector 30 in the measuring device 10, to an averaging frame 50 and a bandpass system 40. The averager 50 is configured to output a first count rate N1 of the pulses at an averager output 59. For this purpose, the averager 50 averages a first number of pulses within a predefined time period. The pulses may comprise the entire frequency spectrum received by the detector 30. Accordingly, the average value of the averager 50 counts all pulses from the detector 30 within the predefined time period.

[0038] The bandpass system 40 comprises a bandpass 45 with an adjustable passband frequency range. The bandpass 45 may be adjusted to a passband frequency range, for example, by means of an FFT module 42. The passband frequency range may correspond to the frequency of the modulated useful signal. The passband frequency range may be set, for example, at the beginning of a measurement and/or during the measurement. By means of the bandpass filter 45, essentially only those pulses are filtered out of the pulses received from the detector 30 that are within the passband frequency range. The bandpass system 40 counts these pulses and passes them—if necessary after normalization—as a second count rate N2 to the bandpass system output 49. The normalization may also be performed subsequently to the bandpass system output 49, in a normalization module 65. The second count rate N2 may be fed to a first output 75 of the measuring device 10.

[0039] A differential count rate N3 is formed in a subtractor 60. The differential count rate N3 corresponds to and/or correlates with a difference between the first count rate N1 and the second count rate N2. The differential count rate N3 may be fed to a second output 70 of the measuring device 10. Thus, a useful signal measurement value is present at the outputs of the measuring device 10, namely at the first output 75, and a interference signal measurement value is present at the second output 70. Both measured values may be used by downstream modules (not shown). The measurement device 10 may comprise, at least in part, one or more processing units 80. In this regard, the processor unit 80 may comprise at least the averaging module 50, the bandpass system 40 and/or the normalization module 65.

[0040] FIG. 2 schematically shows an example of an output signal 39 of a detector 30 (see FIG. 1) which receives a modulated useful signal and an interference signal. The x-axis shows a timeline on which measured values in a time range of 80 s to 150 s are plotted. They axis shows a count rate N as may be measured at the output signal 39 of the detector 30. The sine waves of the modulated useful signal from the gamma emitter 20 are clearly visible. The sine waves are superimposed with an unmodulated interference signal in a time range from 90 s to about 115 s and from 140 s onwards. In the undisturbed range 80 s to 90 s, and 115 s to 140 s, the count rate varies approximately between 0.1 and 1.1×104 pulses per second, and in the disturbed range the count rate varies approximately between 1.6 and 2.6×104 pulses per second. Thus, in this example, an amplitude of the interfering signal is higher than an amplitude of the modulated useful signal. All numerical values are purely exemplary.

[0041] FIG. 3 schematically shows an example of the useful signal of FIG. 2 at the bandpass system output 49 of the bandpass system 40 (see FIG. 1) after bandpass filtering. The x-axis and the y-axis show the same time ranges and count rates, respectively, as FIG. 2. The curve shown represents the useful signal as it may be measured at an output 75 of the measuring device 10. It is clear that the count rate essentially oscillates around a value of 1.0×104 pulses per second. Thus, in the time range shown, the level 97 in the container 95 does not change or changes only marginally.

[0042] FIG. 4 schematically shows an example of the signal of FIG. 2 at the mean value image output 59 of a mean value imager 50 (see FIG. 1). The x-axis and the y-axis show the same time ranges or count rates as FIG. 2. This represents the averaged useful signal plus interference signal.

[0043] FIG. 5 schematically shows an example of the signal of FIG. 2 at the output 70 of a measuring device 10 (see FIG. 1). The x-axis and the y-axis show the same time ranges or count rates as FIG. 2. This represents the pure interference signal, i.e. the differential count rate N3. This signal may be further processed, for example, by comparing the differential count rate N3 with a threshold value N4 (dashed) and triggering an action if the threshold value N4 is exceeded. The action may be, for example, a message “Interference signal present” on a connected display.

[0044] FIG. 6 shows a flowchart 100 illustrating steps of a method according to an embodiment example of the present invention. In a step 101, by means of a detector 30 (see FIG. 1), pulses of a useful signal modulated with a modulation frequency are received from a gamma emitter 20 and, in addition, an interference signal is received from the external radiation source 25. In a step 102, a first count rate N1 is output by means of an averager 50. In a step 103, a second count rate N2 is output by means of a bandpass system 40. The steps 102 may be performed in parallel, quasi-parallel or sequentially (102 after 103, or 103 after 102). In a step 104, a differential count rate N3 is formed by means of a subtractor 60, the differential count rate N3 subtracting the second count rate N2 from the first count rate N1. In a step 104, the differential count rate N3 is output.

[0045] It should be further noted that “comprising” and “comprising” do not exclude other elements or steps, and the indefinite articles one or “a” do not exclude a plurality. It should also be noted that features or steps described by reference to any of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be regarded as limitations.

LIST OF REFERENCE SIGNS

[0046] 10 radiometric measurement device [0047] 20 gamma emitter [0048] 22 modulator [0049] 25 external radiation source [0050] 30 detector [0051] 39 detector output [0052] 40 bandpass system [0053] 42 frequency determination module, FFT module [0054] 45 bandpass filter [0055] 49 bandpass system output [0056] 50 averaging module [0057] 59 averager output [0058] 60 subtractor [0059] 65 normalization module [0060] 75, 70 first and second output of the measurement device [0061] 80 processing unit [0062] 90 fill material [0063] 95 container [0064] 97 fill level [0065] 101-105 steps of flowchart 100