EP1716396A1

EP1716396A1 - Radiometric level gauge

Info

Publication number: EP1716396A1
Application number: EP05716689A
Authority: EP
Inventors: Dietmar Spanke; Holger Steltner; Fabrice Peter; Bernhard Ottenbreit
Original assignee: Endress and Hauser SE and Co KG
Current assignee: Endress and Hauser SE and Co KG
Priority date: 2004-02-16
Filing date: 2005-02-14
Publication date: 2006-11-02
Also published as: AU2005212648A1; RU2337328C2; WO2005078397A1; CN1914488A; AU2005212648B2; RU2006133283A; CN100462695C; US20070278404A1; DE102004007680A1

Abstract

Disclosed is a radiometric gauge which can be installed and operated inexpensively and is to be mounted on a container (3) that can be filled with a filling material (1). Said gauge comprises a radioactive emitter (5) which emits radioactive radiation through the container (3) during operation, at least two detectors (Di) that absorb radiation penetrating the container (3) and generate an electrical pulse rate (Ni) corresponding to the absorbed radiation. The detectors (Di) are interconnected by means of a single wire that extends outside the detectors (Di) while being connected to a higher-level unit (23) via which pulse rates (Ni) and the status of the detectors (Di) are transmitted, said status being transmitted in the form of offsets (Oi).

Description

Description RADIOMETRIC LEVEL MEASURING DEVICE

[001] The invention relates to a radiometric measuring device. By means of radiometric measuring devices, physical quantities, e.g. a level or density of a medium can be measured.

[002] Radiometric measuring devices are usually always used when conventional measuring devices cannot be used at the measuring location due to particularly harsh conditions. For example, very often Extremely high temperatures and pressures at the measuring location or there are chemically and / or mechanically very aggressive environmental influences that make it impossible to use other measuring methods.

In radiometric measurement technology, a radioactive emitter, e.g. a Co 60 or Cs 137 preparation, placed in a radiation protection container and at a measuring location, e.g. attached to a container filled with a filling material. Such a container can e.g. a tank, a container, a pipe, a conveyor belt or any other form of container.

[004] The radiation protection container has a recess through which the radiation emitted by the radiator positioned for measurement is emitted through a wall of the radiation protection container.

Typically, a radiation direction is selected in which the radiation penetrates that area of the container that is to be measured. On the opposite side, the radiation intensity emerging due to a change in fill level or density is detected quantitatively with a detector. The emerging radiation intensity depends on the geometric arrangement and the absorption. The latter is dependent on the amount of the filling material in the container for level measurement and on the density of the filling material for density measurement. The emerging radiation intensity is consequently a measure of the current filling level or the current density of the filling material in the container.

A scintillation detector with a scintillator, for example a scintillation rod, and a photomultiplier is suitable as a detector. The scintillation wand is basically a plexiglass wand that is optically very pure. Flashes of light are emitted by the scintillation material under the influence of gamma radiation. These are detected by the photomultiplier and converted into electrical impulses. A pulse rate with which the pulses occur depends on the radiation intensity and thus a measure of the physical quantity to be measured, for example the fill level or the Density. The scintillator and photomultiplier are usually mounted in a protective tube, for example made of stainless steel. The detector generally has electronics that provide an output signal corresponding to the pulse rate of a higher-level unit. The electronics usually include a controller and a counter. The electrical impulses are counted and a counting rate is derived from which the physical quantity to be measured can be determined.

In addition, a status of the detector is preferably checked. In the simplest case, the status includes an indication of whether the detector is working properly or not. Depending on the status, an error message and / or an alarm may be triggered.

[009] Two lines are generally provided between the detector and the higher-level unit for transmitting the output signal and the status of the detector.

An effective length of the detectors defines the area of the container that can be measured and depends on the required measuring height and the mounting options. Detectors are now available in lengths from approx. 400 mm to approx. 2000 mm. If a length of approx. 2000 mm is not sufficient, two or more detectors can be connected to a radiometric measuring device.

In conventional measuring devices, each detector has its own electronics. To transmit the output signals and the status of each detector, at least two lines are laid from each detector to the higher-level unit. The output signals of the individual detectors are combined in the higher-level unit to form a sum signal, which reflects the total rate of the detected pulses.

When using two or more detectors, the required technical effort increases in proportion to the number of detectors. For each detector, separate electronics with a counter and a controller must be provided, the status of each detector must be checked individually and each detector must be connected to the higher-level unit using two lines, which then checks the status of each detector and the individual output signals summarizes a measurement signal.

Each additional line increases the cost. In particular, if the detectors are used in potentially explosive areas, the costs for additional lines are considerable. It is an object of the invention to provide a radiometric measuring device with two or more detectors, which can be installed and operated inexpensively.

For this purpose, the invention consists in a radiometric measuring device for mounting on a container which can be filled with a filling material, with

[016] - a radioactive emitter operating

Sends radioactive radiation through the container,

[018] - at least two detectors,

[019] - which serve to penetrate through the container

Absorb radiation and one of the

Corresponding recorded radiation

Generate electrical pulse rate

[023] - Offset generators that match the pulse rate of each

[024] detector a status of each

Overlay detector reproducing offset, and

[026] - a manifold,

[027] - that each detector is one of the overlay of the

[028] respective pulse rate and the respective offset

Feeds the corresponding output signal,

[030] ~ the one of superimposing the output signals

[031] corresponding sum signal of a higher-level

Unit feeds,

- The measurement signal based on the sum signal

And / or derives a status of the measuring device.

The invention further consists in a radiometric measuring device for mounting on a container which can be filled with a filling material, with

[036] - a radioactive emitter that is in operation

Sends radioactive radiation through the container,

- at least two detectors,

[039] ~ which serve to penetrate through the container

Absorb radiation and one of the

[041] received radiation corresponding

[042] to generate electrical pulse rate

[043] - Offset generators that match the pulse rate of each

Detector a detector specific offset

Overlay, [046] - Shutdowns, which serve to prevent transmission [047] of the pulse rates and offsets, if [048] the detector is malfunctioning, [049] - a bus line, [050] - which every properly functioning detector is one of the [ 051] Superposition of the respective pulse rate and the output signal corresponding to the [052] offset

[053]

[054] - the one of the superposition of the output signals

[055] corresponding sum signal of a higher-level

[056] feed unit,

- The measurement signal based on the sum signal

And / or derives a status of the measuring device.

[OS] According to an embodiment of the aforementioned radiometric measuring devices, a series of detectors is provided, and the collecting line starts at a first detector of the series, from there leads from one detector to the detector adjacent to it and from the last detector to the higher-level unit.

[060] According to a further embodiment, each detector comprises a scintillator and a photomultiplier connected to it.

[061] According to a development of the latter radiometric measuring device, the offset generators periodically send reference light flashes through the scintillator via an optical fiber.

[062] According to a further embodiment, the higher-level unit is integrated in the last detector in the series.

The invention further consists in a method for measuring a physical quantity using one of the aforementioned radiometric measuring devices, in which

[064] - a setpoint for an offset for each detector

Is assigned to which the offset generators of the

[066] Detectors produce when the detector is working properly

[067] works, and which is greater than a sum of the maximum for the detectors

[068] expected pulse rates is

[069] - the higher-level unit based on the sum signal

Determines an overall count rate,

[071] - the difference from this total count rate and one

[072] corresponding to the sum of the setpoints of the offsets [073] forms count rate, [074] - recognizes that there is an error if the difference [075] is negative, and [076] - derives a measurement signal if the difference is positive. According to one embodiment of the method, if a negative difference is present, the amount of the difference is used to determine which of the detectors is working incorrectly. [078]

The invention further consists in a radiometric measuring device for mounting on a container which can be filled with a filling material

[080] - a radioactive emitter, which during operation [081] sends radioactive radiation through the container,

[082] - a first and a second detector,

[083] - which serve to receive radiation penetrating through the container [084] and one

[085] corresponding to the absorbed radiation

[086] to generate electrical pulse rate

[087] - an offset generator which gives the pulse rate of the [088] first detector a status of the first

[089] detector reflecting offset overlaid, and

[090] - one integrated in the second detector

[091] parent unit,

[092] - with which the first detector over a

[093] connecting line is connected,

[094] - over which the first detector one of the overlay

[095] the pulse rate and the offset

[096] supplies corresponding output signal,

[097] ~ the pulse rate and a status of the second

[098] detector is fed, and

[099] - a measurement signal based on the incoming signals

[100] and / or derives a status of the measuring device.

The invention also consists in a radiometric measuring device for mounting on a container which can be filled with a filling material

[102] - a radioactive emitter that is in operation

[103] sends radioactive radiation through the container, [104] - a first and a second detector, [105] - which serve to record radiation penetrating through the container [106] and to generate [107] an electrical pulse rate corresponding to the received radiation and one of the [109] pulse rate to transmit the corresponding output signal to a higher-level unit [111] integrated in the [110] second detector, [112] - in which the emitter has a strength [113] in which a [114] minimum pulse rate greater than zero can always be expected for each detector is

[115] - in which an isolator is provided in each detector,

[116] of the transmission of the output signal to the

[117] parent unit prevents when the detector

[118] is working incorrectly, and

[119] - in which the parent unit based on the

[120] Output signals a measurement signal and / or a status

[121] of the measuring device.

An advantage of the invention is that the detectors are only connected by a single line, the collecting line or the connecting line, via which both the status information and the measurement information are transmitted by generating a single output signal that contains both information. This is done by superimposing a status-dependent offset on the pulse rate, or by superimposing a detector-specific offset on the pulse rate depending on the status, or by not doing so.

[123] The invention and further advantages will now be explained in more detail with reference to the figures in the drawing, in which seven exemplary embodiments are shown; Identical parts are provided with the same reference symbols in the figures.

[124] Fig. 1 shows a table on a container

[125] mounted radiometric measuring device with two

[126] detectors;

2 shows schematically the construction of a detector;

3 shows a superimposition of

[129] pulse rate and offset;

4 shows one of the superimposition according to FIG. 3 [131] corresponding signal;

5 shows schematically the structure of a measuring device with

[133] three detectors, in which the pulse rate each

[134] Detector one from the status of the respective detector

[135] dependent offset is superimposed;

6 shows schematically the structure of a measuring device

[137] three detectors, where the pulse rate each

[138] a detector-specific offset is superimposed on the detector;

7 shows schematically the construction of a detector, at

[140] which, depending on the status of the detector,

[141] generator for generating a detector-specific offset or a switch is used;

8 shows schematically the structure of a measuring device

[143] two detectors, in which at least one detector

[144] has an offset generator that the

[145] Detector one pulse rate from status

[146] overlaid on the same dependent offset;

9 shows schematically the structure of a measuring device

[148] two detectors, each a switch

[149] have a transmission of the pulse rate

[150] suppressed if the respective detector is not

[151] works properly; and

[152] Fig. 10 shows the construction of a detector with

[153] an offset generator of the scintillator

[154] Feeds reference flashes.

1 shows schematically a measuring arrangement with a radiometric measuring device. The measuring arrangement comprises a container 3 which can be filled with a filling material 1. The radiometric measuring device is mounted on the container 3 and serves to record a physical quantity, e.g. a filling level of the filling material 1 in the container 3 or a density of the filling material 1.

For this purpose, the radiometric measuring device has a radioactive radiator 5, which transmits radioactive radiation through the container 3 during operation. The radiator 5 consists, for example, of a radiation protection container into which a radioactive preparation, for example a Co 60 or Cs 137 preparation, has been introduced. The radiation protection container has an opening through which the radiation emerges at an opening angle α and the container 3 irradiated. [157] The measuring device comprises at least one detector D, which is used to record radiation penetrating through the container 3 and to generate an electrical pulse rate N corresponding to the recorded radiation. Depending on the application, several detectors D can be connected in series to cover a sufficiently large area in which radiation can be recorded. In the embodiment shown in Fig. 1, two detectors, D and D, are provided. 1 2

[158] FIG. 2 shows a simplified construction of a detector D.

[159] This is a scintillation detector with a scintillator 7, here a scintillation rod and a photomultiplier 9 connected to it. The scintillator 7 and photomultiplier 9 are located in a protective tube 11 shown in Fig. 1, e.g. Made of a stainless steel, which is mounted on an outer wall of the container 3 opposite the radiator 5. The scintillation wand is basically a plexiglass wand that is optically very pure. Radiometric radiation impinging on the scintillator 7 generates flashes of light in the scintillation material. These are detected by the photomultiplier 9 and converted into electrical pulses n.

[160] Each detector D comprises electronics 13 which receive the electrical pulses n generated by the photomultiplier 9 and generate a pulse rate N corresponding to the radiation received.

The electronics 13 preferably comprises a counter 15 and a microcontroller 17 connected thereto. The counter 15 counts the incoming electrical pulses n and the microcontroller 17 determines a pulse rate N based on the counted pulses n.

According to a first embodiment, each detector D additionally has an offset generator 19 which generates an offset O corresponding to a status of the respective detector D. The offset generators 19 are preferably integrated in the microcontroller 17, as shown in FIG. 2. For example, a pulse generator is suitable as the offset generator 19, which generates electrical pulses k with a frequency corresponding to the offset O. The offset O is superimposed on the pulse rate N of the respective detector D. 3 schematically shows such an overlay. The pulses k generated by the offset generator 19 are added to the electrical pulses n received by the photomultiplier 9. An output signal corresponding to the superimposition is shown in FIG. 4. There, the pulses k of the offset generator 19 are shown as rectangular pulses. The impulses of the photo multipliers 9 are also shown as rectangular pulses. To distinguish them, dashed lines were used to represent the pulses n of the photomultiplier 9.

The output signal is generated in the microcontroller 17 and is available via an output stage 20 of the microcontroller 17.

A collecting line 21 is provided, to which each detector D supplies its output signal corresponding to the superimposition of the respective pulse rate N and the respective offset O. [165] The collecting line 21 leads from one detector D to the next detector D which is adjacent to it. Fig. 5 shows an embodiment with a series of ι + l three detectors D, D and D connected in series. The collecting line 21 1 2 3 begins at the first detector D of the series. It leads from each detector D to the respective adjacent detector D of the series and ends at the last detector in the series. 5 this is the detector D. It leads from the last detector D to a 3 3 superordinate unit 23. [166] In the collecting line 21, the output signals of the individual detectors D overlap to form a sum signal S that corresponds to the sum of the individual output signals.

[167] The higher-level unit 23 derives a measurement signal M and / or a status of the measuring device based on the sum signal S. Various methods can be used for this.

[168] A first method is explained in more detail below with reference to the exemplary embodiment shown in FIG. 5. Each detector D is assigned a setpoint O for the offset O here. The target values O are to be selected such that they are greater than a sum of the maximum pulse rate N rmx to be expected for the respective detectors D. - smd. [169] 0> Σ N "

[170] If the maximum pulse rate N ^ιm to be expected of each detector D is, for example, less than 20 pulses n per time interval, then the setpoints O in the exemplary embodiment shown in FIG. 5 should be selected to be greater than 60 pulses k per time interval. In the simplest case, the procedure is such that the offset generators 19 of the detectors D generate an offset O which corresponds to the target value O if the respective detector D is working properly and no offset, or an offset of 0 pulses k pro Generate time interval if the detector D is not working properly. The higher-level unit 23 has a counter 25 and an evaluation unit 27 connected to it. The counter 25 counts the incoming pulses n, k. A total count rate G is determined on the basis of the sum signal. The total count rate G is equal to the sum of the individual pulse rates N of the individual detectors D and the individual offsets O. [173] Hence: [174] G = Σ (N + O)

[175] In a next step, the evaluation unit 27 of the higher-level unit 23 forms a difference D from this total count rate G and a count rate corresponding to the sum of the target values O of the offsets O. For this purpose, a memory 28 is connected to the evaluation unit 27, in which the target values O of the offsets O are stored [176].

[177] D = G - Σ O

[178] If all detectors are working properly, this difference is positive and equal to the sum of the pulse rates N of the individual detectors D.

[179] If at least one detector D is not working properly, the difference D is negative. A negative difference D means that there is an error. At least one of the detectors D is not working properly.

[180] The evaluation unit 27 determines whether the difference D is positive or negative. It recognizes that there is an error if the difference D is negative.

[181] In addition, if there is a negative difference D, ie an error, it can be determined from the amount ςDς of the difference D which of the detectors D is working incorrectly. This makes it easier to search for errors subsequent to error detection and to correct the error. For this purpose, for example, in the exemplary embodiment described with reference to FIG. 5, all the setpoints O of the offsets O are selected such that they are different from one another, and the difference between two setpoints O each is greater than the sum of those to be expected for the respective detectors D. maximum pulse rate N ^max , ie:

[186] If, as stated above as an example, N "^ <20, for example the setpoint O = 100, the setpoint O = 200 and the setpoint O = 300 can be selected. S2

[187] If a single detector D is not working properly, then the amount IDI applies Difference D: [188] IDI = l∑ N - OI and thus

[189] O - Σ N ^{,, mx} <IDI <O

[190] If detector D is not working properly, the amount IDI of the difference D is therefore between 40 and 100. If detector D is not working properly, the amount IDI of the 2 difference D is between 140 and 200. If detector D is not working properly, the 3 amount IDI is Difference D between 240 and 300. [191] Based on the amount IDI of the difference D, it can consequently be clearly determined which detector D is not working properly. However, the assignment of the amount IDI of the difference D to the detector D concerned requires that only a single detector D is not working properly.

If one also wants to determine which detectors D, D are for two detectors D and D that are not working properly, then the setpoints O, O of the offsets O, O of each possibly affected detector pair D, D must also apply: [193 ] ^ Osi + Osj g lÖsk - Σ N "^BX; Osk + Σ N ^m I

In order to stay with the example given, the setpoint O sl for the first detector D can be set to 100, the setpoint O for the second detector D 1 s2 2 to 500 and the setpoint O for the third detector D to 1000 s3 3 will be. [195] If only one detector D is not working properly, the difference D applies to the amount IDI: [196] IDI = l∑ N - O I and thus

[197] O - Σ N ^ i 'lDk O

[198] If detector D is not working properly, the amount IDI of difference D is consequently between 40 and 100. If detector D is not working properly, the amount IDI of 2 difference D is between 440 and 500. If detector D is not working properly, the 3 amount IDI is Difference D between 940 and 1000.

[199] If the detectors D and D are not working properly, the> J difference D applies to the amount IDI:

[200] IDI = l∑ N - O - O I and thus

[201] O + O - Σ N ^* <IDk O + O

[202] If the detectors D and D are not working properly, the amount IDI of the 1 2 difference D is therefore between 540 and 600. If the detectors D and D are not working properly, the amount IDI of the difference D is between 1040 and 1100. Working the For detectors D and D, the amount IDI of the difference D is between 2 3 1440 and 1500. [203] If none of the detectors D, D and D is working properly, the amount IDI of the 1 2 3 difference D is between 1540 and 1600. In the exemplary embodiment mentioned, the latter case can therefore also be recognized on the basis of the amount IDI of the difference D. become. [204] If more than three detectors are used, the method must be expanded accordingly. [205] The higher-level unit 23 recognizes the presence of an error on the basis of the difference D and derives the status of the measuring device therefrom. In the simplest case, the status contains the information that all detectors D are working properly or at least one is not. In addition, the status in the presence of an error can contain the information which detector (s) D is not working properly.

[206] In the event of an error, the higher-level unit 23 generates an output signal representing the status, which is supplied, for example, to a measuring device electronics 29 or a process control center. It can also issue an error message and / or trigger an alarm.

[207] If there is no error, the difference D is positive. The higher-level unit 23 recognizes this and generates a measurement signal M based on the sum signal. In the simplest case, the measurement signal M corresponds to the difference D. If all detectors are working properly, this difference is positive and equal to the sum of the individual pulse rates N of the individual detectors D.

[208] 'D = G - Σ O = Σ N

[209] On the basis of this measurement signal, the physical quantity to be measured, e.g. a level or a density of the filling material 1 is determined. This can be done in a conventional manner either by means of measuring device electronics 29 integrated in the higher-level unit 23 or in a remote evaluation unit 31.

If all detectors D are working properly, the higher-level unit 23 can also emit an output signal representing the status. In this way, the error-free operation of the detectors D, for example the measuring device electronics 29, the evaluation unit 31 or another location, for example a process control center, can be displayed. The higher-level unit 23 can be spatially arranged in the last detector of a series; but it can also be arranged separately. The same applies to the measuring device electronics 29. [212] An advantage of the invention is that due to the overlapping of the im- pulse rates N and the offsets O and their merging in the collecting line 21 only a single connecting line, namely the collecting line 21 is required to transmit both the actual measurement information and the status information. This considerably reduces the wiring effort required. Esp. In safety-relevant areas in which radiometric measuring devices are usually used, for example in areas with an increased risk of explosion, there are high safety requirements for connecting lines, which are generally associated with increased acquisition and installation costs. These costs are significantly reduced by the radiometric measuring devices according to the invention. The collecting line 21 can be a very simple connection, for example an optical waveguide or a copper line. It is also possible to replace the collecting line 21 by a radio connection. [213] The transfer can be carried out in a very simple manner. Esp. no transmission protocol is required. Rather, the output signals of the individual detectors D can be transmitted with a corresponding calibration via any type of pulse output to a corresponding pulse input of the higher-level unit 23.

6 shows a further exemplary embodiment of a radiometric measuring device according to the invention. Because of the agreement with the exemplary embodiment described above, only the existing differences are explained in more detail below.

[215] Here too, detectors D are provided which serve to record radiation penetrating through the container 3 and to generate an electrical pulse rate N corresponding to the radiation received.

[216] Each detector D comprises an offset generator 19 which superimposes a detector-specific offset O on the pulse rate N of the respective detector D. In contrast to the previous exemplary embodiment, the offsets O detector specific and independent of the status of the respective detector D.

[217] Each detector D has a switch 33 which serves to suppress transmission of the pulse rate N and the offset O when the detector D is working incorrectly. The switch 33 is, for example, a simple switch which interrupts the connection of the respective detector D to the collecting line 21. The switch 33 can also be integrated in the output stage 20 of the microcontroller 17. In operation, therefore, only every correctly functioning detector D leads one Superposition of the respective pulse rate N speaking output signal of the bus 21. Detectors D that do not function properly, however, do not emit an output signal.

[219] As in the exemplary embodiment described above, the collecting line 21 supplies a sum signal corresponding to the superimposition of the output signals to the higher-level unit 23. As already described in connection with the previous exemplary embodiment, this derives a measurement signal and / or a status of the measurement device on the basis of the sum signal.

[220] If the detector-specific offsets O are selected appropriately, it can be recognized here, just like di in the exemplary embodiment described above, which detector (s) D is not working properly. In addition, a residual count rate R, which is equal to the sum of the count rates N of the properly functioning detectors D, can be determined. [221] It is equal to the difference between the total count rate G and the sum of the offsets O of the properly working detectors D. For example, if the detector D di x is not working properly, the following applies: [222] R = G - Σ ≠ O ι, ι x di

[223] Helpful additional information can be derived from this if necessary. An example is only a level measurement with two detectors, as shown in FIG. 1. If one of the detectors D or D fails, it can be determined on the basis of the 1 2 count rate N of the remaining detector whether the product 1 is in the area of the container 3 covered by the remaining detector. This rudimentary fill level information can be used, for example, for the safety-related control of filling or emptying of the container 3. For example, overfilling or draining of the container 3 can be avoided. As an alternative to the embodiment shown in FIG. 6, the detectors D can also be constructed in such a way that a switch 35 only prevents the overlaying of the detector-specific offset O if the respective detector D di is not working properly. This is shown in FIG. 7. If the detector D is not working properly, the addition of the offset O is prevented by the switch 34. di This is shown in FIG. 7 by an OR combination of offset generator 19 and switch 34. As a result, this combination of offset generator 19 and switch 34 forms an offset generator which emits a status-dependent offset. In this case, the sum signal is operated in exactly the same way as in the exemplary embodiment explained with reference to FIG. 5. 8 shows an exemplary embodiment in which the measuring device has two detectors, namely a first detector D and a second D. The 1 2 measuring device is mounted on the container 3 which can be filled with the filling material 1. The radioactive radiator 5 transmits radioactive radiation through the container 3 during operation. The first and the second detectors D and D serve to receive radiation penetrating through the container 3 and to generate an electrical pulse rate N, N corresponding to the radiation received , [226] The first detector D has an offset generator 19 which overlays the pulse rate N 1 1 of the first detector D with a 1 1 offset O reflecting the status of the first detector D. This happens, for example, exactly as in the exemplary embodiment described in FIG. 5. [227] A higher-level unit 23 is also provided here. It is integrated in the second detector D. The first detector D is connected via a connecting line 37 to 2 1 of the higher-level unit 23, via which the first detector D supplies an output signal corresponding to the superimposition of the pulse rate N and the offsets O. For this purpose, the connecting line 37 is connected to a first input 39 of the higher-level unit 23. [228] In addition, the higher-level unit 23 is supplied with the pulse rate N and the status 2 of the second detector D. 2

For this purpose, just like the first detector D, the second detector D can be equipped with a 2 1 offset generator 19 which overlays the pulse rate N with an offset O reflecting the status of the 2 second detector D. An output signal corresponding to the superimposition is then present at a second input 41 of the higher-level unit 23. [230] Alternatively, the higher-level unit 23 can receive the status information directly via a third input 43. In this embodiment variant, the second detector D then does not need to have an offset generator 19. 8 shows both the offset generator 19 of the second detector D and the alternative third input 43 to be provided. [231] The higher-level unit derives a measuring signal and / or a status of the measuring device on the basis of the incoming signals. [232] This is done analogously to the previously described exemplary embodiments, in that the offsets O and possibly O are assigned a setpoint O, O, which the 1 2 sl s2 respective offset set O, O assumes when the associated detector D, D flawlessly 1 2 1 2 works. If the detector D, D is not working properly, for example none will Offset overlaid. [233] Since the higher-level unit 23 is integrated in the second detector D, the information from the detectors D and D can be processed separately via the inputs 37, 39 and possibly 41, without additional lines 37 running outside the detectors in addition to the connecting line Lines are required. [234] This offers the advantage that the setpoints O and possibly O only have to be sl s2 larger than the maximum pulse rate N ^ιmx to be expected for the respective detector D, D, but definitely smaller than the buzzer of the maximum expected i pulse rate N Can be "" + N ". This improves the measuring accuracy. 1 2

[235] Based on the output signal of the first detector D, the higher-level unit 23 determines a count rate Z, which is equal to the sum of the pulse rate N and the offset O. The difference between this count rate Z and the target value O for the 1 1 sl offset O of the first detector D is then formed. If the difference is positive, detector D works perfectly and the amount of the difference is equal to the pulse rate N of the first detector D. If the difference is negative, the higher-level unit 23 recognizes that the detector D is not working properly. 1

[236] In the embodiment variant in which the second detector D is also equipped with a 2 offset generator 19, the procedure for the second detector D is analogous to 2, i.e. the higher-level unit 23 uses the output signal of the second detector D to determine a count rate Z which is equal to the sum of the pulse rate N 2 2 2 and the offset O. The difference between this count rate Z and the 2 2 setpoint O for the offset O of the second detector D is then formed. If the difference s2 2 2 is positive, detector D works perfectly and the amount of the difference is equal to the 2 pulse rate N of the second detector D. If the difference is negative, the higher-order unit 23 recognizes that the detector D is not working properly. 2

[237] In the alternative embodiment variant, in which the status information is transmitted separately, the higher-level unit 23 immediately recognizes on the basis of the signal present at the third input 43 whether the second detector D is working properly. 2 Furthermore, it determines a count rate Z, which is equal to the pulse rate N of the second 2 2 2 detector D, on the basis of the output signal of the second detector D arriving at the second input 41. 2

[238] In both variants, the status of the first and second detectors D and D is therefore present in the higher-level unit 23. 1 2

[239] If both detectors D, D work properly, they are in the higher-level unit 1 2 23 the pulse rates N and N before. From this, a measurement signal is derived from a simple addition of the pulse rates N and N, which corresponds to the radiation picked up by both detectors D and D. In addition, the measurement information of each individual detector D, D is available via the individual pulse rates 2 N, N. If 1 2 1 2 only one of the detectors D or D is working properly, this additional information, as already described 1 2 above, can be used separately. 9 shows a further exemplary embodiment of a measuring device according to the invention. The structure largely corresponds to the embodiment shown in FIG. 8. Therefore, only the existing differences are explained in more detail below. In the exemplary embodiment shown in FIG. 9, the radiator 5 has a strength at which a minimum pulse rate N ^min greater than zero 1 2 i is always to be expected for each detector D, D. The first detector D is connected via the connecting line 37 to the first input 37, the second detector D is connected directly to the second input 41 of the two higher-level unit 23 integrated in the second detector D. In contrast to the exemplary embodiment shown in FIG. 8, no offset generators 19 and no third input 43 are provided. Instead, a switch 45 is provided in each detector D, D, which prevents the 1 2 transmission of an output signal corresponding to the pulse rate N or N of the respective detector D, D to the higher-level unit if the detector D, D is faulty is working. 1 2

The signals of the detectors D and D fed to the higher-level unit 23 thus correspond to the pulse rate N, N of the detectors D, D if the respective 1 2 1 2 detectors D, D are working properly. 1 2

The higher-level unit 23 preferably has a first counter, which counts the pulses n arriving at the first input 39 and a second counter, which counts the pulses n arriving at the second input 41, and determines the counting rates Z, Z of the incoming pulses n, n. If a counting rate Z, Z is zero pulses per time interval, the higher-level unit 23 recognizes that the associated detector D, D is not working properly. The status of the measuring device is derived from this and corresponding status information is made available. The status information contains the statement that both detectors D and D work perfectly if both 1 2 count rates Z and Z are different from zero. In the event that one or both 1 2 count rates Z, Z are zero, it contains the statement that the measuring device is not working 1 2 properly. In addition, the status information can contain information on which detector (s) D, D are not working properly. 1 2

[246] The status information is provided via an output 47 of the higher-level unit 23, which is preferably also the only output of the second detector D and thus of the measuring device. An alarm can be triggered, for example, on the basis of the status information.

[247] If both count rates Z and Z are different from zero, both detectors D 1 2 1 and D work perfectly and the higher-level unit 23 derives a measurement signal. This 2 is based on the sum of the count rates Z + Z, which in this case is equal to the sum of the 1 2 pulse rates N + N of the detectors D and D. The measurement signal can be a 1 2 1 2 signal that represents the sum of the pulse rates N + N. The measurement signal is then 1 2 supplied, for example, to measuring device electronics 29 or a separate expansion unit 31, which, based on the measuring signal, determines the quantity to be measured with the measuring device, eg a fill country or density. The measuring device electronics 29 is also arranged, for example, in the second detector D. 2

[248] Alternatively, the pulse rates N + N can also be evaluated and / or processed in the higher-level unit 23.

[249] Status and / or measurement signal are available via output 47.

[250] In all measuring devices according to the invention, a single collecting line or a single connecting line is sufficient to transmit both the status and the actual measuring information.

Each detector D can of course only transmit its status to the higher-level unit 23 if the status has been determined beforehand. A number of methods for checking and / or monitoring the correct functioning of detectors are known in measurement technology.

[252] An example of this is the control and / or monitoring of the energy supply to the detectors or individual detector components.

[253] In the case of the detectors D described, it is also possible to control the optical coupling between the scintillator 7 and the photomultiplier 11. [254] For this purpose e.g. Reference light flashes are continuously sent through the scintillator 7 via a light guide 49. Regardless of whether the scintillator 7 is exposed to gamma radiation or not, reference pulses must be present at the output of the photomultiplier 11 due to the reference light flashes. If this is not the case, the respective detector D is not working properly.

In the measuring devices according to the invention, in which the detectors D have offset generators 19, the pulse rate N depends on the status of the respective Overlay detector D dependent offset O, the status determination is preferably carried out in the manner shown in FIG. 10 in that the offset generators 19 of the detectors D are connected to the scintillator 7 via light guides 49. During operation, the offset generators 19 periodically generate reference light flashes 1 and send them through the scintillator 7. [256] The frequency f with which the reference light flashes are emitted is preferably equal to the setpoint value O for the offset O of the respective detector D described at the beginning. If the detector D is working properly, there is a signal at the output that corresponds to the sum of the pulse rate N and the setpoint O. If there is a fault, significantly fewer pulses are detected. If the pulse rate of the detected pulses falls below the target value O, this leads to a negative difference D.

An advantage of the invention is that in all radiometric measuring devices according to the invention only a single connection, namely the collecting line 21 or the connecting line 37, is required in order to transmit both the actual measuring information and the status information. This considerably reduces the wiring effort required. Esp. in safety-relevant areas in which radiometric measuring devices are usually used, e.g. In areas with an increased risk of explosion, there are high safety requirements for connecting lines, which are usually associated with increased acquisition and installation costs. These costs are significantly reduced by the radiometric measuring devices according to the invention. This can be a very simple connection, e.g. an optical fiber or a copper line. It is also possible to design the connection as a radio connection.

[258] The transfer can be carried out in a very simple manner. Esp. no transmission protocol is required. Rather, the output signals of the individual detectors D can be transmitted with a corresponding calibration via any type of pulse output to a corresponding pulse input of the higher-level unit 23.

Claims

Expectations

1. Radiometric measuring device for mounting on a container (3) which can be filled with a filling material (1), with a radioactive emitter (5) which transmits radioactive radiation through the container (3) during operation, - at least two detectors ( D), - which serve to receive radiation penetrating through the container (3) and to generate an electrical pulse rate (N) corresponding to the received radiation, - offset generators (19) which correspond to the pulse rate (N) ii of each detector (D) superimpose a status of the respective detector (D) reproducing li off set (O), - a collecting line (21), - each detector (D) corresponding to the superimposition of the respective pulse rate (N) and the respective off set (O) Output signal supplies - which supplies a sum signal corresponding to the superimposition of the output signals to a higher-level unit (23) - which derives a measurement signal and / or a status of the measuring device on the basis of the sum signal. Radiometric measuring device for mounting on a container (3) which can be filled with a filling material (1), with a radioactive emitter (5) which transmits radioactive radiation through the container (3) during operation, at least two detectors (D), - which serve to receive radiation i penetrating through the container (3) and to generate an electrical pulse rate (N) corresponding to the received radiation, - offset generators (19) which give the pulse rate (N) of each detector (D) a detector-specific one Overlay offset (O), - Abder Suppress offsets (O) when the detector (D) is working incorrectly, a di i collecting line (21), - which every properly functioning detector (D) overlays the respective pulse rate (N) and the respective offset (O) ent- ι supplies the speaking output signal, - which supplies a sum signal corresponding to the superimposition of the output signals to a higher-level unit (23), - which derives a measurement signal and / or a status of the measuring device on the basis of the sum signal. Radiometric measuring device according to claim 1 or 2, in which - a series of detectors (D) is provided, - the manifold (21) begins at a first i detector of the series, - from there from a detector (D) to the leads this i adjacent detector (D) and from the last detector to the superordinate unit (23). Radiometric measuring device according to claim 1 or 2, in which each detector (D) i comprises a scintillator (7) and a photomultiplier '(9) connected thereto. Radiometric measuring device according to claim 4, in which the offset generators (19) periodically send reference light flashes through the scintillator (7) via a light guide (49). Radiometric measuring device according to claim 3, in which the higher-level unit (23) is integrated in the last detector of the series. Method for measuring a physical quantity with a radiometric measuring device according to one of the preceding claims, in which - a setpoint (O, O) for an offset is assigned to each detector, which the si di offset generators (19) of the detectors ( D) generate when the detector (D) ii works properly and which is greater than the sum of the maximum pulse ^rates (N ^ιmx ) to be expected for the detector (D) i, - the higher-level unit (23) i ^uses the sum signal one Total count rate (G) determines, - forms the difference (D) from this total count rate (G) and a count rate corresponding to the sum of the setpoints (O, O) si di the offsets, - recognizes that there is an error if the difference (D ) is negative, and - with a positive difference (D) derives a measurement signal. Method for measuring a physical quantity according to claim 7, in which, in the presence of a negative difference (D), a mathematical method (eg difference) is used to determine which of the detectors (D) i is operating incorrectly. Radiometric measuring device for mounting on a container (3) which can be filled with a filling material (1), with - a radioactive emitter (5) which transmits radioactive radiation through the container (3) during operation, - a first and a second detector (D, D), - which serve to receive penetrating radiation through the container (3) and generate an electrical pulse rate (N, N) corresponding to the radiation received, - an offset generator, (19) overlaid on the pulse rate (N) of the first detector (D) with a status 1 1 of the first detector (D) representing offset (O), and - a higher-level unit (23) integrated in the second detector (D), - with the second first detector (D) is connected via a connecting line (37), - via which the first detector (D) supplies an output signal corresponding to the superimposition of the pulse rate (N) and the offset (O), - which the pulse rate (N) and a 1 2 Status of the second detector (D) is supplied, and - derives a measurement signal and / or a status of the measuring device based on the 2 incoming signals. Radiometric measuring device for mounting on a container (3) which can be filled with a filling material (1), with - a radioactive radiator (5) which transmits radioactive radiation through the container (3) during operation, - a first and a second detector (D, D), - which serve to receive penetrating radiation through the container (3) and generate an electrical pulse rate (N, N) corresponding to the radiation received and an output signal corresponding to the pulse rate (N, N) to a higher-level unit (23) to 1 2, - in which the emitter (5) has a strength at which a minimum pulse rate (N """) greater than zero is always to be expected for each detector (D, D) 1 2 i, - in which is provided in each detector (D, D) with a switch (45) which prevents the transmission of the output signal to the higher-level unit (23) if the detector (D) is operating incorrectly, and - in which the i ordered unit (23) based on the output ssignale derives a measurement signal and / or a status of the measuring device.