Device for determining the fill level of a medium

Abstract

A device for determining the fill level of a medium in a container having at least one electronic device and at least one signal conductor arrangement. The electronic device supplies the signal conductor arrangement 5 with electromagnetic signals. To provide a device for determining the fill level, the signal conductor arrangement has several emitting devices and the electronic device provides at least one measure for an emitting behavior of at least one emitting device.

Claims

1. A device for determining the fill level of a medium in a container, comprising: at least one electronic device, and at least one signal conductor arrangement, wherein the at least one electronic device is constructed for supplying the at least one signal conductor arrangement with electromagnetic signals, wherein the at least one signal conductor arrangement has a plurality of emitting devices, wherein the emitting devices are attached to a support element, wherein the support element is constructed for being inserted into a side wall of a container, wherein the at least one electronic device is adapted for emitting the electromagnetic signals in the interior of the container during operation, wherein the at least one electronic device is adapted for providing at least one measure for an emitting behavior of the plurality of emitting devices, wherein the electronic device is adapted for supplying the plurality of emitting devices with the electromagnetic signals with a predeterminable frequency, wherein the predeterminable frequency essentially corresponds to a resonance frequency of the emitting devices either when out of contact with the medium or when covered by the medium.

2. Device according to claim 1, wherein the electronic device is adapted for evaluating at last one impedance behavior of the at least one emitting device for the measure.

3. The device according to claim 1, wherein the electronic device has at least one reflector circuit.

4. The device according to claim 3, wherein the reflector circuit is constructed to be able to monitor the adaptation of at least one emitting device when supplying the electromagnetic signals.

5. The device according to claim 3, wherein the reflector circuit is assigned to exactly one emitting device and is adapted for providing a measure for the emitting behavior of the assigned one emitting device.

6. The device according to claim 1, wherein, based on the emitting behavior of the emitting device, the electronic device is adapted to determine a conclusion about the medium in addition to a fill level.

7. The device according to claim 6, wherein the conclusion determined by the electronic device in addition to the fill level is a permittivity of the medium.

8. The device according to claim 1, wherein a support element at least partially supports the signal conductor arrangement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic representation of a part of a processing system

(2) FIG. 2 is a top view of a part of a schematically represented signal conductor arrangement of a device for fill level measurement in a first design,

(3) FIG. 3 is a top view of a signal conductor arrangement in a second design,

(4) FIG. 4 is a cross section through a schematic design of a signal conductor arrangement in a third variation,

(5) FIG. 5 is a schematic cross section through the device for fill level determination in use in a processing system,

(6) FIG. 6 is a schematic representation of a first design of a part of an electronics unit,

(7) FIG. 7 is a schematic representation of a second design of a part of an electronics unit,

(8) FIG. 8 is a schematic representation of a third design of a part of an electronics unit,

(9) FIG. 9 is a schematic representation of a fourth design of a part of an electronics unit,

(10) FIG. 10 is eight top views of different signal conductor arrangements,

(11) FIG. 11 is a schematic representation of the processing of the emitting devices of a device according to the invention,

(12) FIG. 12 is a schematic representation of the detection of data via a separation layer with the aid of a device according to the invention,

(13) FIG. 13 is a flow chart for the start-up of a device according to the invention,

(14) FIG. 14 is a schematic flow chart of the self-monitoring of a device according to the invention and

(15) FIG. 15 is a schematic flow chart in respect to the evaluation of the behavior of an emitting device.

DETAILED DESCRIPTION OF THE INVENTION

(16) It is schematically represented in FIG. 1 how the fill level of a medium 2 in a container 3 is monitored by a The device according to the invention in a processing system.

(17) The device 1 is used here, in particular, as overflow protection. Accordingly, the device 1 can, however, also be used here as idle state protection—not shown here.

(18) The device 1 in the shown schematic design has an electronic device 4 and a signal conductor arrangement 5. The electronic device 4 generates electromagnetic signals—preferably via a signal source, not shown here—that are supplied to the signal conductor arrangement 5.

(19) After supplying the signals, the electronics unit 4 evaluates the behavior of the signal conductor arrangement 5 or, respectively, the individual components to be described in the following in terms of whether or not the medium 2 is in contact with the signal conductor arrangement 5.

(20) In the case of overflow protection, the change from uncovered to covered state is detected. Conversely, in the case of idle state protection—not shown here—, it is signalized when the signal conductor arrangement 5 is free of medium.

(21) The dependence of the resonance behavior—and in particular, the resonance frequency—of the signal conductor arrangement 5 or its components on the surroundings of the signal conductor arrangement 5 is utilized when measuring or monitoring the fill level.

(22) In particular, that the resonance behavior is dependent on whether the presence of coverage is from a medium 2 or from ambient air is utilized.

(23) The signal conductor arrangement 5 extends into the wall 14 of the container 3 and is thus a part of the side wall. For this, the wall 14 has a recess that is sealingly closed again by the signal conductor arrangement 5.

(24) FIG. 2 shows a top view of the signal conductor arrangement 5 and its overall six emitting devices 6.

(25) The emitting devices 6 are arranged in a common support element 7. Thereby, this is a ceramic substrate, in or onto which the emitting devices 6 are created. The support element 7, here, is disk-shaped having a circular circumference.

(26) The emitting devices 6 are designed circularly in the shown embodiment and are located along a longitudinal axis 8 at three different levels.

(27) In alternative embodiments—not shown here—not all emitting devices have the same shape or the emitting devices are, e.g., oval or rectangular.

(28) The emitting devices are arranged mirror symmetrically to the longitudinal axis 8 in the shown embodiment and can be separated, here, into three groups at three different levels.

(29) Three emitting devices 6 here shown at the bottom are thereby at levels slightly staggered relative to one another and together monitor a broader strip of the fill level—in the mounted state and under the condition that the longitudinal axis of the support element and the longitudinal axis of the container essentially coincide.

(30) The two outer of the three lower emitting devices 6 are, in turn, located at the same level, so that a redundancy also results especially for monitoring the assigned fill level within this strip.

(31) In the next level, an individual emitting device 6—arranged in the middle here—borders thereon, to which two emitting devices 6 connect.

(32) The two upper emitting devices 6 provide redundancy for the assigned fill level, since they are both located at the same level.

(33) Overall, three different fill levels or fill level ranges to be monitored by the individual emitting devices 6 are obtained. Plausibility considerations can be made using the measuring results at the different levels in order to increase the reliability of fill level determination or monitoring.

(34) The resolution, with which the reaching or falling below of a fill level can be detected, is increased with the number of different levels of the emitting devices—depending on use and evaluation.

(35) For insertion, an outer thread 13 is provided on the outer surface of the circular support element 7. Accordingly, the wall, into which the device 1 is to be mounted, has an inner thread so that the support element 7 can be screwed into the wall and closes it again.

(36) Different end positions of the emitting devices 6 of the signal conductor arrangement 5 result from screwing as means of attachment.

(37) In order to be able to react to this diversity of orientations in relation to each fill level to be monitored due to mounting, the type of evaluation of the emitting devices 6 is not rigidly specified, rather the evaluation or interpretation of the measuring results of the individual emitting devices 6 are each adapted to the use or to the end position.

(38) A further design of the emitting devices 6 on the support element 7 is shown in FIG. 3.

(39) In the illustrated exemplary embodiment, eight emitting devices 6 are rotation-symmetrically arranged around one, single emitting device 6 located in the center.

(40) It can be seen that this number and distribution of emitting devices 6 allows an arbitrary number—created by turning—of end positions of the support element 7, which are each used for monitoring the same or very similar fill levels.

(41) Thereby, depending on the measuring accuracy that can be implemented with the emitting devices 6, significantly more differing levels can possibly also be defined—here, along the longitudinal axis 8 of the support element 7. In the case of greater spread or lower resolution, the measuring sections can also coincide.

(42) Metal strips are provided between the emitting devices 6 that cause a decoupling of the individual emitting devices 6.

(43) Additionally, three lines for electronic connection are provided behind the support element 7.

(44) A third variation of the signal conductor arrangement 5 is seen in FIG. 4.

(45) It can be seen in the cross section that the support element 7 is a multi-layer ceramic being striped in the one case and empty in another, for clarity having, here, three emitting devices 6 inserted between its layers.

(46) The emitting devices 6 are thereby protected against medium—not shown here—by the support element 7, itself, and also by the protective layer 10.

(47) In the shown embodiment, the support element 7 is surrounded by a structure on the side that also bears the outer threading 13 for screwing and attaching into the recess—not shown here—in the wall of the container.

(48) It can be seen in FIG. 5 that two emitting devices 6 as parts of the signal conductor arrangement 5 of the device 1 are arranged within the support element 7 at different levels along the longitudinal axis 9 of the container 3. The container 3 thereby has a corresponding recess that receives the support element 7.

(49) The emitting devices 6 are protected by a dielectric protective layer 10 facing the medium 2, which here are mounted flush with the inner side of the container 3 that contains the medium 2.

(50) The electronic device 4 has a measuring device 12 and two reflector switches 11 that are each assigned to an emitting device 6.

(51) The measuring device 12 generates electromagnetic signals that are given to the emitting devices 6 via the two reflector switches 11.

(52) The reflector switches 11 receive a reflection signal as response signal from their respective emitting devices 6, from which a measure for the resonance conditions of each emitting device 6 results.

(53) This information of the reflector switches 11 is transmitted to the measuring device 12 for further processing. The reflector switches 11 thus represent a sort of preprocessing in the shown design.

(54) Based on the data of the reflector switches 11 it is determined in the measuring device 12 whether the medium 2 covers one of the emitting devices 6.

(55) Then, the reliability of the individual measurement is examined based on the data of all emitting devices 6.

(56) Finally, the measuring device 12 generates at least one switch signal that, here, represents the reaching of a fill level.

(57) Additionally or alternatively, the falling below of a fill level is signalized or, respectively, information about the rising or falling of the fill level is issued. This is possible in that the emitting devices 6 are located at different levels along the longitudinal axis 9 of the container 3, so that at least two fill levels can be monitored.

(58) Exemplary embodiments of components of the electronic device 4 for implementing measurement or monitoring of the fill level are shown in the illustrations in FIGS. 6-9.

(59) Thereby, only one emitting device 6 that is additionally designed as an antenna is shown in each. The shown embodiments are thus possibly to be combined with several emitting devices 6 or each emitting device 6 has one of its own of the shown electronic switches.

(60) Narrow band scalar measurement is implemented as an example in FIG. 6.

(61) The emitting device 6 is continuously supplied with a mono-frequency signal during narrow band scalar measurement.

(62) The supply frequency f.sub.0, i.e., the frequency of the electromagnetic signal, is chosen in one embodiment so that it corresponds to the resonance frequency of the emitting device 6 in the case that only air and, in particular, no medium to be detected is located in front of emitting device 6.

(63) Thus, if the emitting device 6 is supplied with the signals and no medium is located in front of the emitting device 6, then the emitting device 6 emits the electromagnetic signals.

(64) With the aid of the reflector switch 11, the adaptation of the emitting device 6 at the supply frequency f.sub.0 is permanently monitored.

(65) The signal generator 15 permanently supplies the emitting device 6 with the signal of the frequency f.sub.0.

(66) The reflector switch 11 issues a DC voltage that depends on the ratio between the power of the signals of the signal generator 15 and the power reflected at the emitting device 6.

(67) Additionally, a low-pass is provided in the reflector switch 11, here.

(68) In a downstream comparator 16, the DC voltage U1 is compared to an externally applied reference voltage U2 and evaluated with it.

(69) If air is located in front of the emitting device 6, then the emitting device 6 is adapted and its input reflection is small. The reflectometer voltage U1 is, in this case, less than the reference voltage U2, so that the comparator 16 issues a low level as voltage U3.

(70) If a medium that is not air is located in front of the emitting device 6, the resonance frequency of the emitting device 6 is shifted and differs, in particular, from the frequency f.sub.0 of the electromagnetic signals. The emitting device 6 thus has a bad adapting behavior at the applied frequency f.sub.0.

(71) Hereby, a higher input reflection of the emitting device 6 results, so that the DC voltage U1 of the reflector switch 11 also increases.

(72) If the reflector voltage U1 is greater than the reference voltage U2, then the comparator 16, which is comprised essentially of a differential amplifier here, generates a high level that signalizes the reaching of the fill level associated with the emitting device 6.

(73) This means that the downstream evaluation unit—not shown here—only evaluates the voltage U3 or needs to identify the possibly occurring change in voltage in order to evaluate the emitting behavior of the emitting device 6 for the use as level limit switch.

(74) FIG. 7 shows an arrangement for implementing a narrow band phasor measurement.

(75) This embodiment is advantageous, in particular, when the emitting device 6 is covered with a protective layer—not shown here—or when the medium to be detected has a very low permittivity.

(76) For this, the narrow band scalar measurement shown in FIG. 6 is expanded by a further measuring point to a complex measuring reflector switch—or a so-called IQ reflectometer.

(77) The essential change as opposed to the embodiment of FIG. 6, is experienced by the reflector switch 11.

(78) Both the signal generated by the signal generator 15 as well as the reflection signal coming from the emitting device 6 are separated and supplied to a second measuring site for the second measuring site.

(79) In one of the two signal paths, there is a 90° phase shifter.

(80) The first, unchanged measuring site delivers the “in-phase” signal Ui and the second measuring site connected to the phase shifter delivers the “quadrature” signal Uq.

(81) Both signals Ui and Uq are digitized in the measuring device 12 and are further processed in a microprocessor in the shown embodiment.

(82) With the aid of the implemented IQ measuring site, a phase evaluation of the reflected signal can be carried out. It is thereby advantageous that the phase shift that is created by the reflection on the fill level is a very sensitive measure.

(83) FIG. 8 deals with a broadband scalar measurement.

(84) In the case that the medium to be detected has high losses, the adaptation curve of the emitting device is broadened over the frequency.

(85) This can have the result that when the emitting device 6 is covered by the medium, no sufficient reflection can be detected.

(86) For this, a broadband adaptation curve of the emitting device 6 is recorded with the shown embodiment.

(87) The signal generator 15 generates electromagnetic signals for this having different frequencies between two limiting frequencies f.sub.min and f.sub.max.

(88) This occurs, for example, using a PLL phase locked loop operated VCO voltage controlled oscillator. Alternatively, a direct digital synthesis DSS is implemented.

(89) The frequency of the signals is set by a microprocessor in the shown example, which is a part of the measuring device 12 here.

(90) The reflectometer voltage U1 is directly digitized via a analog-digital converter in the shown and exemplary embodiment, so that the respective reflection value of the set frequency of the electromagnetic signals of the signal generator 15 can be assigned.

(91) After a complete frequency sweep, the adaptation curve is evaluated in the measuring device 12, wherein the lowest reflectometer voltage U1 determines the resonance frequency of the emitting device 6.

(92) If the resonance frequency deviates from the frequency that is assigned to the non-covered state, then the reaching of the fill level assigned to the emitting device 6 is signalized.

(93) A broadband phasor measurement can be seen in FIG. 9.

(94) The reflector switch 11 is unchanged to that of the embodiment in FIG. 6 and also generates an “in-phase” signal Ui and a “quadrature” signal Uq.

(95) The signal generator 15 is designed identical to the one in FIG. 8. The electromagnetic signals thus also have different frequencies, wherein the control of the frequency also occurs here with a microprocessor as part of the measuring device 12.

(96) This switch is, in particular, advantageous for the case that a thin protection layer is located in front of the emitting device 6 and, insofar as the influence of the medium on the reflection characteristic is potentially reduced by the protective layer.

(97) The switch is even more advantageous when the medium is additionally strongly lossy. Thus, the combination of phasor evaluation and broadband detection particularly lends itself to this case.

(98) Eight different top views of the side of the signal conductor arrangement 5 which will face the medium in the device according to the invention are shown in FIG. 10.

(99) The longitudinal axis 9 of the container—not shown here—into which the device is inserted is depicted so that it can be identified that the medium will increase from bottom to top.

(100) Embodiments or orientations in relation to the longitudinal axis 9 are located in the upper of the two shown rows, which allow for the detection of two different fill levels. the four embodiments in the lower row allow for the monitoring of three fill levels.

(101) It can be seen that there are four different arrangements of the emitting device 6 on the support element 7, each being present in two different orientations in relation to the longitudinal axis 9. This makes clear the effects of rotary mounting of the signal conductor arrangement 5.

(102) Pairs belonging together are located in the upper and lower rows, each at a first and second position from the left side. Additionally, the embodiments at the second to last position in the upper and last position of the lower row as well as at the last position of the upper and second to last position of the lower row belong together.

(103) Clearly, a partially different measuring geometry in relation to the container or especially to its longitudinal axis 9, along which the medium increases or decreases, results due to the screwing in of the support element 7 during assembly.

(104) This effect is particularly clear in the variations at the second to last and last position: Depending on the angle of rotation, two or three fill levels or can be detected with the same geometry of the emitting devices 6.

(105) In the orientation of the emitting devices 6 in relation to the support element 7, in which the emitting devices are arranged each on a diameter of the circular support element 7 embodiments at first and second position of the two rows, as many fill levels can be detected as there are emitting devices 6. Here, this is two or three fill levels.

(106) An exception then results when all emitting devices 6 are arranged perpendicular to the longitudinal axis 8 of the container. In this case—not shown here—, only one fill level can be monitored, however, as compensation with a correspondingly high redundancy.

(107) The arrangement of the emitting devices 6 in a square for four emitting devices 6 or in the form of a capital V for three emitting devices allows for the monitoring of different amounts of fill levels depending on the rotation or for the redundant monitoring of a fill level or fill level range depending on the rotation.

(108) The dependence of possible measuring levels or the fill levels to be monitored makes the advantage clear, which then results when the type of evaluation of the emitting behavior of the emitting devices 6 is not strictly specified, rather is configured after assembly at the operation site and thus is adapted to the prevailing conditions.

(109) A variation is shown purely schematically in FIG. 11, how nine emitting devices 6 on a support element 7 are evaluated together by an implied measuring device 12.

(110) For clarity, all elements and components are left away that are used for the actual detection of the emitting behavior of the emitting devices 6, so that, here, the emitting devices 6 are directly joined to the components of the measuring device 12 in the schematic sketch.

(111) In the following case, it is observed that the device is used for overflow protection and that the fill level of the medium increases from bottom to top in the drawing level.

(112) Furthermore, the emitting devices 6 each then directly generate a signal when they are covered by the medium.

(113) Eight of the nine emitting devices 6 are arranged radially around the circumference on the support element 7. The ninth emitting device 6 is located in the center, around which the other emitting devices 6 are accordingly rotation symmetrically distributed. Overall, three emitting devices 6 lie on one diameter of the support element 7.

(114) It can thereby be identified that the symmetrical distribution of the emitting devices 6 on the support element 7 and their increased number—in relation to, e.g., the embodiments of FIG. 10—allow for a plurality of different mounting situations, i.e., allow for different end positions after rotation, which essentially lead to the same measuring geometry.

(115) The arrangement of the emitting devices 6 in relation to the container and thus also in relation to the possible fill levels of the medium is understood as measurement geometry.

(116) The nine emitting devices 6 are grouped into three groups that each relate to one fill level or fill level range.

(117) The three middle emitting devices 6 are located at one level and are thus used for monitoring a fill level.

(118) The three upper and the three lower emitting devices 6 are each slightly shifted in height in respect to one another, wherein each of the two outer emitting devices 6 are located at the same level and the middle emitting device 6 is located at a position either higher or lower than its neighbor.

(119) In that each of the three emitting devices 6 of the groups are connected to one another or are evaluated together, the three upper or the three lower emitting devices 6 together monitor a fill level range, i.e., a spatial area that is determined by the geometry of the individual emitting devices 6 and their relative distribution.

(120) In the illustrated embodiment, two each of the emitting devices 6 of the groups are connected to one another by a logical “AND” element 17. This means that this “AND” element 17 supplies a logical “one” when both emitting devices 6 generate the same signal.

(121) Thus, if both emitting devices 6 signalize that they are covered by the medium in that this is derived from the respective emitting behavior, e.g., from the resonance frequency, then the assigned “AND” element 17 issues a “one”.

(122) Thus, with the “and” element 17, it is monitored whether two emitting devices 6 generate the same signal. Thus, the three emitting devices 6 in one group are connected to one another in terms of redundancy.

(123) An “OR” element 18 is subordinate to the three “AND” elements 17 per group, which generates a signal when at least one of the three “AND” elements 17 issues a positive signal.

(124) The “OR” elements 18 thus combine the individual signals of the emitting devices 6 into one group signal.

(125) The “OR” elements 18, in turn, follow the “AND” elements 19 that connect the group signals of the lower and the middle group or the middle and the upper group to one another in order to control the three signal units 20 that act as a sort of traffic light here.

(126) In the following, a possible order of events is observed for the use as overflow protection.

(127) At the beginning, the medium—not shown here—is, for example, still located below all of the emitting devices 6.

(128) The medium increases and reaches the lowest emitting device 6, which generates a corresponding signal.

(129) However, this is only a signal for the reaching of the fill level range within the lower group, thus no signal is given to the outside that indicates coverage. This is prevented by the two “and” elements 17 accordingly assigned to the emitting device 6.

(130) If the level of the medium continues to rise, then it also reaches the two outer emitting devices 6 of the lower group.

(131) Since, thereby, all three emitting devices 6 signalize coverage, the signal for reaching the fill level range results for the lower group and the lower “or” element 18 can directly actuate the lower signal unit 20 connected to it.

(132) If the fill level of the medium continues to rise, then all three emitting devices 6 of the middle group, which are all arranged at the same level, are covered. Thus, all three generate the signal that the fill level has been reached. The “AND” elements 17 pass this information further via the “OR” element 18 to the subsequent “AND” element 19.

(133) The signal of the middle group and the signal of the lower group are connected to one another via the signal from the “AND” element 19.

(134) Thus, the result of the middle group is checked in respect to plausibility.

(135) The middle signal unit 20 can then only display the reaching of the middle fill level when the lower fill level has also been reached or is subsequently exceeded.

(136) If the fill level continues to increase, then the medium reaches the two outer emitting devices 6 of the upper group, which are connected to one another by the lower “AND” element 17 of the three upper “and” elements 17. Thus, the upper group already generates a signal at this fill level, which then can actuate the upper signal unit 20 in conjunction with the signal of the middle group.

(137) Thus, if the medium is found in the fill level range of the upper group, then all three signal units 20 are lit up.

(138) The components of the measuring device 12 shown here for processing the individual results in respect to the emitting behavior of the emitting devices 6 are designed, as an example, as logic components.

(139) The implementation thereby occurs, in an alternative embodiment, in the form of at least one microprocessor and, in an additional embodiment, in the form of at least one FPGA field programmable gate array.

(140) It is shown in FIG. 12, how the location of a separating layer 21 is identified and detected with the device according to the invention.

(141) Separating layers result when the medium is made up of two substances or phases that do not mix. For example, a medium consisting of oil and water is possible.

(142) One side of a container 3 is shown purely schematically, in whose—here back—wall a support element 7 having two emitting devices 6 is located.

(143) Additionally shown, is the medium 2 in front of the container wall, which consists of substances having a separating layer 21 located between them.

(144) In the shown situation, the upper substance already covers the lower emitting device 6 and approaches the upper emitting device 6.

(145) If the medium 2 continues to increase, then the lower emitting device 6 is, at a certain point in time, no longer covered by the upper substance, but rather the lower substance

(146) If the two substances of the medium 2 differ in view of their permittivity, then the change at covering of the lower emitting device 6 leads to a change in the emitting behavior, in particular a change in the resonance frequency.

(147) At a further point in time, the upper substance reaches the upper emitting device 6, which is then not longer free and uncovered, rather is covered, so that its emitting behavior also changes.

(148) Two further time durations are necessary for determined data about the separating layer 21:

(149) This includes a first duration that is found between the points in time at which the emitting devices 6 signalize the change from uncovered, i.e., free, state to a covered state. These are thus the points in time at which the upper substance reaches each of the emitting devices 6.

(150) In combination with the level difference between the two emitting devices 6, the first duration allows for the determination of the increasing or filling speed of the medium 2.

(151) Thereby, the speed at which the medium 2 increases can be determined.

(152) It is assumed, here, that the fill level of the medium 2 increases uniformly and that, e.g that there are no pauses or that the fill level decreases in the meanwhile.

(153) Furthermore, a second duration is also necessary that is located between the points in time, at which a first coverage by the medium or the change of substances is determined by an emitting device.

(154) The second duration is a measure for how fast the upper substance of the two substances extends beyond the assigned emitting device.

(155) Steps for start-up of a device according to the invention and, in particular, for free configuration of the evaluation are shown in FIG. 13.

(156) The device—not shown here—thereby has, as an example, five emitting devices, whose orientation relative to the longitudinal axis of the container is not known as a result of the rotary assembly and would be very difficult to determine since the emitting devices are located in the direction of the container interior.

(157) In step 100, the device is mounted at the measuring site in that the support element is screwed into a recess of the container wall.

(158) Depending on the desired end position, the emitting devices are arranged differently to the container or, in particular, to its longitudinal axis and thus relate to different or same fill levels in an unpredictable manner.

(159) In step 101, normal measuring operation is started, without a fill level to be monitored being deliberately approached and only for calibration.

(160) In step 102, the medium reaches an emitting device of the device according to the invention for the first tie—only as an example here—and covers it, so that the emitting behavior of this emitting devices changes noticeably.

(161) This emitting device is thus assigned the lowest fill level in step 103.

(162) In step 104, the medium reaches two other emitting devices that both accordingly signalize that coverage has occurred.

(163) In step 105, it is checked when the lower emitting device is still covered.

(164) In step 106, the information from the lowest emitting device is combined with signals of the two higher emitting devices so that both emitting devices are assigned a common fill level and that both are coupled to one another in the sense of redundancy. Further, the assignment of fill level to emitting devices is carried out.

(165) In step 107, the fill level further increases and reaches two additional emitting devices.

(166) In step 108, it is concluded from the points in time, at which the two last-mentioned emitting devices signalized contact to the medium, that there is a slight level difference between the two, since there is a time difference between the signals.

(167) In step 109, the two emitting devices are assigned to one group despite the difference and thus also to one fill level range and not to a narrower fill level.

(168) In step 110, the signals from all emitting devices are compared to one another again and calibration is finalized, after the resonance frequencies determined by the individual emitting devices in the case of coverage have been determined and reset.

(169) FIG. 14 shows several steps for identifying a contamination of—not shown here—emitting devices.

(170) In step 200, the resonance frequency is measured in the covered state of an emitting device.

(171) In step 201, a new measurement of the resonance frequency of the emitting device occurs for self-monitoring after a given duration, for which it is necessary that the covered state exists. For example, the measuring signals of the remaining emitting devices are used for this.

(172) In step 202, the current frequency value is compared to the stored value.

(173) If the values are located within a tolerance range, then there is a return to step 201 and the frequency measurement is repeated at the given time.

(174) However, if there is a deviation beyond the tolerance range, then it is shown in step 203 that the emitting device is no longer in a correct state and, in particular, is contaminated.

(175) FIG. 15 shows a general course for the processing of the emitting behavior of an emitting device.

(176) A measure for the emitting behavior of the emitting device is determined in step 300. This is, for example, the resonance frequency.

(177) In step 301, this measure is compared to a stored value and it is determined whether a change exists.

(178) If there is no change, step 300 begins again.

(179) In the case of a change, it is checked in step 302, whether the chosen emitting device is to be considered together with further emitting devices in the sense of redundancy.

(180) If this is not the case, a plausibility check is carried out in step 303.

(181) For example, it is checked, whether the result resulting from the change in emitting behavior of the chosen emitting device agrees with the information of the other emitting devices. If, e.g., the change from “uncovered” to “covered” results, then the emitting devices assigned lower fill levels have to report coverage.

(182) If this plausibility is fulfilled, then it is signalized in step 304 that the fill level of the medium associated with the emitting device has been reached.

(183) However, if there are discrepancies, an error message occurs in step 305.

(184) If it is seen in step 302, that there are further emitting devices that are assigned the same fill level or fill level range, then a corresponding comparison is carried out in step 306.

(185) If the redundancy check in step 306 shows that the state signalized by the change in the emitting behavior of the emitting device agrees with that of the other emitting devices connected to one another by redundancy, then the plausibility check is carried out in step 303.

(186) However, if there are differences, then an error message is also generated in step 305 in the shown embodiment.

(187) Step 304 then finally followed again by step 300.