WO2001046653A1 - Method and device for determining the level of a filling material in a container - Google Patents

Method and device for determining the level of a filling material in a container Download PDF

Info

Publication number
WO2001046653A1
WO2001046653A1 PCT/EP2000/011725 EP0011725W WO0146653A1 WO 2001046653 A1 WO2001046653 A1 WO 2001046653A1 EP 0011725 W EP0011725 W EP 0011725W WO 0146653 A1 WO0146653 A1 WO 0146653A1
Authority
WO
WIPO (PCT)
Prior art keywords
echo signal
level
frequency
filling material
container
Prior art date
Application number
PCT/EP2000/011725
Other languages
German (de)
French (fr)
Inventor
Michael Sinz
Original Assignee
Endress + Hauser Gmbh + Co. Kg
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Endress + Hauser Gmbh + Co. Kg filed Critical Endress + Hauser Gmbh + Co. Kg
Publication of WO2001046653A1 publication Critical patent/WO2001046653A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
    • G01F23/284—Electromagnetic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
    • G01F23/284—Electromagnetic waves
    • G01F23/292—Light, e.g. infrared or ultraviolet
    • G01F23/2921—Light, e.g. infrared or ultraviolet for discrete levels
    • G01F23/2928—Light, e.g. infrared or ultraviolet for discrete levels using light reflected on the material surface
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
    • G01F23/296—Acoustic waves
    • G01F23/2962—Measuring transit time of reflected waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
    • G01S13/103—Systems for measuring distance only using transmission of interrupted, pulse modulated waves particularities of the measurement of the distance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/06—Systems determining the position data of a target
    • G01S15/08—Systems for measuring distance only
    • G01S15/10—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves
    • G01S15/101—Particularities of the measurement of distance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/32—Shaping echo pulse signals; Deriving non-pulse signals from echo pulse signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/288—Coherent receivers
    • G01S7/2883—Coherent receivers using FFT processing

Definitions

  • the invention relates to a method for determining the filling level of a filling material in a container, wherein measuring signals are emitted in the direction of the surface of the filling material and are reflected on the surface as echo signals (useful echo signals) and the level or a change in the filling level is evaluated by evaluating the reflected echo signals of the filling material is determined in the container.
  • Such methods have become known under the name pulse transit time method.
  • a device by implementing the method according to the invention is proposed.
  • Methods that determine the distance to an object via the transit time of measurement or echo signals take advantage of the physical laws, according to which the route is equal to the product of the transit time and the speed of propagation.
  • the route corresponds, for example, to twice the distance between an antenna and the surface of the product
  • the useful echo signal reflected on the surface of the filling material and its transit time are usually determined in the time domain using the so-called intermediate frequency or else using the digital envelope curve when using high-frequency measurement signals. Both the intermediate frequency and the digital hull curve provide the amplitudes of the echo signals as a function of the distance 'antenna - surface of the filling material'.
  • the filling level itself results from the difference between the known distance of the antenna from the bottom of the container and that determined by the measurement Distance of the surface of the product from the antenna
  • a generator generates first microwave pulses and emits them via an antenna with a predetermined transmission repetition frequency in the direction of the surface of the filling material.
  • Another generator generates reference microwave pulses that are the same as the first microwave pulses, differ slightly from these in the retransmission rate.
  • the echo signal and the reference signal are mixed.
  • An intermediate frequency signal is present at the output of the mixer.
  • the intermediate frequency signal has the same course as the echo signal, but is stretched relative to the latter by a time delay factor which is equal to a quotient of the transmission repetition frequency and the frequency difference between the first microwave pulses and the reference microwave pulses.
  • the frequency of the intermediate frequency signal is below 100 kHz.
  • the advantage of the transformation to the intermediate frequency is that relatively slow and therefore inexpensive electronic components can be used for signal detection and / or signal evaluation. Instead of the high-frequency measurement signals such. B. ultrasonic waves, so of course, a transformation to an intermediate frequency is unnecessary.
  • the invention is based on the object of proposing a method for determining the fill level which can be used as an alternative or in addition to the known pulse transit time methods.
  • the object is achieved in that the temporal course of the echo signal is determined, that the echo signal determined in the time domain is transformed into the frequency domain and that on the basis of a change in the phase position of the echo signal in the
  • Frequency range the level of the filling level or a change in the filling level of the filling material in the container is determined.
  • the solution according to the invention is based on the fact that the amplitude spectrum of the echo signals with a constant bandwidth of the measurement signals is independent of the respective filling level of the filling material. However, a change in level is noticeable in a shift in the useful echo signal on the time axis. A shift in the useful echo signal in the time domain corresponds to a phase change in the useful echo signal in the frequency domain.
  • a Fourier transform can be used to move a signal from the time domain to the frequency domain or from the frequency domain to Transform time domain. Mathematically, this is represented as follows: x (t) ⁇ - »X (f), where x (t) identifies the signal in the time domain and X (f) the signal in the frequency domain.
  • phase rotation increases linearly with the frequency f and the shift t 0 . This relationship is referred to as a shift theorem in signal processing.
  • the phase shift is achieved mathematically by multiplying the spectral function X (f) by the complex unit vector
  • the Fourier transform can thus be represented as follows:
  • the echo signal determined in the time domain is transformed from the high-frequency range to the low-frequency range by sequential scanning, and that the echo signal transformed in the low-frequency range is subjected to a Fourier transformation.
  • the advantage of transforming the high-frequency signals into the low-frequency range can be seen in the fact that much cheaper hardware can be used for the evaluation. Depending on the hardware used, it is also possible to evaluate the echo signals in real time.
  • An alternative embodiment of the method according to the invention provides that if high-frequency measurement signals are used, the echo signal determined in the time domain is transformed from the high-frequency range into the low-frequency range by sequential scanning; the time-transformed echo signal is then rectified and digitized. In a final step, the rectified and digitized echo signal is subjected to a Fourier transformation. According to this alternative, the so-called intermediate frequency is not Fourier transformed, but the digital envelope is subjected to a Fourier transformation.
  • the measurement accuracy is known to be increased by the fact that in addition to the maxima (peaks) of the echo signals, which provide amplitude information, the phase positions of the echo signals are also used for the evaluation.
  • the amplitude-modulated intermediate frequency is demodulated and broken down into its complex components. This is achieved e.g. B. by the so-called.
  • Quadrature demodulation ie the intermediate frequency is multiplied once with a sine wave (Q) and once with a cosine wave (I), both vibrations having a similar frequency as the intermediate frequency.
  • the high frequencies resulting from the multiplication are filtered out with a low pass filter.
  • the usual amplitude evaluation then takes place; the respective phase position and the difference between the two phase positions are additionally determined at the locations of the maxima found.
  • the distance between the antenna and the surface of the medium is then made up of a fraction of integer wavelengths, which results from the amplitude evaluation, and a phase remainder.
  • a particularly advantageous embodiment of the method according to the invention can be seen in the fact that in a first method step the fill level in the container is determined on the basis of the time profile of the echo signal; subsequently, the echo signal is then added
  • Multipath propagation means that the echo signals contain, in addition to the actual useful signal, which is reflected directly on the surface of the filling material, also an interference signal component that can be attributed to retro-reflections of the measurement signals on the container wall or on other internals located in the container interior.
  • the cause of the measurement errors which occur as a result of multipath propagation are constructive or destructive interferences between the actual useful echo signal, which is reflected on the surface of the medium, and the proportion of the Useful echo signal, which is reflected by a retroreflector.
  • n is any integer.
  • the same problem also arises as a result of the multimode propagation of wave packets already mentioned in still pipes or in other devices guiding the wave packets.
  • the method according to the invention is therefore also ideally suited to reducing measurement errors which occur due to multimode propagation.
  • the time course of the phase change is corrected so that no phase jumps occur.
  • the problem with the evaluation in the time domain is that the phase is only clear over a range of 360 °.
  • the phase jump correction provides a clear dependency between the phase and the distance to the surface of the filling material or the filling level.
  • a transmission circuit generates measurement signals. These measurement signals are emitted in the direction of the surface of the filling material by means of at least one antenna; the reflected echo waves are received by the at least one antenna.
  • a reception / evaluation circuit which determines the temporal course of the echo signal, transforms the echo signal determined in the time domain into the frequency domain and determines the level of the filling level or a change in the level of the filling material in the container on the basis of a change in the phase position of the echo signal in the frequency range ,
  • the measurement signals are electromagnetic pulses or pulsed electromagnetic waves (eg high-frequency microwave pulses or laser pulses) or ultrasonic pulses.
  • Fig. 5 the amplitude spectrum of the useful echo signals at three different levels
  • Fig. 6 the corrected phase spectra of the useful echo signals at three different levels.
  • Fig. 1 shows a schematic representation of an embodiment of the device according to the invention.
  • a filling material 2 is stored in a container 4.
  • the fill level measuring device 1 which is mounted in an opening 10 in the lid 7 of the container 4, is used to determine the fill level.
  • Pulsed measurement signals in particular microwaves, ultrasound waves or laser beams, are emitted in the direction of the surface 3 of the filling material 2 via the antenna 6 in the signal generation transmission unit 5.
  • the measurement signals are at least partially reflected on the surface 3 as echo signals.
  • These echo signals are in the reception / evaluation unit 8 received and evaluated.
  • the transmission of the measurement signals and reception of the echo signals is coordinated via the transceiver 9.
  • the device 1 z. B. when using microwaves as measuring radiation not only in connection with a freely radiating antenna 6.
  • highly precise measurements of the fill level of liquids or bulk materials in containers are required.
  • measuring instruments are increasingly being used here, in which short electromagnetic high-frequency pulses are coupled into a conductive element and introduced into the container in which the filling material is stored by means of the conductive element.
  • the conductive element is, for example, a rope probe or a rod probe.
  • this measuring method takes advantage of the effect that at the interface between two different media, e.g. B. air and oil or air and water, due to the sudden change (discontinuity) of the dielectric constant of both media, a part of the guided high-frequency pulses or the guided microwaves reflected and the conductive
  • the Element is passed back into the receiving unit.
  • the distance to the interface can be determined on the basis of the transit time of the reflected portion of the high-frequency pulses or of the microwaves. If the empty distance of the container is known, the filling level of the filling material in the container can be calculated.
  • TDR Time Domain Reflectometry
  • the echo signal shown has two amplitude maxima.
  • the left peak characterizes the echo signal which results from the coupling of the measurement signals to the antenna or to the electrically conductive element of a TDR sensor.
  • This echo signal which is only dependent on the sensor used in each case and which maintains its position regardless of the respective fill level, is used as a reference signal in the fill level measurement. Of course, other reference signals can also be used.
  • the right peak represents the actual useful echo signal, which results from the reflection of the measurement signal on the surface of the medium. The level is determined from the distance between the maxima of the useful echo signal and the reference echo signal.
  • the echo signal is shown as a digital envelope in the time domain.
  • Useful echo signal for the maximum of the reference echo signal is used as a measure of the filling level of the filling material 2 in the container 4.
  • the shape of the useful echo signal is invariant to changes in level; however, the position of the useful echo signal changes depending on the respective level. A change in fill level is therefore reflected in a temporal shift in the shape-invariant useful echo signal.
  • the frequency spectrum X (f) of the useful echo signal at different fill levels shows the magnitude or frequency spectrum X (f) of the useful echo signal at different fill levels.
  • the frequency spectrum is independent of the respective filling level of the filling material 2 in the container 4 and is therefore invariant in shape with changes in filling level.
  • phase jump correction rectification is generally known as 'phase unwrapping' in the field of signal processing. A description in connection with the present invention can therefore be dispensed with.
  • the invention takes advantage of the fact that the slope of the change in phase over time depends on the fill level of the filling material 2 in the container 4: the further the surface of the filling material is from the coupling unit generating the reference signal, the smaller the slope of the Phase curve.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Thermal Sciences (AREA)
  • Fluid Mechanics (AREA)
  • Acoustics & Sound (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The invention relates to a method and device for determining the level of a filling material (2) in a container (4), whereby measurement signals are emitted in a direction toward the surface (3) of the filling material (2) and are reflected on the surface (3) as echo signals, and whereby the level or a change in the level of the filling material (2) in the container (4) is determined by evaluating the reflected echo signals. The aim of the invention is to provide a method which can be used alternatively or in addition to known pulse transit time methods. To this end, the temporal progression of the echo signal is determined, the echo signal ascertained in the time domain is transformed into the frequency range, and the height of the level or a change in the level of the filling material (2) in the container (4) is determined based on a change of the phase position of the echo signal in the frequency range.

Description

Verfahren und Vorrichtung zur Bestimmung des Füllstands eines Füllguts in einem Behälter Method and device for determining the filling level of a filling material in a container
Die Erfindung bezieht sich auf ein Verfahren zur Bestimmung des Füllstands eines Füllguts in einem Behälter, wobei Meßsignale in Richtung der Oberfläche des Füllguts ausgesendet und an der Oberflache als Echosignale (Nutzechosignale) reflektiert werden und wobei durch Auswertung der reflektierten Echosignale der Füllstand bzw. eine Fullstandsanderung des Füllguts in dem Behalter bestimmt wird. Derartige Verfahren sind unter dem Namen Impulslaufzeit-Verfahren bekannt geworden. Desweiteren wird eine Vorrichtung durch Durchführung des erfindungsgemaßen Verfahrens vorgeschlagen.The invention relates to a method for determining the filling level of a filling material in a container, wherein measuring signals are emitted in the direction of the surface of the filling material and are reflected on the surface as echo signals (useful echo signals) and the level or a change in the filling level is evaluated by evaluating the reflected echo signals of the filling material is determined in the container. Such methods have become known under the name pulse transit time method. Furthermore, a device by implementing the method according to the invention is proposed.
Verfahren, die die Entfernung zu einem Objekt über die Laufzeit von Meßbzw Echosignalen bestimmen, nutzen die physikalische Gesetzmäßigkeit aus, wonach die Laufstrecke gleich dem Produkt aus Laufzeit und Ausbreitungsgeschwindigkeit ist Im Falle der Fullstandsmessung entspricht die Laufstrecke beispielsweise dem doppelten Abstand zwischen einer Antenne und der Oberflache des FüllgutsMethods that determine the distance to an object via the transit time of measurement or echo signals take advantage of the physical laws, according to which the route is equal to the product of the transit time and the speed of propagation. In the case of full-level measurement, the route corresponds, for example, to twice the distance between an antenna and the surface of the product
Das an der Oberflache des Füllguts reflektierte Nutzechosignal und dessen Laufzeit werden bei Verwendung von hochfrequenten Meßsignalen üblicherweise im Zeitbereich anhand der sog. Zwischenfrequenz oder aber anhand der digitalen Hüllkurve bestimmt. Sowohl die Zwischenfrequenz als auch die digitale Hullkurve liefern die Amplituden der Echosignale als Funkton des Abstandes 'Antenne - Oberflache des Füllguts' Der Füllstand selbst ergibt sich dann aus der Differenz zwischen dem bekannten Abstand der Antenne von dem Boden des Behalters und dem durch die Messung bestimmten Abstand der Oberflache des Füllguts von der AntenneThe useful echo signal reflected on the surface of the filling material and its transit time are usually determined in the time domain using the so-called intermediate frequency or else using the digital envelope curve when using high-frequency measurement signals. Both the intermediate frequency and the digital hull curve provide the amplitudes of the echo signals as a function of the distance 'antenna - surface of the filling material'. The filling level itself results from the difference between the known distance of the antenna from the bottom of the container and that determined by the measurement Distance of the surface of the product from the antenna
In der DE 31 07 444 A1 wird ein hochauflosendes Impulsradarverfahren beschrieben. Ein Generator erzeugt erste Mikrowellenpulse und strahlt sie über eine Antenne mit einer vorgegebenen Sendewiederholfrequenz in Richtung der Oberflache des Füllguts aus. Ein weiterer Generator erzeugt Referenz-Mikrowellenpulse, die gleich den ersten Mikrowellenpulsen sind, sich von diesen jedoch in der Sendewiederholrate geringfügig unterscheiden. Das Echosignal und das Referenzsignal werden gemischt. Am Ausgang des Mischers steht ein Zwischenfrequenzsignal an. Das Zwischenfrequenzsignal hat den gleichen Verlauf wie das Echosignal, ist gegenüber diesem jedoch um einen Zeitverzögerungsfaktor gestreckt, der gleich einem Quotienten aus der Sendewiederholfrequenz und der Frequenzdifferenz zwischen den ersten Mikrowellenpulsen und den Referenz-Mikrowellenpulsen ist. Bei einer Sendewiederholfrequenz von einigen Megahertz, einer Frequenzdifferenz von wenigen Hertz und einer Mikrowellenfrequenz von einigen Gigahertz liegt die Frequenz des Zwischenfrequenzsignals unterhalb von 100 kHz. Der Vorteil der Transformation auf die Zwischenfrequenz ist, daß relativ langsame und damit kostengünstige elektronische Bauteile zur Signalerfassung und/oder Signalauswertung verwendet werden können. Werden anstelle der hochfrequenten Meßsignale z. B. Ultraschallwellen verwendet, so erübrigt sich natürlich eine Transformation auf eine Zwischenfrequenz.DE 31 07 444 A1 describes a high-resolution pulse radar method. A generator generates first microwave pulses and emits them via an antenna with a predetermined transmission repetition frequency in the direction of the surface of the filling material. Another generator generates reference microwave pulses that are the same as the first microwave pulses, differ slightly from these in the retransmission rate. The echo signal and the reference signal are mixed. An intermediate frequency signal is present at the output of the mixer. The intermediate frequency signal has the same course as the echo signal, but is stretched relative to the latter by a time delay factor which is equal to a quotient of the transmission repetition frequency and the frequency difference between the first microwave pulses and the reference microwave pulses. With a transmission repetition frequency of a few megahertz, a frequency difference of a few hertz and a microwave frequency of a few gigahertz, the frequency of the intermediate frequency signal is below 100 kHz. The advantage of the transformation to the intermediate frequency is that relatively slow and therefore inexpensive electronic components can be used for signal detection and / or signal evaluation. Instead of the high-frequency measurement signals such. B. ultrasonic waves, so of course, a transformation to an intermediate frequency is unnecessary.
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Füllstandsbestimmung vorzuschlagen, das alternativ oder additiv zu den bekannten Impulslaufzeitverfahren verwendbar ist.The invention is based on the object of proposing a method for determining the fill level which can be used as an alternative or in addition to the known pulse transit time methods.
Bezüglich des erfindungsgemäßen Verfahrens wird die Aufgabe dadurch gelöst, daß der zeitliche Verlauf des Echosignals bestimmt wird, daß das im Zeitbereich ermittelte Echosignal in den Frequenzbereich transformiert wird und daß anhand einer Änderung der Phasenlage des Echosignals imWith regard to the method according to the invention, the object is achieved in that the temporal course of the echo signal is determined, that the echo signal determined in the time domain is transformed into the frequency domain and that on the basis of a change in the phase position of the echo signal in the
Frequenzbereich die Höhe des Füllstands bzw. eine Füllstandsänderung des Füllguts in dem Behälter bestimmt wird.Frequency range, the level of the filling level or a change in the filling level of the filling material in the container is determined.
Die erfindungsgemäße Lösung basiert darauf, daß das Amplitudenspektrum der Echosignale bei konstanter Bandbreite der Meßsignale unabhängig ist vom jeweiligen Füllstand des Füllguts. Allerdings macht sich eine Füllstandsänderung in einer Verschiebung des Nutzechosignals auf der Zeitachse bemerkbar. Einer Verschiebung des Nutzechosginals im Zeitbereich entspricht also eine Phasenänderung des Nutzechosignals im Frequenzbereich.The solution according to the invention is based on the fact that the amplitude spectrum of the echo signals with a constant bandwidth of the measurement signals is independent of the respective filling level of the filling material. However, a change in level is noticeable in a shift in the useful echo signal on the time axis. A shift in the useful echo signal in the time domain corresponds to a phase change in the useful echo signal in the frequency domain.
Mittels einer Fourier-Transformation läßt sich ein Signal bekanntlich vom Zeitbereich in den Frequenzbereich oder vom Frequenzbereich in den Zeitbereich transformieren. Mathematisch wird dieser Sachverhalt wie folgt dargestellt: x(t) <-» X(f), wobei x(t) das Signal im Zeitbereich und X(f) das Signal im Frequenzbereich kennzeichnet.As is well known, a Fourier transform can be used to move a signal from the time domain to the frequency domain or from the frequency domain to Transform time domain. Mathematically, this is represented as follows: x (t) <- »X (f), where x (t) identifies the signal in the time domain and X (f) the signal in the frequency domain.
Verschiebt man die Zeitfunktion x(t) um die Zeit t0 , so führt dies zu einer gegenläufigen Phasendrehung der positiven und negativen Spektralanteile. Die Phasendrehung wächst linear mit der Frequenz f und der Verschiebung t0. Dieser Zusammenhang wird in der Signalverarbeitung als Verschiebungstheorem bezeichnet. Mathematisch erreicht man die Phasendrehung durch Multiplikation der Spektralfunktion X(f) mit dem komplexen EinheitsvektorMoving the time function x (t) by the time t 0 leads to an opposite phase shift of the positive and negative spectral components. The phase rotation increases linearly with the frequency f and the shift t 0 . This relationship is referred to as a shift theorem in signal processing. The phase shift is achieved mathematically by multiplying the spectral function X (f) by the complex unit vector
exp (-i2πft0) = cos 2πft() - i sin 2πft0 exp (-i2πft 0 ) = cos 2πft () - i sin 2πft 0
Damit läßt sich die Fouriertransformation wie folgt darstellen:The Fourier transform can thus be represented as follows:
x(t - 10) <-» X(f) • exp (-i2πft0) = X(f) • (cos 2πft0 - i sin 2πft0)x (t - 1 0 ) <- »X (f) • exp (-i2πft 0 ) = X (f) • (cos 2πft 0 - i sin 2πft 0 )
Gemäß einer vorteilhaften Weiterbildung des erfindungsgemäßen Verfahrens wird vorgeschlagen, daß für den Fall hochfrequenter Meßsignale das im Zeitbereich ermittelte Echosignal durch sequentielle Abtastung aus dem Hochfrequenzbereich in den Niederfrequenzbereich transformiert wird und daß das in den Niederfrequenzbereich transformierte Echosignal einer Fourier-Transformation unterzogen wird. Der Vorteil der Transformation der hochfrequenten Signale in den Niederfrequenzbereich ist darin zu sehen, daß wesentlich kostengünstigere Hardware zur Auswertung herangezogen werden kann. Je nach verwendeter Hardware ist jedoch auch durchaus eine Auswertung der Echosignale in Echtzeit möglich.According to an advantageous development of the method according to the invention, it is proposed that, in the case of high-frequency measurement signals, the echo signal determined in the time domain is transformed from the high-frequency range to the low-frequency range by sequential scanning, and that the echo signal transformed in the low-frequency range is subjected to a Fourier transformation. The advantage of transforming the high-frequency signals into the low-frequency range can be seen in the fact that much cheaper hardware can be used for the evaluation. Depending on the hardware used, it is also possible to evaluate the echo signals in real time.
Eine alternative Ausgestaltung des erfindungsgemäßen Verfahrens sieht vor, daß im Falle der Verwendung von hochfrequenten Meßsignalen das im Zeitbereich ermittelte Echosignal durch sequentielle Abtastung aus dem Hochfrequenzbereich in den Niederfrequenzbereich transformiert wird; anschließend wird das zeittransformierte Echosignal gleichgerichtet und digitalisiert. In einem letzten Schritt wird das gleichgerichtete und digitalisierte Echosignal einer Fourier-Transformation unterzogen. Gemäß dieser Alternative wird also nicht die sogenannte Zwischenfrequenz fourier- transformiert, sondern die digitale Hüllkurve wird einer Fourier-Transformation unterzogen.An alternative embodiment of the method according to the invention provides that if high-frequency measurement signals are used, the echo signal determined in the time domain is transformed from the high-frequency range into the low-frequency range by sequential scanning; the time-transformed echo signal is then rectified and digitized. In a final step, the rectified and digitized echo signal is subjected to a Fourier transformation. According to this alternative, the so-called intermediate frequency is not Fourier transformed, but the digital envelope is subjected to a Fourier transformation.
Bei der Hüllkurvenauswertung erhöht sich die Meßgenauigkeit bekanntlich dadurch, daß zusätzlich zu den Maxima (Peaks) der Echosignale, die Amplitudeninformation liefern, auch die Phasenlagen der Echosgnale zur Auswertung herangezogen werden. Hierzu wird die amplitudenmodulierte Zwischenfrequenz demoduliert und in ihre komplexen Bestandteile zerlegt. Erreicht wird dies z. B. durch die sog. Quadraturdemodulation, d. h. die Zwischenfrequenz wird einmal mit einer Sinus-Schwingung (Q) und einmal mit einer Cosinus-Schwingung (I) multipliziert, wobei beide Schwingungen eine ähnliche Frequenz haben wie die Zwischenfrequenz. Die durch die Multiplikation entstehenden hohen Frequenzen werden mit einem Tießpaß- filter ausgefiltert. Das Hüllkurvensignal HK wird aus der Wurzel der Summe der Quadrate von I (Inphasekomponente) und Q (Quadraturkomponente) erhalten: HK = 2 + Q2 . Anschließend erfolgt die übliche Amplitudenauswertung; an den gefundenen Orten der Maxima wird zusätzlich die jeweilige Phasenlage und die Differenz der beiden Phasenlagen bestimmt. Der Abstand der Antenne von der Oberfläche des Füllguts setzt sich dann zusammen aus einem Anteil von ganzzahligen Wellenlängen, der sich aus der Amplituden- auswertung ergibt, und einem Phasenrest.When evaluating the envelope curve, the measurement accuracy is known to be increased by the fact that in addition to the maxima (peaks) of the echo signals, which provide amplitude information, the phase positions of the echo signals are also used for the evaluation. For this purpose, the amplitude-modulated intermediate frequency is demodulated and broken down into its complex components. This is achieved e.g. B. by the so-called. Quadrature demodulation, ie the intermediate frequency is multiplied once with a sine wave (Q) and once with a cosine wave (I), both vibrations having a similar frequency as the intermediate frequency. The high frequencies resulting from the multiplication are filtered out with a low pass filter. The envelope signal HK is obtained from the root of the sum of the squares of I (in-phase component) and Q (quadrature component): HK = 2 + Q 2 . The usual amplitude evaluation then takes place; the respective phase position and the difference between the two phase positions are additionally determined at the locations of the maxima found. The distance between the antenna and the surface of the medium is then made up of a fraction of integer wavelengths, which results from the amplitude evaluation, and a phase remainder.
Eine besonders vorteilhafte Ausgestaltung des erfindungsgemäßen Verfahrens ist darin zu sehen, daß in einem ersten Verfahrensschritt der Füllstand in dem Behälter anhand des zeitlichen Verlaufs des Echosignals ermittelt wird; nachfolgend wird dann zusätzlich das Echosignal einerA particularly advantageous embodiment of the method according to the invention can be seen in the fact that in a first method step the fill level in the container is determined on the basis of the time profile of the echo signal; subsequently, the echo signal is then added
Fouriertransformation unterzogen, und es erfolgt eine weitere Auswertung im Frequenzbereich. Diese Ausgestaltung führt insbesondere dann zu einer erhöhten Meßgenauigkeit, wenn Mehrwegeausbreitung oder Mehrmodenausbreitung auftritt. Mehrwegeausbreitung bedeutet, daß die Echosignale neben dem eigentlichen Nutzsignal, das an der Oberfläche des Füllguts direkt reflektiert wird, zusätzlich einen Störsignalanteil enthalten, der auf Retro- reflexionen der Meßsignale an der Behälterwand oder an sonstigen im Behälterinnenraum befindlichen Einbauten zurückzuführen ist. Ursache der Meßfehler, die infolge von Mehrwegeausbreitung auftreten, sind konstruktive bzw. destruktive Interferenzen zwischen dem eigentlichen Nutzechosignal, das an der Oberfläche des Füllguts reflektiert wird, und dem Anteil des Nutzechosignals, das von einem Retroreflektor reflektiert wird. Ist x' der zurückgelegte Weg des eigentlichen Nutzechosignals, das an der Oberfläche des Füllguts reflektiert worden ist, und x" der um Δx längere Wege des Nutzechosignals, das an einem sonstigen Retroreflektor, insbesondere an der Behälterwand, reflektiert worden ist, so treten Interferenzen auf, wenn dieFourier transform, and there is a further evaluation in the frequency domain. This configuration leads in particular to increased measurement accuracy if multipath propagation or multimode propagation occurs. Multipath propagation means that the echo signals contain, in addition to the actual useful signal, which is reflected directly on the surface of the filling material, also an interference signal component that can be attributed to retro-reflections of the measurement signals on the container wall or on other internals located in the container interior. The cause of the measurement errors which occur as a result of multipath propagation are constructive or destructive interferences between the actual useful echo signal, which is reflected on the surface of the medium, and the proportion of the Useful echo signal, which is reflected by a retroreflector. If x 'is the path covered by the actual useful echo signal, which has been reflected on the surface of the filling material, and x "the path of the useful echo signal, which is longer by Δx, and which has been reflected on another retroreflector, in particular on the container wall, then interference occurs , if the
Wegedifferenz die Bedingung Δx = n-λ/2 erfüllt, wobei n eine beliebige ganze Zahl ist. Die Maxima der beiden Signale liegen so dicht beieinander, daß die beiden Peaks nicht voneinander zu trennen sind. Durch das erfindungs- gemäße Verfahren lassen sich nunmehr diese Unsicherheiten erheblich vermindern.Path difference meets the condition Δx = n-λ / 2, where n is any integer. The maxima of the two signals are so close together that the two peaks cannot be separated. These uncertainties can now be significantly reduced by the method according to the invention.
Dasselbe Problem tritt übrigens auch als Folge der bereits erwähnten Mehrmodenausbreitung von Wellenpaketen in Schwallrohren oder in sonstigen die Wellenpakete führenden Einrichtungen auf. Das erfindungs- gemäße Verfahren ist daher auch bestens dazu geeignet, Meßfehler, die aufgrund von Mehrmodenausbreitung auftreten, zu verringern.Incidentally, the same problem also arises as a result of the multimode propagation of wave packets already mentioned in still pipes or in other devices guiding the wave packets. The method according to the invention is therefore also ideally suited to reducing measurement errors which occur due to multimode propagation.
Gemäß einer bevorzugten Weiterbildung des erfindungsgemäßen Verfahrens ist vorgesehen, daß der zeitliche Verlauf der Phasenänderung so korrigiert wird, daß keine Phasensprünge auftreten. Problematisch bei der Auswertung im Zeitbereich ist nämlich, daß die Phase nur über einen Bereich von 360° eindeutig ist. Durch die Phasensprungkorrektur wird eine eindeutige Abhängigkeit zwischen der Phase und dem Abstand zur Oberfläche des Füllguts bzw. dem Füllstand erreicht.According to a preferred development of the method according to the invention, it is provided that the time course of the phase change is corrected so that no phase jumps occur. The problem with the evaluation in the time domain is that the phase is only clear over a range of 360 °. The phase jump correction provides a clear dependency between the phase and the distance to the surface of the filling material or the filling level.
Bezüglich der erfindungsgemäßen Vorrichtung wird die Aufgabe durch folgende Merkmale gelöst: Eine Sendeschaltung erzeugt Meßsignale. Diese Meßsignale werden mittels zumindest einer Antenne in Richtung der Oberfläche des Füllguts aussendet; die reflektierten Echowellen werden von der zumindest einen Antenne empfangen. Weiterhin ist eine Empfangs- /Auswerteschaltung vorgesehen, die den zeitlichen Verlauf des Echosignals bestimmt, das im Zeitbereich ermittelte Echosignal in den Frequenzbereich transformiert und anhand einer Änderung der Phasenlage des Echosignals im Frequenzbereich die Höhe des Füllstands bzw. eine Füllstandsänderung des Füllguts in dem Behälter bestimmt. Gemäß einer vorteilhaften Weiterbildung der erfindungsgemäßen Vorrichtung ist diese so ausgelegt, daß es sich bei den Meßsignalen um elektromagnetische Pulse oder um gepulste elektromagnetische Wellen (z. B. hochfrequente Mikrowellen-Pulse oder Laser-Pulse) oder um Ultraschall-Pulse handelt.With regard to the device according to the invention, the object is achieved by the following features: A transmission circuit generates measurement signals. These measurement signals are emitted in the direction of the surface of the filling material by means of at least one antenna; the reflected echo waves are received by the at least one antenna. Furthermore, a reception / evaluation circuit is provided which determines the temporal course of the echo signal, transforms the echo signal determined in the time domain into the frequency domain and determines the level of the filling level or a change in the level of the filling material in the container on the basis of a change in the phase position of the echo signal in the frequency range , According to an advantageous development of the device according to the invention, it is designed such that the measurement signals are electromagnetic pulses or pulsed electromagnetic waves (eg high-frequency microwave pulses or laser pulses) or ultrasonic pulses.
Die Erfindung wird anhand der nachfolgenden Zeichnungen näher erläutert. Es zeigt:The invention is illustrated by the following drawings. It shows:
Fig. 1 : eine schematische Darstellung einer Ausgestaltung der erfindungsgemäßen Vorrichtung,1: a schematic representation of an embodiment of the device according to the invention,
Fig. 2: eine schematische Darstellung der Zwischenfrequenz im Zeitbereich,2: a schematic representation of the intermediate frequency in the time domain,
Fig. 3: eine schematische Darstellung der digitalen Hüllkurve im Zeitbereich,3: a schematic representation of the digital envelope in the time domain,
Fig. 4: eine schematische Darstellung der Nutzechosignale der digitalen Hüllkurven im Zeitbereich bei drei unterschiedlichen Füllständen,4: a schematic representation of the useful echo signals of the digital envelopes in the time domain at three different fill levels,
Fig. 5: das Amplitudenspektrum der Nutzechosignale bei drei unterschiedlichen Füllständen undFig. 5: the amplitude spectrum of the useful echo signals at three different levels and
Fig. 6: die korrigierten Phasenspektren der Nutzechosignale bei drei unterschiedlichen Füllständen.Fig. 6: the corrected phase spectra of the useful echo signals at three different levels.
Fig. 1 zeigt eine schematische Darstellung einer Ausgestaltung der erfindungsgemäßen Vorrichtung. Ein Füllgut 2 ist in einem Behälter 4 gelagert. Zur Bestimmung des Füllstandes dient das Füllstandsmeßgerät 1 , das in einer Öffnung 10 im Deckel 7 des Behälters 4 montiert ist. Über die Antenne 6 werden in der SignalerzeugungsVSendeeinheit 5 erzeugte gepulste Meßsignale, insbesondere Mikrowellen, Ultraschallwellen oder Laserstrahlen in Richtung der Oberfläche 3 des Füllguts 2 abgestrahlt. An der Oberfläche 3 werden die Meßsignale zumindest teilweise als Echosignale reflektiert. Diese Echosignale werden in der Empfangs-/Auswerteeinheit 8 empfangen und ausgewertet. Die Aussendung der Meßsignale und Empfang der Echosignale wird über die Sende-Empfangsweiche 9 koordiniert.Fig. 1 shows a schematic representation of an embodiment of the device according to the invention. A filling material 2 is stored in a container 4. The fill level measuring device 1, which is mounted in an opening 10 in the lid 7 of the container 4, is used to determine the fill level. Pulsed measurement signals, in particular microwaves, ultrasound waves or laser beams, are emitted in the direction of the surface 3 of the filling material 2 via the antenna 6 in the signal generation transmission unit 5. The measurement signals are at least partially reflected on the surface 3 as echo signals. These echo signals are in the reception / evaluation unit 8 received and evaluated. The transmission of the measurement signals and reception of the echo signals is coordinated via the transceiver 9.
Selbstverständlich ist die erfindungsgemäße Vorrichtung 1 z. B. bei Verwen- düng von Mikrowellen als Meßstrahlung nicht nur in Verbindung mit einer frei abstrahlenden Antenne 6 einsetzbar. Bei einer Vielzahl von Einsatzgebieten, beispielsweise in der Petrochemie, Chemie und Lebensmittelindustrie, sind hochgenaue Messungen des Füllstandes von Flüssigkeiten oder Schüttgütern in Behältern (Tanks, Silos, usw. ) gefordert. Deshalb kommen hier in zunehmendem Maße Meßgeräte zum Einsatz, bei denen kurze elektromagnetische Hochfrequenzimpulse in ein leitfähiges Element eingekoppelt und mittels des leitfähigen Elements in den Behälter, in dem das Füllgut gelagert ist, hineingeführt werden. Bei dem leitfähigen Element handelt es sich beispielsweise um eine Seilsonde oder um eine Stabsonde.Of course, the device 1 z. B. when using microwaves as measuring radiation not only in connection with a freely radiating antenna 6. In a large number of areas of application, for example in the petrochemical, chemical and food industries, highly precise measurements of the fill level of liquids or bulk materials in containers (tanks, silos, etc.) are required. For this reason, measuring instruments are increasingly being used here, in which short electromagnetic high-frequency pulses are coupled into a conductive element and introduced into the container in which the filling material is stored by means of the conductive element. The conductive element is, for example, a rope probe or a rod probe.
Physikalisch gesehen wird bei dieser Meßmethode der Effekt ausgenutzt, daß an der Grenzfläche zwischen zwei verschiedenen Medien, z. B. Luft und Öl oder Luft und Wasser, infolge der sprunghaften Änderung (Diskontinuität) der Dielektrizitätszahlen beider Medien ein Teil der geführten Hochfrequenz- Impulse bzw. der geführten Mikrowellen reflektiert und über das leitfähigeFrom a physical point of view, this measuring method takes advantage of the effect that at the interface between two different media, e.g. B. air and oil or air and water, due to the sudden change (discontinuity) of the dielectric constant of both media, a part of the guided high-frequency pulses or the guided microwaves reflected and the conductive
Element zurück in die Empfangseinheit geleitet wird. Der reflektierte Anteil ist dabei um so größer, je größer der Unterschied in den Dielektrizitätszahlen der beiden Medien ist. Anhand der Laufzeit des reflektierten Anteils der Hochfrequenz-Impulse bzw. der Mikrowellen läßt sich die Entfernung zur Grenzfläche bestimmen. Bei Kenntnis der Leerdistanz des Behälters kann der Füllstand des Füllguts in dem Behälter berechnet werden. Eine entsprechende Vorrichtung wird beispielsweise in der US-PS 5,361 ,070 beschrieben. Dieses Verfahren ist übrigens unter dem Namen TDR (Time Domain Reflectometry) bekannt.Element is passed back into the receiving unit. The greater the difference in the dielectric numbers of the two media, the greater the reflected portion. The distance to the interface can be determined on the basis of the transit time of the reflected portion of the high-frequency pulses or of the microwaves. If the empty distance of the container is known, the filling level of the filling material in the container can be calculated. A corresponding device is described, for example, in US Pat. No. 5,361,070. Incidentally, this method is known under the name TDR (Time Domain Reflectometry).
Fig. 2 zeigt eine graphische Darstellung der Zwischenfrequenz des Echosignals im Zeitbereich. Insbesondere sind hier die Spannungsamplituden der Zwischenfrequenz gegen die Abtastpunkte aufgetragen, wobei die Anzahl der Abtastpunkte pro Längeneinheit das Auflösungsvermögen des Füllstands- meßgeräts bestimmt. Jeder Abtastpunkt entspricht somit einem definierten Füllstand. Das dargestellte Echosignal weist zwei Amplitudenmaxima auf. Der linke Peak charakterisiert das Echosignal, das von der Einkopplung der Meßsignaie auf die Antenne oder auf das elektrische leitende Element eines TDR-Sensors herrührt. Dieses nur vom jeweils verwendeten Sensor abhängige Echosignal, das seine Lage unabhängig von dem jeweiligen Füllstand beibehält, wird bei der Füllstandsmessung als Referenzsignal verwendet. Selbstverständlich können auch andere Referenzsignale herangezogen werden. Der rechte Peak repräsentiert das eigentliche Nutzechosignal, das von der Reflexion des Meßsignals an der Oberfläche des Füllguts herrührt. Der Füllstand wird aus dem Abstand der Maxima von Nutzechosignal und Referenz-Echosignal bestimmt.2 shows a graphic representation of the intermediate frequency of the echo signal in the time domain. In particular, the voltage amplitudes of the intermediate frequency are plotted against the sampling points, the number of sampling points per unit length determining the resolution of the fill level measuring device. Each sampling point thus corresponds to a defined level. The echo signal shown has two amplitude maxima. The left peak characterizes the echo signal which results from the coupling of the measurement signals to the antenna or to the electrically conductive element of a TDR sensor. This echo signal, which is only dependent on the sensor used in each case and which maintains its position regardless of the respective fill level, is used as a reference signal in the fill level measurement. Of course, other reference signals can also be used. The right peak represents the actual useful echo signal, which results from the reflection of the measurement signal on the surface of the medium. The level is determined from the distance between the maxima of the useful echo signal and the reference echo signal.
In Fig. 3 ist das Echosignals als digitale Hüllkurve im Zeitbereich dargestellt. Ebenso wie bei der Auswertung über die Zwischenfrequenz wird auch bei der Auswertung über die digitale Hüllkurve der Abstand vom Maximum desIn Fig. 3, the echo signal is shown as a digital envelope in the time domain. As with the evaluation via the intermediate frequency, the distance from the maximum of the
Nutzechosignals zum Maximum des Referenz-Echosignals als Maß für den Füllstand des Füllguts 2 in dem Behälter 4 herangezogen.Useful echo signal for the maximum of the reference echo signal is used as a measure of the filling level of the filling material 2 in the container 4.
In Fig. 4 sind die Hüllkurven der Echosignale bei drei unterschiedlichen Füllständen, also bei drei unterschiedlichen Laufzeiten, gezeigt. Die Form des Nutzechosignals ist invariant gegenüber Füllstandsänderungen; jedoch ändert sich die Lage des Nutzechosignals in Abhängigkeit vom jeweiligen Füllstand. Eine Füllstandsänderung schlägt sich somit in einer zeitlichen Verschiebung des forminvarianten Nutzechosignals nieder.4 shows the envelope curves of the echo signals at three different fill levels, that is to say at three different transit times. The shape of the useful echo signal is invariant to changes in level; however, the position of the useful echo signal changes depending on the respective level. A change in fill level is therefore reflected in a temporal shift in the shape-invariant useful echo signal.
In Fig. 5 ist das Betrags- bzw. Frequenzspektrum X(f) des Nutzechosignals bei unterschiedlichen Füllständen dargestellt. Wie bereits an vorhergehender Stelle erläutert, ist das Frequenzspektrum unabhängig vom jeweiligen Füllstand des Füllguts 2 in dem Behälter 4 und daher forminvariant unter Füllstandsänderungen.5 shows the magnitude or frequency spectrum X (f) of the useful echo signal at different fill levels. As already explained at the previous point, the frequency spectrum is independent of the respective filling level of the filling material 2 in the container 4 and is therefore invariant in shape with changes in filling level.
In Fig. 6 ist das Phasenspektrum θ (t - 1 n ) = arctan 2πft0 des Nutzechosignals bei unterschiedlichen Füllständen dargestellt. Um das Phasenspektrum als stetige Funktion darstellen zu können - in die Phasenberechnung geht der Arcustangens ein, der nur innerhalb eines Bereichs von 360° eindeutig ist -, wurde eine Phasensprungkorrektur vorgenommen. Diese Phasensprungkor- rektur ist unter dem Begriff 'phase unwrapping' im Bereich der Signalverarbeitung allgemein bekannt. Auf eine Beschreibung kann daher im Zusammenhang mit der vorliegenden Erfindung verzichtet werden.6 shows the phase spectrum θ (t − 1 n ) = arctan 2πft 0 of the useful echo signal at different fill levels. In order to be able to represent the phase spectrum as a continuous function - the arctangent, which is only unique within a range of 360 °, is included in the phase calculation - a phase jump correction was carried out. This phase jump correction rectification is generally known as 'phase unwrapping' in the field of signal processing. A description in connection with the present invention can therefore be dispensed with.
Die Erfindung nutzt die Tatsache aus, daß die Steigung der zeitlichen Änderung der Phase abhängig ist von dem Füllstand des Füllguts 2 in dem Behälter 4: Je weiter die Oberfläche des Füllguts von der das Referenzsignal erzeugenden Einkoppeleinheit entfernt ist, um so geringer fällt die Steigung des Phasenverlaufs aus. The invention takes advantage of the fact that the slope of the change in phase over time depends on the fill level of the filling material 2 in the container 4: the further the surface of the filling material is from the coupling unit generating the reference signal, the smaller the slope of the Phase curve.

Claims

Patentansprücheclaims
1 Verfahren zur Bestimmung des Füllstands eines Füllguts in einem Behalter, wobei Meßsignale in Richtung der Oberflache des Füllguts ausgesendet und an der Oberflache als Echosignale reflektiert werden und wobei durch Auswertung der reflektierten Echosignale der Füllstand in dem Behalter bestimmt wird, dadurch gekennzeichnet, daß der zeitliche Verlauf des Echosignals bestimmt wird, daß das im Zeitbereich ermittelte Echosignal in den Frequenzbereich transformiert wird und daß anhand einer Änderung der Phasenlage des Echosignals im Frequenzbereich der Hohe des Füllstands bzw eine Fullstandsanderung des Füllguts (2) in dem Behalter (4) bestimmt wird1 method for determining the filling level of a filling material in a container, wherein measurement signals are emitted in the direction of the surface of the filling material and reflected on the surface as echo signals and wherein the level is determined in the container by evaluating the reflected echo signals, characterized in that the temporal It is determined in the course of the echo signal that the echo signal determined in the time domain is transformed into the frequency domain and that a change in the phase position of the echo signal in the frequency domain determines the level of the filling level or a change in the level of the filling material (2) in the container (4)
2 Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß für den Fall hochfrequenter Meßsignale das im Zeitbereich ermittelte Echosignal durch sequentielle Abtastung aus dem Hochfrequenzbereich in den Niederfrequenzbereich transformiert wird und daß das in den Niederfrequenzbereich transformierte Echosignal einer Fourier-Transformation unterzogen wird2 The method according to claim 1, characterized in that in the case of high-frequency measurement signals, the echo signal determined in the time domain is transformed by sequential scanning from the high-frequency area into the low-frequency area and that the echo signal transformed into the low-frequency area is subjected to a Fourier transformation
3 Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß für den Fall hochfrequenter Meßsignale das im Zeitbereich ermittelte Echosignal durch sequentielle Abtastung aus dem Hochfrequenzbereich in den Niederfrequenzbereich transformiert wird, daß das zeittransformierte Echosignal gleichgerichtet und digitalisiert wird, und daß das gleichgerichtete und digitalisierte Echosignal einer Fourier- Transformation unterzogen wird 4 Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß vorab der Füllstand in dem Behalter (4) anhand des zeitlichen Verlaufs des Echosignals ermittelt wird und daß nachfolgend das Echosignal im Frequenzbereich ausgewertet wird3 The method according to claim 1, characterized in that in the case of high-frequency measurement signals, the echo signal determined in the time domain is transformed by sequential scanning from the high-frequency range into the low-frequency range, that the time-transformed echo signal is rectified and digitized, and that the rectified and digitized echo signal is a Fourier - undergoes transformation 4 The method according to claim 1, characterized in that the fill level in the container (4) is determined in advance on the basis of the time profile of the echo signal and that the echo signal is subsequently evaluated in the frequency domain
5 Verfahren nach einem oder mehreren der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der zeitliche Verlauf der Phasenanderung so korrigiert wird, daß keine Phasensprunge auftreten5 The method according to one or more of the preceding claims, characterized in that the time course of the phase change is corrected so that no phase jumps occur
6 Vorrichtung zur Durchfuhrung des Verfahrens nach einem oder mehreren der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß eine Signalerzeugungseinheit (5) zur Erzeugung von Meßsignalen vorgesehen ist, daß zumindest eine Antenne (6) vorgesehen ist, die die Meßsignale in Richtung der Oberflache (3) des Füllguts (2) aussendet und/oder die die reflektierten Echowelien empfangt, und daß eine EmpfangsVAuswerteschaltung (8) vorgesehen ist, die den zeitlichen Verlauf des Echosignals bestimmt das im Zeitbereich ermittelte Echosignal in den Frequenzbereich transformiert und anhand einer Änderung der Phasenlage des Echosignals im Frequenzbereich die Hohe des Füllstands bzw eine Fullstandsanderung des Füllguts (2) in dem Behalter (4) bestimmt6 Device for carrying out the method according to one or more of claims 1 to 5, characterized in that a signal generating unit (5) is provided for generating measuring signals, that at least one antenna (6) is provided, which the measuring signals in the direction of the surface ( 3) of the filling material (2) and / or which receives the reflected echo waves, and that a receiving evaluation circuit (8) is provided which determines the time course of the echo signal, transforms the echo signal determined in the time domain into the frequency domain and uses a change in the phase position of the Echo signal in the frequency range determines the level of the filling level or a change in the level of the filling material (2) in the container (4)
7 Verfahren nach Anspruch 6, dadurch gekennzeichnet, daß es sich bei den Meßsignalen um Ultraschall-Pulse, um hochfrequente Mikrowellen-Pulse oder um Laser-Pulse handelt 7 The method according to claim 6, characterized in that the measurement signals are ultrasonic pulses, high-frequency microwave pulses or laser pulses
PCT/EP2000/011725 1999-12-22 2000-11-24 Method and device for determining the level of a filling material in a container WO2001046653A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19961855A DE19961855B4 (en) 1999-12-22 1999-12-22 Method and device for determining the fill level of a product in a container
DE19961855.0 1999-12-22

Publications (1)

Publication Number Publication Date
WO2001046653A1 true WO2001046653A1 (en) 2001-06-28

Family

ID=7933697

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2000/011725 WO2001046653A1 (en) 1999-12-22 2000-11-24 Method and device for determining the level of a filling material in a container

Country Status (2)

Country Link
DE (1) DE19961855B4 (en)
WO (1) WO2001046653A1 (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1936403A1 (en) * 2006-12-20 2008-06-25 Pepperl + Fuchs Gmbh Ultrasonic sensor and method for determining the distance of an object from an ultrasonic sensor
US7954378B2 (en) 2007-02-07 2011-06-07 Pepperl + Fuchs Gmbh Ultrasonic sensor and method for determining a separation of an object from an ultrasonic sensor
WO2014009068A1 (en) * 2012-07-09 2014-01-16 Endress+Hauser Gmbh+Co. Kg Method and apparatus for the laser-based determination of the filling level of a filling material in a container
US8730093B2 (en) 2011-09-27 2014-05-20 Rosemount Tank Radar Ab MFPW radar level gauging with distance approximation
US8854253B2 (en) 2011-09-27 2014-10-07 Rosemount Tank Radar Ab Radar level gauging with detection of moving surface
US8872694B2 (en) 2010-12-30 2014-10-28 Rosemount Tank Radar Ab Radar level gauging using frequency modulated pulsed wave
US20150323370A1 (en) * 2012-12-20 2015-11-12 Endress+Hauser Gmbh+Co. Kg Method for Evaluation for Measurement Signals of a Level Gauge
WO2016108073A1 (en) * 2014-12-30 2016-07-07 Universidad Cooperativa De Colombia System for measuring rain and snow
US9513153B2 (en) 2010-12-30 2016-12-06 Rosemount Tank Radar Ab Radar level gauging using frequency modulated pulsed wave

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10149423B4 (en) * 2001-10-06 2014-07-17 Eads Deutschland Gmbh Method and device for measuring distances in optically opaque media
DE102014112228A1 (en) * 2014-08-26 2016-03-03 Endress + Hauser Gmbh + Co. Kg Method for avoiding phase jumps
US10816385B2 (en) * 2018-06-21 2020-10-27 Rosemount Tank Radar Ab Radar level gauge

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998002760A1 (en) * 1996-06-28 1998-01-22 Milkovich Systems Engineering Improved fast fourier transform sensor processor using enhanced frequency domain principles
US5847567A (en) * 1994-09-30 1998-12-08 Rosemount Inc. Microwave level gauge with remote transducer

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4443792A (en) * 1980-08-29 1984-04-17 Coal Industry (Patents) Limited Electromagnetic position detector employing fast fourier transform analysis
DE3107444C2 (en) * 1981-02-27 1984-01-12 Dornier System Gmbh, 7990 Friedrichshafen High resolution coherent pulse radar
US5361070B1 (en) * 1993-04-12 2000-05-16 Univ California Ultra-wideband radar motion sensor
DE19629593A1 (en) * 1996-07-23 1998-01-29 Endress Hauser Gmbh Co Arrangement for generating and transmitting microwaves, especially for a level measuring device
DE19723978C2 (en) * 1997-06-06 1999-03-25 Endress Hauser Gmbh Co Method for measuring the level of a product in a container according to the radar principle

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5847567A (en) * 1994-09-30 1998-12-08 Rosemount Inc. Microwave level gauge with remote transducer
WO1998002760A1 (en) * 1996-06-28 1998-01-22 Milkovich Systems Engineering Improved fast fourier transform sensor processor using enhanced frequency domain principles

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ENTWISTLE H F: "SURVEY OF LEVEL INSTRUMENTS", ADVANCES IN INSTRUMENTATION AND CONTROL,US,INSTRUMENT SOCIETY OF AMERICA, RESEARCH TRIANGLE PARK, vol. 46, no. PART 02, 1991, pages 1319 - 1354, XP000347569, ISSN: 1054-0032 *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1936403A1 (en) * 2006-12-20 2008-06-25 Pepperl + Fuchs Gmbh Ultrasonic sensor and method for determining the distance of an object from an ultrasonic sensor
US7954378B2 (en) 2007-02-07 2011-06-07 Pepperl + Fuchs Gmbh Ultrasonic sensor and method for determining a separation of an object from an ultrasonic sensor
US8872694B2 (en) 2010-12-30 2014-10-28 Rosemount Tank Radar Ab Radar level gauging using frequency modulated pulsed wave
US9513153B2 (en) 2010-12-30 2016-12-06 Rosemount Tank Radar Ab Radar level gauging using frequency modulated pulsed wave
US8730093B2 (en) 2011-09-27 2014-05-20 Rosemount Tank Radar Ab MFPW radar level gauging with distance approximation
US8854253B2 (en) 2011-09-27 2014-10-07 Rosemount Tank Radar Ab Radar level gauging with detection of moving surface
WO2014009068A1 (en) * 2012-07-09 2014-01-16 Endress+Hauser Gmbh+Co. Kg Method and apparatus for the laser-based determination of the filling level of a filling material in a container
US20150323370A1 (en) * 2012-12-20 2015-11-12 Endress+Hauser Gmbh+Co. Kg Method for Evaluation for Measurement Signals of a Level Gauge
WO2016108073A1 (en) * 2014-12-30 2016-07-07 Universidad Cooperativa De Colombia System for measuring rain and snow
EP3242149A4 (en) * 2014-12-30 2018-02-21 Universidad Cooperativa De Colombia System for measuring rain and snow

Also Published As

Publication number Publication date
DE19961855A1 (en) 2001-06-28
DE19961855B4 (en) 2007-11-29

Similar Documents

Publication Publication Date Title
EP2128576B1 (en) Evaluation of an echo shape of filling level sensors
EP1069438A1 (en) Method and device for highly accurate determination of the level of a product in a container
EP1701142B1 (en) Method for measuring the level of a medium inside a container based on the radar principle
DE69316080T2 (en) Level measurement using autocorrelation
EP1412710B1 (en) Method for evaluating the measuring signals of a propagation-time based measuring device
DE69730416T2 (en) Level measurement radar
DE60001111T2 (en) LIQUID LEVEL SENSOR
DE60027644T2 (en) MEASURING THE DIELECTRICITY CONSTANT OF A PROCESS PRODUCT BY MEANS OF A WEAK-RADAR RADAR LEVEL TRANSMITTER
DE102005063079B4 (en) Method for detecting and monitoring the level of a medium in a container
WO1994014037A1 (en) Microwave-operated level gauge
WO1995008780A1 (en) Level measurement process based on the radar principle
DE19961855B4 (en) Method and device for determining the fill level of a product in a container
DE102012107146A1 (en) Method for determining and / or monitoring the level of a medium in a container
WO1995008128A1 (en) Radar telemeter
WO1997009637A2 (en) Rangefinder
DE102014101904A1 (en) Efficient dispersion correction for FMCW radar in a tube
EP1454117B1 (en) Device for the determination and/or monitoring of the filling level of the charge in a container
EP1191315A2 (en) Apparatus and method for determining the position of the interface of two different media
DE102005011778A1 (en) Container e.g. tank, medium e.g. fluid, fill level measuring method, involves evaluating portion of microwave signal reflected, from medium, in phase-sensitive manner to assign fill level corresponding to delay of microwave signal
EP1072871B1 (en) Device for measuring the filling level of a product in a container
EP1004858A1 (en) Filling level gauge
DE4331353A1 (en) Radar distance measurement equipment
EP1186869A2 (en) Fluid level measuring device
EP1039273B1 (en) Fluid level measurement method
WO2013017534A1 (en) Linear relationship between tracks

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE TR

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
122 Ep: pct application non-entry in european phase