WO2013092100A1 - Procédé et appareil pour mesurer les distances - Google Patents

Procédé et appareil pour mesurer les distances Download PDF

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Publication number
WO2013092100A1
WO2013092100A1 PCT/EP2012/073347 EP2012073347W WO2013092100A1 WO 2013092100 A1 WO2013092100 A1 WO 2013092100A1 EP 2012073347 W EP2012073347 W EP 2012073347W WO 2013092100 A1 WO2013092100 A1 WO 2013092100A1
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WO
WIPO (PCT)
Prior art keywords
signal
time
reflector
determined
frequency
Prior art date
Application number
PCT/EP2012/073347
Other languages
German (de)
English (en)
Inventor
Markus Vogel
Alexey Malinovskiy
Stefan Gorenflo
Dietmar Spanke
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
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Application filed by Endress+Hauser Gmbh+Co. Kg filed Critical Endress+Hauser Gmbh+Co. Kg
Publication of WO2013092100A1 publication Critical patent/WO2013092100A1/fr

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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
    • 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
    • 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
    • G01F23/296—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
    • 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
    • G01S7/288—Coherent receivers

Definitions

  • the invention relates to a method and a measuring device for distance measurement, esp. For level measurement, according to the transit time principle, in which by means of a transmission and
  • an auxiliary signal is derived, which reproduces a received in the received amplitude and phase information of the received signal as a function of the associated running time over a predetermined time range, based on the auxiliary signal, the duration of the reflection on the Transmitter signal is determined at the reflector back to leading signal component, and on the basis of this term and a
  • Propagation speed of the signal pulses the distance to the reflector is determined.
  • Such distance measuring devices operating on the transit time principle are used in a wide range of industrial measurement technology for distance measurement. There, they are esp. Used for the measurement of levels of contained in containers contents. In this case, a distance between the transmitting and receiving device of a
  • An instrumentation group of this type used in industrial metrology form fill level measuring devices using microwaves according to the pulse radar method.
  • the latter are sold, for example, by the applicant under the product name Micropilot.
  • a predetermined repetition rate e.g. a repetition frequency of the order of 1 to 2 MHz, short
  • an auxiliary signal is regularly derived from the received signal that reproduces the amplitude and phase information of the received signal contained in the received signal as a function of the associated propagation time. Due to the high signal frequencies and the generally very short runtimes or transit time differences to be resolved, an auxiliary signal often referred to as an intermediate frequency signal is generated for this purpose, which is a time-stretched image of the received signal.
  • the auxiliary signal is usually subsequently rectified and fed via a low-pass filter and an analog-to-digital converter to an evaluation unit. Since the amplitude of the received signals decreases with the square of the traveled distance, the received signal can have very different amplitudes. In order to make these accessible to a better metrological detection, the auxiliary signal is preferably additionally logarithmiert. The measurement of the propagation time of the signal component reflected at the reflector to be measured in the distance now takes place by an envelope of the rectified and logarithmized auxiliary signal, frequently referred to as an envelope, being produced by filtering and then to the following
  • the envelope represents the course of the amplitude of the time-extended received signal as a function of the transit time.
  • feeding back signal components of the received signal cause in the envelope a maximum in the time required for the path to the associated reflector and back. Accordingly, the duration of the maximum results from the
  • EP 1324 067 A2 describes improving the measuring accuracy of these measuring devices by measuring a phase difference between the transmitted and the received signal in addition to the transit time measured using the envelope and using it to correct the maximum transit time determined by the envelope ,
  • the phase information is derived parallel to the derivative of the envelope based on the logarithmic intermediate frequency signal.
  • the logarithmic intermediate frequency signal is differentiated two times after the runtime via a differentiation stage. At the output of the differentiating stage, an output signal is thus available that has pronounced peaks at the zero crossings of the
  • Intermediate frequency signal has corresponding maturities.
  • the propagation times of the zero crossings and thus the phase position of the received signal can be determined without requiring digitization of the output signal by standardizing the peak amplitudes, for example with the aid of a Schmitt trigger, and detecting the associated propagation times with the aid of a timer.
  • Another instrumentation group of this type used in industrial metrology form fill level measuring instruments using ultrasound according to the pulse transit time method. The latter are marketed, for example, by the Applicant under the product name Prosonic.
  • Receiving device received back reflected signal components after a dependent of the distance traveled runtime.
  • the frequencies of the ultrasonic pulses are generally in the range of 1 kHz to 200 kHz, so that a time extension of the received signal received via the ultrasonic transducer is not required.
  • an auxiliary signal corresponding to the amplified received signal is derived here.
  • the auxiliary signal is digitized by means of an analog-to-digital converter, optionally logarithmic, and it is derived an envelope, the course of the amplitudes of the received signal as a function of the associated for the way from the transmitting and receiving unit to the respective reflector and back required transit time reproduces.
  • envelope curve the maximum of the envelope attributable to the reflection of the reflector to be measured in the distance is also determined here, and the sought distance is calculated on the basis of its transit time.
  • Distance measuring devices of this type have the disadvantage that for the preparation of the envelope and its digitization, a high component cost is required, which adversely affects both the production costs of such distance measuring device as well as their energy consumption.
  • the main contribution, both in terms of cost and in terms of energy consumption, is the logarithmizer normally required and the high-quality analog-to-digital converter which is absolutely necessary for the generation of the envelope.
  • the invention comprises a method for distance measurement after
  • Receive signal is derived as a function of the associated transit time over a predetermined delay range reproducing auxiliary signal
  • Half corresponds to the period of the signal pulses corresponding to the period
  • Reflector reflected signal components of the distance to the reflector is determined.
  • the runtime range is divided into discrete segments of the same segment length
  • the runtime range is subdivided into segments of different lengths on the basis of the transit times of the auxiliary function zero crossings, between which the periods of time lie between, and
  • the time window is set in each position such that it includes a predetermined number of successive periods.
  • the individual positions of the time window are each assigned the one runtime over which a window center of the time window is located in the respective position.
  • the recorded frequency distribution is filtered by means of a filter, in particular a finite impulse response (FIR) filter, and
  • a filter in particular a finite impulse response (FIR) filter
  • the attributable to the reflection at the reflector maximum and the duration of the reflector portions reflected signal components is determined on the basis of the filtered frequency distribution.
  • Frequency distributions filtering or averaging with respect to corresponding frequency values of the frequency distributions recorded in the successive measuring cycles
  • the transmission signals are periodically sent at the repetition frequency
  • the auxiliary signal is a time-expanded image of the received signal.
  • the transmission signals are periodically transmitted at the repetition frequency ultrasonic pulses.
  • the invention further comprises a method for using the method according to the invention in a distance measuring method with higher measuring accuracy, in which - Determined on the basis of the frequency distribution calculated transit time of the reflected signal to the reflector or the measured distance determined by the frequency distribution, a limited transit time, in which are due to the reflection at the reflector signal components of the received signal or the auxiliary signal, and
  • Runtime range is limited.
  • the invention comprises a distance measuring device for carrying out the
  • the distance measuring device comprises the measuring and
  • Unit in particular a microcontroller.
  • the measuring device comprises a complex programmable logic module.
  • the distance measuring device determined by the measured distance and a
  • a significant advantage of the method according to the invention is that the distance measurement is based exclusively on an evaluation of the frequencies contained in the received signal, and the frequency information is obtained in a cost-effective and energy-efficient manner based on the zero crossings of the auxiliary signal.
  • Fig. 1 shows a schematic representation of a level measuring arrangement
  • Fig. 2 shows: a derived with the level gauge of Fig. 1
  • Fig. 3 shows: an output signal of the differentiating stage of Fig. 1 in a in Fig. 2 marked runtime area;
  • FIG. 4 shows: a frequency distribution of the frequencies with those in the
  • Fig. 5 shows: a schematic representation of a level measuring arrangement
  • Distance measuring device for carrying out this method is described below first using the example of a level measuring device with a pulse radar level gauge.
  • FIG. 1 shows a schematic representation of a fill level measuring arrangement for measuring a fill level L of a filling material 3 located in a container 1 with a pulse radar fill level measuring device with a measuring and evaluation unit 5 according to the invention.
  • the distance measuring device comprises a transmitting and receiving device 7, with which it sends in the measuring mode transmission signals S in the direction of a located in the distance D to be measured reflector 9, here the Golfgutober Structure.
  • the transmission signals S consist of a predetermined repetition frequency f r generated signal pulses predetermined frequency f s and duration.
  • the transmitting and receiving device 7 comprises a transmission signal generator 1 1, which generates at the predetermined repetition frequency f r microwave pulses of the predetermined frequency f s and fed via a directional coupler 13 to an above the reflector 9 mounted antenna 15, the transmission signal from the generator 1 transmitted signal S sends in the direction of the reflector 9.
  • a transmission signal generator 1 which generates at the predetermined repetition frequency f r microwave pulses of the predetermined frequency f s and fed via a directional coupler 13 to an above the reflector 9 mounted antenna 15, the transmission signal from the generator 1 transmitted signal S sends in the direction of the reflector 9.
  • the transmission signal generator 1 1 comprises, for example, an oscillator 17 which oscillates at the repetition frequency f r and is followed by a pulse generator 19.
  • Pulse generator 19 generates based on the oscillator signal a control signal from short successive rectangular pulses with which a microwave source 21 is driven.
  • the microwave source 21 is, for example, a Gunn diode. It can either be as shown here via the control signal used for this purpose as a trigger signal be turned on and off, or permanently generate microwaves of the predetermined frequency f s , which are then fed to a gate, which opens or blocks depending on the control signal.
  • a gate which opens or blocks depending on the control signal.
  • Derived auxiliary signal ZF which reproduces a received in the signal E amplitude and phase information of the received signal E as a function of the associated running time t over a predetermined time range.
  • the travel time range begins in each measurement cycle with a start time t 0 at which the first microwave pulse of the transmission signal S is transmitted.
  • the total duration of the maturity range is up through the
  • Refresh frequency f r corresponding repetition period 1 / f r limited and can be additionally limited by specifying a maximum distance to be measured D.
  • the auxiliary signal ZF is also here, as in the prior art described above, preferably a time-expanded image of the received signal E.
  • the auxiliary signal ZF is generated by means of an input circuit in which the received signal E is fed via the directional coupler 13 to a mixer 23 and there to a suitable reference signal K. is superimposed. To achieve the desired time expansion is as a reference signal K on
  • Microwave pulses existing signal used which is identical in frequency and pulse duration of the microwave pulses to the transmission signal S, but in which the microwave pulses are generated at a repetition frequency 1 r -, which is slightly smaller than the repetition frequency f r of the transmitted microwave pulses.
  • the reference signal K is generated in the embodiment shown by means of a reference signal generator 25, which is apart from the lower repetition frequency 1 r - identical to the transmit signal generator 1 1.
  • the mixer 23 is followed by a low-pass filter 27, which filters out the desired due to the time-correspondingly lower frequencies of the time-extended received signal E, and is impermeable to the higher frequencies of the received signal E.
  • a low-pass filter 27 At the output of the low-pass filter 27 is thus the auxiliary signal ZF available, which is compared to the received signal E by a time expansion factor ⁇ temporally stretched equal to a quotient of the transmission repetition frequency f r and a frequency difference Af between the repetition frequency f r of the transmission signal S and the repetition frequency ⁇ (of the reference signal K is:
  • auxiliary signal ZF is supplied to the measuring and evaluation unit 5 according to the invention, where it is rectified on the input side by means of a rectifier 29.
  • Fig. 2 shows a greatly simplified for ease of understanding example of one with the
  • Measuring arrangement of Fig. 1 derived rectified auxiliary signal
  • the first image A1 is due to crosstalk of the transmission signal S in the transmitting and receiving device 7, via which a signal component of the transmission signal S is transmitted directly via the mixer 23 to the measuring and evaluation unit 5.
  • the second image A2 corresponds to the reflector 9 and reflected by a distance D dependent transit time t L of the transmitting and receiving device. 7
  • the auxiliary signal IF between the two images A1, A2 would have an amplitude of zero.
  • the auxiliary signal ZF also has a non-zero, temporally varying amplitude, which is essentially due to noise, in regions located outside the two images A1, A2, which are referred to below as noise region B.
  • Auxiliary signal ZF determined as a function of their transit time t is a function of their transit time t.
  • the circuit structure described in EP 1324 067 A2 mentioned above can be used.
  • ZF points to the maturities t , where the
  • Zero crossings of the auxiliary signal ZF are, in each case a minimum.
  • a differential stage 31 implemented, for example, by a bandpass filter, which performs a two-time differentiation of the rectified auxiliary signal
  • P (t) available that the two-time derivative
  • the output signal P of the differentiating stage 31 has a pronounced peak P at all transit times t 1 at which the auxiliary signal ZF has a zero crossing.
  • This output signal P is then fed to a measuring device 33, which detects the peaks P, in the output signal P and determines the associated transit times t.
  • Measuring device 33 may in the simplest case, for example, a to a
  • Timing device connected comparator which always has a
  • Time recording triggers when the incoming output signal P exceeds a predetermined threshold.
  • the time recording can be carried out by means of an internal clock which measures the times at which the peaks P occur, first absolute, ie without reference to the transit time t.
  • the assignment of these measured times to the actual transit times t can then be made later by using the following Evaluation of the auxiliary signal ZF the start time t 0 determined in relation to the time measured by the clock as an offset and the time scale is converted in total according to the set time expansion factor ⁇ .
  • the reference between the start time t 0 and the time of the internal clock can be transmitted via a control line from the transmitting and receiving device 7 to the measuring device 33.
  • the measuring device 33 the start of the respective measurement cycle, during which sent from periodically transmitted microwave pulses transmit signal S and was derived by stroboscopic sampling of the associated received signal E with the corresponding reference signal K, the present auxiliary signal ZF , possibly taking into account a circuit-related delay time indicates.
  • the transit times t, determined by the measuring device 33, at which the zero crossings of the auxiliary function ZF occur, are supplied for further processing to an intelligent electronic unit 35, for example a microcontroller.
  • the time periods T, of all time intervals lying between successive zero crossings of the auxiliary signal ZF are subsequently determined, and with reference to the respective transit time t, at which they occur
  • FIG. 3 shows by way of illustration a section of the output signal P (t) of the differentiation stage 31, in the transit time range marked e in FIG. In this
  • Running time range C is in the auxiliary signal ZF, a transition from the noise region B in the region of the second image A2.
  • the time periods T each equal to the difference t i + - 1, the transit times t i + , t, at which the corresponding two adjacent peaks P ,, P i + were detected in the output signal P.
  • Each time duration T is assigned the runtime t, at which it occurs.
  • the time duration T, the transit time t, of the previously detected peak P is assigned.
  • the time periods T, the transit time t i + of the respectively associated later detected peak P i + or an average value of the transit times t i , t i + 1 of the two associated peaks P i , P i + could be assigned.
  • the durations T, in the propagation time range of the image A2 are relatively constant, while the durations T, in the noise region, vary greatly. The reason for this is that signal components returning to a reflection of the transmitted microwave pulses of predetermined frequency f s in the received signal E have essentially the same frequency f s as the transmitted microwave pulses.
  • Signal components with a frequency which is equal to twice the frequency f s of the transmitted microwave pulses reduced by the time expansion factor. Accordingly, the period duration of these signal components, referred to hereinafter as the reference period duration T R , in the rectified auxiliary signal
  • noise signals are characterized by a broader frequency spectrum, which reflects again in strongly varying time durations T, in the noise region.
  • Temporal range is divided into discrete segments of equal segment length, and a time window F whose length is equal to a predetermined multiple of the
  • Segment length is.
  • the time window F is gradually shifted over the entire runtime range beginning at the start time t 0 . It is offset in each step by one segment length. Each of the thereby occupied by the time window F
  • time window F in FIG. 3 is shown in an example position which lies completely in the region of FIG.
  • the segmentation of the transit time axis is also indicated in FIG. 3 by short vertical lines.
  • the transit time range can be divided into segments based on the transit times t, the zero crossings of the auxiliary function ZF, between which the time periods T 1 occur
  • the time window is defined by comprising a predetermined number n of consecutive time periods T j to T j + n .
  • a frequency # is determined with which durations T, whose length lies in the range of the reference period T R , occur in the travel time range covered by the time window F in the respective position .
  • a preferably very narrow tolerance range +/- ⁇ is specified by the reference period T R. Accordingly, in the frequency determination all occurring within the time window F in the respective position periods T, are taken into account, which are within the tolerance range T R +/- ⁇ to the reference period T R.
  • the frequency distributions # (t) derived in the manner described above are preferably filtered.
  • Frequency distributions # (t) are filtered by themselves.
  • a low-pass filtering of the frequency values of the frequency distribution # (t) is suitable.
  • the filtering of the frequency values can be carried out, for example, by means of a first-order finite impulse response (FIR) filter, and overall smooths the frequency distribution # (t).
  • FIR finite impulse response
  • filtering may be performed with respect to corresponding frequency values of successive measurement cycles
  • a low-pass filter esp. A FIR filter.
  • This filtering causes a smoothing of the filtered frequency distributions # (t).
  • an averaging can be carried out over, preferably filtered, frequency distributions # (t) derived in successive measuring cycles.
  • the described derivation of the frequency distribution # (t) can be easily executed by the electronic unit 35 with appropriate programming.
  • the determination of the durations Ti (ti) as a function of the associated transit time t can be effected by a suitably designed circuit in hardware and from this the frequency distribution # (t) can be generated as a function of the transit time t via a corresponding digital filter.
  • a further alternative is to execute the determinations of the durations Tj (tj) and the frequency distribution # (t) as a function of the transit time t as a whole by means of a complex programmable logic device (CPLD), to which the output signal P of the differentiation stage 31 is supplied for this purpose.
  • CPLD complex programmable logic device
  • the measuring device 33 comprises only the logic module (CPLD).
  • the time profile of the frequency distribution # (t) is qualitatively consistent with the course of the envelope curve described in the prior art described above.
  • the sought distance D is measured by determining the maximum M L of the frequency distribution # (t) attributable to a reflection of the transmission signal S at the distance D to be measured from the transmitting and receiving device 7, and based on the maximum M L the transit time t L of the signal components attributable to the reflection at the reflector 9 is determined.
  • the determination of the maximum M L and the determination of its transit time t L preferably ensues on the basis of the frequency distribution filtered in the manner described above and / or filtered or averaged over several measuring cycles.
  • the sought distance D then results directly from the time required for the way t L and the propagation speed of the signals.
  • the transit time t L of the signal components attributable to the reflection at the reflector 9 can be determined as the transit time t at which the maximum M L has its maximum value. Since the position of the maximum value of relatively broad maxima only with a certain
  • Measurement uncertainty can alternatively also first a threshold value Running time t s are determined in which - as shown here - a rising or falling edge of the maximum M L exceeds a predetermined threshold # s or below, and from this on the basis of additional information on the shape of the maximum M L the running time t L of be determined on the reflection at the reflector 9 attributable signal components.
  • auxiliary signal ZF is rectified, logarithmized, filtered and digitized for generating the envelope representing the course of the amplitude of the time-extended received signal E as a function of the transit time t
  • the logarithmization nor the digitization of the auxiliary signal is necessary for the generation of the frequency distribution # (t) ZF required.
  • the inventive method over this prior art saves two expensive components with high energy consumption. Accordingly, the distance measuring devices for carrying out the method according to the invention in comparison are cheaper and more energy efficient.
  • the distance measuring method according to the invention is completely analogous also in distance measuring devices operating with ultrasound according to the transit time principle, especially in fill level measuring devices operating with ultrasound.
  • Fig. 5 shows a schematic
  • a transmitting and receiving device 7 'arranged above the container 1 filled with the filling material 3 is provided by means of the transmitted transmission signal S transmitted at a predetermined repetition rate f r for a given frequency f s and duration in the direction of the filling material 3 and the latter Signal portions R reflected on the product surface 9 are received after a travel time t dependent on the distance traveled.
  • the transmitting and receiving device 7 ' comprises a transmission signal generator 37, which generates an electrical alternating voltage signal Us corresponding to the transmission signal S, which is supplied to an ultrasonic transducer 39 which is used here as a transmitting transducer and a receiving transducer.
  • the core of the ultrasound transducer 39 is preferably a piezoelectric element which receives the alternating voltage signal U s applied thereto via an electrode 41
  • ultrasonic transducer 39 Transmits ultrasonic signal and sends out as a transmission signal S.
  • ultrasonic signals received by the ultrasonic transducer 39 in this case the signal components R reflected on the product surface, are converted by the ultrasonic transducer 39 into a corresponding one
  • the auxiliary signal H is then fed to the measuring and evaluation unit 5 already described above in connection with the fill level measuring device operating with microwaves, which then determines the frequency distribution # (t) in the manner described above on the basis of the auxiliary signal H and, as already described above, using the example of FIG with pulsed radar level gauge described the sought distance D determined.
  • the method according to the invention With the method according to the invention, adequate measurement accuracies can be achieved in a cost-effective and energy-efficient manner for most applications.
  • a microwave fill level measuring device with a frequency f s of the signal pulses in the gigahertz range
  • measuring accuracies for the distance measurement in the range of +/- 10 mm can be achieved.
  • the method according to the invention can also be used in distance measuring methods with higher measuring accuracy.
  • the signal conditioning and signal processing required to carry out more accurate methods is generally more complex and complex, the higher the measurement accuracy to be achieved.
  • An example of more accurate distance measuring methods are those in which a
  • Phase difference between transmit and receive signal determines, and are used to more accurately determine the duration of the attributable to the reflection at the reflector 9 signal component. Examples of this are described in DE 44 07 369 A1 and WO 02/065066 A1.
  • the method according to the invention can be used to drastically limit the travel time range over which the more accurate distance measuring method has to be performed.
  • the transit time t L determined by the maximum M L of the frequency distribution # (t) determines the signal components to be returned to the reflection of the transmission signal S at the reflector 9 or the transit time range based on the measured distance D predetermined, in which the reflection on the reflector (9) attributable signal components of the received signal (E) or the auxiliary signal ZF, H are.
  • the transit time range is preferably arranged symmetrically to the transit time t L, which is determined based on the maximum M L of the frequency distribution # (t), and to the signal components to be led back to the reflection of the transmission signal S at the reflector 9.
  • the width of the propagation time range is predetermined as a function of the width of the image A2 in the auxiliary function ZF, H, which is largely attributable to the pulse duration of the signal pulses and to the reflection at the reflector.

Abstract

L'invention concerne un procédé réalisable de manière peu onéreuse et énergétiquement efficace pour la mesure des distances selon le principe du temps de propagation ainsi qu'un appareil de mesure de la distance pour réaliser ce procédé, dans lequel des impulsions de signal d'une fréquence prédéfinie (fs) sont émises périodiquement vers un réflecteur (9) se trouvant à la distance (D) à mesurer, et les proportions (R) de signal réfléchies en retour par le réflecteur (9) sont reçues après un temps de propagation (t) dépendant du trajet parcouru comme signal reçu (E), des passages par zéro d'un signal auxiliaire (ZF, H) dérivé à l'aide du signal reçu (E), reflétant l'information d'amplitude et de phase du signal reçu (E) en fonction du temps de propagation (t), sont déterminés, des durées (Ti) entre les passages par zéro consécutifs sont déterminées, une fenêtre de temps (F) d'une longueur prédéfinie est déplacée pas à pas sur la plage du temps de propagation et une fréquence (#), à laquelle des durées (Ti) surviennent dans la fenêtre de temps (F) dans chaque position, dont la longueur correspond à une moitié de la durée périodique correspondant à la fréquence (fs) des impulsions de signal, est déterminée pour chaque position de la fenêtre de temps (F), une répartition (#(tM)) des fréquences (#) en fonction des temps de propagation (tM) associés aux positions de la fenêtre de temps (F) est déterminée, un maximum (ML) de la répartition des fréquences (#(t)) à attribuer à une réflexion des signaux émis (S) sur le réflecteur (9) est déterminé, un temps de propagation (tL) des proportions de signal (R) réfléchies par le réflecteur (9) est déterminé à l'aide du maximum (ML) et la distance (D) par rapport au réflecteur (9) est déterminée à l'aide de la vitesse de propagation des impulsions de signal et du temps de propagation (t) des proportions de signal (R) réfléchies sur le réflecteur (9).
PCT/EP2012/073347 2011-12-20 2012-11-22 Procédé et appareil pour mesurer les distances WO2013092100A1 (fr)

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DE201110089152 DE102011089152A1 (de) 2011-12-20 2011-12-20 Verfahren und Messgerät zur Abstandsmessung
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