CN1466674A - Method for detecting the limit state of a material and device thereof - Google Patents
Method for detecting the limit state of a material and device thereof Download PDFInfo
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- CN1466674A CN1466674A CNA018163866A CN01816386A CN1466674A CN 1466674 A CN1466674 A CN 1466674A CN A018163866 A CNA018163866 A CN A018163866A CN 01816386 A CN01816386 A CN 01816386A CN 1466674 A CN1466674 A CN 1466674A
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- 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
- G01F23/2845—Electromagnetic waves for discrete levels
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Abstract
The invention relates to a method and device for detecting the limit state of a material having a given dielectric constant. To this end, the invention uses a holding device, inside of which two electrically conductive rods are arranged. When a limit state is attained, said rods are immersed into the material to be monitored and are connected to an electric circuit. Said circuit generates high-frequency transmit pulses, which are fed to the rods via the line according to the principle of time-domain reflectometry. The signals reflected into the air by the boundary layer of the material are evaluated on the basis of their waveform.
Description
The present invention relates to a method, be used to measure the limit state that has known dielectric constant material, use support to go between as process, wherein be provided with the contact rod of an end at least, its other end immerses in the material that will monitor when reaching capacity material level, wherein, the rod end that is in the support is connected with the circuit that produces the high-frequency emission pulse by electric wire, circuit has echo amplifier for receiving echo, wherein, the high-frequency emission pulse is as the microwave that is guided, according to the otdr measurement method, TDR-mensuration principle, be sent on the rod by lead, wherein, led Huis twt amplifier to the signal of air reflection on the material critical layer and be used for evaluation, base expansion during reflected signal, and be divided into three zones continuous in time, be transponder pulse (I section), transit time (II section) and time scan window (III section), wherein, the moving together time point of time scan window begins, according to the preamble of claim 1.Equally, the invention still further relates to the domain reflectometer that claim 1 is used.
Be to determine the limit state or the material level of container medium, disclose that (time domain reflectometry uses sensor measurement material level or limit state on basis TDR), this US-A-5.609.059 is introduced to some extent in the otdr measurement method.This sensor is as continuous system works, and to measure along the transit time of the electromagnetic signal of an exposed waveguide transmission, promptly to the transit time with reflex to pulse evaluation on the waveguide.According to the material level of medium, waveguide stretches into or does not stretch in the medium, utilizes signal to transmit a ultimate value under first kind of described situation.Waveguide for example is Suo Mofei (Sommerfeld) lead, Gu Bo (Goubau) lead, concentric cable, microwave band or coaxial or two leads that be arranged in parallel, for example two detector bars.If they contact with medium, so, wave impedance is owing to the specific inductive capacity that is different from air changes.Medium with the critical surface of surrounding medium on or also under the situation that the medium interior layer forms, because the great-jump-forward of its dielectric property changes, cause the uncontinuity in the transport property of the waveguide that immerses, to such an extent as to along or on these positions, obtain reflection to small part in the pulse of waveguide internal transmission.Therefore, the time point of time point by will receiving the retroeflection pulse and emission compares distance or the height that can determine critical layer from the signal of retroeflection.In this case, the evaluation by echo-amplitude carries out the transit time measurement.If the DK value is lower, then can not carry out the amplitude evaluation.
Wolfgang Hillberg has introduced the pulse process on the lead: " pulse on the lead ", Oldenbourg publishing house, 1981.As long as it is identical that wire characteristic, particularly xsect keep, ripple is just continuity unchangeably on lead.If this point flip-flop, so, on this position, forward wave is split into the subwave of backhaul of reflection and the subwave that continues to advance of fracture.Reflection wave on the joint has the shape identical with forward wave; Just the traffic direction of reflection wave and amplitude obtain changing.If steep wave is sent on the nuditing wire end of a lead, just in certain wave impedance during to wave impedance ∞ transition and on the input end under the matching relationship situation, so, the voltage of backhaul ripple doubles, opposite current.Under conductor wire end short circuit situation, reflection has the voltage of inverted sign, and electric current doubles when same-sign.
In the TDR-operating sensor, along with each cycle of emission-trigger pip all produces and send transponder pulse.The backhaul reflected signal is transported to signal scanning circuit, but so that can show and evaluation time basic expansion process in short-term.This point is along with the trigger pip of sweep frequency obtains triggering, and wherein, periodic signal is scanned on scanning-triggering-time point.By the delay that scanning-trigger pip is directly proportional with the time with respect to emission-trigger pip, scanister produces output signal, and its amplitude variations produces by the corresponding instantaneous value of detectable signal.Output signal shows the time basic image expanding of detectable signal thus.After amplification and filtering, this output signal or its time slot form the reflection distribution plan, and the transit time that therefrom can measure the backhaul reflected signal is also measured the distance of critical layer thus.
Problem in this type sensor is to have higher interference sensitivity with respect to high-frequency interferencing signal.The undesired signal and the backhaul reflected signal that are coupling on the waveguide are overlapping, and are measured by the broadband scanning circuit equally.Typical narrow-band interference signal when testing, by the carrier oscillation of 80MHz to 1GHz basic frequency, is utilizing low frequency amplitude modulation (for example 1kHz) to duplicate to electromagnetic compatibility (EMV).If carrier frequency be in the sweep frequency integral multiple near, just be in the inside of what is called " frequency receive window ", so, this interference can not be curbed by the low-pass filtering according to scanister.Because undesired signal utilizes sweep frequency to be scanned according to the type of bandpass filtering scanning, so with respect to noiseless situation, the covering that the reflection distribution plan is vibrated makes its evaluation become difficult, error may occur.According to adopting broadband reception circuit and the measuring principle that plays the probe of stick antenna effect, the coupling factor of interference is very high.Therefore, under the situation in interference is in the frequency receive window, general being difficult to the useful signal evaluation.
DE 298 15 069 U1 disclose a kind of TDR-limit state sensor, it is made of the waveguide that immerses in the material, connect a sampling circuit on the waveguide, sampling circuit has a firing pulse generator, be used to produce the high frequency waves signal of pulse, one receiver, be used to receive the high frequency waves signal, an emission-/receive separation vessel, be used to distinguish emission with the high frequency waves signal that receives, the one scan device, be used to scan the high frequency waves signal of reception, the one scan pulse producer is used for the gated sweep device, also have an intermediate store, be used for the temporary transient high frequency waves signal that receives that stores.Sampling circuit has two oscillators, and wherein at least one can change in frequency, a control emission generator, another gated sweep pulse producer.Frequency mixer forms difference from two frequencies, be used for time base spreading coefficient is adjusted to ratings.Yet the reflected signal evaluation of this device is very poor or very difficult, because signal and reflected signal are almost overlapping, and have only and spends very high construction expenditure very difficultly and just can be enough to make a distinction.
The objective of the invention is to, a kind of method is provided, be used to measure the limit state of material and the specific inductive capacity of definite material, one domain reflectometer is provided simultaneously, the limit state that is used to measure material as the ultimate value switch for this method of enforcement, domain reflectometer has the anti-interference of raising on the one hand, can be general, promptly do not rely on temperature, pressure, perhaps particularly do not rely on the characteristic of medium one liquid or bulk material, and be applicable to the material that has than low-k DK (DK is between 1.8 to 5) yet.
This purpose is achieved by the following method, promptly be used to measure the method for the limit state that has known dielectric constant material, use support to go between as process, wherein be provided with the contact rod of an end at least, its other end immerses in the material that will monitor when reaching capacity material level, wherein, the rod end that is in the support is connected with the circuit that produces the high-frequency emission pulse by electric wire, circuit has echo amplifier for receiving echo, wherein, the high-frequency emission pulse is as the microwave that is guided, according to the otdr measurement method, TDR-mensuration principle, be sent on the rod by lead, wherein, the signal that reflects in air on the material critical layer is led Huis twt amplifier and is used for evaluation, base expansion during reflected signal, and be divided into three zones continuous in time, be transponder pulse (I section), transit time (II section) and time scan window (III section), wherein, the moving together time point of time scan window begins, and has following feature:
A) to measure under two kinds of running statuses of material, promptly cover, short circuit or quick short circuit, and do not have covering, during no-load running, the reflected signal on rod-medium or rod-air critical layer produces by the variation of wave impedance, this variation is present on rod-medium or the rod-air critical layer
The curve shape of the time base spread reflection signal of b) receiving on the echo amplifier is used for determining limit state, wherein, inside at the time scan window, at least three of reflected signal significant points are carried out numeral or by means of curve practice evaluation, and measure reference voltage the curvilinear motion during at least one II section, wherein
C) there is not covering, no-load running, can discern thus: the reflected signal of time scan window interior has following characteristic:
Only have a depth measurement point, it is in below first boundary line of predesignating, and the boundary line comes by biasing and reference voltage difference,
D) first kind of covering state, can discern thus: the reflected signal of time scan window interior has following characteristic:
Exist one to survey high point, it be in second boundary line predesignating above, wherein, this second boundary line measured from reference voltage and biasing equally,
E) second kind of different covering state, can discern thus: the reflected signal of time scan window interior has following characteristic:
There are two depth measurement points,
In chronological sequence come second depth measurement point and be lower than first depth measurement point with the quantity of predesignating,
F) the third different covering state, can discern thus: the reflected signal of time scan window interior has following characteristic:
Have a depth measurement point, it is in below first boundary line of predesignating, and the boundary line comes by biasing and reference voltage difference,
Between the start time point of time scan window and depth measurement point a turning point is arranged, it is in local a survey between a high point and the local depth measurement point, wherein, and local depth measurement point and locally survey high putting above the minor increment of predesignating.
In addition, this purpose is achieved by a domain reflectometer, it is used to measure the limit state that has known dielectric constant material as the ultimate value switch, having support goes between as process, wherein be provided with the contact rod of an end at least, its other end immerses in the material that will monitor when reaching capacity material level, wherein, the rod end that is in the support is connected with the circuit that produces the high-frequency emission pulse by electric wire, circuit is for receiving reflected signal, echo, has echo amplifier, wherein, the high-frequency emission pulse is as the microwave that is guided, according to the otdr measurement method, TDR-mensuration principle, can be sent on the rod by lead, and the signal that reflects in air on the material critical layer is led back and time base expansion advances in the echo amplifier to be used for evaluation, wherein, the wave impedance of rod and process lead-in wire is selected like this, in evaluation, can be divided into three zones continuous in time, be transponder pulse (I section), transit time (II section) and time scan window (III section), wherein, the curve shape of the reflected signal that the time scan window interior is measured is used for determining limit state.
The formation that other have advantage of the present invention is shown in the dependent claims.
Major advantage of the present invention is, and is opposite with prior art, though under the low situation of DK value also evaluation reliably.
The domain reflectometer that is used to measure the limit state that has known dielectric constant material as the ultimate value switch, by forming as the support of process lead-in wire, wherein be provided with the contact rod of an end at least, its other end immerses in the material that will monitor when reaching capacity material level, wherein, the rod end that is in the support is connected with the circuit that produces the high-frequency emission pulse by electric wire, pulse is as the microwave that is guided, according to the otdr measurement method, TDR-mensuration principle, can send on the rod by lead, wherein, the signal that reflects in air on the material critical layer is led the telegram in reply road and is used for evaluation, wherein, the wave impedance of rod is selected like this, the wave impedance difference of it and material is come, and the curve shape of the reflected signal that obtains is used for determining limit state, and until three of curve shape significant points are carried out evaluation.Preferred feed has the specific inductive capacity greater than 1.8.
The present invention is from this fact, and the ripple that reflects on joint has the shape identical with forward wave; Just the traffic direction and the amplitude of backhaul ripple change to some extent.Use under the situation of two parallel bars in the process lead-in wire, the wave impedance between the rod obtains changing by the material that is in therebetween.The wave impedance of this set is pressed following calculating:
Z wave impedance/Ohm
ε
ΓRelative dielectric constant (DK-value)
Distance/mm between the α rod center
D rod diameter/mm
The no-load running measurement is interpreted as that from exomonental that reflected signal it reflexes on the rod end when no-load running, this means, the rod end does not contact with material.Under the limit state situation, the intensity of reflection depends on the DK-value, causes obtaining reflection from air largest portion in the medium transition when the DK-value is higher, and almost also variation exerts an influence the rod end in the immersion material to signal.
According to the present invention, to the pulse shape evaluation of reflection, because under different wave impedance situations, not only reflection has the amplitude of differing heights and different polarity, and the specific inductive capacity-DK-value and the excellent reflected signal that is soaked by material that depend on material can be out of shape.If the DK-value of material greater than 10, so, almost completely opposite pulse occurs on the rod end, because quick short circuit.The typical media that has higher DK-value is a water, ε
Γ≈ 80 or Pril ε
Γ≈ 40.
Average DK-value is in the 5-10 scope; Here typical medium is vinegar, honey and ethanol., only constitute high reflection on the rod conditionally here, however more much higher than having under the situation that is lower than 5DK-value medium.Low DK-value is in＞the 1-5 scope in, wherein, 1 is the DK-value of air.Typical medium is coffee powder, gypsum, rice, salt and sugar in this scope.In these DK-values, only constitute less reflection on the rod, because DK-value and air do not have too big difference, to such an extent as to therefore almost all there is the situation that has the exposed end lead.Certainly, the identification of the material that has DK-value＞1.8 has been covered the spectrum of all materials 95% that in the process automation scope, use.
When material had the high dielectric constant of DK-value＞10, recognition feature was d), when material has 5 between 10 during the medium specific inductive capacity of DK-value, recognition feature is e), when material have DK-value＜5 than low-k the time, recognition feature is f).
The result who adopts the present invention to obtain shows, the present invention is suitable for having adhesion characteristics according to ultimate value fully in outstanding mode and discerns various types of media, particularly bulk material or liquid or resisting medium, as honey, because also can stand the adhesion of certain limit and error can not occur as domain reflectometer according to method of the present invention, and can identify all the time and do not have material or medium on the rod., also insensitive to the medium that sticks on the rod when the DK-of medium value is hanged down according to the material of domain reflectometer of the present invention identification obviously more than the disclosed sensor of prior art, even and under the lower situation of DK-value also evaluation reliably.
The wave impedance and the size of process lead-in wire are preferably selected like this, thereby form the reflected signal with maximum six the significant points that are used for reliable evaluation limit state thus.Preferably thus maximum six significant points of curve shape are carried out evaluation.The curve shape of reflected signal scans by circuit after being preferably in the A/D-conversion, wherein, the mensuration curve shape is in the significant point in the time scan window, particularly surveys high point, depth measurement point, local high point, the local depth measurement point surveyed, and evaluation is carried in its position.The evaluation of the curve shape by foundation uniqueness of the present invention, what have advantage is, even also can use short excellent length under the rise time situation quite slowly at the about 300-600ps of transponder pulse.Comparing with the amplitude evaluation that must use obvious longer rod than the practicality of stub length is another advantage.
Process lead-in wire particularly process bolt connects.In the present invention one preferred embodiment, the process lead-in wire has an insulator at least in the inside of process lead-in wire, as the insulating support of rod and same rod for the tubular process lead-in wire of band external metallization screw thread.
The time scan window can change, and the start time point of the same window can determine thus that promptly reflected signal departs from reference value with the value of predesignating, and perhaps particularly is lower than reference value with the value of predesignating.
Preferably use two rods that are set in parallel in the support, wherein, use coaxial cable as lead, its selectable length is used for predesignating the transit time between transponder pulse that prolongs forward and the reflected signal that returns, therefore and be used for its detectability in short-term, wherein, the inner wire that has a coaxial cable of a rod is connected with the ground connection of circuit by outer conductor with another rod or electric capacity is connected with ground connection.
Circuit preferably has delay circuit, produce exomonental rectangular voltage in the circuit, be transported to two branch roads and delay subsequently, wherein, the delay of first branch road provides transponder pulse, and greater than the delay of second branch road that scanning impulse is provided, wherein, the time base expansion carry out by means of order-sampling-on-off circuit.Time base spreading coefficient in this regard needn't be known.
In the present invention one preferred embodiment, the signal of reflection is by four-diode-sampling circuit scanning, and be transported to microprocessor or microcontroller by echo amplifier and by the A/D-converter, its is to signal evaluation of reflection, and result's " cover identification " or " not having the identification of covering " are sent to display unit or convert switching signal to.
The start time point of time scan window generally can be all the time by reflection identification, and the transit time lead is connected the process lead-in wire and goes up owing to different wave impedance produces reflection.
The advantage brought of the start time point of Ce Dinging is in this manner, and the time base spreading coefficient of circuit only need have precision approximately ± 10% to ± 20%, to such an extent as to circuit can be realized with expense seldom.
Most curve distribution during the II section, can for example determine that a baseline is as reference voltage by on most curves, averaging, wherein, the start time point of time scan window is determined thus, be that reflected signal departs from baseline with the value of predesignating, and measure from reflected signal, obtain the time base expansion signal in the time scan window, whether have the high point of survey, first depth measurement point, second depth measurement point and/or local depth measurement point and local high point and the turning point surveyed.
The signal that the time base that obtains from reflected signal is expanded can repeatedly carry out analog-to-digital conversion and evaluation in one-period, wherein, measure most values and therefrom produce voltage-mean value, this mean value is as the baseline of surveying high some evaluation, whether the value of the signal of base expansion is lower than the value of baseline above the value of predesignating when determining in view of the above, determine the start time point of reflection thus, after this in other cycles from the start time point of this mensuration, base spread signal when utilizing the maximum repetition rate that scans to measure, and whether contain in the when inquiry base spread signal and survey high point, second depth measurement point or local depth measurement point and the high point of part survey.
Be the determination limit material level, perhaps use wave filter, for example the FIR-wave filter, perhaps use two counters, and counter is used for " covering identification ", and a counter is used for " not having the identification of covering ", and identification is in view of the above sent on one of them counter.
Two parallel rods preferably are set in support.Lead is coaxial cable preferably, its selectable length is used for predesignating the transit time between transponder pulse that prolongs forward and the reflected signal that returns, therefore and be used for its distinguishability by circuit, therefore and be transit time lead on the process lead-in wire, wherein, the inner wire that has one of them excellent coaxial cable is connected with the ground connection of circuit by outer conductor with another rod.Therefore the transit time lead is connected on the process lead-in wire.
The wave impedance of coaxial cable can be selected not match with the wave impedance of process lead-in wire.Yet in the present invention one preferred embodiment, the wave impedance of coaxial cable is selected not match with the wave impedance of process lead-in wire.
In one embodiment of the present invention, the inner insulator of process lead-in wire hierarchically is made up of the different materials that has differing dielectric constant, for example Peek and teflon, to such an extent as to this insulator is a layer dielectric, wherein, these materials are the seal process lead-in wire on the one hand, has minimum thickness on the other hand, and it determines that for being formed for the time scan window starting time reflected signal of point is essential.The process lead-in wire is preferably cylindrical, preferably by electrically insulating material, forms as teflon (PTFE) or PEEK, and rod is in wherein.When this material can also use in the chemical corrosion medium rod is protected.
In the present invention one preferred embodiment, rod has coating, teflon for example, and pottery or PEEK wherein, are using under teflon or the PEEK situation, and coating thickness is preferably between 0.1 to 1mm.In one embodiment of the present invention, the length that rod stretches out from process lead-in wire is 2 to 15cm, is preferably between 5 to 7cm.
The transit time lead is in the length on the end the process lead-in wire from circuit to being connected at rod, is at least 30cm in one embodiment of the present invention, and best 30cm to 60cm is so that the separation in short-term between simplification transponder pulse and the reflected signal.The spacing of rod is preferably between 10mm and the 30mm.Wave impedance can be selected by the ratio of this spacing and excellent diameter.The height of process lead-in wire is preferably between 2cm and the 5cm.In an embodiment of the present invention, the process lead-in wire is airtight construction, preferably is no more than the pressure of 30bar.
Brief Description Of Drawings, wherein:
Fig. 1 illustrates the block scheme of measurement mechanism, has process lead-in wire disposed thereon,
Fig. 2 a, b illustrate the equivalent circuit diagram (a) of process lead-in wire, have the affiliated voltage (b) of equivalent circuit diagram,
Fig. 3 illustrates the echo curve of the different material that measures,
Fig. 4 illustrates the diagram xsect of process lead-in wire,
Fig. 5 illustrates the FB(flow block) of an evaluation algorithm, is used for determination limit material level under " identification " and " nonrecognition " two counter situations of use,
Fig. 6 a-d illustrates each echo curve that has for the employed ultimate value of its evaluation.
Fig. 1 illustrates the basic structure of metering circuit, has cylindrical process lead-in wire 12, and it stretches in the container 10 that contains material medium 11.Concentric cable 13 is connected on the rear end of rod 3,4, and plays the effect of transit time lead.Concentric cable 13 finishes having in the TDR-circuit of two branch roads 18,19.
In service at TDR-sensor or TDR-sensor electrical clamp mechanism 14, utilize each cycle of emission-trigger pip XTS, this trigger pip is produced by triggering-generator 23 and postpones constant duration and have pulse to recheck frequency f PRF by means of first delay-level 20, produces and send transponder pulse XS by emitting stage 17.Typical pulse is rechecked frequency and is in 100kHz between several MHz.
In the signal scanning circuit of TDR-circuit 14, here be four-diode-sampling-circuit 22, the transponder pulse XS of emitting stage 17 and reflected signal XSonde are subjected to scanning and time base is expanded, signal thus, for example can be in microcontroller or microprocessor evaluation more simply.
Periodically backhaul reflected signal XSonde is transported to signal scanning circuit 22, so as can the time base expansion ground show and evaluation process in short-term.This circuit utilizes the trigger pip XTA of sweep frequency fA to trigger, and wherein, trigger pip XTA utilizes second delay-level 21 and postpones a duration that changes, at scanning-triggered time spot scan cyclical signal XSonde.The delay of this variation can be influenced by microprocessor 16.The delay that is directly proportional with the time with respect to emission-trigger pip by scanning-trigger pip, the frequency that reduces slightly with respect to emission-trigger pip XTS by scanning-trigger pip XTA for example, perhaps by the phase modulation (PM) of scanning-trigger pip XTA with respect to emission-trigger pip XTS, signal scanning device 22 produces output signal, and its amplitude variations is learnt by the corresponding instantaneous value of detectable signal.Therefore output signal shows the time basic image expanding of detectable signal XSonde.
After amplification and the filtering, the time slot of this output signal or same signal forms reflection distribution plan XVideo in echo amplifier 15, and therefore the transit time that therefrom can measure the backhaul reflected signal also measures the distance of critical layer.Reflection distribution plan XVideo is transported to microprocessor 16 by A/D-converter 24, microprocessor, and sends to result's " cover identification " or " not having the identification of covering " for example display unit 25 or converts switching signal to according to evaluation of the present invention the reflection distribution plan.
The measurement curve of reflected signal is as previously mentioned according to the software evaluation, and definite maximal value and/or minimum value and/or turning point.From these unique curve point, draw reflected signal and when differing dielectric constant DK, change, to such an extent as to adopt mode that the present invention also can approximate value to determine a kind of DK-value of material.In principle all the time similarly curvilinear motion important difference is arranged aspect the DK-value of material will measuring.Can learn that from curvilinear motion the DK-value of material is high more, transmit and reflected signal between also just high more according to the increasing degree of curve.
Just when the DK-of material value is low, just can encounter difficulties, if these materials are lower than DK 2.2...3 value, yet, having the 2.2...3 order of magnitude still can accurately differentiate with the material of the low DK-value that is lower than this order of magnitude, particularly under the situation of the rod that uses two distributions parallel to each other, wherein, utilize, no matter have higher or the effective evaluation of the material that has low DK-value according to process lead-in wire of the present invention.
Fig. 2 a, b illustrate the process lead-in wire, and (Fig. 2 equivalent circuit diagram a) has the affiliated voltage (Fig. 2 b) of equivalent circuit diagram.In Fig. 2 a, for introducing the equivalent circuit diagram that the present invention shows the process lead-in wire, the TDR-on-off circuit is played on a left side, and subsequent is the transit time lead on the rod in the guiding process lead-in wire.TDR-on-off circuit and transit time lead have and for example respectively are the wave impedance of 75Ohm.The process lead-in wire for example is tubular metal process lead-in wire, has the insulating material of the differing dielectric constant of a plurality of merging, and the metal bar conduct respectively is arranged on wherein with the probe of an end, and wherein, rod can soak or discharge by the rising or the decline of material surface level.Insulating material for example has the wave impedance of 140Ohm or 170Ohm, this wave impedance as-245Ohm of metal process lead-in wire.Rod for example has the wave impedance of 250Ohm; The wave impedance of material or rod end is unexposed.
Order is the voltage that utilizes positive voltage when excitation sudden change reflected signal shown in Fig. 2 b accordingly therewith.In this case importantly, under the no-load running situation of two rods, reflected signal is compared with transponder pulse and is shown on the one hand too highly, has the symbol identical with transponder pulse on the other hand again.Under the short circuit situation, the change in voltage of reflected signal shows decline, has the symbol opposite with transponder pulse.
Fig. 3 illustrates the echo curve of the different material that measures, and they are to obtain when pulse 30 excitations that utilize according to the process lead-in wire of Fig. 4.The left side of curve map is the transponder pulse that sends on the rod.Its right is listed and is comprised no-load running curve L
No-load runningAt interior different material, i.e. the different reflections of Pril, honey and coffee.A quite straight curved portion L is arranged between transponder pulse and reflected signal
No-load running, its reflection transit time lead also can be realized enough separating in short-term with reflected signal with transponder pulse.
The curve shape of the time base spread reflection signal that obtains on echo amplifier is used for determining limit state, wherein, for example significant to three of reflected signal, the point that is in the time scan window interior of predesignating carries out numeral or by means of curve practice evaluation.
As can be seen, the no-load running curve is equivalent to have the reflected signal with transponder pulse same-sign direction.If the magnitude of voltage of reflected signal or time base spread signal surpasses the value of predesignating, so, free ends single or two rods are identified as and do not soak, and rod is in the no-load running.If rod carries out the transition in the no-load running just at the right time, obtain switching signal so.
If only identification is in the high point of the survey of predesignating above the voltage boundary line, corresponding to the symbol direction identification depth measurement point that transmits, and survey high point and have the symbol direction opposite with transponder pulse (quick-short circuit), the limit state of material just is regarded as identification.In this case, material has＞10 DK-value.If discern two in short-term apart from each other and have a depth measurement point with transponder pulse same-sign direction, and the voltage difference of measuring between two depth measurement points surpasses the boundary line of predesignating, or corresponding to two high points of survey of exomonental symbol direction identification, identification has the limit state of DK-value material between 5 to 10 so, equally.
If identification has and the depth measurement point of transponder pulse same-sign direction and having and the high point of the survey of transponder pulse contrary sign direction subsequently, or corresponding to the high point of exomonental symbol direction identification survey, they are almost adjacent one another are in short-term and form thus surely-turning point, and the voltage difference of measuring between depth measurement point and the high point of survey surpasses the boundary line of predesignating, and discerns the limit state of material equally.Standard-the turning point of coffee curve is here determined according to minimum value and the maximal value of Fig. 3 by two limit points almost adjacent one another are in short-term.
If material has the high-k of 10 above DK-values, the feature of high point only appears surveying in identification, and it is higher than the voltage boundary line of predesignating and has the symbol direction opposite with transponder pulse (short circuit fast).
If material has the medium specific inductive capacity of 5 to 10DK-values, the feature of two depth measurement points appears in identification, they are at apart from each other in short-term and have identical symbol direction as transponder pulse, and wherein, the voltage difference of measurement is above the boundary line of predesignating between two depth measurement points.
If material had＜low-k of 5DK-value, identification occurs having with transponder pulse same-sign direction depth measurement point and has the feature of surveying high point with transponder pulse contrary sign direction subsequently, they are almost adjacent and constitute standard-turning point thus in short-term, wherein, the voltage difference of measuring between depth measurement point and the high point of survey surpasses the boundary line of predesignating.
Two depth measurement points of the apart from each other in short-term of reflected signal have for example distance in short-term between 3 to 10msec.In contrast, the depth measurement point of surveying high point subsequently of reflected signal in the material that has low DK-value between the 1.5-5, has typical only 0.1 to 3msec distance in short-term.
Ultimate principle according to the TDR-sensor, the signal that the time base that obtains from reflected signal is expanded can repeatedly carry out analog-to-digital conversion and evaluation in one-period, wherein, measure most values and therefrom produce voltage-mean value, survey the high datum line of putting as starting point that is used for scanning window release time and evaluation, baseline, whether the value of the signal that base is expanded when determining has in view of the above surpassed the value of predesignating below the datum line, determine the start time point of reflection thus, after this in other cycles from the start time point of this mensuration, base spread signal when utilizing the high-repetition-rate that scans to measure, and whether contain in the when inquiry base spread signal and survey high point, second depth measurement point or standard-turning point.
Be the determination limit material level, preferably use two counters, and a counter is used for " identification ", a counter is used for " nonrecognition ", wherein, for example uses the evaluation algorithm according to the FB(flow block) of Fig. 5.The detection of state " covering " or " not covering " preferably for example by the FIR-filter filtering, is just sent then.Rechecking frequency for example can improve for increasing anti-interfering purpose.
The diagram xsect of the lead-in wire of process shown in Fig. 4.The process lead-in wire for example is on the head tank, for going between 11 with metal threaded cylindrical process, support 8,9 and the rod 3,4 that is made of insulating material arranged in the inside of process lead-in wire, respectively introduce the lead 6,7 of coaxial cable 5 on their end, they are transit time leads.The wave impedance of coaxial cable can be mated with the wave impedance of circuit, yet it does not mate with the wave impedance of process lead-in wire, to such an extent as to form sudden change between wave impedance, and on the process lead-in wire, also forming desired reflection thus, its effect is to determine that clearly reflected signal begins.The wave impedance of coaxial cable and circuit for example can be between 65Ohm and the 85Ohm, is preferably 75Ohm.
Electrically insulating material 8 can be a teflon sheet 8, and wherein, the end of rod 3,4 passes additional PEEK (poly-ethyl ketone) sheet 9, and it is placed on the teflon sheet.Cylindrical process lead-in wire 1 has the height s of about 4cm.Rod 3,4 is symmetricly set on the inside of right cylinder 1, passes teflon-right cylinder 1. Rod 3,4 has between 2 to 15cm best 5 to 7cm free excellent length.
The process lead-in wire also can be cylindrical process lead-in wire, only is made of a kind of electrically insulating material, and as the thermoplastics teflon (PTFE) or PEEK (poly-ethyl ketone) formation of part crystal, the process that rod is in same material goes between inner.Here, the wave impedance of process lead-in wire or is not exclusively mated with the wave impedance of transit time lead or coaxial cable.
The advantage that has according to domain reflectometer of the present invention is, particularly because the rod of two parallel distributions, realize the good reflectivity of reflected impulse thus, reflected impulse has and transponder pulse enough separating in time by the transit time lead, to such an extent as to reflection characteristic, be the curve shape that reflected signal produces, can obtain good evaluation.In another enforcement of domain reflectometer changed, rod adopted teflon or ceramic coat, and wherein, when using teflon, the teflon bed thickness is preferably between the 0.1mm to 1mm.In another embodiment of the present invention, the spacing (d) of rod be between the 10mm to 30mm, and the height (s) that goes between as process also can be between 2cm and the 5cm.
Fig. 6 a-d illustrates each echo curve that has for the employed ultimate value of its evaluation.Fig. 6 a illustrates no-load running-echo curve.If the reflected signal of time scan window interior has following characteristic: only have a depth measurement point TP, it is in below first boundary line (boundary line 1) of predesignating, promptly is identified as no-load running, does not have to cover.Boundary line 1 is measured from baseline and the biasing predesignated.
Fig. 6 b illustrates the echo curve of Pril.If the reflected signal of time scan window interior has following characteristic: exist one to survey high some HP, it be in second boundary line (boundary line 2) of predesignating above, promptly discern first kind of covering state thus.Boundary line 2 is measured from baseline and the biasing predesignated.
Fig. 6 c illustrates the echo curve of honey.If the reflected signal of time scan window interior has following characteristic:
-there are two depth measurement point TP1, TP2, they have the direction identical with transponder pulse.
-the second depth measurement point TP2 with the quantity Δ s that predesignates be in depth measurement point TP1 below.
Promptly discern second kind of covering state thus.
Fig. 6 d illustrates the echo curve of coffee.If the reflected signal of time scan window interior has following characteristic:
-only there is a depth measurement point TP, it is in below first boundary line (boundary line 1) of predesignating.Boundary line 1 is measured from baseline and the biasing predesignated.
-between the start time point of time scan window and depth measurement point TP, there is turning point, it is in local depth measurement point LTP and local the survey between the high some LHP.Local depth measurement point LTP and the local height point of surveying surpass the minor increment of predesignating in this case.
Promptly discern the third covering state thus.
The following in this regard mensuration of the start time point of time scan window:
Baseline in the-mensuration II section.
-be lower than baseline in the III section with the quantity of predesignating.
The start time point of time scan window generally can be all the time by reflection identification, and the transit time lead is gone up owing to different wave impedance produces reflection with the coupling of process lead-in wire.The advantage brought of the start time point of Ce Dinging is in this manner, and the time base spreading coefficient of circuit 14 only need have precision approximately ± 10% to ± 20%, to such an extent as to circuit 14 can expense seldom be realized.
Claims (21)
1. method that is used to measure the limit state of the material (11) that has the known dielectric constant, use support (1) to go between as process, a contact rod (3 that has an end wherein is set at least, 4), its other end immerses when reaching capacity material level in the material (11) that will monitor, wherein, be in the rod (3 in the support (1), 4) end is by electric wire (5,13) be connected with the circuit (14) that produces the high-frequency emission pulse, circuit has echo amplifier (15) for receiving echo, wherein, the high-frequency emission pulse is as the microwave that is guided, according to the otdr measurement method, TDR-mensuration principle, by lead (5,12) be sent to rod (3,4) on, wherein, the signal that reflects in air on material (11) critical layer is led Huis twt amplifier (15) and is used for evaluation, base expansion during reflected signal, and be divided into three zones continuous in time, be transponder pulse (I section), transit time (II section) and time scan window (III section), wherein, the moving together time point of time scan window begins, and has following feature:
A) to measure under two kinds of running statuses of material (11), promptly cover, short circuit or quick short circuit, and do not have covering, during no-load running, the reflected signal on rod-medium or rod-air critical layer produces by the variation of wave impedance, this variation is present on rod-medium or the rod-air critical layer
The curve shape of the time base spread reflection signal of b) receiving on the echo amplifier (15) is used for determining limit state, wherein, inside at the time scan window, at least three of reflected signal significant points are carried out numeral or by means of curve practice evaluation, and measure reference voltage the curvilinear motion during at least one II section, wherein
C) do not have covering, no-load running can be discerned thus, and the reflected signal of time scan window interior has following characteristic:
Only have a depth measurement point (TP), it is in below first boundary line of predesignating, and the boundary line comes by biasing and reference voltage difference,
D) first kind of covering state can be discerned thus, and the reflected signal of time scan window interior has following characteristic:
Exist one to survey high point (HP), it be in second boundary line predesignating above, wherein, this second boundary line measured from reference voltage and biasing equally,
E) second kind of different covering state can be discerned thus, and the reflected signal of time scan window interior has following characteristic:
Exist two depth measurement points (TP1, TP2),
Last second depth measurement point of time (TP2) with the quantity of predesignating be in first depth measurement point (TP1) below,
F) the third different covering state can be discerned thus, and the reflected signal of time scan window interior has following characteristic:
Have a depth measurement point (TP), it is in below first boundary line of predesignating, and the boundary line comes by biasing and reference voltage difference,
Between the start time point of time scan window and depth measurement point (TP), a turning point is arranged, it is in local a survey between a high point (LHP) and the local depth measurement point (LTP), wherein, local depth measurement point (LTP) and the local high point (LHP) of surveying surpass the minor increment of predesignating.
2. by the described method of claim 1, it is characterized in that the start time point of time scan window determines that thus promptly reflected signal departs from reference value with the value of predesignating.
3. by claim 1 or 2 described methods, it is characterized in that, use two rods (3 that are set in parallel in the support (1), 4), wherein, use coaxial cable (5 as lead, 13), its selectable length is used for predesignating the transit time between transponder pulse that prolongs forward and the reflected signal that returns, and therefore is used for its detectability in short-term, wherein, have a rod (3, the inner wire of coaxial cable 4) (5,13) and another rod (3,4) are connected with the ground connection of circuit (14) by outer conductor or electric capacity is connected with ground connection.
4. by the described method of claim 1, it is characterized in that, when material has the high-k of DK-value＞10, recognition feature is d), when material has 5 between 10 during the medium specific inductive capacity of DK-value, recognition feature is e), when material had the low-k of DK-value＜5, recognition feature was f).
5. by the described method of claim 2, it is characterized in that,
Determine a baseline-most curvilinear motions during the II section as reference voltage,
The start time point of-time scan window determines thus, promptly reflected signal with the value of predesignating depart from baseline and
-be determined at the time basic signal of expanding that the time scan window interior obtains from reflected signal, whether have the high point of survey, first depth measurement point, second depth measurement point or local depth measurement point and local survey height point and turning point.
6. by one of aforementioned claim described method, it is characterized in that, be the determination limit material level, perhaps use wave filter, for example the FIR-wave filter perhaps uses two counters, and a counter is used for " covering identification ", a counter is used for " not having the identification of covering ", and identification is in view of the above sent on one of counter.
7. by one of aforementioned claim described method, it is characterized in that, maximum six significant points (TP, TP1, TP2, HP, LTP, LHP) evaluations of curve shape.
8. domain reflectometer, use as the ultimate value switch, be used for measuring the limit state that has known dielectric constant material (11), use support (1) as process lead-in wire (1,12), a contact rod (3 that has an end wherein is set at least, 4), its other end immerses when reaching capacity material level in the material (11) that will monitor, wherein, be in the rod (3 in the support (1), 4) end is by electric wire (5,13) be connected with the circuit (14) that produces the high-frequency emission pulse, circuit is for receiving reflected signal, echo, has echo amplifier (15), wherein, the high-frequency emission pulse is as the microwave that is guided, according to the otdr measurement method, TDR-mensuration principle, can be sent on the rod (3,4) by lead (5,13), and the signal that reflects in air on the material critical layer is led back and time base expansion is advanced echo amplifier (15) and is used for evaluation, wherein, rod (3,4) and process lead-in wire (1,12) wave impedance is selected like this, make in evaluation, to be divided into three zones continuous in time i.e. transponder pulse (I section), transit time (II section) and time scan window (III section), the curve shape of the reflected signal that wherein, time scan window interior is measured is used for determining limit state.
9. by the described domain reflectometer of claim 8, it is characterized in that, maximum six significant points (TP, TP1, TP2, HP, LTP, LHP) evaluations of curve shape.
10. by the described domain reflectometer of claim 8, it is characterized in that, two parallel rods (3 are set in support (1), 4), lead is a coaxial cable (5,13), its selectable length is used for predesignating the transit time between transponder pulse that prolongs forward and the reflected signal that returns, therefore and be used for its distinguishability by circuit (14), therefore and be transit time lead on the process lead-in wire (1,12), wherein, the inner wire that has the coaxial cable (5,13) of a rod is connected by the ground connection of outer conductor with circuit (14) with another rod.
11., it is characterized in that the wave impedance of coaxial cable (5,13) is selected not match with the wave impedance of process lead-in wire (1,12) by the described domain reflectometer of claim 10.
12., it is characterized in that process lead-in wire (1 by the described domain reflectometer of claim 8,12) for being with the tubular process lead-in wire (12) of external metallization screw thread, inside at the process lead-in wire has an insulator at least, as the insulating support of rod (3,4) and same rod.
13. by one of claim 8 to 12 described domain reflectometer, it is characterized in that, process lead-in wire (1,12) Nei Bu insulator is made up of the different materials that has different specific inductive capacity with layered mode, for example Peek and teflon, and be a layer dielectric therefore, wherein, these materials are the seal process lead-in wire on the one hand, has minimum thickness on the other hand, and it determines that for being formed for the time scan window starting time reflected signal of point is essential.
14., it is characterized in that process lead-in wire (1,12) is cylindrical by the described domain reflectometer of claim 12, by electrically insulating material, to form as teflon (PTFE) or PEEK, rod (3,4) is in wherein.
15., it is characterized in that rod (3,4) has coating by the described domain reflectometer of one of claim 12 to 14, teflon for example, pottery or PEEK wherein, are using under teflon or the PEEK situation, and coating thickness is preferably between the 0.1mm to 1mm.
16., it is characterized in that the length that rod stretches out is 2 to 15cm, between best 5 to 7cm by the described domain reflectometer of one of claim 12 to 15 from process lead-in wire (1,12).
17., it is characterized in that transit time lead (5) to the length that is connected on rod (3, the 4) end that is in the process lead-in wire (1,12), is at least 30cm from circuit (14) by one of claim 12 to 16 described domain reflectometer, preferably 30cm to 60cm.
18., it is characterized in that the spacing (d) of rod (3,4) is between 10mm and 30mm by one of claim 12 to 17 described domain reflectometer.
19., it is characterized in that the height of process lead-in wire (1,12) is between 2cm and 5cm by one of claim 12 to 18 described domain reflectometer.
20., it is characterized in that the process lead-in wire is airtight construction by one of claim 12 to 19 described domain reflectometer, preferably reach as high as the pressure of 30bar.
21. by one of claim 8 to 20 described domain reflectometer, it is characterized in that, the signal of reflection is by four-diode-sampling circuit scanning, and be transported to microprocessor (16) by echo amplifier (15) and by A/D-converter (24), microprocessor is to the signal evaluation of reflection, and result's " cover identification " or " not having the identification of covering " are sent to display unit (25) or convert switching signal to.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE20016962U DE20016962U1 (en) | 2000-09-27 | 2000-09-27 | Time-domain reflectometer for use as a limit switch to record the limit level of a good |
| DE20016962.9 | 2000-09-27 | ||
| DE10115150A DE10115150A1 (en) | 2000-09-27 | 2001-03-27 | Process for detecting the limit level of a good and device therefor |
| DE10115150.0 | 2001-03-27 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1466674A true CN1466674A (en) | 2004-01-07 |
| CN1250944C CN1250944C (en) | 2006-04-12 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN01816386.6A Expired - Fee Related CN1250944C (en) | 2000-09-27 | 2001-09-19 | Method for detecting the limit state of a material and device thereof |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP1322922A2 (en) |
| JP (1) | JP2004519661A (en) |
| CN (1) | CN1250944C (en) |
| AU (1) | AU2002218183A1 (en) |
| CA (1) | CA2423781C (en) |
| WO (1) | WO2002027349A2 (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013189124A1 (en) * | 2012-06-19 | 2013-12-27 | Guo Yunchang | Method of determining material-level curve in continuous-type passive nucleonic level gauge |
| CN105784064A (en) * | 2015-01-13 | 2016-07-20 | 克洛纳测量技术有限公司 | Device For Determining The Filling Level Of Medium |
| CN105841773A (en) * | 2015-02-03 | 2016-08-10 | Vega格里沙贝两合公司 | Limit level switch with integrated position sensor |
| CN107505027A (en) * | 2016-06-14 | 2017-12-22 | Vega格里沙贝两合公司 | Microwave reflection barrier |
| CN110073226A (en) * | 2016-11-11 | 2019-07-30 | 莱尼电缆有限公司 | For monitoring the method and measuring device of route |
| CN110160599A (en) * | 2018-02-14 | 2019-08-23 | Vega格里沙贝两合公司 | Level radar with attachment detector |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10360711A1 (en) | 2003-12-19 | 2005-07-14 | Endress + Hauser Gmbh + Co. Kg | Level measuring device and method for level measurement and monitoring |
| DE102005057053A1 (en) | 2005-11-30 | 2007-05-31 | Vega Grieshaber Kg | High frequency module for e.g. liquid level radar device, has tap for decoupling reference signal from transmission line, and delay unit arranged after tap for delaying transmission signal on its path to antenna or sensor |
| DE102007007024A1 (en) | 2007-02-08 | 2008-08-21 | KROHNE Meßtechnik GmbH & Co. KG | Use of a working according to the radar level gauge |
| GB0822283D0 (en) * | 2008-12-06 | 2009-01-14 | Mobrey Ltd | Improvements in or relating to level sensors |
| DE102014103212A1 (en) * | 2014-03-11 | 2015-09-17 | Sick Ag | Sensor and method for detecting an object located on a roller conveyor |
| DE102015100417A1 (en) * | 2015-01-13 | 2016-07-14 | Krohne Messtechnik Gmbh | Method for determining the level of a medium in a container |
| DE102015202448A1 (en) * | 2015-02-11 | 2016-08-11 | Vega Grieshaber Kg | Evaluation procedure for a TDR limit switch |
| DE102021201364A1 (en) * | 2021-02-12 | 2022-08-18 | Vega Grieshaber Kg | Measuring device with position sensor |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4407369C2 (en) * | 1994-03-05 | 1999-09-30 | Grieshaber Vega Kg | Method and circuit arrangement for measuring the transit time and their use |
| US5884231A (en) * | 1995-12-21 | 1999-03-16 | Endress & Hauser Gmbh & Co. | Processor apparatus and method for a process measurement signal |
| US6085589A (en) * | 1996-12-23 | 2000-07-11 | Venture Measurement Company Llc | Material level sensing system calibration |
| US5943908A (en) * | 1997-09-08 | 1999-08-31 | Teleflex Incorporated | Probe for sensing fluid level |
| EP1128169A1 (en) * | 1999-12-29 | 2001-08-29 | Endress + Hauser GmbH + Co. | Method and apparatus for determining a limit filling level of a product in a container |
-
2001
- 2001-09-19 AU AU2002218183A patent/AU2002218183A1/en not_active Abandoned
- 2001-09-19 CN CN01816386.6A patent/CN1250944C/en not_active Expired - Fee Related
- 2001-09-19 EP EP01985756A patent/EP1322922A2/en not_active Withdrawn
- 2001-09-19 JP JP2002530876A patent/JP2004519661A/en active Pending
- 2001-09-19 WO PCT/EP2001/010813 patent/WO2002027349A2/en active Application Filing
- 2001-09-19 CA CA002423781A patent/CA2423781C/en not_active Expired - Fee Related
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013189124A1 (en) * | 2012-06-19 | 2013-12-27 | Guo Yunchang | Method of determining material-level curve in continuous-type passive nucleonic level gauge |
| CN105784064A (en) * | 2015-01-13 | 2016-07-20 | 克洛纳测量技术有限公司 | Device For Determining The Filling Level Of Medium |
| CN105784064B (en) * | 2015-01-13 | 2020-10-09 | 克洛纳测量技术有限公司 | Device for determining the fill level of a medium |
| CN105841773A (en) * | 2015-02-03 | 2016-08-10 | Vega格里沙贝两合公司 | Limit level switch with integrated position sensor |
| CN105841773B (en) * | 2015-02-03 | 2020-05-22 | Vega格里沙贝两合公司 | Limit switch with integrated orientation sensor |
| CN107505027A (en) * | 2016-06-14 | 2017-12-22 | Vega格里沙贝两合公司 | Microwave reflection barrier |
| US10704948B2 (en) | 2016-06-14 | 2020-07-07 | Vega Grieshaber Kg | Reflection microwave barrier |
| CN110073226A (en) * | 2016-11-11 | 2019-07-30 | 莱尼电缆有限公司 | For monitoring the method and measuring device of route |
| US11041899B2 (en) | 2016-11-11 | 2021-06-22 | Leoni Kabel Gmbh | Method and measuring assembly for monitoring a line |
| CN110073226B (en) * | 2016-11-11 | 2022-02-01 | 莱尼电缆有限公司 | Method and measuring device for monitoring a line |
| CN110160599A (en) * | 2018-02-14 | 2019-08-23 | Vega格里沙贝两合公司 | Level radar with attachment detector |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2004519661A (en) | 2004-07-02 |
| CN1250944C (en) | 2006-04-12 |
| WO2002027349A2 (en) | 2002-04-04 |
| AU2002218183A1 (en) | 2002-04-08 |
| CA2423781A1 (en) | 2003-03-26 |
| CA2423781C (en) | 2009-02-24 |
| EP1322922A2 (en) | 2003-07-02 |
| WO2002027349A3 (en) | 2002-10-24 |
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