CN105841645B - A kind of thickness measuring method based on electromagnetic acoustic - Google Patents
A kind of thickness measuring method based on electromagnetic acoustic Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
- G01B17/02—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring thickness
Abstract
The present invention relates to a kind of thickness measuring method based on electromagnetic acoustic, contrast and Conventional piezoelectric ultrasound, electromagnetic acoustic detection can realize non-contact detecting, adapt to certain lift-off, to coating, corrosion layer can realize detection, and electromagnetic acoustic detection can be very good to adapt to high temperature detection environment, avoid the waste of a large amount of couplants of coupling needs.The method of the present invention passes through a set of embedded digital acquisition system, AD samplings are carried out to digital signal by field programmable gate array, compress detection, correlation is average, transfer to central processing unit to carry out data correlation algorithm, average algorithm, peak value successively to digital waveform signal after caching and retain algorithm, automatic gain, determine current echo times, segment rf data extraction algorithm, zero crossing thickness measuring algorithm, obtain final thickness as a result, finally obtaining results of measuring.The method of the present invention Wave data relatively low to signal-to-noise ratio has carried out digital processing, has evaded the cumbersome of regulating gate, without being manually operated parameter, you can detection workpiece, not only can display real-time waveform, but also open-and-shut intuitively can observe Thickness sensitivity result.
Description
Technical field
This algorithm is based on electromagnetic acoustic and carries out Thickness sensitivity to steel pipe, steel plate, Conventional piezoelectric ultrasound is different from, for high temperature
State, the detection environment without couplant have good detection result.This algorithm core content is examined primarily directed to electromagnetic acoustic
The characteristic of survey time ripple is handled, and obtains undistorted, the good detection echo waveform of signal-to-noise ratio, so as to calculate thickness measuring result.
Background technology
At present, domestic market and technically conventional thickness measuring are to be come with piezoelectric supersonic excitation ultrasound ripple to steel pipe, steel plate
Deng progress Thickness sensitivity, this thickness measuring mode determines to must assure that during thickness measuring to be always maintained at well between probe and workpiece
Coupling, and pop one's head in incident angle cannot have big offset.And during on-line real-time measuremen, it has been found that to expire
This 2 conditions of foot, all have higher requirements the precision and stability of plant machinery device, and to the environment of surrounding (such as temperature
Degree) also it there are certain requirements.And the ripple mould that electromagnetic ultrasonic thickness measuring is used is a kind of shear wave of vertical incidence, this ultrasonic wave is in work
Produced inside part, so when the angle of probe changes a lot, the transmission of ripple is still to hang down along the wall thickness direction of workpiece
It is straight incident, do not interfere with the accuracy of testing result；It is not required couplant to couple between this detection mode probe and workpiece,
Therefore shake occurs in detection process and during lift-off for probe, will not produce detection error；Since Conventional piezoelectric ultrasound can not produce
The shear wave of vertical incidence, therefore what is taken is compressional wave thickness measuring mode, because transverse wave velocity is one times smaller than longitudinal wave velocity, so equal frequency
Accuracy of detection doubles than Conventional piezoelectric ultrasound under rate.
But the relatively ripe piezoelectric supersonic detection of electromagnetic acoustic detection contrast, has sensitivity relatively low, makes an uproar at random
Sound is relatively more, the inferior positions such as detection echo is relatively unstable, and the present invention is i.e. for this some inferior position extraction effective detection directly perceived
Echo, is calculated thickness measuring result.
The content of the invention
In order to effectively utilize the detection advantage of electromagnetic ultrasonic thickness measuring, and peak value shakiness in electromagnetic acoustic detection can be solved,
Random noise is higher, the relatively low technical difficulty of sensitivity, and object of the present invention is to provide one kind effectively to be surpassed based on electromagnetism
The thickness measuring method of sound, this method corresponds to the Center Scheme of horizontal level based on storage zero crossing, by the relatively low original ripple of to-noise ratio
Graphic data obtains accurate thickness measuring result after respective handling.
The technical solution adopted by the present invention is：
A kind of thickness measuring method based on electromagnetic acoustic, is established on the basis of a set of digital acquisition circuit system, numeral is adopted
Collector system includes：Electromagnetic ultrasonic probe, analog circuit, digital sampling circuitry, field programmable gate array, central processing
Device, USB communicating circuits, LED display, electromagnetic ultrasonic probe are connected by probe wire with analog circuit, analog circuit and numeral
Sample circuit is connected, and field programmable gate array is connected with analog circuit, digital sampling circuitry, central processing unit respectively, center
Processor is connected with USB communicating circuits, LCD display respectively；The analog circuit includes amplifying circuit and filter circuit；Its
It is characterized in that carrying out according to the following steps：
Analog circuit receives the faint alternation inductive signal that detects of electromagnetic ultrasonic probe after frequency-selecting is amplified, filtered,
Digital waveform signal is obtained via the analog-to-digital conversion of digital sampling circuitry；It is input to field programmable gate array, field-programmable
Gate array carries out data exchange with central processing unit by data/address bus, and digital waveform signal is carried out successively by central processing unit
Data correlation algorithm, average algorithm, peak value retain algorithm, and peak value retains algorithm and obtains the peak value of waveform, in order to obtain accurately
Measurement result, peak value must reach certain requirement, so increase wave amplitude feedback function, that is, automatic gain, automatic gain is basis
Peak value retains the peak computational value of feedback that algorithm obtains and acts on analog circuit, peak value is reached corresponding requirement, then carries out again
Determine current echo times, segment rf data extraction algorithm, zero crossing thickness measuring algorithm, obtain final thickness as a result, passing through USB
Communicating circuit downloads the thickness results of central processing unit and printing reports, passes through LCD display display waveform.
Thickness measuring flow and calculating concretely comprise the following steps：
(1) sound velocity calibration and zero bias calibration, the rf wave figurate number obtained according to digital sampling circuitry must be carried out before thickness measuring
After carrying out detection compression to radio frequency waveform data according to, field programmable gate array, according to peak value reservation method and determine to work as pre-echo
The peak level time location that effective echo is recorded without gate peaking of number, peak value, which retains, is denoted as T1, and T1 can compile for scene
The number count value of the corresponding rf data current AD sample of present peak value of journey gate array storage；
(2) via remembering velocity of sound V after reference block sound velocity calibration；Using 1.5mm before T1 as efficiently sampling initial position, in sound
In the case of known to fast, the leveled time position of the rf data first sampling point of required record zero point is tried to achieve, is denoted as T2；Similarly
The 1.5mm using after T1 is denoted as T3 as end position；
(3) sampled using T2 as Sampling starting point for original radio frequency Wave data, through field programmable gate array
Do streamlined average after sampling caching, the waveform averagely obtained transfers to central processing unit after being cached by field programmable gate array
Reason；It is respectively T4, T5 that central processing unit, which is recorded the corresponding horizontal level in this section of Wave data of positive and negative threshold value and corresponded to,；
Then required zero point position T6 corresponding in this section of rf data is (T4+T5)/2；
(4) T6 corresponds to the Sampling starting point of a bit of rf data rather than whole frame data, and required dead-center position pair
It should be T2+T6 in the position of whole frame data, be denoted as T7；
(5) time location of zero point needed for corresponding to is tried to achieve, but not can determine that this is the corresponding zero point of which echo；By
Peak value reservation method and the adjacent peak position T7 of peak value that corresponding T1 is tried to achieve without gate peaking for determining current echo times, according to
According to T1/ | T1-T7 | the corresponding N of T1 are tried to achieve, N is the corresponding echo times of T1；
(6) the number of samples count value that T7 refers to, it is known that AD sample frequencys are f, velocity of sound V, then thickness
D=(T6*V)/2fN, measurement accuracy 1/f.
The characteristics of this algorithm is to entangle waveform peak without using gate, without manually adjusting waveform position, velocity of sound school
Thickness measuring result can intuitively be obtained after standard after probe contacts workpiece in 2 seconds.
Brief description of the drawings
Fig. 1 is the circuit diagram of the present invention.
Fig. 2 is the FB(flow block) of the present invention.
Fig. 3 is the logic diagram of the data correlation algorithm of the present invention.
Fig. 4 is the average algorithm logic chart of the present invention.
Fig. 5 is to strive peak phenomenon schematic diagram.
Fig. 6 is to determine current echo times schematic diagram.
Fig. 7 is zero crossing thickness measuring algorithm schematic diagram.
Embodiment
As shown in Figure 1, 2, the present invention is established on the basis of a set of digital acquisition circuit system, digital acquisition circuit system
Including：Electromagnetic ultrasonic probe, analog circuit, digital sampling circuitry, field programmable gate array, central processing unit, USB communication electricity
Road, LED display, electromagnetic ultrasonic probe are connected by probe wire with analog circuit, and analog circuit is connected with digital sampling circuitry,
Field programmable gate array is connected with analog circuit, digital sampling circuitry, central processing unit respectively, central processing unit respectively with
USB communicating circuits, LCD display are connected；The analog circuit includes amplifying circuit and filter circuit；It is characterized in that by with
Lower step carries out：
Analog circuit receives the faint alternation inductive signal that detects of electromagnetic ultrasonic probe after frequency-selecting is amplified, filtered,
Digital waveform signal is obtained via the analog-to-digital conversion of digital sampling circuitry；It is input to field programmable gate array, field-programmable
Gate array carries out data exchange with central processing unit by data/address bus, and digital waveform signal is carried out successively by central processing unit
Data correlation algorithm, average algorithm, peak value retain algorithm, and peak value retains algorithm and obtains the peak value of waveform, in order to obtain accurately
Measurement result, peak value must reach certain requirement, so increase wave amplitude feedback function, that is, automatic gain, automatic gain is basis
Peak value retains the peak computational value of feedback that algorithm obtains and acts on analog circuit, peak value is reached corresponding requirement, then carries out again
Determine current echo times, segment rf data extraction algorithm, zero crossing thickness measuring algorithm, obtain final thickness as a result, passing through USB
Communicating circuit downloads the thickness results of central processing unit and printing reports, passes through LCD display display waveform.
1. data correlation algorithm.
If the digital waveform obtained after analog-to-digital conversion transfers to central processing unit real-time on liquid crystal display without any processing
It has been shown that, the random noise of digital waveform is very big, or even some moment have exceeded the height of effective detection echo, therefore can be to extraction
Useful signal causes erroneous effects.
The data correlation algorithm concretely comprises the following steps：To several frame data of Coutinuous store in same position corresponding number
Value carries out corresponding to comparison, extracts the minimum value after comparing on each position, and the new data of one frame of recomposition are shown as waveform
Master data；Since random noise is the irregular random sampling baseline value occurred and be higher than standard, so via data phase
After closing algorithm, most random noise can be all filtered out.
Fig. 3 is the logic diagram of data correlation algorithm, wherein two digit counters of T1-, M1, M2, and M3, M4- are 512 × 8Bit
Memory, C1, C2, C3-8 are less than comparator.
From the figure 3, it may be seen that front and rear 4 frame sampling data, are compared, finally obtain each adopt two-by-two in each clock sampling point
The minimum Wave data at hour during sample, the new minimum Wave data of one frame of composition, the master data shown as waveform.
2. average algorithm
Data after data correlation algorithm filter out most of random noise, but the stability of waveform and bad,
Peak Jitter obtains terribly, in order to lower the unstable calculating mistake brought of waveform as far as possible, it is also necessary to by the waveform number after correlation
It is streamlined average according to carrying out.
Average algorithm is streamlined average algorithm, is concretely comprised the following steps：First establish the buffer of average time, each frame data
Write each buffer from front to back successively, then to average after the data investigation in these buffers, and latched, such as Fig. 4.
Wherein tri- digit counters of T1-, M1, M2, M3, M4, M5, M6, M7, M8- are 512 × 8Bit memories, and A1-8 inputs 8 additions
Device.
As shown in Figure 4, field programmable gate array has embedded adder, and front and rear 8 frame sampling data are added and are latched, on
CPU is transmitted to, division is done by CPU, obtains 8 average values, then CPU carries out next step calculating again.
Streamlined average benefit is not interfere with repetition rate averagely, so the display to waveform, and the speed of algorithm, is
The fluency of system is all beneficial.After Wave data after average algorithm carries out after being stored by the hardware bottom layer of central processing unit
Continuous processing.
3. peak value reservation method
Particularly step is peak value reservation method：Peak value is found in any one frame Wave data, records the peak level
Position, centered on the peak level position, front and rear each extension 1.5mm, common 3mm is as sampling interval；Because scope is drawn
It can be seen that, the width of each echo is all without more than 3mm after stretching, so by the use of the 3mm comprising peak value as sampling interval, then zero point
Signal is certainly existed in the sampling interval.Previously mentioned, the waveform after detection, which occurs, strives peak phenomenon, can cause peak value sampling ripple
It is dynamic, it is fluctuated to see that Fig. 5, Ha and Hb occur, causes the corresponding horizontal level of peak value to switch among Aa and Ab, thus samples
Section is unstable, causes result inaccurate.Therefore after probe contacts workpiece, using first peak value of appearance as measuring point,
There is peak value in the section of the 3mm of each 1.5mm of measuring point or so all to ignore, occur peak value outside 3mm and just record, at this moment remember
The peak value of record is the peak value of next echo.
4. determine current echo times
Conventional calibrator is that the peak value that two neighboring echo is entangled with double-gate is believed to read the corresponding position of peak value
Breath, and the peak value reservation method that this algorithm is related to is also required to obtain the peak value of detection echo, in order to reduce the operating procedure of instrument, more
Fast, more intuitively thickness measuring is obtained as a result, special envoy has been used without gate algorithm.
Because the presence of starting ripple, is detected there may be certain blind area, first echo beyond blind area is as effective
Echo；Electromagnetic acoustic detection is without couplant, after being tested in different steel test blocks, it is found that blind area is basically unchanged, with blind area outside
Starting point a little is used as close to blind area, peak value is asked in Wave data behind；Terminating point following sampling terminal change and
Change, is analogous to gate, and simply gate starting point is constant, and terminating point is servo-actuated；Found after test experience by different test blocks,
Detecting might not be linearly gradually weak between echo and echo times, it is possible that phenomenon low after preceding height, therefore peak value
Not necessarily obtained on first echo.
After starting point determines, found in the Wave data of the foundation peak value reservation method described previously of central processing unit behind
Simultaneously stored waveform is highly denoted as H1 to peak value, and peak position is denoted as A1, has been re-used as with this peak position preceding 1.5mm or rear 1.5mm
Initial point, finds forward or backward the maximum point that first height is higher than H1/2 (6dB), is denoted as A2, the corresponding height of A2 is H2；Before
Text carried, due to striving peak phenomenon, so avoiding storing using front or rear each 1.5mm as starting point after finding first peak value same
Another peak value of one echo, causes result mistake；A2 is the echo-peak with adjacent A1, in order to ensure that A2 is adjacent with A1, and is
Effective echo, therefore determined in A1, when A2 is found using H1/2 as datum line, it is necessary to assure on the datum line higher than H1/2,
Wave data is first on the rise, after rising to fixed point A2, follows downward trend closely, and can drop to H2/2, it is ensured that this A2 is
The peak value of efficient neighbor echo, is shown in Fig. 6.And during A2 is sought, the priority searched forward with A1 peak values is more than with A1 peaks
The priority that value is searched backward, i.e., as found A2 forward, just no longer find, such as do not find A2 forward, then find backward backward.
After trying to achieve A1, A2, it not can determine that A1, A2 are which corresponding time echoes, since electromagnetic acoustic detection is not required to coupling
Mixture, therefore the zero bias calibration of waveform is only influenced by digital sample delay, without the influence of examined environment.Therefore can be by A1
And | A1-A2 | to determine A1 for which time echo.| A1-A2 | for the general thickness value of detection test block, only because strive peak without
Can be accurate, and the peak value that A1 is certain detection echo, A1-0 are about the corresponding detecting distance of this echo, with (A1-0)/|
A1-A2 | which time echo i.e. definite A1 corresponding is.
5. zero crossing thickness measuring algorithm
The thickness measuring method of conventional is to calculate the thickness of workpiece by the peak value of two effective echoes, is referred to as peak
It is worth thickness measuring method.And this application can see by display waveform, the waveform of same position has two close peaks after detection
Value, and peak constantly is being striven, see Fig. 5.Since if the unstable thickness measuring computational methods with routine of peak value can be to causing peak position pair
The error for answering horizontal level to record, influences final result of calculation.Therefore intend a kind of algorithm of new record zero point of sampling, it is referred to as
Zero crossing thickness measuring method.It can be seen that waveform morphology after from the point of view of any detection echo is amplified under radio frequency state, it can be seen that at certain
In a period of time, waveform is monotonic decreasing and must be the baseline that have passed through sampling, sees Fig. 7.When recording arbitrary neighborhood two
First such zero point in a detection echo, you can be analogous to peak value thickness measuring method to calculate thickness measuring result.Zero crossing thickness measuring pair
Than in the peak value thickness measuring method the advantages of：Peak value thickness measuring method wants peaking to have to stablize in horizontal level, and no it will cause mistake knot
Fruit, and there are 2 peak values after detection due to striving summit after positive and negative two peak detections in this application, in order to meet in any detection
Waveform under state can be carried out the calculating of thickness measuring result in showing, it is therefore apparent that zero crossing thickness measuring algorithm is surveyed better than peak value
Thick method.
6. segment rf data extraction algorithm
Although waveform after data correlation algorithm has filtered most random noise, it can be seen that some are needed
The detection echo sensitivity recorded is very low, substantially similar with baseline noise, signal and makes an uproar while improving gain
Sound is all improving at the same time.Due to can not differentiate effective waveform where, zero crossing thickness measuring algorithm will be impacted.By
During data acquisition, for the requirement to detection range and the limitation of system data amount, more than certain detection range
Wave data all got through overcompression, be original radio frequency signal has been carried out under current sampling frequency rule one
Fixed discrete sampling, so the Wave data that bottom software is used for handling cannot accurately position radio frequency waveform dead-center position institute
.Therefore, it based on Wave data is original radiofrequency signal that zero crossing thickness measuring, which is,.
The limitation of the data volume due to detection range and digital display circuit is previously mentioned, digital acquisition system can not collect whole
All original radio frequency signals in a detection range.But zero crossing thickness measuring method is built on the basis of original radio frequency signal again,
Therefore, can only be by extracting wherein one section of characteristic for including radiofrequency signal zero point, base to the Wave data after detection
In the reason for original signal random noise is higher, segment rf data extraction algorithm is exactly to need the radiofrequency signal collected again
By it is streamlined it is average after latch (see above-mentioned average algorithm), then this section of Wave data signal of latch is sampled again and
Record to obtain zero signal.
7. store and calculate zero point and correspond to horizontal level
One section of original radio frequency data after average have obtained, the symmetry based on waveform, and center line is sampled as base using AD
Standard, positive and negative all as a reference point with certain waveform height ratio, improving gain makes the peak value of waveform more than or equal to this ginseng
The height of examination point.In underlying algorithm, using the two positive and negative reference points as two threshold values, with the Wave data in threshold value
Monotonic decreasing extracts the time location of positive and negative two threshold values, the centre position of the two threshold values is as basis for estimation
Dead-center position.After dead-center position is found and store, for carrying out the THICKNESS CALCULATION (THICKNESS CALCULATION that specific formula for calculation sees below
Detailed step), see Fig. 7.
8. automatic gain
Since this algorithm is there are positive and negative reference value, Wave data, which must reach this benchmark, could effectively read zero point position
Put.Difference based on workpiece, the sensitivity of waveform is discrepant, differs surely reach positive and negative threshold value sometimes, in order to
Reduce operation, rapid and convenient, so being increased automatically to all data before programmable gate array stored waveform data at the scene
Benefit.Automatic gain refers to using peak height as basis for estimation, no matter current form data peaks where, all pass through hair
Code control, by controlling amplifier to carry out gain control, the reference point for being risen to or being down to setting (ensures the ginseng for DA conversions
The height of examination point is more than positive and negative threshold value), when the waveform peak shown on LCD highly reaches this setting reference value, automatically
Gain stops, and otherwise continues.This ensures that the requirement for asking for zero point can be reached, Fig. 7 is seen.
What is arranged above is some specific algorithm steps, hereafter with regard to whole thickness measuring flow and calculating process supplement step in detail
Suddenly：
Sound velocity calibration and zero bias calibration must be carried out before thickness measuring, caused by zero bias are due to whole digital acquisition system algorithm
System delay, since coupling factor is not present in electromagnetic ultrasonic thickness measuring, so zero bias are only related with the constant time lag of system, and due to
Zero crossing thickness measuring algorithm be based on zero point, so during zero bias also will with based on zero point come school zero bias.
(1) the radio frequency waveform data sampled according to hardware AD, field programmable gate array to radio frequency waveform data into
After row detection compression, the peak level time location of effective echo, peak value are recorded according to previously described no gate peaking method
Reservation is denoted as T1, and T1 is the number meter of the corresponding rf data current AD sample of present peak value of field programmable gate array storage
Numerical value；
(2) via remembering velocity of sound V after reference block sound velocity calibration；By described previously, risen by efficiently sampling of 1.5mm before T1
Beginning position, in the case of known to the velocity of sound, try to achieve needed for record zero point rf data first sampling point leveled time position,
It is denoted as T2；Similarly the 1.5mm using after T1 is denoted as T3 as end position；
(3) sampled using T2 as Sampling starting point for original radio frequency Wave data, through field programmable gate array
Do streamlined average after sampling caching, the waveform averagely obtained transfers to central processing unit after being cached by field programmable gate array
Reason；It is respectively T4, T5 that central processing unit, which is recorded the corresponding horizontal level in this section of Wave data of positive and negative threshold value and corresponded to,；
Then required zero point position T6 corresponding in this section of rf data is (T4+T5)/2；
(4) T6 corresponds to the Sampling starting point of a bit of rf data rather than whole frame data, and required dead-center position pair
It should be T2+T6 in the position of whole frame data, be denoted as T7；
(5) above-mentioned steps have tried to achieve the time location of zero point needed for correspondence, but not can determine which echo pair this is
The zero point answered；The adjacent peak position T7 of the peak value of corresponding T1 is tried to achieve as described in no gate peaking, according to T1/ | T1-T7 | ask
It is the corresponding echo times of T1 to obtain T1 corresponding N, N；
(6) the number of samples count value that T7 refers to, it is known that AD sample frequencys are f, velocity of sound V, then thickness d=(T6*V)/
2fN, measurement accuracy 1/f.
Claims (1)
1. a kind of thickness measuring method based on electromagnetic acoustic, is established on the basis of a set of digital acquisition circuit system, digital collection
Circuit system includes：Electromagnetic ultrasonic probe, analog circuit, digital sampling circuitry, field programmable gate array, central processing unit,
USB communicating circuits, LED display, electromagnetic ultrasonic probe are connected by probe wire with analog circuit, analog circuit and digital sample
Circuit is connected, and field programmable gate array is connected with analog circuit, digital sampling circuitry, central processing unit respectively, central processing
Device is connected with USB communicating circuits, LCD display respectively；The analog circuit includes amplifying circuit and filter circuit；Its feature
It is to carry out according to the following steps：
Analog circuit receives the faint alternation inductive signal that detects of electromagnetic ultrasonic probe after frequency-selecting is amplified, filtered, via
The analog-to-digital conversion of digital sampling circuitry obtains digital waveform signal；It is input to field programmable gate array, field-programmable gate array
Row carry out data exchange with central processing unit by data/address bus, and data are carried out successively to digital waveform signal by central processing unit
Related algorithm, average algorithm, peak value retain algorithm, and automatic gain is the peak computational value of feedback obtained according to peak value reservation algorithm
Analog circuit is acted on, peak value is reached corresponding requirement, is then determined current echo times, the extraction of segment rf data again
Algorithm, zero crossing thickness measuring algorithm, obtain final thickness as a result, downloading the thickness knot of central processing unit by USB communicating circuits
Fruit and printing reports, pass through LCD display display waveform；
Thickness measuring flow and calculating concretely comprise the following steps：
（1）Sound velocity calibration and zero bias calibration must be carried out before thickness measuring, the radio frequency waveform data obtained according to digital sampling circuitry are existing
After field programmable gate array carries out detection compression to radio frequency waveform data, according to peak value reservation method and current echo times are determined
No gate peaking records the peak level time location of effective echo, and peak value, which retains, is denoted as T1, and T1 is field-programmable gate array
Arrange the number count value of the corresponding rf data current AD sample of present peak value of storage；
（2）Via remembering velocity of sound V after reference block sound velocity calibration；Using 1.5mm before T1 as efficiently sampling initial position, in the velocity of sound
In the case of knowing, the leveled time position of the rf data first sampling point of required record zero point is tried to achieve, is denoted as T2；Similarly with T1
1.5mm is denoted as T3 as end position afterwards；
（3）Sampled using T2 as Sampling starting point for original radio frequency Wave data, sampled through field programmable gate array
Do streamlined average after caching, the waveform averagely obtained transfers to central processing unit to handle after being cached by field programmable gate array；
It is respectively T4, T5 that central processing unit, which is recorded the corresponding horizontal level in this section of Wave data of positive and negative threshold value and corresponded to,；Then
Required zero point position T6 corresponding in this section of rf data is（T4+T5）/2；
（4）T6 corresponds to the Sampling starting point of a bit of rf data rather than whole frame data, and required dead-center position corresponds to
The position of whole frame data is T2+T6, is denoted as T7；
（5）The time location of zero point needed for corresponding to is tried to achieve, but not can determine that this is the corresponding zero point of which echo；By peak value
Reservation method and the adjacent peak position T7 of peak value that corresponding T1 is tried to achieve without gate peaking for determining current echo times, foundation
T1/ | T1-T7 | the corresponding N of T1 are tried to achieve, N is the corresponding echo times of T1；
（6）The number of samples count value that T7 refers to, it is known that AD sample frequencys are f, velocity of sound V, then thickness
D=(T6 * V)/2fN, measurement accuracy 1/f.
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| CN111121678B (en) * | 2018-10-31 | 2021-06-01 | 中国石油天然气股份有限公司 | Pipeline wall thickness detection method and device |
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