CN101526498A - Magnetic nondestructive detector with high signal-to-noise ratio - Google Patents
Magnetic nondestructive detector with high signal-to-noise ratio Download PDFInfo
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- CN101526498A CN101526498A CN200910081924A CN200910081924A CN101526498A CN 101526498 A CN101526498 A CN 101526498A CN 200910081924 A CN200910081924 A CN 200910081924A CN 200910081924 A CN200910081924 A CN 200910081924A CN 101526498 A CN101526498 A CN 101526498A
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Abstract
A magnetic nondestructive detector with high signal-to-noise ratio relates to the technical field of magnetic nondestructive detectors. The probe of the invention is placed with a permanent magnet for establishing static magnetic field and magnetizing the strong magnetic oxide in the checked tube. A magnetic field sensitive component is installed for detecting the stray magnetic field established by the oxide and converting the stray magnetic field to output voltage signal. A magnetic field sensitive component for noise reduction is installed. The magnetic field sensitive component is a linear Hall component with same magnetic field sensitivity same with the magnetic field sensitive component for detection. Two magnetic field sensitive components are parallely installed with a same polarity. The magnetic field sensitive component for detection is positioned at the side of tube wall next to the checked tube in the operating state of probe. The magnetic field sensitive component for noise reduction is positioned at the side far from the checked tube in the probe. The detection signal of probe is output by the output signals of the magnetic field sensitive component for detection and magnetic field sensitive component for noise reduction through a differential mode and is transmitted to the detection instrument. The magnetic nondestructive detection probe according to the invention has the advantages of low back noise signal and high signal-to-noise ratio, and is especially suitable for detecting the thick-wall tube with weaker detection signal.
Description
Technical field
The present invention relates to the magnetic nondestructive testing field, a kind of magnetic damage-free detection device of austenitic stainless steel tube inner oxide is provided, be used for Non-Destructive Testing Austenitic stainless steel pipe road inner oxide.The back of the body back noise signal of magnetic non-destructive control probe of the present invention is low, signal to noise ratio (S/N ratio) is high, is specially adapted to more weak posted sides pipeline of detection signal etc. is detected.
Background technology
Austenitic stainless steel pipe road in the boiler of power plant is inwall generation oxidation in operational process, can the thermal stress effect when reaching certain thickness and peel off, and be deposited under the pipeline near the elbow and influence the safe operation of boiler, need detect by the method for Non-Destructive Testing.
A kind of magnetic lossless detection method and pick-up unit have been provided among the ZL 03 1 09490.2.In this detection method, the steady magnetic field that permanent magnet in the detection probe is set up magnetizes oxide in the steel pipe outside, the stray magnetic field signal that the magnetic-field-sensitive element produces from pipeline external detection oxide, the existence of judging the pipeline inner oxide by means of this detection signal whether.The pick-up unit that is provided adopts linear hall element as the magnetic-field-sensitive element.This magnetic-field-sensitive element has formed noise at the bottom of a kind of back of the body of pick-up unit for the induced signal that detects back of the body magnetic field, the end in the pipeline surrounding environment, it is irrelevant with the oxide of being examined in the pipeline.The dimensional orientation variation that is embodied in pick-up unit causes the detection signal fluctuation, below it is called the dimensional orientation noise.Settling the probe of single magnetic-field-sensitive element, can reach generally speaking ± 0.6mV (do not pass through the original signal intensity of signal processing and amplifying, down with) for the corresponding this dimensional orientation noise that causes of terrestrial magnetic field self.Like this, in the pick-up unit of two magnetic pole modes, the separate space orientation of detection probe and reference probe changes the detection signal fluctuation maximum that may cause and can reach about 2mV.Consider the influence in the magnetic field in other sources again, perhaps in the terrestrial magnetic field, magnetize and make and carry on the back the reinforcement of magnetic field, the end that influence also can be bigger at a large amount of metallic conduits of boiler internal.
Magnetic damage-free detection device of the prior art, its detection signal reduces along with the increase of being examined pipeline wall thickness is index law.So when the wall thickness of pipeline increased, the intensity of detection signal can be reduced to the level of having only several mV.At this moment, existing pick-up unit signal to noise ratio (S/N ratio) is low excessively, meets difficulty during the ferromagnetic oxide that may exist in detecting posted sides pipeline.
In addition, it is the immediate cause that causes pipeline accident that the stainless steel pipes inner oxide peels off, and its root then is the oxidation that pipeline self takes place.Reality is verified, and existing magnetic lossless detection method and device can produce enough strong induced signal to the oxide that still adheres on the duct wall, and this detection signal of normal pipeline is not higher than 8mV usually, and mostly between 2～5mV.If utilize this signal to come the thickness situation of the oxide skin of adhering on the quantitative analysis pipeline, thereby the oxidation situation for pipeline is assessed, also must remove of the interference of factor such as terrestrial magnetic field, eliminate the dimensional orientation noise of pick-up unit, improve signal to noise ratio (S/N ratio) for the output signal of pick-up unit.
Summary of the invention
Target of the present invention provides a kind of magnetic damage-free detection device of high s/n ratio, eliminate the dimensional orientation noise of probe detection signal, thereby can realize that the thin oxide layer that Austenitic stainless steel pipe road inner oxide and inner-walls of duct for thick tube wall still adhere to accurately detects.
Magnetic damage-free detection device of the present invention comprises probe and measuring instrument, be mounted with in the probe that permanent magnet is set up steady magnetic field, magnetization is subjected to ferromagnetic oxide in the inspection pipe, be mounted with the stray magnetic field of magnetic-field-sensitive element testing oxide foundation and be translated into output voltage signal, the output voltage signal of probe flows to measuring instrument by the lead connection.Wherein, be mounted with noise reduction magnetic-field-sensitive element 4 in probe 1, magnetic-field-sensitive element 4 is the linear hall element with same magnetic field sensitivity with detecting with magnetic-field-sensitive element 3, both same polarity ground arranged parallel; Detection is positioned at tube wall one side of pressing close to be examined pipe 7 under probe 1 duty with magnetic-field-sensitive element 3, and noise reduction is in the probe 1 away from being subjected to inspection to manage 7 one sides with magnetic-field-sensitive element 4; Export pop one's head in 1 detection signal with the output signal of magnetic-field-sensitive element 4 by differential mode by detecting, be transported to measuring instrument with magnetic-field-sensitive element 3 and noise reduction.
In a kind of composition structure of the present invention, when described probe 1 adopts two magnetic pole mode, for noise reduction with balance permanent magnet of magnetic-field-sensitive element 4 configurations, as strip permanent magnet 5.By regulating this bar permanent magnet 5 and the relative position of noise reduction with magnetic-field-sensitive element 4, signal at the bottom of 1 the back of the body of reducing to pop one's head in preferably makes back of the body end signal be reduced to zero.The strip permanent magnet 5 of described configuration provides a balance magnetic field for noise reduction with magnetic-field-sensitive element 4, when this balance magnetic field component that permanent magnet 2 makes progress the detection side who detects with magnetic-field-sensitive element 3 in component that noise reduction makes progress with the detection side of magnetic-field-sensitive element 4 and probe 1 is identical, can eliminate the influence of the basic output signal of Hall element, make probe 1 the back of the body at the bottom of signal be reduced to zero.Thus, noise reduction has also possessed the compensate function of the coupling probe of being made up of detection probe and reference probe in the prior art simultaneously with the strip permanent magnet 5 of magnetic-field-sensitive element 4 and configuration, thereby makes pick-up unit need not to equip in addition the reference probe.
In another kind of the composition in the structure of the present invention, when described probe 1 adopts single magnetic pole mode, detection by adjusting the same polarity arranged parallel with magnetic-field-sensitive first 3 and noise reduction with near the position of magnetic-field-sensitive element 4 two magnetic poles of the strip permanent magnet 6 of setting up steady magnetic field, the signal at the bottom of 1 the back of the body that reduces to pop one's head in preferably makes back of the body end signal be reduced to zero.Here, be used for being carried out magnetized strip-shaped permanent-magnet body 6 to examining the oxide 8 that may exist in the pipe 7, the balance permanent magnet that has had both special configuration in the top described composition structure provides the function in balance magnetic field, thereby makes probe 1 structure simpler.
The invention has the advantages that:
(1) pick-up unit of the present invention, be parallel to detection noise reduction magnetic-field-sensitive element of magnetic-field-sensitive component positioning by same polarity ground in the probe, the probe detection signal, differential output by them forms, wherein no longer change and change along with the dimensional orientation of popping one's head in, overcome terrestrial magnetic field and other sources, on the locus, change the influence in magnetic field more slowly, eliminated a main back of the body end noise in the detection signal, increase substantially signal to noise ratio (S/N ratio), improved the reliability that detects under the more weak situation of detection signal.
(2) in the pick-up unit of the present invention, by in the probe of two magnetic pole mode of magnetizations, being noise reduction magnetic-field-sensitive arrangements of components balance permanent magnet, perhaps utilize the strip permanent magnet self of setting up steady magnetic field in the probe of single magnetic pole mode of magnetization, make detect with and the magnetic-field component balance that makes progress their detection side with the magnetic-field-sensitive element of noise reduction, thereby signal at the bottom of the back of the body that has reduced to pop one's head in, even the basic output signal that makes probe reaches zero, possessed the function of eliminating back of the body end signal simultaneously.Like this, pick-up unit of the present invention is than the not only not extra component units that increases of one type of prior art syringe, in the pick-up unit that uses two magnetic pole modes to pop one's head in, self and detection probe profile of the prior art, the size of popping one's head in is all very approaching, keep its compactness, light and handy characteristics, and need not to dispose again the reference probe in the pick-up unit.
(3) utilize pick-up unit of the present invention, can accurately detect the accumulation of thick tube wall Austenitic stainless steel pipe road inner oxide and the carrying out that still is attached to the thin oxide layer on the tube wall.
In addition, pick-up unit of the present invention, not only can be used for the magnetic inner oxide in the Austenitic stainless steel pipe road is detected, also can detect the magnetic foreign body in other source, it also is applicable to carries out Non-Destructive Testing to any magnetisable material in the no magnetic condenser, be particularly useful for surveying be in the not very big container of those wall thickness comparison near on the inner wall position, under not really strong magnetic field, will be magnetized and whether show than the existence of the material of the higher magnetization.
Description of drawings
The theory structure synoptic diagram of of the prior art pair of magnetic pole mode of Fig. 1 detection probe.Wherein, 1 is detection probe, and 2 for setting up the U-shaped permanent magnet of steady magnetic field, and 3 are detection magnetic-field-sensitive element.(Comparative Examples)
When Fig. 2 detection probe shown in Figure 1 rotates a circle in the surface level of Beijing area, the variation of output signals curve of pick-up unit.(Comparative Examples)
In Fig. 3 pick-up unit of the present invention, has a kind of theory structure synoptic diagram of forming frame mode that two magnetic pole modes of decrease of noise functions are popped one's head in.Wherein, 1 is probe, and 2 for setting up the U-shaped permanent magnet of steady magnetic field, and 3 is to detect to use the magnetic-field-sensitive element, and 4 are noise reduction magnetic-field-sensitive element, and 5 is the strip permanent magnet of magnetic-field-sensitive element 4 configurations.The output signal of probe 1 is the differential output signal of two magnetic-field-sensitive elements 3 and 4.Give the oxide 8 of being examined pipe 7 and wherein may existing among the figure, the working position of probe when pick-up unit work is described.
Fig. 4 uses the pick-up unit embodiment of the present invention of probe shown in Figure 3, and its detection signal is along with rotate a circle in surface level change curve in the process of probe 1.
In Fig. 5 pick-up unit of the present invention, has a kind of theory structure synoptic diagram of forming frame mode that single magnetic pole mode of decrease of noise functions is popped one's head in.Wherein, 6 is permanent magnet, and it sets up steady magnetic field, and provides balance magnetic field with magnetic-field-sensitive element 3 and noise reduction with magnetic-field-sensitive element 4 for detecting simultaneously.
Embodiment
Below embodiment by pick-up unit the present invention is further specified.Working condition when as a comparison, an embodiment who has provided the pick-up unit of prior art detects.
Of the prior art pair of magnetic pole type detection probe 1 shown in Figure 1, the magnetic field on detection usefulness magnetic-field-sensitive element 3 its present position of detection wherein is along its detection side's upward component.Owing to be fixed in the detection probe 1, the magnetic-field component direction that detects with magnetic-field-sensitive element 3 detected can change along with the direction of detection probe 1 and change.When detection probe 1 rotated a circle in surface level, magnetic-field-sensitive element 3 wherein also rotated a circle synchronously around the vertical line direction.
As shown in Figure 2, the detection probe 1 of pick-up unit is in the process that rotates a circle in surface level, and the probe of the reference in the maintenance pick-up unit is motionless, the detection signal of pick-up unit is along with angle θ roughly presents sinusoidal variation, and the difference between maximal value max and the minimum value min, just the amplitude of variation of detection signal is 1.2mV.Therefore, the pick-up unit detection signal of prior art has the dimensional orientation noise along with the dimensional orientation of detection probe 1 changes and changes.The direction in space noise of this detection signal maintains static in detection probe 1, thereby mobile measuring instrument also can show when changing the dimensional orientation of reference probe.
Shown in Figure 2 is that detection probe 1 among Fig. 1 is for the change curve of the terrestrial magnetic field response signal of Beijing area.The intensity of terrestrial magnetic field is approximately 0.6Oe, and the detection that pick-up unit adopts is approximately 1.3mV/Oe with the sensitivity of magnetic-field-sensitive element 3.In the present embodiment, when detection probe 1 is rotated in surface level, the detection signal correspondence be the terrestrial magnetic field in surface level 360 the degree all directions on component.So the terrestrial magnetic field changes according to sine relation at the component that the detection side who detects with magnetic-field-sensitive element 3 makes progress, and maximal phase is terrestrial magnetic field peaked 2 times of component in the horizontal direction to variation, is approximately 0.8Oe.Can confirm that thus the terrestrial magnetic field is exactly the source of the dimensional orientation noise of pick-up unit shown in Figure 2.
In the on-the-spot testing process of boiler, detection probe 1 is subjected on inspection pipe 7 outer walls in order to be close to all the time, and its space bit is to the needs randomly changing; The reference probe that is placed in the measuring instrument also can the random variation dimensional orientation, cause thus wherein detection with the detection side of magnetic-field-sensitive element 3 to random variation almost, comprise the reverses its direction of 180 degree.This just makes the output signal of each Hall element produce fluctuation, thus the fluctuation back of the body end that causes the detection signal of pick-up unit to have the dimensional orientation sensitivity.Terrestrial magnetic field self can reach the magnitude of 1mV respectively for the influence of the output signal in detection probe 1 and reference magnetic field.Like this, in the pick-up unit of two magnetic pole modes, detection probe 1 separates, changes independently dimensional orientation separately fully with the reference probe, the detection signal of pick-up unit---just from the differential output signal of the Hall element in these two probes, only the influence of terrestrial magnetic field just may produce the fluctuation that is about 2mV to the maximum on same position.Consider the influence in the magnetic field in other sources again, perhaps be subjected to the influence of a large amount of metallic conduits at boiler internal, the terrestrial magnetic field may cause the metal magnetization and be strengthened, and influence also can be bigger.
Because each boiler internal activity space is narrow relatively, it is unpractical wanting to keep detection probe 1 direction of maintenance geographic orientation when work to immobilize; And the geographic orientation of each boiler, position difference, also there is the intensity difference in the terrestrial magnetic field.Like this, when the testing result of the different time of different pipelines in different boilers, the boiler and same pipe was compared, the influence of this terrestrial magnetic field and the background magnetic field relevant with it had randomness, just became noise at the bottom of the back of the body of detection signal.
Fig. 3 has provided in the pick-up unit of the present invention, the pop one's head in theory structure synoptic diagram of a kind of embodiment of 1 of the two magnetic pole modes with decrease of noise functions.Adopt identical numeric character mark with the element of identical function in the detection probe 1 of prior art shown in Figure 1, they can be settled according to the mode of two magnetic pole mode detection probe 1 in the prior art equally.
In the probe 1 of the present invention, with detection noise reduction of magnetic-field-sensitive element 3 same polarities ground arranged parallel magnetic-field-sensitive element 4.Detection is used and noise reduction all is linear with magnetic-field- sensitive element 3,4, and has identical magnetic field sensitivity.Two sheet Hall elements that magnetic-field- sensitive element 3,4 is vertical paper in the diagram, the magnetic-field component on their detections and self the sheet plane vertical direction.So, detect with noise reduction with the arranged parallel of magnetic-field- sensitive element 3,4 by their the sheet plane parallel or parallel realization of vertical direction on their sheet plane.The vertical direction on sheet Hall element sheet plane be exactly detect with and the detection side of noise reduction usefulness magnetic-field- sensitive element 3,4 to.Detect with and noise reduction with the installation position of magnetic-field- sensitive element 3,4, make probe 1 when detecting, detect the outer wall of pressing close to be examined pipeline 7 with magnetic-field-sensitive element 3, and noise reduction is tried one's best away from being examined pipeline 7 with magnetic-field-sensitive element 4.
In the pick-up unit of the present invention, same polarity ground arranged parallel to detect and is used and noise reduction magnetic-field- sensitive element 3,4 in the probe 1, their output voltage and linear proportional relations of magnetic field intensity of making progress of their common detection side separately, and the scale-up factor between the two is identical.Like this, the terrestrial magnetic field in the check point surrounding environment because along with the variation of position is very slow, detect with and noise reduction with magnetic-field- sensitive element 3 and 4 residing positions on variation very little, thereby to both output voltage influence much at one.Like this, cancel each other in the detection signal by the formed pick-up unit of they differential outputs, thereby eliminated the influence of terrestrial magnetic field 1 the detection signal of popping one's head in.The magnetic field that other magnetisable materials around the same principle, detection site produce, so long as along with the variation of locus changes lentamente, their influence can both be eliminated in pick-up unit of the present invention.With respect to these magnetic field that slowly changes along with the locus, by being examined the magnetic field that 8 magnetization of pipe 7 subscales produce, in near its pipeline outside, particularly tube wall the area of space,, the increase of the distance on the vertical tube wall direction decays rapidly along with being index law.So, as long as guarantee in the probe 1 detection with and noise reduction with magnetic-field- sensitive element 3,4 and examined and manage 7 tube wall vertical range and have bigger differently, just can guarantee that detection signal is enough strong.
Provided among Fig. 4 and adopted the present invention shown in Figure 3 to pop one's head in 1, the detection signal of pick-up unit is along with rotate a circle in surface level change curve in the process of probe 1.Here, the fluctuating range of detection signal is ± 0.1mV, is lower than the fluctuating range (Fig. 1 and 2) of the detection probe 1 of prior art very significantly, and this fluctuation presents randomness, no longer is sine-shaped Changing Pattern.This shows: probe 1 of the present invention has been eliminated the dimensional orientation noise effectively.Simultaneously, the remarkable reduction of the fluctuating range of detection signal makes the signal to noise ratio (S/N ratio) of pick-up unit of the present invention increase substantially, and can guarantee the reliability when detection signal is reduced to the magnitude of several mV even is lower than 1mV.
In the probe 1 of the present invention, for noise reduction has disposed a strip permanent magnet 5 as the balance permanent magnet with magnetic-field-sensitive element 4.Here, the strip permanent magnet 5 that is disposed provides a balance magnetic field for noise reduction with magnetic-field-sensitive element 4.By the relative position of suitable selection between the two, the component that this balance magnetic field is made progress with the detection side of magnetic-field-sensitive element 4 at noise reduction, the U-shaped permanent magnet 2 of setting up steady magnetic field in 1 with probe is near each other in the magnetic-field component that the detection side who detects with magnetic-field-sensitive element 3 makes progress, eliminate the influence of detection usefulness and noise reduction with the basic output signal of magnetic-field- sensitive element 3,4, signal at the bottom of 1 the back of the body reduces to pop one's head in, when these two magnetic-field components reach balance, can make that signal reaches zero at the bottom of this back of the body.Like this, noise reduction has also possessed the compensate function of the coupling probe of being made up of detection probe and reference probe in the prior art simultaneously with the strip permanent magnet 5 of magnetic-field-sensitive element 4 and configuration, thereby makes pick-up unit need not to equip in addition the reference probe.
Schematically provided the theory structure of a kind of embodiment that single magnetic pole mode of having decrease of noise functions among the present invention pops one's head among Fig. 5.In the probe 1 of single magnetic pole mode, in two contrary sign magnetic pole near zones setting up the strip permanent magnet 6 that steady magnetic field uses, detection usefulness magnetic-field-sensitive unit 3 and the noise reduction magnetic-field-sensitive element 4 settled respectively, their want the arrangement parallel to each other of same polarity ground, thereby possess the dimensional orientation noise that cause in magnetic field at the bottom of the back of the body of eliminating gradually changeables such as terrestrial magnetic field.Simultaneously, suitably regulate near " element to " position two magnetic poles of permanent magnet 6 that detection parallel to each other is formed with magnetic-field-sensitive element 4 with magnetic-field-sensitive first 3 and noise reduction, make permanent magnet 6 near each other in the magnetic-field component that their detection side makes progress, signal at the bottom of 1 the back of the body just can reduce to pop one's head in, when reaching balance fully, can make that signal is reduced to zero at the bottom of this back of the body.Here, be used for being carried out magnetized strip-shaped permanent-magnet body 6 to examining the oxides 8 that pipe may exist in 7, the function that balance magnetic field is provided of the balance permanent magnet of special configuration among the described embodiment above having had both, from but sonde configuration is simpler.
Pick-up unit of the present invention is not limited to the foregoing description.It is key of the present invention that probe possesses the dimensional orientation noise function that magnetic field produced at the bottom of the back of the body of eliminating testing environment in the detection signal.For this reason, can consider in two magnetic pole type probes, to adopt and set up U-shaped permanent magnet 2 equidimensions of steady magnetic field, the U-shaped permanent magnet of reverse opening, perhaps use the U-shaped permanent magnet of reduced size, perhaps the permanent magnet of other arbitrary shapes is as the balance permanent magnet, provide magnetic field to come balance detection with magnetic field magnetic-field-sensitive element 3 present positions on for noise reduction with magnetic-field-sensitive element 4 by them, eliminate back of the body end signal and make the basic output of probe reach zero; Also can in single magnetic pole type probe, adopt the strip permanent magnet of variable cross-section or the permanent magnet of other shape of cross sections, also can settle permanent magnet in addition even use other strong magnetic material to come to provide balance magnetic field with magnetic-field-sensitive element 4 as noise reduction, or the like.Similarly implement to become example and all belong to category of the present invention.
In addition, the detection signal numerical value that provides in the instructions of the present invention all is " original " numerical value that adopts commercial Hall element to obtain, and can correspondingly increase along with the numerical value change of the supply voltage of Hall element or reduce; The detection signal of probe then can be handled by electronic circuit.Therefore, the absolute figure size of detection signal can not be as the criterion that whether surmounts the scope of the invention.
Claims (3)
1, a kind of magnetic damage-free detection device of high s/n ratio, comprise probe and measuring instrument, being mounted with the permanent magnet of setting up steady magnetic field in the probe magnetizes and is subjected to ferromagnetic oxide in the inspection pipe, be mounted with the stray magnetic field of magnetic-field-sensitive element testing oxide foundation and be translated into output voltage signal, the output voltage signal of probe flows to measuring instrument by the lead connection, it is characterized in that, be mounted with noise reduction magnetic-field-sensitive element (4) in the probe (1), noise reduction is with magnetic-field-sensitive element (4) and detect the linear hall element that has same magnetic field sensitivity with magnetic-field-sensitive element (3), both same polarities ground arranged parallel; Detection is positioned at tube wall one side of pressing close to be subjected to inspection pipe (7) under probe (1) duty with magnetic-field-sensitive element (3), and noise reduction is in the probe (1) away from being subjected to inspection pipe (7) one sides with magnetic-field-sensitive element (4); Export the detection signal of probe (1) with the output signal of magnetic-field-sensitive element (4) by differential mode with magnetic-field-sensitive element (3) and noise reduction by detecting, be transported to measuring instrument.
2, the magnetic damage-free detection device of high s/n ratio as claimed in claim 1, it is characterized in that, in a kind of composition structure of the present invention, when described probe (1) adopts two magnetic pole mode, for noise reduction disposes a strip permanent magnet (5) with magnetic-field-sensitive element (4), by regulating strip permanent magnet (5) and the relative position of noise reduction with magnetic-field-sensitive element (4), reduce signal at the bottom of the back of the body of probe (1), make this back of the body at the bottom of signal be reduced to zero.
3, the magnetic damage-free detection device of high s/n ratio as claimed in claim 1, it is characterized in that, the another kind of composition in the structure of the present invention, when described probe (1) adopts single magnetic pole mode, use near the position of magnetic-field-sensitive element (4) two magnetic poles of the permanent magnet (6) of bar shaped by the detection of adjusting the same polarity arranged parallel with magnetic-field-sensitive unit (3) and noise reduction, reduce signal at the bottom of the back of the body of probe (1), make back of the body end signal be reduced to zero.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103760223A (en) * | 2014-02-19 | 2014-04-30 | 华中科技大学 | Internal and external flaw magnetic flux leakage detection distinguishing method and device based on superficial reversed field |
| CN104793151A (en) * | 2015-04-16 | 2015-07-22 | 三峡大学 | Magnetic-field measuring device and method for magnetic components |
| CN110749647A (en) * | 2019-10-21 | 2020-02-04 | 杭州西奥电梯有限公司 | Sheet metal part model checking method and system based on conveying line or electronic work order |
-
2009
- 2009-04-08 CN CN200910081924A patent/CN101526498A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103760223A (en) * | 2014-02-19 | 2014-04-30 | 华中科技大学 | Internal and external flaw magnetic flux leakage detection distinguishing method and device based on superficial reversed field |
| CN103760223B (en) * | 2014-02-19 | 2015-04-15 | 华中科技大学 | Internal and external flaw magnetic flux leakage detection distinguishing method and device based on superficial reversed field |
| CN104793151A (en) * | 2015-04-16 | 2015-07-22 | 三峡大学 | Magnetic-field measuring device and method for magnetic components |
| CN104793151B (en) * | 2015-04-16 | 2017-08-01 | 三峡大学 | The magnetic field measuring device and measuring method of a kind of magnetic element |
| CN110749647A (en) * | 2019-10-21 | 2020-02-04 | 杭州西奥电梯有限公司 | Sheet metal part model checking method and system based on conveying line or electronic work order |
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Open date: 20090909 |