A kind of pulse eddy current thicknessmeter
Technical field
The utility model relates to the Technology of Precision Measurement field, relates in particular to a kind of metal material pulse eddy current thicknessmeter.
Background technology
In many important commercial Application, usually run into the problem of metal material thickness measure.For example, nuclear reaction fuel-rod coating layer, the thickness of aircraft wing thickness and pressure vessels for the chemical industry etc.The fifties in last century, thickness measurement technique only was in conceptual phase, yet passed through the research and development of decades, and thickness measurement technique is extensively promoted and used.
At present, the traditional metal materials method for measuring thickness of domestic use all has its certain defective:
1, artificial kind of calliper is meant by the workman and finishes thickness measure with milscale is manual, though easy to use, easy to maintenance and cheap, it influences speed of production, and production efficiency is not high.
2, the mechanical type measurement is meant and adopts the method for Mechanical Contact formula to measure, though it is easy to use, measuring accuracy is higher, but under tested metal high-speed motion situation, Long contact time can cause the wearing and tearing of sensor between sensor and the tested metal, thereby influence measuring accuracy, also can scratch the metal surface when serious and reduce the quality of product.
3, the rays method measurement is meant by radiographic source and produces ray, when passing measured object, the ray of part by the metallic element in the material absorb be the portion of energy of ray by absorbed, the intensity of ray decays along with the variation in thickness that sees through material, utilizes this principle sheet material measurement thickness.Though the rays method response is fast, the precision height, X-ray ga(u)ging method and gamma-rays thickness measuring method all have the danger and the operating voltage height of radiation, exist serious radiographic source protection question, complicated operation costs an arm and a leg, and the while very easily damages operating personnel's health.
4, electric vortex method is measured.Traditional current vortex detection technique is to adopt single sinusoidal frequency drive coil, detects for thickness mainly to be divided into two kinds:
1), the distance between holding coil and the measured material is constant, use the low frequency signal drive coil, in coil, produce alternating magnetic field, in alternating magnetic field, the eddy current of the metal inside of different-thickness has different hindrance functions to coil, by impedance plane diagram, amplitude and the phase place of directly analyzing impedance (and voltage) detect metal thickness.What this method received is the changes in amplitude of impedance, so material thickness becomes nonlinear relationship with the receiving coil impedance, needs gamma correction, and this will certainly cause the error of measurement.
2), place coil respectively, fix the position of two coils, use high-frequency signal to encourage two lateral coils respectively,, finally measure the thickness of tested metal by measuring the distance between coil and the metal surface in the metal both sides.Making and measuring the variable in distance and the impedance variation of coming in this way is nonlinear relationship, carry out gamma correction and can produce error, what secondly measure employing is as excitation frequency with high frequency, be vulnerable to The noise, therefore the precision of influence measurement, and the result who measures also can be subjected to the influence of variation of ambient temperature generation drift.
The utility model content
It is not high in order to overcome in the existing metal material thickness measurement technology measuring accuracy that the purpose of this utility model is exactly, measuring method some shortcomings dangerous, not aspect such as science and a kind of reliable in quality is provided, stable, measuring accuracy height, the pulse eddy current thicknessmeter that measurement range is wide.
The purpose of this utility model can be achieved through the following technical solutions: a kind of pulse eddy current thicknessmeter, comprise the MCU main control module, the button display module, the digital regulation resistance module, power amplifier module, drive coil, detecting element, the instrument amplifier module, AD modular converter and power module, it is characterized in that: described button display module connects the MCU main control module of the square-wave pulse pumping signal that can produce frequency and EDM Generator of Adjustable Duty Ratio, described MCU main control module, the digital regulation resistance module, power amplifier module links to each other successively with drive coil, described detecting element, the instrument amplifier module, the AD modular converter also links to each other successively with the MCU main control module, and described power module provides the working power of each module.
Described MCU main control module comprises single-chip minimum system circuit, serial communication circuit, and described single-chip microcomputer adopts chip U1, and its model is the mixed-signal processor MSP430F413 of 16 super low-power consumptions of TI company release; Described button display module adopts the LCD12864 LCD MODULE circuit of independent button keyboard circuit and Changsha sun people company; Described digital regulation resistance module adopts chip U2, the 256 node 10k Ω digital regulation resistance MAX5402 that its model is produced for Maxim company; Described power amplifier module adopts chip U3, and its model is general J-FET dual operational amplifier TL082; What described drive coil adopted is the single turn square coil that can produce even high field and add magnetic core; What described detecting element adopted is the hollow circular coil of single turn; Described instrument amplifier module adopts chip U4, and its model is the typical instrument operational amplifier chip AD620 of AD company; Described AD modular converter adopts chip U5, and its model is 16 high precision analogue conversion chip ADS5560 of TI company; Described power module adopts circuit of three-terminal voltage-stabilizing integrated 7805 and switching mode lowering and stabilizing blood pressure device LM2575-3.3.
The principle of work of above-mentioned pulse eddy current thicknessmeter is for producing the square-wave pulse pumping signal of frequency and EDM Generator of Adjustable Duty Ratio by the MCU main control module, this pulse signal is under the effect of digital regulation resistance module, the amplitude of signal is carried out fixed ampllitude regulates, pulse signal after regulating is sent into power amplifier module amplify the rear drive drive coil, drive coil can produce a pulsed magnetic field of decay fast, the magnetic field that changes induces instantaneous eddy current in the conductor test specimen, to conductor test specimen internal communication, and induce a fast eddy current magnetism of decay, decay along with eddy current magnetism, will induce time dependent transient state induced voltage signal on the detecting element, this feeble signal is behind the amplification of prime amplifier instrument amplifier module, send into the MCU main control module after converting the simulating signal of obtaining to digital signal by the AD modular converter, the MCU main control module carries out showing by the LCD MODULE in the button display module after the analyzing and processing to signal.
Compared with prior art, the beneficial effects of the utility model are as follows:
1, the utility model system antijamming capability is strong, and the linearity is good, and response speed is fast, the degree of accuracy height, and high safety, operation and maintenance is convenient.
2, the utility model system can realize the accurate measurement of thickness at the metal material of unlike material, different-thickness scope, and measurement range is wide.
3, the utility model system is except that the measurement fast and safely that can realize metal material thickness, can also realize that material do not tear overlayer open and detect, and simultaneity factor has effectively suppressed temperature floats, and is very suitable for the detection of complex environment.
4, the utility model system is the further deeply application of theoretical research of harmlessization of impulse eddy current detection method, China's Non-Destructive Testing theory and application and the development of technology have been promoted in fields of measurement, break the monopolization in market at home of external same category of device, have certain dissemination.
Description of drawings
Fig. 1 is the utility model system architecture diagram;
Fig. 2 is the utility model system works schematic diagram;
Fig. 3 is transient state induced voltage and a time relation curve map on the detecting element in the utility model;
Fig. 4 is the utility model single-chip minimum system figure;
Fig. 5 is the utility model LCD MODULE circuit diagram;
Fig. 6 is the utility model digital regulation resistance module circuit diagram;
Fig. 7 is the utility model power amplifier module circuit diagram;
Fig. 8 is the utility model instrument amplifier module circuit diagram;
Fig. 9 is the utility model AD modular converter circuit diagram.
Embodiment
Below in conjunction with the drawings and specific embodiments the utility model is elaborated.
Embodiment:
A kind of pulse eddy current thicknessmeter as shown in Figure 1 comprises MCU main control module, button display module, digital regulation resistance module, power amplifier module, drive coil, detecting element, instrument amplifier module, AD modular converter and power module.Wherein the MCU main control module connects button display module, digital regulation resistance module and AD modular converter, the digital regulation resistance module connects power amplifier module, power amplifier module connects drive coil, detecting element connects the instrument amplifier module, the instrument amplifier module connects the AD modular converter, and power module provides the working power of each module.
Fig. 2 is the fundamental diagram of pulse eddy current thicknessmeter, and Fig. 3 is that detecting element (magnetic test coil W2) is gone up transient state induced voltage and time relation curve map.Transmitting coil W1 and receiving coil W2 place the upper and lower of tested metal material respectively among Fig. 2, behind square-wave pulse signal stimulated emission coil W1 with certain dutycycle, transmitting coil W1 can produce the pulsed magnetic field of quick decay, the magnetic field that changes induces instantaneous eddy current in measured object, to the measured object internal communication, and induce a fast eddy current magnetism of decay, decay along with eddy current magnetism, will induce time dependent transient state induced voltage signal on the magnetic test coil W2, as shown in Figure 3.Wherein the distance between coil and the measured object is
The measured object reactance is
The thickness of measured object is
When distance between system's fixed coil and the measured object and maximum reduction reactance, come the thickness of high-precision measuring metallic materials by gathering the induction electromotive force that obtains.
In the present embodiment, the pulse excitation signal that is adopted can be selected very low frequency for use, is not subject to disturb.Pulse signal contains all frequency contents from the direct current to the high frequency, and the test specimen information of reflection is also abundanter.Especially under the rugged surroundings that have liquid, gas and dust and under the situation of metal fast moving, can both measure accurately.Therefore, the pulse eddy current thickness measurement technology not only has the advantage of traditional thickness measurement technology, can also remedy the deficiency of traditional thickness measurement technology.
In the present embodiment, described MCU main control module comprises single-chip minimum system circuit, serial communication circuit etc., and wherein single-chip microcomputer adopts chip U1, and its model is the mixed-signal processor MSP430F413 of 16 super low-power consumptions of TI company release.Serial communication circuit adopts typical R S485 telecommunication circuit.The square-wave pulse pumping signal that single-chip microcomputer can produce frequency and EDM Generator of Adjustable Duty Ratio according to the actual needs of metal material unlike material and different-thickness scope drives drive coil generation magnetic field, realize the control function of total system simultaneously, its minimum system circuit as shown in Figure 4.
In the present embodiment, described button display module adopts the LCD12864 LCD MODULE circuit of independent button keyboard circuit and Changsha sun people company, mainly finishes the mutual of selection that function switches and man-machine interface.The I/O pin that can directly connect single-chip microcomputer after wherein free-standing key board connects by resistance, and the LCD MODULE circuit adopts the serial ports connected mode, only need 4 I/O pins of single-chip microcomputer connect respectively liquid crystal CS pin, STD pin, SCLK pin ,/the RST pin gets final product, provide adjustable potentiometer to connect 1 pin, 2 pin, 3 pin simultaneously, the power supply power supply gets final product work, and display circuit connects as shown in Figure 5.
In the present embodiment, described digital regulation resistance module adopts chip U2, the 256 node 10k Ω digital regulation resistance MAX5402 that its model is produced for Maxim company.Mainly be to be used for the amplitude of regulating impulse pumping signal, the amplitude stabilization that makes signal is in certain scope.The physical circuit connected mode is to connect 3,4,5 pin respectively after the I/O pin of single-chip microcomputer connects pull-up resistor, connect 8 pin again after connecting adjustable potentiometer, and the output of 1 pin connects power supply ground, 7 pin output signal to power amplifier module, the power supply power supply, this modular circuit connects as shown in Figure 6.
In the present embodiment, described power amplifier module adopts chip U3, and its model is the J-FET dual operational amplifier TL082 that volume is little, output power is big, distortion is little.Again signal is cushioned, isolates by follower after earlier signal being amplified through the homophase input amplifying circuit, adopt the effect of one group of Darlington power transistor TIP122 and TIP127 that feeble signal is carried out processing and amplifying at last and directly drive drive coil, can make drive coil produce stronger magnetic field like this, the collection and the features extraction that help the later stage signal, its typical connected mode as shown in Figure 7.
In the present embodiment, what described drive coil adopted is the single turn square coil that can produce even high field and add magnetic core, and what described detecting element adopted is the hollow circular coil of the smaller single turn of sectional area.The purpose that drive coil adopts the single turn square coil to add magnetic core simultaneously is to improve pulsed magnetic field intensity and detection speed; And detecting element adopts single turn hollow cylinder coil can make the magnetic field energy in the magnetic test coil institute limitation scope regard as uniformly, can improve the sensitivity of detection again, most importantly can reduce the influence of coil to measured object induction reactance simultaneously.
In the present embodiment, described instrument amplifier module adopts chip U4, and its model is the typical instrument operational amplifier chip AD620 of AD company.Because detected signal is faint, synchronous signal is by noise pollution, if want the curve of picked up signal decay, must be with signal through filtering and amplification, therefore adopt that common-mode rejection ratio is enough high amplifies feeble signal with the instrument amplifier with balance input impedance as prime amplifier, simultaneously signal is carried out Filtering Processing.Wherein connect power supply ground behind 2 pin, the external 1M resistance of 3 pin, simultaneously as signal input part, 4 pin, 7 pin connect positive source, 5 pin connect power supply ground, the potentiometer of 1 pin, the indirect 50K of 8 pin is realized the adjusting of enlargement factor, 6 pin are sent into signal in the AD modular converter after connecing filtering circuit as signal output part, and this modular circuit connects as shown in Figure 8.
In the present embodiment, described AD modular converter adopts chip U5, and its model is 16 high precision analogue conversion chip ADS5560 of TI company.This chip has the switching rate of 40MSPS and 16 high precision simultaneously as the modulus conversion chip with perfect adaptation of super low-power consumption and highest signal to noise ratio, satisfy the needs of actual samples fully, make sampling and measuring more accurate, circuit adopts parallel connection simultaneously, can change signal more fast, its concrete connecting circuit as shown in Figure 9.
In the present embodiment, described power module adopts circuit of three-terminal voltage-stabilizing integrated 7805 and switching mode lowering and stabilizing blood pressure device LM2575-3.3.Wherein 7805 as integrated regulator, the voltage of direct-flow voltage regulation of exportable positive 5V, and design provides part of module required 5V operating voltage in the system; And switching mode lowering and stabilizing blood pressure device LM2575-3.3 provides part of module work required 3.3V operating voltage, has so not only satisfied the needs of 3.3V voltage module but also provides interface for the use of 5V device.
By above embodiment as can be seen, the present embodiment system architecture is simple, and is easy to use, and superior performance can satisfy the needs of thickness measure fully.By the utilization of present embodiment, effectively guaranteed the accurate measurement of metal material thickness.
In conjunction with the accompanying drawings the utility model has been carried out exemplary description above; obviously the utility model specific implementation is not subjected to the restriction of aforesaid way; as long as the various improvement of having adopted method design of the present utility model and technical scheme to carry out; or directly apply to other occasion without improvement, all within protection domain of the present utility model.