SU1265586A1 - Probe-type magnetic-field flaw detector - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to control the integrity or quality of the ferromagnetic products in all areas of engineering. The aim of the invention is to expand the operational capabilities and reduce energy consumption by simplifying the manufacturing technology, reducing the size, power consumption and expanding the range of the measured magnetic field. For this, the block of flux-gate transducers is made in the form of a linear series of choke-type flux-probes, which with the help of a switch 7, implemented as a distributor of 8 pulses, and a block of 9 electronic switches, each of which is connected to one of the flux-probes, are alternately connected to the excitation unit 3, configured as a source 4, a constant electronic key 5, and a generator 6 of control rectangular pulses. The new (О С execution of the block 3 of excitation and switching 7 with the corresponding lasers provides identical conditions for the excitation of each fluxgate and the same sensitivity to the magnetic field. 4 Il.

Description

The invention refers to non-destructive testing and; It can be used to control the continuity or quality of the structure of ferromagnetic products in all areas of engineering. The aim of the invention is to expand the operational capabilities and reduce energy consumption by simplifying the manufacturing technology, reducing the size, power consumption and expanding the range of the measured magnetic field. Figure 1 shows the functional block diagram of the device; Fig. 2 is an equivalent circuit diagram of a ferrosonde excitation circuit; in FIG. 3, the magnetization curve B (H) of the core of the fluxgate; Fig. 4 shows time diagrams explaining the operation of the device {c i-output pulses of the generator of rectangular pulses; B- pulses at the output of the distributor; B is the voltage pulse shape on the inductance of the fluxgate; r is the peak detector control pulses; 3 is the step voltage across the storage capacitor c). Figures with indexes TJf, Up, etc. means the channel numbers of the device's number of outputs. I. The device contains a block of 1 flux-gate transducers installed near the object 2 of the control, which creates a magnetic flux during scattering, the block of block 1 of flux-gate transducers is executed as a linear series of choke-type fluxguns, block 3 of the hinge of flux-gate transducers, made as a source 4 constant voltage, electronic key 5, the potential input of which is connected with the output of the constant voltage source 4, and generator 6 of the pulsed square, the first output of which connected to the control input of the electronic key 5, the output of which is connected to the first input of the fluxgate transducer unit 1, the switch 7, made in the form of serially connected pulse distributor 8, the input connected to the second daughter generator of the 6 rectangular pulses and the electronic switch unit 9, associated with the flux-probes, the indicator 10, made in the form of a sequence of 6 but connected cascade and delay, the input of which is connected to the second output of the generator 6 of rectangular pulses, the generator 12 controls constituent pulses controllably peak detector 13, a second input connected to the output of unit 1 fluxgate transducer, amplifier 14, DC and oscilloscope 15, sleduyuschim.obrazom device operates. The control object 2 is progressively displaced near the stationary block 1 of magnetically sensitive flux-gate transducers of the elements. Under the influence of an external magnetic field near the surface of the control object 2, a certain magnetic relief is created, acting on the flux-gates of the transducer, which read the normal components of the stray fields. The sensors are excited using the 3 "block. The output signals of the sensors are fed to the indicator 10. The switch 7 is used to alternately connect the flux-probes to the excitation unit 3 and the indicator 10. The frequency of polling of the sensors is determined by the frequency of the 6-square pulse generator, which is also an element of the device block 3 excitation. The state of the core of the fluxgate is determined by the magnitude of the normal component H | The field of the scattering acting on the sensor at its location, and the magnitude of the pulse field of the excitation signal, which is proportional to the current 1 flowing in the winding of the ferrosonde. For normal operation of the converter, an excitation field is necessary, which provides the magnetization of the core to the state of technical saturation В. (ind: hkci is saturated), therefore its am1: scaled Itz value is chosen from the condition tt 2H. This provides the possibility of stable operation of the converter in the field range –H t, l P the excitation of the fluxgate with unipolar pulses. The excitation of a flux probe, with the help of a constant voltage source with negligible internal resistance, and a controlled electronic key 5, which is a transistor connected according to a common emitter circuit, whose resistance is changed from a saturation to a closed state from several ohms to mom and is a function of time t, the amplitude of the pulse is opposite to the supply voltage of the polarity arising on the inductance of the fluxgate due to transient when locking the electronic key 5, when a number of conditions are proportional to the Nd-H. The linear dependence of the amplitude of the EMF induction is used to measure constant or time-varying magnetic fields in a wide amplitude and frequency ranges and laid the basis for the operation of chokes of fluxgate used as a magnetically sensitive element of a fluxgate transducer. The frequency of the pulses of the field of excitation is equal to the frequency of the pulses of the generator 6 rectangular pulses and the amplitude is proportional to the current generated by the source 4 (the magnitude and such that the condition H, + H) is fulfilled. Only one transistor (electronic key 5) participates in the process of excitation pulse generation, therefore the condition of the equal sensitivity of all sensors to the magnetic field is o6ecrfe, because only one flux probe is excited by this pulse at each instant. The time separation of the flux-probes is performed using the switch 7 as follows. The pulses produced by the generator 6 (Fig. AA) are distributed among the m outputs distributed, bodies 8. Each output of the distributor is connected to one of the keys of the electronic key block, which, in turn, is connected to one of the sensors of the block 1 magnetically sensitive ferrozondov. The pulses from the output of the distributor 8 (Fig, 4 &) open the corresponding key, and through it, a square-shaped voltage pulse coming from the output of the exciter 3 is applied to the ferrosonde. The key switching process is carried out with the arrival of each pulse from the generator of 6 rectangular pulses, therefore the excitation frequency of each fluxgate differs from the generator frequency 6 times (m is the number of probes), the duration of the control pulses (Fig. 4) of the distributor 8 is determined by the period following the generator 6, the moments of switching of the flux-probes and the switching of the electronic key 5 from the valued state to the locked state are separated in time, therefore, the operation of the switch does not degrade the characteristics of the converter. Due to transients, the shape of the excitation pulse is distorted. As a result, the voltage on the inductance of the fluxgate has a different shape than the rectangular one (Fig. Ab). This input arrives at the input of the indicator 10, which creates a visual image of the magnetic relief of the control object. Information about the magnitude of the dissipated field H, acting on each probe, carries only a negative half-wave voltage pulse and, whose amplitude is proportional, the extraction of useful information is carried out using a controlled diode peak detector 11, which is connected to the output of block 1 of magnetically sensitive ferrozondov. Due to the use of a diode, the storage capacitor of the peak detector 1 3 receives only the voltage that occurs on the inductance when the electronic switch 5 is switched from a saturated state to a locked state, i.e. impulse voltage opposite to the supply voltage polarity. Simultaneously with the appearance of an input pulse in the control circuit of the detector 13, a gating pulse is applied and conditions are created for charging the capacitor from detector 13 to an extreme value of the input pulse - 1 "ax. If the next pulse coming from the next fluxgate turns out to be large in absolute value, then the capacitor additionally charged to the amplitude value of this pulse. If, on the contrary, the value of the next pulse is less in absolute value, the capacitor is discharged, and the voltage on it becomes equal to the new value. Thus, the voltage across the capacitor from the peak detector I3 follows the change in the amplitude of 1, 1 of the output pulses. The pulses coming from the output of the unit 1 of magnetic-sensitive flux-gate transducers. During the pauses between the pulses, the voltage across the capacitor remains almost unchanged, maintaining the amplitude value of the input voltage for the entire period.

The peak detector 13 is controlled by short pulses from a control pulse generator 12, which is triggered with a delay relative to the pulse front of the flux probe (Fig. 4). The required delay time is set by a delay stage 11, which is connected to the output of a square pulse generator.

When the transducer acts on the non-uniform magnetic field of the object 2, the amplitude of the pulses will change when going from one flux-gate to another in accordance with the change of the H field acting on the cores, therefore a step voltage is formed on the storage capacitor C of the peak detector 13 (Fig. 45) which is then amplified by the direct current amplifier 14 and fed to the input of the oscilloscope 15. As a result, a visual image is created on its screen, which is equivalent to the magnetic relief of the magnetic field th object 2. This relief is correlated with the properties of the ferromagnetic material of the controlled object.

According to the specified visual image, it is possible to determine, for example, a discontinuity in this object or a poor-quality structure of the material under study. Thus, the use of throttle-type flux-probes and an excitation device made as a constant voltage source and an electronic switch controlled by a square pulse generator ensures that conditions are met that the amplitude of the voltage pulse is opposite to the supply voltage arising on the inductance of a flux-gate due to transients when the electronic key is switched from a saturated state to a locked state, is proportional to and, they, can serve as an informative parameter for measuring the magnitude of magnetic field strength H, acting on the core probe. Thanks

selection of the core material with a discontinuous change (uc / (Fig. 3) it is possible to obtain an almost linear dependence on

Zmax

(HK) In a wide range of magnetic fields from + H with. to –H while maintaining a high sensitivity to variable magnetic fields and to the phase of the measured signal. The value of H may vary widely depending on the demagnetizing factor of the core.

As a result of the application of a source of constant voltage, controlled electronic key, a block of magnetically sensitive elements, made in the form of a linear series of ferroson-. The throttle and switchboard switches, made in the form of a pulse distributor coming from a square pulse generator, and an electronic switch unit connected with fluxing probes, have been able to expand the range of fields in which the converter can work steadily up to t300 A / cm since this allowed The alternating excitation of the flux-probes with pulses of high porosity and low power made it possible to use cores with a large demagnetizing factor.

Claims (1)

Invention Formula A fluxgate flaw detector containing a flux-gate transducer block, an excitation transducer block and a switch connected respectively to its first and second inputs, and an indicator connected to the output of the flux-gate transducer block, is also distinguished by the fact that energy consumption, the flux-gate converter unit is designed as a linear series of throttle-type flux-probes, the power converter unit is designed as a constant source an electronic key, the potential input of which is connected to the output of a constant voltage source, and a generator of rectangular pulses, the first output of which is connected to the control input of the electronic key, the output of which is connected to the first input of the fluxgate transducer unit the switch is made in the form of serially connected distributor, the input connected to the second output of the generator of rectangular pulses, and the unit of electronic keys, output connected to the fluxgate, and the indicator is made in the form of series-connected cascade Delays, the input of which is connected to the second output of a square pulse generator, a control pulse generator, a controlled peak detector connected by a second input to the output of the fluxgate transducer unit, a DC amplifier and an oscilloscope. About HS n Fig.Z