SU1165966A1 - Electric contact flaw detector for checking conducting media - Google Patents

Abstract

ELECTROCONTACT DEFECTOR FOR MONITORING THE CONDUCTING MEDIUM, containing a generator of rectangular pulses, the output of which is connected to the input of the shift register, the first and second outputs of which are connected respectively to the first inputs of the first and second multiplication units, and the third, third output of the shift register is connected to the input of the voltage converter current, the first and second pairs of electrodes arranged in parallel and coaxially with the interelectrode distance in pairs, commensurate with the linear transverse size of the inhomogeneity, measured from regarding the direction of its control, the first and second electrodes of the first pair are connected respectively to the first and second inputs of the first amplifier, the output of which is connected to the second input of the multiplication unit, the output of which is connected to the first input of the differential amplifier through serially connected low-pass filter and the first and second electrodes of the second pair are connected respectively to the first and second inputs of the second amplifier, the output of which is connected to the second input of the second multiplication unit, output d which through a second low-pass filter connected in series and a second voltage divider are connected to a second differential amplifier input, the output of which through a serially connected comparator differentiating element is connected to the input of a recording unit, characterized in that, in order to increase sensitivity and localize inhomogeneity along the length of the defect, an integrator, a video indication unit, two current electrodes are entered into it, with the output of the differential amplifier through an integrator with The first and second outputs of the voltage to current converter are connected to the first and second current electrodes, respectively, the first and second pairs of electrodes of the genera are parallel to the line connecting the first and second current electrodes; o, d, and distance The gap between the indicated pairs of electrodes is the differential of the length of the inhomogeneity, measured in the direction of its control.

Description

The invention relates to the field of instrumentation technology and can be used in rejection devices based on physical signs of heterogeneity, mainly for well-conducting media, for example, in the inspection of welded joints as well as rivets, threaded joints, etc., in the control of painting quality.

An electronic contact defectoscope for monitoring paint coatings is known, which contains a blocking generator, a probe, and an indicator in the form of an audible tone-tone alarm device 1.

A disadvantage of this device is the inability to reproduce the nature of the conductivity measurement in the area of the defect.

The closest to the invention to the technical essence is a device for quantitative accounting of moving objects, capable of controlling the state of conducting media by a contact method, containing a generator of rectangular pulses, the output of which is connected to the input of the shift register, the first and second outputs of which are connected respectively to the first inputs of the first and second multiplication units, and the third output of the shift register is connected to the input of the first voltage to current converter, the first and second pairs of electrodes, parallel and coaxial with the interelectrode distance in pairs, commensurate with the linear transverse size of the inhomogeneity, measured relative to the direction of its control, the first and second parallel electrodes of the first pair are connected respectively to the first and second inputs of the first amplifier, the output of which is connected to the second input of the multiplication unit, the output of which is connected in series through a low-pass filter and the first voltage divider is connected to the first input of a differential amplifier, the first and second pairs Secondary electrodes of the second pair are connected respectively to the first and second inputs of the second amplifier, the output of which is connected to the second input of the second multiplication unit, the output of which is connected to the second input of the differential amplifier through the serially connected second low-pass filter and the second voltage divider. comparator, differentiating element connected to the input of the registration unit. In addition, the fourth output of the shift register is connected to the input of the second voltage to current converter, the first and second outputs of which are connected respectively to the first and second inputs of the second amplifier, and the first and second outputs of the first voltage to current converter are connected respectively to the first and the second inputs of the first amplifier 2.

The disadvantages of the known device are low sensitivity in the control of defects, for example, weld groove due to the influence of contact resistances on the electrodes, as well as the absence of localization of non-uniformity along the length of the defect.

The aim of the invention is to increase the sensitivity and ensure the localization of heterogeneity along the length of the defect.

This goal is achieved by the fact that the electrocontact flaw detector for controlling conducting media, comprising a square pulse generator, the output of which is connected to the input of the shift register, the first and second outputs of which are connected respectively to the first inputs of the first and second multiplication units, and the third output of the shift register connected to the input of the voltage converter into the current, the first and second pairs of electrodes arranged in parallel and coaxially with the interelectrode distance in pairs, commensurate with the linear

0 with a transverse dimension of inhomogeneity, measured relative to the direction of its control, the first and second electrodes of the first pair are connected respectively to the first and second inputs of the first amplifier, output

5 of which is connected to the second input of the multiplication unit, the output of which is connected through a low-pass filter connected in series and the first voltage divider is connected to the first input of a differential amplifier, the first and second electrodes of the second pair are connected respectively to the first and second inputs of the second amplifier, the output of which is connected to the second input of the second multiplication unit, the output of which is connected through the second low-pass filter and the second divider of a voltage 5 sequentially connected to the second input of the differential amplifier; The integrator, the output of which is connected through a series-connected comparator, the differentiating element is connected to the input of the registration unit,

0 video indication unit, two current electrodes, the output of the differential amplifier through the integrator connected to the input of the video indication unit, the first and second outputs of the voltage to current converter

5 are connected respectively to the first and second current electrodes, the first and second pairs of electrodes are parallel to the line connecting the first and second current electrodes, and the distance between said pairs of electrodes is

0 differential from length of heterogeneity, measured in the direction of its control.

FIG. 1 shows the flow chart of the flaw detector; in fig. 2 and 3 - time. variable diagrams of the corresponding voltage.

The flaw detector (Fig. 1) contains a generator of 1 rectangular pulses, the output of which is connected to the input of the shift register 2, a voltage-to-current converter 3, the first 4.1 and 4.2, and the second 5.1 and 5.2 pairs of electrodes parallel and coaxial, the electrodes 6.1 and 6.2 . Moreover, 4.1 and 5.1 are the first electrodes of the first and second pairs, respectively, and 4.2 and 5.2 are the second electrodes of the first and second pairs, respectively. The first and second outputs of the voltage-to-current converter 3 are connected to the first 5.1 and second 5.2 current electrodes, respectively. The first 4.1 and 4.2 second electrodes of the first pair are connected respectively to the first and second inputs of the first amplifier 7. The first 5.1 and 5.2 second electrodes of the second pair are connected respectively to the first and second inputs of the second amplifier 8; The output of the first amplifier 7 is connected to one of the inputs of the first multiplication unit 9. The output of the second amplifier 8 is connected to one of the inputs of the second multiplication unit 10. One of the inputs of the first multiplication unit 9 is connected to the first output of the shift register 2, and one of the inputs of the second multiplication unit 10 is connected to the second output of the shift register 2, the third output of which is connected to the input of the voltage-to-current converter 3. The output of the first multiplication unit 9 through the first lowpass filter 11 and the first voltage divider 12 is connected to the first input of the differential amplifier 13. The output of the second multiplication unit 10 is connected via the second lowpass filter 14 and the second voltage divider 15 to the second input differential amplifier 13. The output of the differential amplifier 13 is connected through series-connected comparator 16 and the differentiating element 17 is connected to the block 18 of the registration. In addition, the output of the amplifier 13 is connected through the integrator 19 to the input of the video indication unit 20. FIG. 1 also shows controlled heterogeneity 21.

The generator 1 is designed to create a rectangular pulse voltage. The lower frequency of the oscillator pulse signal is 3-5 times higher than the maximum possible linear velocity of control of objects, and the upper frequency is determined by the attenuation conditions of the signal (or its propagation) in the corresponding medium. Shift register 2 is designed to provide alternate output of rectangular pulses, ensuring the time distribution of the measurement process on nepBoji 4.1 and 4.2 and the second 5.1 and 5.2 pairs of electrodes. Converter 3 is designed to provide a predetermined amount of current passing through an inhomogeneity in a controlled environment. The first 6.1 and second 6.2 current electrodes are designed to consistently transfer current to the medium and to ensure reliable contact with the medium in which the heterogeneity is controlled. Electrodes 4.1, 4.2, 5.1 and 5.2 are electrical

probes that ensure contact with the material of the medium, for example, with a metallic surface, sufficient to measure voltages with an instrument with a large input resistance. Structurally, these electrodes can be located along the vertices of a rectangular carriage, the length of which is commensurate with the transverse exchange of controlled heterogeneity, for example, the width of the welded joint, and the width is commensurate

0 with the differential length of the heterogeneity, for example, weld along its length. In this case, the electrodes can be made in the form of rotating wheel contacts of the movable carriage, mounted on spring supports insulated from each other. Amplifiers 7 and 8 are designed to amplify voltage signals appearing on electrodes 4.1, 4.2, 5.1 and 5.2, for example, when a non-uniformity passes between the electrodes of each pair. With this input

0 the resistance of the amplifiers should be significantly greater than the possibly greater resistance of each of the contacts of the electrodes 4.1, 4.2, 5.1 and 5.2 with the surface of the object. Blocks 9 and 10 multiplications are designed to separate the information signal that occurs when there is a change between electrodes 4.1, 4.2, 5.1 and 5.2 due to non-uniform conductivity along the length.

Low-pass filters 11 and 14 are designed to separate and form low Q frequency information signals. The time constant of these filters is chosen such that the values of the pulse voltages coming from the respective multiplier outputs, i.e. to convert

5 pulse information signals in a continuous current signal.

Voltage dividers 12 and 15 are designed to balance the signals coming from filters 11 and 14, so that in the absence of any disturbances in the zone where the electrodes are located, the output of amplifier 13 has zero voltage. Resistive potentiometers can be used as these voltage dividers.

5 Differential amplifier 13 provides a comparison of the signals supplied (through the appropriate blocks) from the first 4.1 and 4.2, respectively, and the second 5.1 and 5.2 pairs of electrodes.

The comparator 16 generates a constant amplitude signal, the sign of which is determined by the phase sign of the difference signal at the output of the amplifier 13. The differentiating element 17 generates pulses, the polarity of which is determined by the sign of the slope (difference) of the voltage of the comparator at the time of its change in phase.

The registration unit 18 is designed to indicate the result of counting pulses from the differentiating element 17.j

The integrator 19 forms an envelope (a function of a change in conductivity, e.g., along the length of a welded joint).

The non-indication unit 20 is intended to indicate the function of changing the conductivity along the length of the defect, for which an oscilloscope with a horizontal scan can be used, commensurate with the speed of the relative movement of the carriage with the electrodes. An audible alarm is also provided in the display unit 20. Electrocontact flaw detector works as follows.

Generator 1 generates rectangular, polarized, symmetric pulse signals arriving at shift register 2. The pulse signal Ui (Fig. 2o) from the corresponding output of register 2 is fed to the input of voltage converter 3 into current, and then through current electrodes 6.1 and 6.2 to the inhomogeneity control zone 21, forming a three-dimensional structure of distributed currents and correspondingly potential fields in the medium. Moreover, these current electrodes should be positioned on the line, perpendicular to the trajectory of the heterogeneity, for example, the weld. Pulse signals Uj and U; j shifted by half of clock pulses U j. (Fig. 26 and c), from the corresponding outputs of register 2, the first inputs of the corresponding blocks 9 and 10 of the multiplication are received. The voltages U (Fig. 2d) and Uj (not shown) formed on electrode pairs 4.1 and 4.2, 5.1 and 5.2 are amplified by amplifiers 7 and 8, respectively, and are transformed across the spectrum in multiples 9 and 10.

Each of these blocks operates in a mixer mode so that, if there is no interelectrode conductivity in any pair of electrodes, Ug pulses are generated at the output of the corresponding multiplication unit (Fig. 2e). In the presence of interelectrode conductivity, the voltage U takes the form of a voltage Ufi (Fig. 2e). The impulse voltages from the outputs of blocks 9 and 10 of the multiplication are fed to the inputs of the corresponding filters 11 and 14 of the lower frequencies. The voltage of the symmetric pulses at the output of the corresponding multiplication unit (Fig. 2e) after the corresponding low-pass filter takes a zero value, and the voltage of the asymmetric pulses (Fig. 2e) is converted to the appropriate level of constant voltage (Fig. 2g:) From the outputs of the filters 11 and 14, the voltage through the corresponding voltage dividers 12 and 15 (potentiometers) is fed to the inputs of the differential amplifier 13. In the absence of heterogeneity in the interelectrode zone, both inputs of the amplifier 13 are the same voltage, which are folded in antiphase so that there is no voltage at the output of the specified amplifier (otherwise adjustment of the potentiometers ensures complete equality of the voltages at both inputs of the amplifier 13). If, for example, there is an weld-welded object in the quality of a controlled object and the current lines of the electric field of the current flow are perpendicular to it, a non-uniform electric field is formed in the area of the weld. Measuring the potential difference of this field near and along the well in each of the electrode pairs 4.1 and 4.2, 5.1 and 5.2 will determine the corresponding voltages U (x), and (x + lx), where X is the coordinate of the path of the ground. FIG. 2c shows the variation of the potential difference Ug in the first pair of electrodes 4.1 and 4.2 as it moves along the weld (the pair of electrodes is located perpendicular to the weld). FIG. Pros and b, respectively, show signals Ug and Uio, proportional to the change in voltage across the respective pairs of electrodes. Both signals after summing in the amplifier 13 form the difference signal Un (Fig. Sv). With a close (L) and parallel arrangement of electrode pairs at the output, a differentiation function of 3 (x) is obtained, describing a different polarity of the signal depending on the ratio of the voltages on the first 4.1 and 4.2 and the second 5.1 and 5.2 pairs of electrodes. The difference signal Uij after the comparator 16 (Fig. 3g) is fed to the input of the differentiating element 17, at the output of which a counting pulse Ua (Fig. 3d) is generated, which enters the registration unit 18. The polarity of the indicated counting pulses in the registration block 18 is matched with the sign of the change in function. The number of positive or negative pulses is characterized by the number of maxima of the increment or by the decrease in conductivity along the weld per unit of its length. The incoming voltage and (x) from the output of the amplifier 13 carries information about the rate of change in conductivity between the electrodes. The law of variation of the conductivity U (x) is obtained by integrating the function (x) in the integrator 19. As a result of the integration operation over the time of the day (with a uniform movement of the carriage with electrodes along the weld joint), the output of the integrator 19 is obtained as Ui4 (Fig. Ze ). From the output of the integrator 19, the signal enters video-indication unit 20, which allows to determine the degree of heterogeneity of an object, for example, a weld joint, by video and sound signals, as well as by a dial indicator.

The proposed device improves the accuracy of the flaw detection by using the method of differentiation by spatial coordinates when moving the measuring system by using the counter of maxima of the change in conductivity, and also provides the possibility of visual observation of the conductivity along the entire length of the defect.

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Claims (1)

ELECTRIC CONTACT DEFECTOSCOPE FOR CONTROL OF CONDUCTING MEDIA, containing a rectangular pulse generator, the output of which is connected to the input of the shift register, the first and second outputs of which are connected respectively to the first inputs of the first and second blocks of multiplication, and the third output of the shift register is connected to the input of the voltage to current converter, the first and second pairs of electrodes located parallel and coaxial with the interelectrode distance in pairs, commensurate with the linear transverse size of the inhomogeneity, measured relative about the direction of its control, the first and second electrodes of the first pair are connected respectively to the first and second inputs of the first amplifier, the output of which is connected to the second input of the multiplication unit, the output of which is connected through the low-pass filter and the first voltage divider to the first input of the differential amplifier, the first and the second electrodes of the second pair are connected respectively to the first and second inputs of the second amplifier, the output of which is connected to the second input of the second multiplication unit, the output of which is h the second low-pass filter and the second voltage divider are connected in series to the second input of the differential amplifier, the output of which through a series-connected comparator, the differentiating element is connected to the input of the registration unit, characterized in that, in order to increase the sensitivity and ensure the localization of the heterogeneity along the length defect, it introduced an integrator, a block of video | w deindication, two current electrodes, - 1 ^ than the output of a differential amplifier through | the integrator is connected to the input of the video g-display unit, the first and second outputs of the voltage-to-current converter are connected respectively to the first and second current electrodes, the first and second pairs of electrodes are parallel to the line connecting the first and second current electrodes, and the distance between the indicated pairs of electrodes is the differential of the length of the heterogeneity, measured in the direction of its control.